Merge pull request #4310 from pks-t/pks/common-parser

Common parser interface

8 files changed, 945 insertions, 943 deletions

diff --git a/src/config_file.c b/src/config_file.c
index cc4e7b3b7..792a3de7a 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -17,6 +17,7 @@
 #include "git2/types.h"
 #include "strmap.h"
 #include "array.h"
+#include "config_parse.h"
 
 #include <ctype.h>
 #include <sys/types.h>
@@ -75,20 +76,6 @@ typedef struct git_config_file_iter {
 		 (iter) && (((tmp) = CVAR_LIST_NEXT(iter) || 1));\
 		 (iter) = (tmp))
 
-struct config_file {
-	git_oid checksum;
-	char *path;
-	git_array_t(struct config_file) includes;
-};
-
-struct reader {
-	struct config_file *file;
-	git_buf buffer;
-	char *read_ptr;
-	int line_number;
-	int eof;
-};
-
 typedef struct {
 	git_atomic refcount;
 	git_strmap *values;
@@ -107,6 +94,8 @@ typedef struct {
 	git_config_level_t level;
 	const git_repository *repo;
 
+	git_array_t(git_config_parser) readers;
+
 	bool locked;
 	git_filebuf locked_buf;
 	git_buf locked_content;
@@ -120,19 +109,13 @@ typedef struct {
 	diskfile_backend *snapshot_from;
 } diskfile_readonly_backend;
 
-static int config_read(git_strmap *values, const git_repository *repo, struct config_file *file, git_config_level_t level, int depth);
+static int config_read(git_strmap *values, const git_repository *repo, git_config_file *file, git_config_level_t level, int depth);
 static int config_write(diskfile_backend *cfg, const char *orig_key, const char *key, const regex_t *preg, const char *value);
 static char *escape_value(const char *ptr);
 
 int git_config_file__snapshot(git_config_backend **out, diskfile_backend *in);
 static int config_snapshot(git_config_backend **out, git_config_backend *in);
 
-static void set_parse_error(struct reader *reader, int col, const char *error_str)
-{
-	giterr_set(GITERR_CONFIG, "failed to parse config file: %s (in %s:%d, column %d)",
-		error_str, reader->file->path, reader->line_number, col);
-}
-
 static int config_error_readonly(void)
 {
 	giterr_set(GITERR_CONFIG, "this backend is read-only");
@@ -293,7 +276,6 @@ static int config_open(git_config_backend *cfg, git_config_level_t level, const
 	if ((res = refcounted_strmap_alloc(&b->header.values)) < 0)
 		return res;
 
-	/* It's fine if the file doesn't exist */
 	if (!git_path_exists(b->file.path))
 		return 0;
 
@@ -307,11 +289,11 @@ static int config_open(git_config_backend *cfg, git_config_level_t level, const
 
 static int config_is_modified(int *modified, struct config_file *file)
 {
-	struct config_file *include;
+	git_config_file *include;
 	git_buf buf = GIT_BUF_INIT;
 	git_oid hash;
 	uint32_t i;
-	int error;
+	int error = 0;
 
 	*modified = 0;
 
@@ -341,7 +323,7 @@ static int config_refresh(git_config_backend *cfg)
 {
 	diskfile_backend *b = (diskfile_backend *)cfg;
 	refcounted_strmap *values = NULL, *tmp;
-	struct config_file *include;
+	git_config_file *include;
 	int error, modified;
 	uint32_t i;
 
@@ -885,397 +867,6 @@ int git_config_file__snapshot(git_config_backend **out, diskfile_backend *in)
 	return 0;
 }
 
-static int reader_getchar_raw(struct reader *reader)
-{
-	int c;
-
-	c = *reader->read_ptr++;
-
-	/*
-	Win 32 line breaks: if we find a \r\n sequence,
-	return only the \n as a newline
-	*/
-	if (c == '\r' && *reader->read_ptr == '\n') {
-		reader->read_ptr++;
-		c = '\n';
-	}
-
-	if (c == '\n')
-		reader->line_number++;
-
-	if (c == 0) {
-		reader->eof = 1;
-		c = '\0';
-	}
-
-	return c;
-}
-
-#define SKIP_WHITESPACE (1 << 1)
-#define SKIP_COMMENTS (1 << 2)
-
-static int reader_getchar(struct reader *reader, int flags)
-{
-	const int skip_whitespace = (flags & SKIP_WHITESPACE);
-	const int skip_comments = (flags & SKIP_COMMENTS);
-	int c;
-
-	assert(reader->read_ptr);
-
-	do {
-		c = reader_getchar_raw(reader);
-	} while (c != '\n' && c != '\0' && skip_whitespace && git__isspace(c));
-
-	if (skip_comments && (c == '#' || c == ';')) {
-		do {
-			c = reader_getchar_raw(reader);
-		} while (c != '\n' && c != '\0');
-	}
-
-	return c;
-}
-
-/*
- * Read the next char, but don't move the reading pointer.
- */
-static int reader_peek(struct reader *reader, int flags)
-{
-	void *old_read_ptr;
-	int old_lineno, old_eof;
-	int ret;
-
-	assert(reader->read_ptr);
-
-	old_read_ptr = reader->read_ptr;
-	old_lineno = reader->line_number;
-	old_eof = reader->eof;
-
-	ret = reader_getchar(reader, flags);
-
-	reader->read_ptr = old_read_ptr;
-	reader->line_number = old_lineno;
-	reader->eof = old_eof;
-
-	return ret;
-}
-
-/*
- * Read and consume a line, returning it in newly-allocated memory.
- */
-static char *reader_readline(struct reader *reader, bool skip_whitespace)
-{
-	char *line = NULL;
-	char *line_src, *line_end;
-	size_t line_len, alloc_len;
-
-	line_src = reader->read_ptr;
-
-	if (skip_whitespace) {
-		/* Skip empty empty lines */
-		while (git__isspace(*line_src))
-			++line_src;
-	}
-
-	line_end = strchr(line_src, '\n');
-
-	/* no newline at EOF */
-	if (line_end == NULL)
-		line_end = strchr(line_src, 0);
-
-	line_len = line_end - line_src;
-
-	if (GIT_ADD_SIZET_OVERFLOW(&alloc_len, line_len, 1) ||
-		(line = git__malloc(alloc_len)) == NULL) {
-		return NULL;
-	}
-
-	memcpy(line, line_src, line_len);
-
-	do line[line_len] = '\0';
-	while (line_len-- > 0 && git__isspace(line[line_len]));
-
-	if (*line_end == '\n')
-		line_end++;
-
-	if (*line_end == '\0')
-		reader->eof = 1;
-
-	reader->line_number++;
-	reader->read_ptr = line_end;
-
-	return line;
-}
-
-/*
- * Consume a line, without storing it anywhere
- */
-static void reader_consume_line(struct reader *reader)
-{
-	char *line_start, *line_end;
-
-	line_start = reader->read_ptr;
-	line_end = strchr(line_start, '\n');
-	/* No newline at EOF */
-	if(line_end == NULL){
-		line_end = strchr(line_start, '\0');
-	}
-
-	if (*line_end == '\n')
-		line_end++;
-
-	if (*line_end == '\0')
-		reader->eof = 1;
-
-	reader->line_number++;
-	reader->read_ptr = line_end;
-}
-
-GIT_INLINE(int) config_keychar(int c)
-{
-	return isalnum(c) || c == '-';
-}
-
-static int parse_section_header_ext(struct reader *reader, const char *line, const char *base_name, char **section_name)
-{
-	int c, rpos;
-	char *first_quote, *last_quote;
-	git_buf buf = GIT_BUF_INIT;
-	size_t quoted_len, alloc_len, base_name_len = strlen(base_name);
-
-	/*
-	 * base_name is what came before the space. We should be at the
-	 * first quotation mark, except for now, line isn't being kept in
-	 * sync so we only really use it to calculate the length.
-	 */
-
-	first_quote = strchr(line, '"');
-	if (first_quote == NULL) {
-		set_parse_error(reader, 0, "Missing quotation marks in section header");
-		goto end_error;
-	}
-
-	last_quote = strrchr(line, '"');
-	quoted_len = last_quote - first_quote;
-
-	if (quoted_len == 0) {
-		set_parse_error(reader, 0, "Missing closing quotation mark in section header");
-		goto end_error;
-	}
-
-	GITERR_CHECK_ALLOC_ADD(&alloc_len, base_name_len, quoted_len);
-	GITERR_CHECK_ALLOC_ADD(&alloc_len, alloc_len, 2);
-
-	if (git_buf_grow(&buf, alloc_len) < 0 ||
-	    git_buf_printf(&buf, "%s.", base_name) < 0)
-		goto end_error;
-
-	rpos = 0;
-
-	line = first_quote;
-	c = line[++rpos];
-
-	/*
-	 * At the end of each iteration, whatever is stored in c will be
-	 * added to the string. In case of error, jump to out
-	 */
-	do {
-
-		switch (c) {
-		case 0:
-			set_parse_error(reader, 0, "Unexpected end-of-line in section header");
-			goto end_error;
-
-		case '"':
-			goto end_parse;
-
-		case '\\':
-			c = line[++rpos];
-
-			if (c == 0) {
-				set_parse_error(reader, rpos, "Unexpected end-of-line in section header");
-				goto end_error;
-			}
-
-		default:
-			break;
-		}
-
-		git_buf_putc(&buf, (char)c);
-		c = line[++rpos];
-	} while (line + rpos < last_quote);
-
-end_parse:
-	if (git_buf_oom(&buf))
-		goto end_error;
-
-	if (line[rpos] != '"' || line[rpos + 1] != ']') {
-		set_parse_error(reader, rpos, "Unexpected text after closing quotes");
-		git_buf_free(&buf);
-		return -1;
-	}
-
-	*section_name = git_buf_detach(&buf);
-	return 0;
-
-end_error:
-	git_buf_free(&buf);
-
-	return -1;
-}
-
-static int parse_section_header(struct reader *reader, char **section_out)
-{
-	char *name, *name_end;
-	int name_length, c, pos;
-	int result;
-	char *line;
-	size_t line_len;
-
-	line = reader_readline(reader, true);
-	if (line == NULL)
-		return -1;
-
-	/* find the end of the variable's name */
-	name_end = strrchr(line, ']');
-	if (name_end == NULL) {
-		git__free(line);
-		set_parse_error(reader, 0, "Missing ']' in section header");
-		return -1;
-	}
-
-	GITERR_CHECK_ALLOC_ADD(&line_len, (size_t)(name_end - line), 1);
-	name = git__malloc(line_len);
-	GITERR_CHECK_ALLOC(name);
-
-	name_length = 0;
-	pos = 0;
-
-	/* Make sure we were given a section header */
-	c = line[pos++];
-	assert(c == '[');
-
-	c = line[pos++];
-
-	do {
-		if (git__isspace(c)){
-			name[name_length] = '\0';
-			result = parse_section_header_ext(reader, line, name, section_out);
-			git__free(line);
-			git__free(name);
-			return result;
-		}
-
-		if (!config_keychar(c) && c != '.') {
-			set_parse_error(reader, pos, "Unexpected character in header");
-			goto fail_parse;
-		}
-
-		name[name_length++] = (char)git__tolower(c);
-
-	} while ((c = line[pos++]) != ']');
-
-	if (line[pos - 1] != ']') {
-		set_parse_error(reader, pos, "Unexpected end of file");
-		goto fail_parse;
-	}
-
-	git__free(line);
-
-	name[name_length] = 0;
-	*section_out = name;
-
-	return 0;
-
-fail_parse:
-	git__free(line);
-	git__free(name);
-	return -1;
-}
-
-static int skip_bom(struct reader *reader)
-{
-	git_bom_t bom;
-	int bom_offset = git_buf_text_detect_bom(&bom,
-		&reader->buffer, reader->read_ptr - reader->buffer.ptr);
-
-	if (bom == GIT_BOM_UTF8)
-		reader->read_ptr += bom_offset;
-
-	/* TODO: reference implementation is pretty stupid with BoM */
-
-	return 0;
-}
-
-/*
-	(* basic types *)
-	digit = "0".."9"
-	integer = digit { digit }
-	alphabet = "a".."z" + "A" .. "Z"
-
-	section_char = alphabet | "." | "-"
-	extension_char = (* any character except newline *)
-	any_char = (* any character *)
-	variable_char = "alphabet" | "-"
-
-
-	(* actual grammar *)
-	config = { section }
-
-	section = header { definition }
-
-	header = "[" section [subsection | subsection_ext] "]"
-
-	subsection = "." section
-	subsection_ext = "\"" extension "\""
-
-	section = section_char { section_char }
-	extension = extension_char { extension_char }
-
-	definition = variable_name ["=" variable_value] "\n"
-
-	variable_name = variable_char { variable_char }
-	variable_value = string | boolean | integer
-
-	string = quoted_string | plain_string
-	quoted_string = "\"" plain_string "\""
-	plain_string = { any_char }
-
-	boolean = boolean_true | boolean_false
-	boolean_true = "yes" | "1" | "true" | "on"
-	boolean_false = "no" | "0" | "false" | "off"
-*/
-
-static int strip_comments(char *line, int in_quotes)
-{
-	int quote_count = in_quotes, backslash_count = 0;
-	char *ptr;
-
-	for (ptr = line; *ptr; ++ptr) {
-		if (ptr[0] == '"' && ptr > line && ptr[-1] != '\\')
-			quote_count++;
-
-		if ((ptr[0] == ';' || ptr[0] == '#') &&
-			(quote_count % 2) == 0 &&
-			(backslash_count % 2) == 0) {
-			ptr[0] = '\0';
-			break;
-		}
-
-		if (ptr[0] == '\\')
-			backslash_count++;
-		else
-			backslash_count = 0;
-	}
-
-	/* skip any space at the end */
-	while (ptr > line && git__isspace(ptr[-1])) {
-		ptr--;
-	}
-	ptr[0] = '\0';
-
-	return quote_count;
-}
-
 static int included_path(git_buf *out, const char *dir, const char *path)
 {
 	/* From the user's home */
@@ -1285,9 +876,6 @@ static int included_path(git_buf *out, const char *dir, const char *path)
 	return git_path_join_unrooted(out, path, dir, NULL);
 }
 
