filter: Beautiful refactoring

Comments soothe my soul.

4 files changed, 235 insertions, 115 deletions

diff --git a/src/blob.c b/src/blob.c
index 245326157..e1f4a7f6a 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -115,19 +115,18 @@ static int write_file_filtered(
 	if (error < GIT_SUCCESS)
 		return error;
 
-	error = git_filter__apply(&dest, &source, filters);
+	error = git_filters_apply(&dest, &source, filters);
 
-	if (error < GIT_SUCCESS) {
-		git_buf_free(&source);
-		git_buf_free(&dest);
-		return error;
-	}
+	/* Free the source as soon as possible. This can be big in memory,
+	 * and we don't want to ODB write to choke */
+	git_buf_free(&source);
 
-	error = git_odb_write(oid, odb, dest.ptr, dest.size, GIT_OBJ_BLOB);
+	if (error == GIT_SUCCESS) {
+		/* Write the file to disk if it was properly filtered */
+		error = git_odb_write(oid, odb, dest.ptr, dest.size, GIT_OBJ_BLOB);
+	}
 
-	git_buf_free(&source);
 	git_buf_free(&dest);
-
 	return GIT_SUCCESS;
 }
 
@@ -186,18 +185,25 @@ int git_blob_create_fromfile(git_oid *oid, git_repository *repo, const char *pat
 		error = write_symlink(oid, odb, full_path.ptr, (size_t)size);
 	} else {
 		git_vector write_filters = GIT_VECTOR_INIT;
+		int filter_count;
 
-		if ((error = git_filter__load_for_file(
-			&write_filters, repo, path, GIT_FILTER_TO_ODB)) < GIT_SUCCESS)
-			goto cleanup;
+		/* Load the filters for writing this file to the ODB */
+		filter_count = git_filters_load(&write_filters, repo, path, GIT_FILTER_TO_ODB);
 
-		if (write_filters.length == 0) {
+		if (filter_count < 0) {
+			/* Negative value means there was a critical error */
+			error = filter_count;
+			goto cleanup;
+		} else if (filter_count == 0) {
+			/* No filters need to be applied to the document: we can stream
+			 * directly from disk */
 			error = write_file_stream(oid, odb, full_path.ptr, size);
 		} else {
+			/* We need to apply one or more filters */
 			error = write_file_filtered(oid, odb, full_path.ptr, &write_filters);
 		}
 
-		git_filter__free(&write_filters);
+		git_filters_free(&write_filters);
 
 		/*
 		 * TODO: eventually support streaming filtered files, for files which are bigger
diff --git a/src/crlf.c b/src/crlf.c
index d8dd1c382..feaa687ee 100644
--- a/src/crlf.c
+++ b/src/crlf.c
@@ -102,18 +102,74 @@ static int crlf_load_attributes(struct crlf_attrs *ca, git_repository *repo, con
 	return error;
 }
 
-static int crlf_apply_to_odb(git_filter *self, git_buf *dest, const git_buf *source)
+static int drop_crlf(git_buf *dest, const git_buf *source)
 {
+	size_t psize = source->size - 1;
 	size_t i = 0;
+
+	/* Initial scan: see if we can reach the end of the document
+	 * without finding a single carriage return */
+	while (i < psize && source->ptr[i] != '\r')
+		i++;
+
+	/* Clean file? Tell the library to skip this filter */
+	if (i == psize)
+		return -1;
+
+	/* Main scan loop. Keep moving forward until we find a carriage
+	 * return, and then copy the whole chunk to the destination
+	 * buffer.
+	 *
+	 * Note that we only scan until `size - 1`, because we cannot drop a
+	 * carriage return if it's the last character in the file (what a weird
+	 * file, anyway)
+	 */
+	while (i < psize) {
+		size_t org = i;
+
+		while (i < psize && source->ptr[i] != '\r')
+			i++;
+
+		if (i > org)
+			git_buf_put(dest, source->ptr + org, i - org);
+
+		/* We found a carriage return. Is the next character a newline?
+		 * If it is, we just keep moving. The newline will be copied
+		 * to the dest in the next chunk.
+		 *
+		 * If it's not a newline, we need to insert the carriage return
+		 * into the dest buffer, because we don't drop lone CRs.
+		 */
+		if (source->ptr[i + 1] != '\n') {
+			git_buf_putc(dest, '\r');
+		}
+		
+		i++;
+	}
+
+	/* Copy the last character in the file */
+	git_buf_putc(dest, source->ptr[psize]);
+	return 0;
+}
+
+static int crlf_apply_to_odb(git_filter *self, git_buf *dest, const git_buf *source)
+{
 	struct crlf_filter *filter = (struct crlf_filter *)self;
 
 	assert(self && dest && source);
 