-static const char *escapes = "ntb\"\\";
-static const char *escaped = "\n\t\b\"\\";
-
 /* Escape the values to write them to the file */
 static char *escape_value(const char *ptr)
 {
@@ -1305,9 +893,9 @@ static char *escape_value(const char *ptr)
 		return NULL;
 
 	while (*ptr != '\0') {
-		if ((esc = strchr(escaped, *ptr)) != NULL) {
+		if ((esc = strchr(git_config_escaped, *ptr)) != NULL) {
 			git_buf_putc(&buf, '\\');
-			git_buf_putc(&buf, escapes[esc - escaped]);
+			git_buf_putc(&buf, git_config_escapes[esc - git_config_escaped]);
 		} else {
 			git_buf_putc(&buf, *ptr);
 		}
@@ -1322,254 +910,6 @@ static char *escape_value(const char *ptr)
 	return git_buf_detach(&buf);
 }
 
-/* '\"' -> '"' etc */
-static int unescape_line(
-	char **out, bool *is_multi, const char *ptr, int quote_count)
-{
-	char *str, *fixed, *esc;
-	size_t ptr_len = strlen(ptr), alloc_len;
-
-	*is_multi = false;
-
-	if (GIT_ADD_SIZET_OVERFLOW(&alloc_len, ptr_len, 1) ||
-		(str = git__malloc(alloc_len)) == NULL) {
-		return -1;
-	}
-
-	fixed = str;
-
-	while (*ptr != '\0') {
-		if (*ptr == '"') {
-			quote_count++;
-		} else if (*ptr != '\\') {
-			*fixed++ = *ptr;
-		} else {
-			/* backslash, check the next char */
-			ptr++;
-			/* if we're at the end, it's a multiline, so keep the backslash */
-			if (*ptr == '\0') {
-				*is_multi = true;
-				goto done;
-			}
-			if ((esc = strchr(escapes, *ptr)) != NULL) {
-				*fixed++ = escaped[esc - escapes];
-			} else {
-				git__free(str);
-				giterr_set(GITERR_CONFIG, "invalid escape at %s", ptr);
-				return -1;
-			}
-		}
-		ptr++;
-	}
-
-done:
-	*fixed = '\0';
-	*out = str;
-
-	return 0;
-}
-
-static int parse_multiline_variable(struct reader *reader, git_buf *value, int in_quotes)
-{
-	char *line = NULL, *proc_line = NULL;
-	int quote_count;
-	bool multiline;
-
-	/* Check that the next line exists */
-	line = reader_readline(reader, false);
-	if (line == NULL)
-		return -1;
-
-	/* We've reached the end of the file, there is no continuation.
-	 * (this is not an error).
-	 */
-	if (line[0] == '\0') {
-		git__free(line);
-		return 0;
-	}
-
-	quote_count = strip_comments(line, !!in_quotes);
-
-	/* If it was just a comment, pretend it didn't exist */
-	if (line[0] == '\0') {
-		git__free(line);
-		return parse_multiline_variable(reader, value, quote_count);
-		/* TODO: unbounded recursion. This **could** be exploitable */
-	}
-
-	if (unescape_line(&proc_line, &multiline, line, in_quotes) < 0) {
-		git__free(line);
-		return -1;
-	}
-	/* add this line to the multiline var */
-
-	git_buf_puts(value, proc_line);
-	git__free(line);
-	git__free(proc_line);
-
-	/*
-	 * If we need to continue reading the next line, let's just
-	 * keep putting stuff in the buffer
-	 */
-	if (multiline)
-		return parse_multiline_variable(reader, value, quote_count);
-
-	return 0;
-}
-
-GIT_INLINE(bool) is_namechar(char c)
-{
-	return isalnum(c) || c == '-';
-}
-
-static int parse_name(
-	char **name, const char **value, struct reader *reader, const char *line)
-{
-	const char *name_end = line, *value_start;
-
-	*name = NULL;
-	*value = NULL;
-
-	while (*name_end && is_namechar(*name_end))
-		name_end++;
-
-	if (line == name_end) {
-		set_parse_error(reader, 0, "Invalid configuration key");
-		return -1;
-	}
-
-	value_start = name_end;
-
-	while (*value_start && git__isspace(*value_start))
-		value_start++;
-
-	if (*value_start == '=') {
-		*value = value_start + 1;
-	} else if (*value_start) {
-		set_parse_error(reader, 0, "Invalid configuration key");
-		return -1;
-	}
-
-	if ((*name = git__strndup(line, name_end - line)) == NULL)
-		return -1;
-
-	return 0;
-}
-
-static int parse_variable(struct reader *reader, char **var_name, char **var_value)
-{
-	const char *value_start = NULL;
-	char *line;
-	int quote_count;
-	bool multiline;
-
-	line = reader_readline(reader, true);
-	if (line == NULL)
-		return -1;
-
-	quote_count = strip_comments(line, 0);
-
-	/* If there is no value, boolean true is assumed */
-	*var_value = NULL;
-
-	if (parse_name(var_name, &value_start, reader, line) < 0)
-		goto on_error;
-
-	/*
-	 * Now, let's try to parse the value
-	 */
-	if (value_start != NULL) {
-		while (git__isspace(value_start[0]))
-			value_start++;
-
-		if (unescape_line(var_value, &multiline, value_start, 0) < 0)
-			goto on_error;
-
-		if (multiline) {
-			git_buf multi_value = GIT_BUF_INIT;
-			git_buf_attach(&multi_value, *var_value, 0);
-
-			if (parse_multiline_variable(reader, &multi_value, quote_count) < 0 ||
-				git_buf_oom(&multi_value)) {
-				git_buf_free(&multi_value);
-				goto on_error;
-			}
-
-			*var_value = git_buf_detach(&multi_value);
-		}
-	}
-
-	git__free(line);
-	return 0;
-
-on_error:
-	git__free(*var_name);
-	git__free(line);
-	return -1;
-}
-
-static int config_parse(
-	struct reader *reader,
-	int (*on_section)(struct reader *reader, const char *current_section, const char *line, size_t line_len, void *data),
-	int (*on_variable)(struct reader *reader, const char *current_section, char *var_name, char *var_value, const char *line, size_t line_len, void *data),
-	int (*on_comment)(struct reader *reader, const char *line, size_t line_len, void *data),
-	int (*on_eof)(struct reader *reader, const char *current_section, void *data),
-	void *data)
-{
-	char *current_section = NULL, *var_name, *var_value, *line_start;
-	char c;
-	size_t line_len;
-	int result = 0;
-
-	skip_bom(reader);
-
-	while (result == 0 && !reader->eof) {
-		line_start = reader->read_ptr;
-
-		c = reader_peek(reader, SKIP_WHITESPACE);
-
-		switch (c) {
-		case '\0': /* EOF when peeking, set EOF in the reader to exit the loop */
-			reader->eof = 1;
-			break;
-
-		case '[': /* section header, new section begins */
-			git__free(current_section);
-			current_section = NULL;
-
-			if ((result = parse_section_header(reader, &current_section)) == 0 && on_section) {
-				line_len = reader->read_ptr - line_start;
-				result = on_section(reader, current_section, line_start, line_len, data);
-			}
-			break;
-
-		case '\n': /* comment or whitespace-only */
-		case ';':
-		case '#':
-			reader_consume_line(reader);
-
-			if (on_comment) {
-				line_len = reader->read_ptr - line_start;
-				result = on_comment(reader, line_start, line_len, data);
-			}
-			break;
-
-		default: /* assume variable declaration */
-			if ((result = parse_variable(reader, &var_name, &var_value)) == 0 && on_variable) {
-				line_len = reader->read_ptr - line_start;
-				result = on_variable(reader, current_section, var_name, var_value, line_start, line_len, data);
-			}
-			break;
-		}
-	}
-
-	if (on_eof)
-		result = on_eof(reader, current_section, data);
-
-	git__free(current_section);
-	return result;
-}
-
 struct parse_data {
 	const git_repository *repo;
 	const char *file_path;
@@ -1578,7 +918,7 @@ struct parse_data {
 	int depth;
 };
 
-static int parse_include(struct reader *reader,
+static int parse_include(git_config_parser *reader,
 	struct parse_data *parse_data, const char *file)
 {
 	struct config_file *include;
@@ -1680,7 +1020,7 @@ static const struct {
 	{ "gitdir/i:", conditional_match_gitdir_i }
 };
 
-static int parse_conditional_include(struct reader *reader,
+static int parse_conditional_include(git_config_parser *reader,
 	struct parse_data *parse_data, const char *section, const char *file)
 {
 	char *condition;
@@ -1714,7 +1054,7 @@ static int parse_conditional_include(struct reader *reader,
 }
 
 static int read_on_variable(
-	struct reader *reader,
+	git_config_parser *reader,
 	const char *current_section,
 	char *var_name,
 	char *var_value,
@@ -1769,12 +1109,13 @@ static int read_on_variable(
 static int config_read(
 	git_strmap *values,
 	const git_repository *repo,
-	struct config_file *file,
+	git_config_file *file,
 	git_config_level_t level,
 	int depth)
 {
 	struct parse_data parse_data;
-	struct reader reader;
+	git_config_parser reader;
+	git_buf contents = GIT_BUF_INIT;
 	int error;
 
 	if (depth >= MAX_INCLUDE_DEPTH) {
@@ -1782,22 +1123,20 @@ static int config_read(
 		return -1;
 	}
 
-	git_buf_init(&reader.buffer, 0);
-
-	if ((error = git_futils_readbuffer(&reader.buffer, file->path)) < 0)
+	if ((error = git_futils_readbuffer(&contents, file->path)) < 0)
 		goto out;
 
-	if ((error = git_hash_buf(&file->checksum, reader.buffer.ptr, reader.buffer.size)) < 0)
+	git_parse_ctx_init(&reader.ctx, contents.ptr, contents.size);
+
+	if ((error = git_hash_buf(&file->checksum, contents.ptr, contents.size)) < 0)
 		goto out;
 
 	/* Initialize the reading position */
 	reader.file = file;
-	reader.line_number = 0;
-	reader.read_ptr = reader.buffer.ptr;
-	reader.eof = 0;
+	git_parse_ctx_init(&reader.ctx, contents.ptr, contents.size);
 
 	/* If the file is empty, there's nothing for us to do */
-	if (*reader.read_ptr == '\0')
+	if (!reader.ctx.content || *reader.ctx.content == '\0')
 		goto out;
 
 	parse_data.repo = repo;
@@ -1806,10 +1145,10 @@ static int config_read(
 	parse_data.level = level;
 	parse_data.depth = depth;
 
-	error = config_parse(&reader, NULL, read_on_variable, NULL, NULL, &parse_data);
+	error = git_config_parse(&reader, NULL, read_on_variable, NULL, NULL, &parse_data);
 
 out:
-	git_buf_free(&reader.buffer);
+	git_buf_free(&contents);
 	return error;
 }
 
@@ -1909,7 +1248,7 @@ static int write_value(struct write_data *write_data)
 }
 
 static int write_on_section(
-	struct reader *reader,
+	git_config_parser *reader,
 	const char *current_section,
 	const char *line,
 	size_t line_len,
@@ -1945,7 +1284,7 @@ static int write_on_section(
 }
 
 static int write_on_variable(
-	struct reader *reader,
+	git_config_parser *reader,
 	const char *current_section,
 	char *var_name,
 	char *var_value,
@@ -1995,7 +1334,7 @@ static int write_on_variable(
 	return write_value(write_data);
 }
 
-static int write_on_comment(struct reader *reader, const char *line, size_t line_len, void *data)
+static int write_on_comment(git_config_parser *reader, const char *line, size_t line_len, void *data)
 {
 	struct write_data *write_data;
 
@@ -2006,7 +1345,7 @@ static int write_on_comment(struct reader *reader, const char *line, size_t line
 }
 
 static int write_on_eof(
-	struct reader *reader, const char *current_section, void *data)
+	git_config_parser *reader, const char *current_section, void *data)
 {
 	struct write_data *write_data = (struct write_data *)data;
 	int result = 0;
@@ -2044,36 +1383,30 @@ static int config_write(diskfile_backend *cfg, const char *orig_key, const char
 	int result;
 	char *orig_section, *section, *orig_name, *name, *ldot;
 	git_filebuf file = GIT_FILEBUF_INIT;
-	git_buf buf = GIT_BUF_INIT;
-	struct reader reader;
+	git_buf buf = GIT_BUF_INIT, contents = GIT_BUF_INIT;
+	git_config_parser reader;
 	struct write_data write_data;
 
 	memset(&reader, 0, sizeof(reader));
-	git_buf_init(&reader.buffer, 0);
 	reader.file = &cfg->file;
 
 	if (cfg->locked) {
-		result = git_buf_puts(&reader.buffer, git_buf_cstr(&cfg->locked_content));
+		result = git_buf_puts(&contents, git_buf_cstr(&cfg->locked_content));
 	} else {
 		/* Lock the file */
 		if ((result = git_filebuf_open(
 			     &file, cfg->file.path, GIT_FILEBUF_HASH_CONTENTS, GIT_CONFIG_FILE_MODE)) < 0) {
-			git_buf_free(&reader.buffer);
+			git_buf_free(&contents);
 			return result;
 		}
 
 		/* We need to read in our own config file */
-		result = git_futils_readbuffer(&reader.buffer, cfg->file.path);
+		result = git_futils_readbuffer(&contents, cfg->file.path);
 	}
 
 	/* Initialise the reading position */
-	if (result == GIT_ENOTFOUND) {
-		reader.read_ptr = NULL;
-		reader.eof = 1;
-		git_buf_clear(&reader.buffer);
-	} else if (result == 0) {
-		reader.read_ptr = reader.buffer.ptr;
-		reader.eof = 0;
+	if (result == 0 || result == GIT_ENOTFOUND) {
+		git_parse_ctx_init(&reader.ctx, contents.ptr, contents.size);
 	} else {
 		git_filebuf_cleanup(&file);
 		return -1; /* OS error when reading the file */
@@ -2100,7 +1433,12 @@ static int config_write(diskfile_backend *cfg, const char *orig_key, const char
 	write_data.preg = preg;
 	write_data.value = value;
 
-	result = config_parse(&reader, write_on_section, write_on_variable, write_on_comment, write_on_eof, &write_data);
+	result = git_config_parse(&reader,
+		write_on_section,
+		write_on_variable,
+		write_on_comment,
+		write_on_eof,
+		&write_data);
 	git__free(section);
 	git__free(orig_section);
 	git_buf_free(&write_data.buffered_comment);
@@ -2122,6 +1460,7 @@ static int config_write(diskfile_backend *cfg, const char *orig_key, const char
 
 done:
 	git_buf_free(&buf);
-	git_buf_free(&reader.buffer);
+	git_buf_free(&contents);
+	git_parse_ctx_clear(&reader.ctx);
 	return result;
 }
diff --git a/src/config_parse.c b/src/config_parse.c
new file mode 100644
index 000000000..586bba8ed
--- /dev/null
+++ b/src/config_parse.c
@@ -0,0 +1,519 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "config_parse.h"
+
+#include "buf_text.h"
+
+#include <ctype.h>
+
+static void set_parse_error(git_config_parser *reader, int col, const char *error_str)
+{
+	giterr_set(GITERR_CONFIG, "failed to parse config file: %s (in %s:%"PRIuZ", column %d)",
+		error_str, reader->file->path, reader->ctx.line_num, col);
+}
+
+
+GIT_INLINE(int) config_keychar(int c)
+{
+	return isalnum(c) || c == '-';
+}
+
+static int strip_comments(char *line, int in_quotes)
+{
+	int quote_count = in_quotes, backslash_count = 0;
+	char *ptr;
+
+	for (ptr = line; *ptr; ++ptr) {
+		if (ptr[0] == '"' && ptr > line && ptr[-1] != '\\')
+			quote_count++;
+
+		if ((ptr[0] == ';' || ptr[0] == '#') &&
+			(quote_count % 2) == 0 &&
+			(backslash_count % 2) == 0) {
+			ptr[0] = '\0';
+			break;
+		}
+
+		if (ptr[0] == '\\')
+			backslash_count++;
+		else
+			backslash_count = 0;
+	}
+
+	/* skip any space at the end */
+	while (ptr > line && git__isspace(ptr[-1])) {
+		ptr--;
+	}
+	ptr[0] = '\0';
+
+	return quote_count;
+}
+
+
+static int parse_section_header_ext(git_config_parser *reader, const char *line, const char *base_name, char **section_name)
+{
+	int c, rpos;
+	char *first_quote, *last_quote;
+	git_buf buf = GIT_BUF_INIT;
+	size_t quoted_len, alloc_len, base_name_len = strlen(base_name);
+
+	/*
+	 * base_name is what came before the space. We should be at the
+	 * first quotation mark, except for now, line isn't being kept in
+	 * sync so we only really use it to calculate the length.
+	 */
+
+	first_quote = strchr(line, '"');
+	if (first_quote == NULL) {
+		set_parse_error(reader, 0, "Missing quotation marks in section header");
+		goto end_error;
+	}
+
+	last_quote = strrchr(line, '"');
+	quoted_len = last_quote - first_quote;
+
+	if (quoted_len == 0) {
+		set_parse_error(reader, 0, "Missing closing quotation mark in section header");
+		goto end_error;
+	}
+
+	GITERR_CHECK_ALLOC_ADD(&alloc_len, base_name_len, quoted_len);
+	GITERR_CHECK_ALLOC_ADD(&alloc_len, alloc_len, 2);
+
+	if (git_buf_grow(&buf, alloc_len) < 0 ||
+	    git_buf_printf(&buf, "%s.", base_name) < 0)
+		goto end_error;
+
+	rpos = 0;
+
+	line = first_quote;
+	c = line[++rpos];
+
+	/*
+	 * At the end of each iteration, whatever is stored in c will be
+	 * added to the string. In case of error, jump to out
+	 */
+	do {
+
+		switch (c) {
+		case 0:
+			set_parse_error(reader, 0, "Unexpected end-of-line in section header");
+			goto end_error;
+
+		case '"':
+			goto end_parse;
+
+		case '\\':
+			c = line[++rpos];
+
+			if (c == 0) {
+				set_parse_error(reader, rpos, "Unexpected end-of-line in section header");
+				goto end_error;
+			}
+
+		default:
+			break;
+		}
+
+		git_buf_putc(&buf, (char)c);
+		c = line[++rpos];
+	} while (line + rpos < last_quote);
+
+end_parse:
+	if (git_buf_oom(&buf))
+		goto end_error;
+
+	if (line[rpos] != '"' || line[rpos + 1] != ']') {
+		set_parse_error(reader, rpos, "Unexpected text after closing quotes");
+		git_buf_free(&buf);
+		return -1;
+	}
+
+	*section_name = git_buf_detach(&buf);
+	return 0;
+
+end_error:
+	git_buf_free(&buf);
+
+	return -1;
+}
+
+static int parse_section_header(git_config_parser *reader, char **section_out)
+{
+	char *name, *name_end;
+	int name_length, c, pos;
+	int result;
+	char *line;
+	size_t line_len;
+
+	git_parse_advance_ws(&reader->ctx);
+	line = git__strndup(reader->ctx.line, reader->ctx.line_len);
+	if (line == NULL)
+		return -1;
+
+	/* find the end of the variable's name */
+	name_end = strrchr(line, ']');
+	if (name_end == NULL) {
+		git__free(line);
+		set_parse_error(reader, 0, "Missing ']' in section header");
+		return -1;
+	}
+
+	GITERR_CHECK_ALLOC_ADD(&line_len, (size_t)(name_end - line), 1);
+	name = git__malloc(line_len);
+	GITERR_CHECK_ALLOC(name);
+
+	name_length = 0;
+	pos = 0;
+
+	/* Make sure we were given a section header */
+	c = line[pos++];
+	assert(c == '[');
+
+	c = line[pos++];
+
+	do {
+		if (git__isspace(c)){
+			name[name_length] = '\0';
+			result = parse_section_header_ext(reader, line, name, section_out);
+			git__free(line);
+			git__free(name);
+			return result;
+		}
+
+		if (!config_keychar(c) && c != '.') {
+			set_parse_error(reader, pos, "Unexpected character in header");
+			goto fail_parse;
+		}
+
+		name[name_length++] = (char)git__tolower(c);
+
+	} while ((c = line[pos++]) != ']');
+
+	if (line[pos - 1] != ']') {
+		set_parse_error(reader, pos, "Unexpected end of file");
+		goto fail_parse;
+	}
+
+	git__free(line);
+
+	name[name_length] = 0;
+	*section_out = name;
+
+	return 0;
+
+fail_parse:
+	git__free(line);
+	git__free(name);
+	return -1;
+}
+
+static int skip_bom(git_parse_ctx *parser)
+{
+	git_buf buf = GIT_BUF_INIT_CONST(parser->content, parser->content_len);
+	git_bom_t bom;
+	int bom_offset = git_buf_text_detect_bom(&bom, &buf, parser->content_len);
+
+	if (bom == GIT_BOM_UTF8)
+		git_parse_advance_chars(parser, bom_offset);
+
+	/* TODO: reference implementation is pretty stupid with BoM */
+
+	return 0;
+}
+
+/*
+	(* basic types *)
+	digit = "0".."9"
+	integer = digit { digit }
+	alphabet = "a".."z" + "A" .. "Z"
+
+	section_char = alphabet | "." | "-"
+	extension_char = (* any character except newline *)
+	any_char = (* any character *)
+	variable_char = "alphabet" | "-"
+
+
+	(* actual grammar *)
+	config = { section }
+
+	section = header { definition }
+
+	header = "[" section [subsection | subsection_ext] "]"
+
+	subsection = "." section
+	subsection_ext = "\"" extension "\""
+
+	section = section_char { section_char }
+	extension = extension_char { extension_char }
+
+	definition = variable_name ["=" variable_value] "\n"
+
+	variable_name = variable_char { variable_char }
+	variable_value = string | boolean | integer
+
+	string = quoted_string | plain_string
+	quoted_string = "\"" plain_string "\""
+	plain_string = { any_char }
+
+	boolean = boolean_true | boolean_false
+	boolean_true = "yes" | "1" | "true" | "on"
+	boolean_false = "no" | "0" | "false" | "off"
+*/
+
+/* '\"' -> '"' etc */
+static int unescape_line(
+	char **out, bool *is_multi, const char *ptr, int quote_count)
+{
+	char *str, *fixed, *esc;
+	size_t ptr_len = strlen(ptr), alloc_len;
+
+	*is_multi = false;
+
+	if (GIT_ADD_SIZET_OVERFLOW(&alloc_len, ptr_len, 1) ||
+		(str = git__malloc(alloc_len)) == NULL) {
+		return -1;
+	}
+
+	fixed = str;
+
+	while (*ptr != '\0') {
+		if (*ptr == '"') {
+			quote_count++;
+		} else if (*ptr != '\\') {
+			*fixed++ = *ptr;
+		} else {
+			/* backslash, check the next char */
+			ptr++;
+			/* if we're at the end, it's a multiline, so keep the backslash */
+			if (*ptr == '\0') {
+				*is_multi = true;
+				goto done;
+			}
+			if ((esc = strchr(git_config_escapes, *ptr)) != NULL) {
+				*fixed++ = git_config_escaped[esc - git_config_escapes];
+			} else {
+				git__free(str);
+				giterr_set(GITERR_CONFIG, "invalid escape at %s", ptr);
+				return -1;
+			}
+		}
+		ptr++;
+	}
+
+done:
+	*fixed = '\0';
+	*out = str;
+
+	return 0;
+}
+
+static int parse_multiline_variable(git_config_parser *reader, git_buf *value, int in_quotes)
+{
+	char *line = NULL, *proc_line = NULL;
+	int quote_count;
+	bool multiline;
+
+	/* Check that the next line exists */
+	git_parse_advance_line(&reader->ctx);
+	line = git__strndup(reader->ctx.line, reader->ctx.line_len);
+	if (line == NULL)
+		return -1;
+
+	/* We've reached the end of the file, there is no continuation.
+	 * (this is not an error).
+	 */
+	if (line[0] == '\0') {
+		git__free(line);
+		return 0;
+	}
+
+	quote_count = strip_comments(line, !!in_quotes);
+
+	/* If it was just a comment, pretend it didn't exist */
+	if (line[0] == '\0') {
+		git__free(line);
+		return parse_multiline_variable(reader, value, quote_count);
+		/* TODO: unbounded recursion. This **could** be exploitable */
+	}
+
+	if (unescape_line(&proc_line, &multiline, line, in_quotes) < 0) {
+		git__free(line);
+		return -1;
+	}
+	/* add this line to the multiline var */
+
+	git_buf_puts(value, proc_line);
+	git__free(line);
+	git__free(proc_line);
+
+	/*
+	 * If we need to continue reading the next line, let's just
+	 * keep putting stuff in the buffer
+	 */
+	if (multiline)
+		return parse_multiline_variable(reader, value, quote_count);
+
+	return 0;
+}
+
+GIT_INLINE(bool) is_namechar(char c)
+{
+	return isalnum(c) || c == '-';
+}
+
+static int parse_name(
+	char **name, const char **value, git_config_parser *reader, const char *line)
+{
+	const char *name_end = line, *value_start;
+
+	*name = NULL;
+	*value = NULL;
+
+	while (*name_end && is_namechar(*name_end))
+		name_end++;
+
+	if (line == name_end) {
+		set_parse_error(reader, 0, "Invalid configuration key");
+		return -1;
+	}
+
+	value_start = name_end;
+
+	while (*value_start && git__isspace(*value_start))
+		value_start++;
+
+	if (*value_start == '=') {
+		*value = value_start + 1;
+	} else if (*value_start) {
+		set_parse_error(reader, 0, "Invalid configuration key");
+		return -1;
+	}
+
+	if ((*name = git__strndup(line, name_end - line)) == NULL)
+		return -1;
+
+	return 0;
+}
+
+static int parse_variable(git_config_parser *reader, char **var_name, char **var_value)
+{
+	const char *value_start = NULL;
+	char *line;
+	int quote_count;
+	bool multiline;
+
+	git_parse_advance_ws(&reader->ctx);
+	line = git__strndup(reader->ctx.line, reader->ctx.line_len);
+	if (line == NULL)
+		return -1;
+
+	quote_count = strip_comments(line, 0);
+
+	/* If there is no value, boolean true is assumed */
+	*var_value = NULL;
+
+	if (parse_name(var_name, &value_start, reader, line) < 0)
+		goto on_error;
+
+	/*
+	 * Now, let's try to parse the value
+	 */
+	if (value_start != NULL) {
+		while (git__isspace(value_start[0]))
+			value_start++;
+
+		if (unescape_line(var_value, &multiline, value_start, 0) < 0)
+			goto on_error;
+
+		if (multiline) {
+			git_buf multi_value = GIT_BUF_INIT;
+			git_buf_attach(&multi_value, *var_value, 0);
+
+			if (parse_multiline_variable(reader, &multi_value, quote_count) < 0 ||
+				git_buf_oom(&multi_value)) {
+				git_buf_free(&multi_value);
+				goto on_error;
+			}
+
+			*var_value = git_buf_detach(&multi_value);
+		}
+	}
+
+	git__free(line);
+	return 0;
+
+on_error:
+	git__free(*var_name);
+	git__free(line);
+	return -1;
+}
+
+int git_config_parse(
+	git_config_parser *parser,
+	git_config_parser_section_cb on_section,
+	git_config_parser_variable_cb on_variable,
+	git_config_parser_comment_cb on_comment,
+	git_config_parser_eof_cb on_eof,
+	void *data)
+{
+	git_parse_ctx *ctx;
+	char *current_section = NULL, *var_name, *var_value;
+	int result = 0;
+
+	ctx = &parser->ctx;
+
+	skip_bom(ctx);
+
+	for (; ctx->remain_len > 0; git_parse_advance_line(ctx)) {
+		const char *line_start = parser->ctx.line;
+		size_t line_len = parser->ctx.line_len;
+		char c;
+
+		if (git_parse_peek(&c, ctx, GIT_PARSE_PEEK_SKIP_WHITESPACE) < 0 &&
+		    git_parse_peek(&c, ctx, 0) < 0)
+			continue;
+
+		switch (c) {
+		case '[': /* section header, new section begins */
+			git__free(current_section);
+			current_section = NULL;
+
+			if ((result = parse_section_header(parser, &current_section)) == 0 && on_section) {
+				result = on_section(parser, current_section, line_start, line_len, data);
+			}
+			break;
+
+		case '\n': /* comment or whitespace-only */
+		case ' ':
+		case '\t':
+		case ';':
+		case '#':
+			if (on_comment) {
+				result = on_comment(parser, line_start, line_len, data);
+			}
+			break;
+
+		default: /* assume variable declaration */
+			if ((result = parse_variable(parser, &var_name, &var_value)) == 0 && on_variable) {
+				result = on_variable(parser, current_section, var_name, var_value, line_start, line_len, data);
+			}
+			break;
+		}
+
+		if (result < 0)
+			goto out;
+	}
+
+	if (on_eof)
+		result = on_eof(parser, current_section, data);
+
+out:
+	git__free(current_section);
+	return result;
+}
diff --git a/src/config_parse.h b/src/config_parse.h
new file mode 100644
index 000000000..6c1863952
--- /dev/null
+++ b/src/config_parse.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "common.h"
+#include "array.h"
+#include "oid.h"
+#include "parse.h"
+
+static const char *git_config_escapes = "ntb\"\\";
+static const char *git_config_escaped = "\n\t\b\"\\";
+
+typedef struct config_file {
+	git_oid checksum;
+	char *path;
+	git_array_t(struct config_file) includes;
+} git_config_file;
+
+typedef struct {
+	struct config_file *file;
+	git_parse_ctx ctx;
+} git_config_parser;
+
+typedef int (*git_config_parser_section_cb)(
+	git_config_parser *parser,
+	const char *current_section,
+	const char *line,
+	size_t line_len,
+	void *data);
+
+typedef int (*git_config_parser_variable_cb)(
+	git_config_parser *parser,
+	const char *current_section,
+	char *var_name,
+	char *var_value,
+	const char *line,
+	size_t line_len,
+	void *data);
+
+typedef int (*git_config_parser_comment_cb)(
+	git_config_parser *parser,
+	const char *line,
+	size_t line_len,
+	void *data);
+
+typedef int (*git_config_parser_eof_cb)(
+	git_config_parser *parser,
+	const char *current_section,
+	void *data);
+
+int git_config_parse(
+	git_config_parser *parser,
+	git_config_parser_section_cb on_section,
+	git_config_parser_variable_cb on_variable,
+	git_config_parser_comment_cb on_comment,
+	git_config_parser_eof_cb on_eof,
+	void *data);
diff --git a/src/diff_parse.c b/src/diff_parse.c
index 78da3b675..2838314a2 100644
--- a/src/diff_parse.c
+++ b/src/diff_parse.c
@@ -83,7 +83,7 @@ int git_diff_from_buffer(
 	ctx = git_patch_parse_ctx_init(content, content_len, NULL);
 	GITERR_CHECK_ALLOC(ctx);
 
-	while (ctx->remain_len) {
+	while (ctx->parse_ctx.remain_len) {
 		if ((error = git_patch_parse(&patch, ctx)) < 0)
 			break;
 
diff --git a/src/parse.c b/src/parse.c
new file mode 100644
index 000000000..6b8902c35
--- /dev/null
+++ b/src/parse.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#include "parse.h"
+
+int git_parse_ctx_init(git_parse_ctx *ctx, const char *content, size_t content_len)
+{
+	if (content_len)
+		ctx->content = content;
+	else
+		ctx->content = NULL;
+
+	ctx->content_len = content_len;
+	ctx->remain = ctx->content;
+	ctx->remain_len = ctx->content_len;
+	ctx->line = ctx->remain;
+	ctx->line_len = git__linenlen(ctx->line, ctx->remain_len);
+	ctx->line_num = 1;
+
+	return 0;
+}
+
+void git_parse_ctx_clear(git_parse_ctx *ctx)
+{
+	memset(ctx, 0, sizeof(*ctx));
+}
+
+void git_parse_advance_line(git_parse_ctx *ctx)
+{
+	ctx->line += ctx->line_len;
+	ctx->remain_len -= ctx->line_len;
+	ctx->line_len = git__linenlen(ctx->line, ctx->remain_len);
+	ctx->line_num++;
+}
+
+void git_parse_advance_chars(git_parse_ctx *ctx, size_t char_cnt)
+{
+	ctx->line += char_cnt;
+	ctx->remain_len -= char_cnt;
+	ctx->line_len -= char_cnt;
+}
+
+int git_parse_advance_expected(
+	git_parse_ctx *ctx,
+	const char *expected,
+	size_t expected_len)
+{
+	if (ctx->line_len < expected_len)
+		return -1;
+
+	if (memcmp(ctx->line, expected, expected_len) != 0)
+		return -1;
+
+	git_parse_advance_chars(ctx, expected_len);
+	return 0;
+}
+
+int git_parse_advance_ws(git_parse_ctx *ctx)
+{
+	int ret = -1;
+
+	while (ctx->line_len > 0 &&
+		ctx->line[0] != '\n' &&
+		git__isspace(ctx->line[0])) {
+		ctx->line++;
+		ctx->line_len--;
+		ctx->remain_len--;
+		ret = 0;
+	}
+
+	return ret;
+}
+
+int git_parse_advance_nl(git_parse_ctx *ctx)
+{
+	if (ctx->line_len != 1 || ctx->line[0] != '\n')
+		return -1;
+
+	git_parse_advance_line(ctx);
+	return 0;
+}
+
+int git_parse_advance_digit(int64_t *out, git_parse_ctx *ctx, int base)
+{
+	const char *end;
+	int ret;
+
+	if (ctx->line_len < 1 || !git__isdigit(ctx->line[0]))
+		return -1;
+
+	if ((ret = git__strntol64(out, ctx->line, ctx->line_len, &end, base)) < 0)
+		return -1;
+
+	git_parse_advance_chars(ctx, (end - ctx->line));
+	return 0;
+}
+
+int git_parse_peek(char *out, git_parse_ctx *ctx, int flags)
+{
+	size_t remain = ctx->line_len;
+	const char *ptr = ctx->line;
+
+	while (remain) {
+		char c = *ptr;
+
+		if ((flags & GIT_PARSE_PEEK_SKIP_WHITESPACE) &&
+		    git__isspace(c)) {
+			remain--;
+			ptr++;
+			continue;
+		}
+
+		*out = c;
+		return 0;
+	}
+
+	return -1;
+}
diff --git a/src/parse.h b/src/parse.h
new file mode 100644
index 000000000..419014e93
--- /dev/null
+++ b/src/parse.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#include "common.h"
+
+typedef struct {
+	/* Original content buffer */
+	const char *content;
+	size_t content_len;
+
+	/* The remaining (unparsed) buffer */
+	const char *remain;
+	size_t remain_len;
+
+	const char *line;
+	size_t line_len;
+	size_t line_num;
+} git_parse_ctx;
+
+int git_parse_ctx_init(git_parse_ctx *ctx, const char *content, size_t content_len);
+void git_parse_ctx_clear(git_parse_ctx *ctx);
+
+#define git_parse_err(...) \
+	( giterr_set(GITERR_PATCH, __VA_ARGS__), -1 )
+
+#define git_parse_ctx_contains_s(ctx, str) \
+	git_parse_ctx_contains(ctx, str, sizeof(str) - 1)
+
+GIT_INLINE(bool) git_parse_ctx_contains(
+	git_parse_ctx *ctx, const char *str, size_t len)
+{
+	return (ctx->line_len >= len && memcmp(ctx->line, str, len) == 0);
+}
+
+void git_parse_advance_line(git_parse_ctx *ctx);
+void git_parse_advance_chars(git_parse_ctx *ctx, size_t char_cnt);
+int git_parse_advance_expected(
+	git_parse_ctx *ctx,
+	const char *expected,
+	size_t expected_len);
+
+#define git_parse_advance_expected_str(ctx, str) \
+	git_parse_advance_expected(ctx, str, strlen(str))
+
+int git_parse_advance_ws(git_parse_ctx *ctx);
+int git_parse_advance_nl(git_parse_ctx *ctx);
+int git_parse_advance_digit(int64_t *out, git_parse_ctx *ctx, int base);
+
+enum GIT_PARSE_PEEK_FLAGS {
+	GIT_PARSE_PEEK_SKIP_WHITESPACE = (1 << 0)
+};
+
+int git_parse_peek(char *out, git_parse_ctx *ctx, int flags);
diff --git a/src/patch_parse.c b/src/patch_parse.c
index fad892d8a..fee6afad6 100644
--- a/src/patch_parse.c
+++ b/src/patch_parse.c
@@ -12,9 +12,6 @@
 #include "diff_parse.h"
 #include "path.h"
 
-#define parse_err(...) \
-	( giterr_set(GITERR_PATCH, __VA_ARGS__), -1 )
-
 typedef struct {
 	git_patch base;
 
@@ -36,89 +33,21 @@ typedef struct {
 	char *old_prefix, *new_prefix;
 } git_patch_parsed;
 
-
-GIT_INLINE(bool) parse_ctx_contains(
-	git_patch_parse_ctx *ctx, const char *str, size_t len)
-{
-	return (ctx->line_len >= len && memcmp(ctx->line, str, len) == 0);
-}
-
-#define parse_ctx_contains_s(ctx, str) \
-	parse_ctx_contains(ctx, str, sizeof(str) - 1)
-
-static void parse_advance_line(git_patch_parse_ctx *ctx)
-{
-	ctx->line += ctx->line_len;
-	ctx->remain_len -= ctx->line_len;
-	ctx->line_len = git__linenlen(ctx->line, ctx->remain_len);
-	ctx->line_num++;
-}
-
-static void parse_advance_chars(git_patch_parse_ctx *ctx, size_t char_cnt)
-{
-	ctx->line += char_cnt;
-	ctx->remain_len -= char_cnt;
-	ctx->line_len -= char_cnt;
-}
-
-static int parse_advance_expected(
-	git_patch_parse_ctx *ctx,
-	const char *expected,
-	size_t expected_len)
-{
-	if (ctx->line_len < expected_len)
-		return -1;
-
-	if (memcmp(ctx->line, expected, expected_len) != 0)
-		return -1;
-
-	parse_advance_chars(ctx, expected_len);
-	return 0;
-}
-
-#define parse_advance_expected_str(ctx, str) \
-	parse_advance_expected(ctx, str, strlen(str))
-
-static int parse_advance_ws(git_patch_parse_ctx *ctx)
-{
-	int ret = -1;
-
-	while (ctx->line_len > 0 &&
-		ctx->line[0] != '\n' &&
-		git__isspace(ctx->line[0])) {
-		ctx->line++;
-		ctx->line_len--;
-		ctx->remain_len--;
-		ret = 0;
-	}
-
-	return ret;
-}
-
-static int parse_advance_nl(git_patch_parse_ctx *ctx)
-{
-	if (ctx->line_len != 1 || ctx->line[0] != '\n')
-		return -1;
-
-	parse_advance_line(ctx);
-	return 0;
-}
-
 static int header_path_len(git_patch_parse_ctx *ctx)
 {
 	bool inquote = 0;
-	bool quoted = (ctx->line_len > 0 && ctx->line[0] == '"');
+	bool quoted = git_parse_ctx_contains_s(&ctx->parse_ctx, "\"");
 	size_t len;
 
-	for (len = quoted; len < ctx->line_len; len++) {
-		if (!quoted && git__isspace(ctx->line[len]))
+	for (len = quoted; len < ctx->parse_ctx.line_len; len++) {
+		if (!quoted && git__isspace(ctx->parse_ctx.line[len]))
 			break;
-		else if (quoted && !inquote && ctx->line[len] == '"') {
+		else if (quoted && !inquote && ctx->parse_ctx.line[len] == '"') {
 			len++;
 			break;
 		}
 
-		inquote = (!inquote && ctx->line[len] == '\\');
+		inquote = (!inquote && ctx->parse_ctx.line[len] == '\\');
 	}
 
 	return len;
@@ -130,10 +59,10 @@ static int parse_header_path_buf(git_buf *path, git_patch_parse_ctx *ctx)
 
 	path_len = header_path_len(ctx);
 
-	if ((error = git_buf_put(path, ctx->line, path_len)) < 0)
+	if ((error = git_buf_put(path, ctx->parse_ctx.line, path_len)) < 0)
 		goto done;
 
-	parse_advance_chars(ctx, path_len);
+	git_parse_advance_chars(&ctx->parse_ctx, path_len);
 
 	git_buf_rtrim(path);
 
@@ -173,24 +102,17 @@ static int parse_header_git_newpath(
 
 static int parse_header_mode(uint16_t *mode, git_patch_parse_ctx *ctx)
 {
-	const char *end;
-	int32_t m;
-	int ret;
-
-	if (ctx->line_len < 1 || !git__isdigit(ctx->line[0]))
-		return parse_err("invalid file mode at line %"PRIuZ, ctx->line_num);
+	int64_t m;
 
-	if ((ret = git__strntol32(&m, ctx->line, ctx->line_len, &end, 8)) < 0)
-		return ret;
+	if ((git_parse_advance_digit(&m, &ctx->parse_ctx, 8)) < 0)
+		return git_parse_err("invalid file mode at line %"PRIuZ, ctx->parse_ctx.line_num);
 
 	if (m > UINT16_MAX)
 		return -1;
 
 	*mode = (uint16_t)m;
 
-	parse_advance_chars(ctx, (end - ctx->line));
-
-	return ret;
+	return 0;
 }
 
 static int parse_header_oid(
@@ -200,17 +122,17 @@ static int parse_header_oid(
 {
 	size_t len;
 
-	for (len = 0; len < ctx->line_len && len < GIT_OID_HEXSZ; len++) {
-		if (!git__isxdigit(ctx->line[len]))
+	for (len = 0; len < ctx->parse_ctx.line_len && len < GIT_OID_HEXSZ; len++) {
+		if (!git__isxdigit(ctx->parse_ctx.line[len]))
 			break;
 	}
 
 	if (len < GIT_OID_MINPREFIXLEN || len > GIT_OID_HEXSZ ||
-		git_oid_fromstrn(oid, ctx->line, len) < 0)
-		return parse_err("invalid hex formatted object id at line %"PRIuZ,
-			ctx->line_num);
+		git_oid_fromstrn(oid, ctx->parse_ctx.line, len) < 0)
+		return git_parse_err("invalid hex formatted object id at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
-	parse_advance_chars(ctx, len);
+	git_parse_advance_chars(&ctx->parse_ctx, len);
 
 	*oid_len = (uint16_t)len;
 
@@ -220,17 +142,19 @@ static int parse_header_oid(
 static int parse_header_git_index(
 	git_patch_parsed *patch, git_patch_parse_ctx *ctx)
 {
+	char c;
+
 	if (parse_header_oid(&patch->base.delta->old_file.id,
 			&patch->base.delta->old_file.id_abbrev, ctx) < 0 ||
-		parse_advance_expected_str(ctx, "..") < 0 ||
+		git_parse_advance_expected_str(&ctx->parse_ctx, "..") < 0 ||
 		parse_header_oid(&patch->base.delta->new_file.id,
 			&patch->base.delta->new_file.id_abbrev, ctx) < 0)
 		return -1;
 
-	if (ctx->line_len > 0 && ctx->line[0] == ' ') {
+	if (git_parse_peek(&c, &ctx->parse_ctx, 0) == 0 && c == ' ') {
 		uint16_t mode;
 
-		parse_advance_chars(ctx, 1);
+		git_parse_advance_chars(&ctx->parse_ctx, 1);
 
 		if (parse_header_mode(&mode, ctx) < 0)
 			return -1;
@@ -329,19 +253,15 @@ static int parse_header_copyto(
 
 static int parse_header_percent(uint16_t *out, git_patch_parse_ctx *ctx)
 {
-	int32_t val;
-	const char *end;
+	int64_t val;
 
-	if (ctx->line_len < 1 || !git__isdigit(ctx->line[0]) ||
-		git__strntol32(&val, ctx->line, ctx->line_len, &end, 10) < 0)
+	if (git_parse_advance_digit(&val, &ctx->parse_ctx, 10) < 0)
 		return -1;
 
-	parse_advance_chars(ctx, (end - ctx->line));
-
-	if (parse_advance_expected_str(ctx, "%") < 0)
+	if (git_parse_advance_expected_str(&ctx->parse_ctx, "%") < 0)
 		return -1;
 
-	if (val > 100)
+	if (val < 0 || val > 100)
 		return -1;
 
 	*out = val;
@@ -352,8 +272,8 @@ static int parse_header_similarity(
 	git_patch_parsed *patch, git_patch_parse_ctx *ctx)
 {
 	if (parse_header_percent(&patch->base.delta->similarity, ctx) < 0)
-		return parse_err("invalid similarity percentage at line %"PRIuZ,
-			ctx->line_num);
+		return git_parse_err("invalid similarity percentage at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
 	return 0;
 }
@@ -364,8 +284,8 @@ static int parse_header_dissimilarity(
 	uint16_t dissimilarity;
 
 	if (parse_header_percent(&dissimilarity, ctx) < 0)
-		return parse_err("invalid similarity percentage at line %"PRIuZ,
-			ctx->line_num);
+		return git_parse_err("invalid similarity percentage at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
 	patch->base.delta->similarity = 100 - dissimilarity;
 
@@ -375,13 +295,13 @@ static int parse_header_dissimilarity(
 static int parse_header_start(git_patch_parsed *patch, git_patch_parse_ctx *ctx)
 {
 	if (parse_header_path(&patch->header_old_path, ctx) < 0)
-		return parse_err("corrupt old path in git diff header at line %"PRIuZ,
-			ctx->line_num);
+		return git_parse_err("corrupt old path in git diff header at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
-	if (parse_advance_ws(ctx) < 0 ||
+	if (git_parse_advance_ws(&ctx->parse_ctx) < 0 ||
 		parse_header_path(&patch->header_new_path, ctx) < 0)
-		return parse_err("corrupt new path in git diff header at line %"PRIuZ,
-			ctx->line_num);
+		return git_parse_err("corrupt new path in git diff header at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
 	return 0;
 }
@@ -451,10 +371,10 @@ static int parse_header_git(
 	parse_header_state state = STATE_START;
 
 	/* Parse remaining header lines */
-	for (; ctx->remain_len > 0; parse_advance_line(ctx)) {
+	for (; ctx->parse_ctx.remain_len > 0; git_parse_advance_line(&ctx->parse_ctx)) {
 		bool found = false;
 
-		if (ctx->line_len == 0 || ctx->line[ctx->line_len - 1] != '\n')
+		if (ctx->parse_ctx.line_len == 0 || ctx->parse_ctx.line[ctx->parse_ctx.line_len - 1] != '\n')
 			break;
 
 		for (i = 0; i < ARRAY_SIZE(transitions); i++) {
@@ -462,7 +382,7 @@ static int parse_header_git(
 			size_t op_len = strlen(transition->str);
 
 			if (transition->expected_state != state ||
-			    memcmp(ctx->line, transition->str, min(op_len, ctx->line_len)) != 0)
+			    git__prefixcmp(ctx->parse_ctx.line, transition->str) != 0)
 				continue;
 
 			state = transition->next_state;
@@ -471,16 +391,16 @@ static int parse_header_git(
 			if (transition->fn == NULL)
 				goto done;
 
-			parse_advance_chars(ctx, op_len);
+			git_parse_advance_chars(&ctx->parse_ctx, op_len);
 
 			if ((error = transition->fn(patch, ctx)) < 0)
 				goto done;
 
-			parse_advance_ws(ctx);
+			git_parse_advance_ws(&ctx->parse_ctx);
 
-			if (parse_advance_expected_str(ctx, "\n") < 0 ||
-			    ctx->line_len > 0) {
-				error = parse_err("trailing data at line %"PRIuZ, ctx->line_num);
+			if (git_parse_advance_expected_str(&ctx->parse_ctx, "\n") < 0 ||
+			    ctx->parse_ctx.line_len > 0) {
+				error = git_parse_err("trailing data at line %"PRIuZ, ctx->parse_ctx.line_num);
 				goto done;
 			}
 
@@ -489,14 +409,14 @@ static int parse_header_git(
 		}
 
 		if (!found) {
-			error = parse_err("invalid patch header at line %"PRIuZ,
-				ctx->line_num);
+			error = git_parse_err("invalid patch header at line %"PRIuZ,
+				ctx->parse_ctx.line_num);
 			goto done;
 		}
 	}
 
 	if (state != STATE_END) {
-		error = parse_err("unexpected header line %"PRIuZ, ctx->line_num);
+		error = git_parse_err("unexpected header line %"PRIuZ, ctx->parse_ctx.line_num);
 		goto done;
 	}
 
@@ -509,17 +429,17 @@ static int parse_number(git_off_t *out, git_patch_parse_ctx *ctx)
 	const char *end;
 	int64_t num;
 
-	if (!git__isdigit(ctx->line[0]))
+	if (!git__isdigit(ctx->parse_ctx.line[0]))
 		return -1;
 
-	if (git__strntol64(&num, ctx->line, ctx->line_len, &end, 10) < 0)
+	if (git__strntol64(&num, ctx->parse_ctx.line, ctx->parse_ctx.line_len, &end, 10) < 0)
 		return -1;
 
 	if (num < 0)
 		return -1;
 
 	*out = num;
-	parse_advance_chars(ctx, (end - ctx->line));
+	git_parse_advance_chars(&ctx->parse_ctx, (end - ctx->parse_ctx.line));
 
 	return 0;
 }
@@ -528,7 +448,7 @@ static int parse_int(int *out, git_patch_parse_ctx *ctx)
 {
 	git_off_t num;
 
-	if (parse_number(&num, ctx) < 0 || !git__is_int(num))
+	if (git_parse_advance_digit(&num, &ctx->parse_ctx, 10) < 0 || !git__is_int(num))
 		return -1;
 
 	*out = (int)num;
@@ -539,43 +459,44 @@ static int parse_hunk_header(
 	git_patch_hunk *hunk,
 	git_patch_parse_ctx *ctx)
 {
-	const char *header_start = ctx->line;
+	const char *header_start = ctx->parse_ctx.line;
+	char c;
 
 	hunk->hunk.old_lines = 1;
 	hunk->hunk.new_lines = 1;
 
-	if (parse_advance_expected_str(ctx, "@@ -") < 0 ||
+	if (git_parse_advance_expected_str(&ctx->parse_ctx, "@@ -") < 0 ||
 		parse_int(&hunk->hunk.old_start, ctx) < 0)
 		goto fail;
 
-	if (ctx->line_len > 0 && ctx->line[0] == ',') {
-		if (parse_advance_expected_str(ctx, ",") < 0 ||
+	if (git_parse_peek(&c, &ctx->parse_ctx, 0) == 0 && c == ',') {
+		if (git_parse_advance_expected_str(&ctx->parse_ctx, ",") < 0 ||
 			parse_int(&hunk->hunk.old_lines, ctx) < 0)
 			goto fail;
 	}
 
-	if (parse_advance_expected_str(ctx, " +") < 0 ||
+	if (git_parse_advance_expected_str(&ctx->parse_ctx, " +") < 0 ||
 		parse_int(&hunk->hunk.new_start, ctx) < 0)
 		goto fail;
 
-	if (ctx->line_len > 0 && ctx->line[0] == ',') {
-		if (parse_advance_expected_str(ctx, ",") < 0 ||
+	if (git_parse_peek(&c, &ctx->parse_ctx, 0) == 0 && c == ',') {
+		if (git_parse_advance_expected_str(&ctx->parse_ctx, ",") < 0 ||
 			parse_int(&hunk->hunk.new_lines, ctx) < 0)
 			goto fail;
 	}
 
-	if (parse_advance_expected_str(ctx, " @@") < 0)
+	if (git_parse_advance_expected_str(&ctx->parse_ctx, " @@") < 0)
 		goto fail;
 
-	parse_advance_line(ctx);
+	git_parse_advance_line(&ctx->parse_ctx);
 
 	if (!hunk->hunk.old_lines && !hunk->hunk.new_lines)
 		goto fail;
 
-	hunk->hunk.header_len = ctx->line - header_start;
+	hunk->hunk.header_len = ctx->parse_ctx.line - header_start;
 	if (hunk->hunk.header_len > (GIT_DIFF_HUNK_HEADER_SIZE - 1))
-		return parse_err("oversized patch hunk header at line %"PRIuZ,
-			ctx->line_num);
+		return git_parse_err("oversized patch hunk header at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
 	memcpy(hunk->hunk.header, header_start, hunk->hunk.header_len);
 	hunk->hunk.header[hunk->hunk.header_len] = '\0';
@@ -584,7 +505,7 @@ static int parse_hunk_header(
 
 fail:
 	giterr_set(GITERR_PATCH, "invalid patch hunk header at line %"PRIuZ,
-		ctx->line_num);
+		ctx->parse_ctx.line_num);
 	return -1;
 }
 
@@ -600,21 +521,24 @@ static int parse_hunk_body(
 	int newlines = hunk->hunk.new_lines;
 
 	for (;
-		ctx->remain_len > 1 &&
+		ctx->parse_ctx.remain_len > 1 &&
 		(oldlines || newlines) &&
-		(ctx->remain_len <= 4 || memcmp(ctx->line, "@@ -", 4) != 0);
-		parse_advance_line(ctx)) {
+		!git_parse_ctx_contains_s(&ctx->parse_ctx, "@@ -");
+		git_parse_advance_line(&ctx->parse_ctx)) {
 
+		char c;
 		int origin;
 		int prefix = 1;
 
-		if (ctx->line_len == 0 || ctx->line[ctx->line_len - 1] != '\n') {
-			error = parse_err("invalid patch instruction at line %"PRIuZ,
-				ctx->line_num);
+		if (ctx->parse_ctx.line_len == 0 || ctx->parse_ctx.line[ctx->parse_ctx.line_len - 1] != '\n') {
+			error = git_parse_err("invalid patch instruction at line %"PRIuZ,
+				ctx->parse_ctx.line_num);
 			goto done;
 		}
 
-		switch (ctx->line[0]) {
+		git_parse_peek(&c, &ctx->parse_ctx, 0);
+
+		switch (c) {
 		case '\n':
 			prefix = 0;
 
@@ -635,7 +559,7 @@ static int parse_hunk_body(
 			break;
 
 		default:
-			error = parse_err("invalid patch hunk at line %"PRIuZ, ctx->line_num);
+			error = git_parse_err("invalid patch hunk at line %"PRIuZ, ctx->parse_ctx.line_num);
 			goto done;
 		}
 
@@ -644,16 +568,16 @@ static int parse_hunk_body(
 
 		memset(line, 0x0, sizeof(git_diff_line));
 
-		line->content = ctx->line + prefix;
-		line->content_len = ctx->line_len - prefix;
-		line->content_offset = ctx->content_len - ctx->remain_len;
+		line->content = ctx->parse_ctx.line + prefix;
+		line->content_len = ctx->parse_ctx.line_len - prefix;
+		line->content_offset = ctx->parse_ctx.content_len - ctx->parse_ctx.remain_len;
 		line->origin = origin;
 
 		hunk->line_count++;
 	}
 
 	if (oldlines || newlines) {
-		error = parse_err(
+		error = git_parse_err(
 			"invalid patch hunk, expected %d old lines and %d new lines",
 			hunk->hunk.old_lines, hunk->hunk.new_lines);
 		goto done;
@@ -664,19 +588,19 @@ static int parse_hunk_body(
 	 * localized.  Because `diff` optimizes for the case where you
 	 * want to apply the patch by hand.
 	 */
-	if (parse_ctx_contains_s(ctx, "\\ ") &&
+	if (git_parse_ctx_contains_s(&ctx->parse_ctx, "\\ ") &&
 		git_array_size(patch->base.lines) > 0) {
 
 		line = git_array_get(patch->base.lines, git_array_size(patch->base.lines) - 1);
 
 		if (line->content_len < 1) {
-			error = parse_err("cannot trim trailing newline of empty line");
+			error = git_parse_err("cannot trim trailing newline of empty line");
 			goto done;
 		}
 
 		line->content_len--;
 
-		parse_advance_line(ctx);
+		git_parse_advance_line(&ctx->parse_ctx);
 	}
 
 done:
@@ -689,18 +613,15 @@ static int parse_patch_header(
 {
 	int error = 0;
 
-	for (ctx->line = ctx->remain;
-		ctx->remain_len > 0;
-		parse_advance_line(ctx)) {
-
+	for (; ctx->parse_ctx.remain_len > 0; git_parse_advance_line(&ctx->parse_ctx)) {
 		/* This line is too short to be a patch header. */
-		if (ctx->line_len < 6)
+		if (ctx->parse_ctx.line_len < 6)
 			continue;
 
 		/* This might be a hunk header without a patch header, provide a
 		 * sensible error message. */
-		if (parse_ctx_contains_s(ctx, "@@ -")) {
-			size_t line_num = ctx->line_num;
+		if (git_parse_ctx_contains_s(&ctx->parse_ctx, "@@ -")) {
+			size_t line_num = ctx->parse_ctx.line_num;
 			git_patch_hunk hunk;
 
 			/* If this cannot be parsed as a hunk header, it's just leading
@@ -711,17 +632,17 @@ static int parse_patch_header(
 				continue;
 			}
 
-			error = parse_err("invalid hunk header outside patch at line %"PRIuZ,
+			error = git_parse_err("invalid hunk header outside patch at line %"PRIuZ,
 				line_num);
 			goto done;
 		}
 
 		/* This buffer is too short to contain a patch. */
-		if (ctx->remain_len < ctx->line_len + 6)
+		if (ctx->parse_ctx.remain_len < ctx->parse_ctx.line_len + 6)
 			break;
 
 		/* A proper git patch */
-		if (parse_ctx_contains_s(ctx, "diff --git ")) {
+		if (git_parse_ctx_contains_s(&ctx->parse_ctx, "diff --git ")) {
 			error = parse_header_git(patch, ctx);
 			goto done;
 		}
@@ -746,27 +667,30 @@ static int parse_patch_binary_side(
 	git_off_t len;
 	int error = 0;
 
-	if (parse_ctx_contains_s(ctx, "literal ")) {
+	if (git_parse_ctx_contains_s(&ctx->parse_ctx, "literal ")) {
 		type = GIT_DIFF_BINARY_LITERAL;
-		parse_advance_chars(ctx, 8);
-	} else if (parse_ctx_contains_s(ctx, "delta ")) {
+		git_parse_advance_chars(&ctx->parse_ctx, 8);
+	} else if (git_parse_ctx_contains_s(&ctx->parse_ctx, "delta ")) {
 		type = GIT_DIFF_BINARY_DELTA;
-		parse_advance_chars(ctx, 6);
+		git_parse_advance_chars(&ctx->parse_ctx, 6);
 	} else {
-		error = parse_err(
-			"unknown binary delta type at line %"PRIuZ, ctx->line_num);
+		error = git_parse_err(
+			"unknown binary delta type at line %"PRIuZ, ctx->parse_ctx.line_num);
 		goto done;
 	}
 
-	if (parse_number(&len, ctx) < 0 || parse_advance_nl(ctx) < 0 || len < 0) {
-		error = parse_err("invalid binary size at line %"PRIuZ, ctx->line_num);
+	if (git_parse_advance_digit(&len, &ctx->parse_ctx, 10) < 0 ||
+	    git_parse_advance_nl(&ctx->parse_ctx) < 0 || len < 0) {
+		error = git_parse_err("invalid binary size at line %"PRIuZ, ctx->parse_ctx.line_num);
 		goto done;
 	}
 
-	while (ctx->line_len) {
-		char c = ctx->line[0];
+	while (ctx->parse_ctx.line_len) {
+		char c;
 		size_t encoded_len, decoded_len = 0, decoded_orig = decoded.size;
 
+		git_parse_peek(&c, &ctx->parse_ctx, 0);
+
 		if (c == '\n')
 			break;
 		else if (c >= 'A' && c <= 'Z')
@@ -775,32 +699,32 @@ static int parse_patch_binary_side(
 			decoded_len = c - 'a' + (('z' - 'a') + 1) + 1;
 
 		if (!decoded_len) {
-			error = parse_err("invalid binary length at line %"PRIuZ, ctx->line_num);
+			error = git_parse_err("invalid binary length at line %"PRIuZ, ctx->parse_ctx.line_num);
 			goto done;
 		}
 
-		parse_advance_chars(ctx, 1);
+		git_parse_advance_chars(&ctx->parse_ctx, 1);
 
 		encoded_len = ((decoded_len / 4) + !!(decoded_len % 4)) * 5;
 
-		if (encoded_len > ctx->line_len - 1) {
-			error = parse_err("truncated binary data at line %"PRIuZ, ctx->line_num);
+		if (encoded_len > ctx->parse_ctx.line_len - 1) {
+			error = git_parse_err("truncated binary data at line %"PRIuZ, ctx->parse_ctx.line_num);
 			goto done;
 		}
 
 		if ((error = git_buf_decode_base85(
-			&decoded, ctx->line, encoded_len, decoded_len)) < 0)
+			&decoded, ctx->parse_ctx.line, encoded_len, decoded_len)) < 0)
 			goto done;
 
 		if (decoded.size - decoded_orig != decoded_len) {
-			error = parse_err("truncated binary data at line %"PRIuZ, ctx->line_num);
+			error = git_parse_err("truncated binary data at line %"PRIuZ, ctx->parse_ctx.line_num);
 			goto done;
 		}
 
-		parse_advance_chars(ctx, encoded_len);
+		git_parse_advance_chars(&ctx->parse_ctx, encoded_len);
 
-		if (parse_advance_nl(ctx) < 0) {
-			error = parse_err("trailing data at line %"PRIuZ, ctx->line_num);
+		if (git_parse_advance_nl(&ctx->parse_ctx) < 0) {
+			error = git_parse_err("trailing data at line %"PRIuZ, ctx->parse_ctx.line_num);
 			goto done;
 		}
 	}
@@ -822,27 +746,27 @@ static int parse_patch_binary(
 {
 	int error;
 
-	if (parse_advance_expected_str(ctx, "GIT binary patch") < 0 ||
-		parse_advance_nl(ctx) < 0)
-		return parse_err("corrupt git binary header at line %"PRIuZ, ctx->line_num);
+	if (git_parse_advance_expected_str(&ctx->parse_ctx, "GIT binary patch") < 0 ||
+		git_parse_advance_nl(&ctx->parse_ctx) < 0)
+		return git_parse_err("corrupt git binary header at line %"PRIuZ, ctx->parse_ctx.line_num);
 
 	/* parse old->new binary diff */
 	if ((error = parse_patch_binary_side(
 			&patch->base.binary.new_file, ctx)) < 0)
 		return error;
 
-	if (parse_advance_nl(ctx) < 0)
-		return parse_err("corrupt git binary separator at line %"PRIuZ,
-			ctx->line_num);
+	if (git_parse_advance_nl(&ctx->parse_ctx) < 0)
+		return git_parse_err("corrupt git binary separator at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
 	/* parse new->old binary diff */
 	if ((error = parse_patch_binary_side(
 			&patch->base.binary.old_file, ctx)) < 0)
 		return error;
 
-	if (parse_advance_nl(ctx) < 0)
-		return parse_err("corrupt git binary patch separator at line %"PRIuZ,
-			ctx->line_num);
+	if (git_parse_advance_nl(&ctx->parse_ctx) < 0)
+		return git_parse_err("corrupt git binary patch separator at line %"PRIuZ,
+			ctx->parse_ctx.line_num);
 
 	patch->base.binary.contains_data = 1;
 	patch->base.delta->flags |= GIT_DIFF_FLAG_BINARY;
@@ -853,13 +777,13 @@ static int parse_patch_binary_nodata(
 	git_patch_parsed *patch,
 	git_patch_parse_ctx *ctx)
 {
-	if (parse_advance_expected_str(ctx, "Binary files ") < 0 ||
-		parse_advance_expected_str(ctx, patch->header_old_path) < 0 ||
-		parse_advance_expected_str(ctx, " and ") < 0 ||
-		parse_advance_expected_str(ctx, patch->header_new_path) < 0 ||
-		parse_advance_expected_str(ctx, " differ") < 0 ||
-		parse_advance_nl(ctx) < 0)
-		return parse_err("corrupt git binary header at line %"PRIuZ, ctx->line_num);
+	if (git_parse_advance_expected_str(&ctx->parse_ctx, "Binary files ") < 0 ||
+		git_parse_advance_expected_str(&ctx->parse_ctx, patch->header_old_path) < 0 ||
+		git_parse_advance_expected_str(&ctx->parse_ctx, " and ") < 0 ||
+		git_parse_advance_expected_str(&ctx->parse_ctx, patch->header_new_path) < 0 ||
+		git_parse_advance_expected_str(&ctx->parse_ctx, " differ") < 0 ||
+		git_parse_advance_nl(&ctx->parse_ctx) < 0)
+		return git_parse_err("corrupt git binary header at line %"PRIuZ, ctx->parse_ctx.line_num);
 
 	patch->base.binary.contains_data = 0;
 	patch->base.delta->flags |= GIT_DIFF_FLAG_BINARY;
@@ -873,7 +797,7 @@ static int parse_patch_hunks(
 	git_patch_hunk *hunk;
 	int error = 0;
 
-	while (parse_ctx_contains_s(ctx, "@@ -")) {
+	while (git_parse_ctx_contains_s(&ctx->parse_ctx, "@@ -")) {
 		hunk = git_array_alloc(patch->base.hunks);
 		GITERR_CHECK_ALLOC(hunk);
 
@@ -896,9 +820,9 @@ done:
 static int parse_patch_body(
 	git_patch_parsed *patch, git_patch_parse_ctx *ctx)
 {
-	if (parse_ctx_contains_s(ctx, "GIT binary patch"))
+	if (git_parse_ctx_contains_s(&ctx->parse_ctx, "GIT binary patch"))
 		return parse_patch_binary(patch, ctx);
-	else if (parse_ctx_contains_s(ctx, "Binary files "))
+	else if (git_parse_ctx_contains_s(&ctx->parse_ctx, "Binary files "))
 		return parse_patch_binary_nodata(patch, ctx);
 	else
 		return parse_patch_hunks(patch, ctx);
@@ -914,10 +838,10 @@ int check_header_names(
 		return 0;
 
 	if (two_null && strcmp(two, "/dev/null") != 0)
-		return parse_err("expected %s path of '/dev/null'", old_or_new);
+		return git_parse_err("expected %s path of '/dev/null'", old_or_new);
 
 	else if (!two_null && strcmp(one, two) != 0)
-		return parse_err("mismatched %s path names", old_or_new);
+		return git_parse_err("mismatched %s path names", old_or_new);
 
 	return 0;
 }
@@ -950,7 +874,7 @@ static int check_prefix(
 	}
 
 	if (remain_len || !*path)
-		return parse_err(
+		return git_parse_err(
 			"header filename does not contain %"PRIuZ" path components",
 			prefix_len);
 
@@ -969,10 +893,10 @@ static int check_filenames(git_patch_parsed *patch)
 	bool deleted = (patch->base.delta->status == GIT_DELTA_DELETED);
 
 	if (patch->old_path && !patch->new_path)
-		return parse_err("missing new path");
+		return git_parse_err("missing new path");
 
 	if (!patch->old_path && patch->new_path)
-		return parse_err("missing old path");
+		return git_parse_err("missing old path");
 
 	/* Ensure (non-renamed) paths match */
 	if (check_header_names(
@@ -1005,7 +929,7 @@ static int check_filenames(git_patch_parsed *patch)
 
 	if (!patch->base.delta->old_file.path &&
 		!patch->base.delta->new_file.path)
-		return parse_err("git diff header lacks old / new paths");
+		return git_parse_err("git diff header lacks old / new paths");
 
 	return 0;
 }
@@ -1026,7 +950,7 @@ static int check_patch(git_patch_parsed *patch)
 			!(delta->flags & GIT_DIFF_FLAG_BINARY) &&
 			delta->new_file.mode == delta->old_file.mode &&
 			git_array_size(patch->base.hunks) == 0)
-		return parse_err("patch with no hunks");
+		return git_parse_err("patch with no hunks");
 
 	if (delta->status == GIT_DELTA_ADDED) {
 		memset(&delta->old_file.id, 0x0, sizeof(git_oid));
@@ -1052,19 +976,11 @@ git_patch_parse_ctx *git_patch_parse_ctx_init(
 	if ((ctx = git__calloc(1, sizeof(git_patch_parse_ctx))) == NULL)
 		return NULL;
 
-	if (content_len) {
-		if ((ctx->content = git__malloc(content_len)) == NULL) {
-			git__free(ctx);
-			return NULL;
-		}
-
-		memcpy((char *)ctx->content, content, content_len);
+	if ((git_parse_ctx_init(&ctx->parse_ctx, content, content_len)) < 0) {
+		git__free(ctx);
+		return NULL;
 	}
 
-	ctx->content_len = content_len;
-	ctx->remain = ctx->content;
-	ctx->remain_len = ctx->content_len;
-
 	if (opts)
 		memcpy(&ctx->opts, opts, sizeof(git_patch_options));
 	else
@@ -1079,7 +995,7 @@ static void patch_parse_ctx_free(git_patch_parse_ctx *ctx)
 	if (!ctx)
 		return;
 
-	git__free((char *)ctx->content);
+	git_parse_ctx_clear(&ctx->parse_ctx);
 	git__free(ctx);
 }
 
@@ -1154,15 +1070,15 @@ int git_patch_parse(
 	patch->base.delta->status = GIT_DELTA_MODIFIED;
 	patch->base.delta->nfiles = 2;
 
-	start = ctx->remain_len;
+	start = ctx->parse_ctx.remain_len;
 
 	if ((error = parse_patch_header(patch, ctx)) < 0 ||
 		(error = parse_patch_body(patch, ctx)) < 0 ||
 		(error = check_patch(patch)) < 0)
 		goto done;
 
-	used = start - ctx->remain_len;
-	ctx->remain += used;
+	used = start - ctx->parse_ctx.remain_len;
+	ctx->parse_ctx.remain += used;
 
 	patch->base.diff_opts.old_prefix = patch->old_prefix;
 	patch->base.diff_opts.new_prefix = patch->new_prefix;
diff --git a/src/patch_parse.h b/src/patch_parse.h
index f27651e39..140629da8 100644
--- a/src/patch_parse.h
+++ b/src/patch_parse.h
@@ -9,24 +9,15 @@
 
 #include "common.h"
 
+#include "parse.h"
 #include "patch.h"
 
 typedef struct {
 	git_refcount rc;
 
-	/* Original content buffer */
-	const char *content;
-	size_t content_len;
-
 	git_patch_options opts;
 
-	/* The remaining (unparsed) buffer */
-	const char *remain;
-	size_t remain_len;
-
-	const char *line;
-	size_t line_len;
-	size_t line_num;
+	git_parse_ctx parse_ctx;
 } git_patch_parse_ctx;
 
 extern git_patch_parse_ctx *git_patch_parse_ctx_init(