+	/* Empty file? Nothing to do */
+	if (source->size == 0)
+		return 0;
+
+	/* Heuristics to see if we can skip the conversion.
+	 * Straight from Core Git.
+	 */
 	if (filter->attrs.crlf_action == GIT_CRLF_AUTO ||
 		filter->attrs.crlf_action == GIT_CRLF_GUESS) {
 
 		git_text_stats stats;
-		git_text__stat(&stats, source);
+		git_text_gather_stats(&stats, source);
 
 		/*
 		 * We're currently not going to even try to convert stuff
@@ -126,7 +182,7 @@ static int crlf_apply_to_odb(git_filter *self, git_buf *dest, const git_buf *sou
 		/*
 		 * And add some heuristics for binary vs text, of course...
 		 */
-		if (git_text__is_binary(&stats))
+		if (git_text_is_binary(&stats))
 			return -1;
 
 #if 0
@@ -144,50 +200,42 @@ static int crlf_apply_to_odb(git_filter *self, git_buf *dest, const git_buf *sou
 			return -1;
 	}
 
-	/* TODO: do not copy anything if there isn't a single CR */
-	while (i < source->size) {
-		size_t org = i;
-
-		while (i < source->size && source->ptr[i] != '\r')
-			i++;
-
-		if (i > org)
-			git_buf_put(dest, source->ptr + org, i - org);
-
-		i++;
-
-		if (i >= source->size || source->ptr[i] != '\n') {
-			git_buf_putc(dest, '\r');
-		}
-	}
-
-	return 0;
+	/* Actually drop the carriage returns */
+	return drop_crlf(dest, source);
 }
 
-int git_filter__crlf_to_odb(git_filter **filter_out, git_repository *repo, const char *path)
+int git_filter_add__crlf_to_odb(git_vector *filters, git_repository *repo, const char *path)
 {
-	struct crlf_filter filter;
+	struct crlf_attrs ca;
+	struct crlf_filter *filter;
 	int error;
 
-	filter.f.apply = &crlf_apply_to_odb;
-	filter.f.do_free = NULL;
-
-	if ((error = crlf_load_attributes(&filter.attrs, repo, path)) < 0)
+	/* Load gitattributes for the path */
+	if ((error = crlf_load_attributes(&ca, repo, path)) < 0)
 		return error;
 
-	filter.attrs.crlf_action = crlf_input_action(&filter.attrs);
+	/*
+	 * Use the core Git logic to see if we should perform CRLF for this file
+	 * based on its attributes & the value of `core.auto_crlf`
+	 */
+	ca.crlf_action = crlf_input_action(&ca);
 
-	if (filter.attrs.crlf_action == GIT_CRLF_BINARY)
+	if (ca.crlf_action == GIT_CRLF_BINARY)
 		return 0;
 
-	if (filter.attrs.crlf_action == GIT_CRLF_GUESS && repo->filter_options.auto_crlf == GIT_AUTO_CRLF_FALSE)
+	if (ca.crlf_action == GIT_CRLF_GUESS && repo->filter_options.auto_crlf == GIT_AUTO_CRLF_FALSE)
 		return 0;
 
-	*filter_out = git__malloc(sizeof(struct crlf_filter));
-	if (*filter_out == NULL)
+	/* If we're good, we create a new filter object and push it
+	 * into the filters array */
+	filter = git__malloc(sizeof(struct crlf_filter));
+	if (filter == NULL)
 		return GIT_ENOMEM;
 
-	memcpy(*filter_out, &filter, sizeof(struct crlf_attrs));
-	return 0;
+	filter->f.apply = &crlf_apply_to_odb;
+	filter->f.do_free = NULL;
+	memcpy(&filter->attrs, &ca, sizeof(struct crlf_attrs));
+
+	return git_vector_insert(filters, filter);
 }
 
diff --git a/src/filter.c b/src/filter.c
index f517512dd..92b3566af 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -13,7 +13,7 @@
 #include "git2/config.h"
 
 /* Fresh from Core Git. I wonder what we could use this for... */
-void git_text__stat(git_text_stats *stats, const git_buf *text)
+void git_text_gather_stats(git_text_stats *stats, const git_buf *text)
 {
 	size_t i;
 
@@ -65,7 +65,7 @@ void git_text__stat(git_text_stats *stats, const git_buf *text)
 /*
  * Fresh from Core Git
  */
-int git_text__is_binary(git_text_stats *stats)
+int git_text_is_binary(git_text_stats *stats)
 {
 	if (stats->nul)
 		return 1;
@@ -84,32 +84,74 @@ int git_text__is_binary(git_text_stats *stats)
 	return 0;
 }
 
-int git_filter__load_for_file(git_vector *filters, git_repository *repo, const char *path, int mode)
+static int load_repository_settings(git_repository *repo)
+{
+	static git_cvar_map map_eol[] = {
+		{GIT_CVAR_FALSE, NULL, GIT_EOL_UNSET},
+		{GIT_CVAR_STRING, "lf", GIT_EOL_LF},
+		{GIT_CVAR_STRING, "crlf", GIT_EOL_CRLF},
+		{GIT_CVAR_STRING, "native", GIT_EOL_NATIVE}
+	};
+
+	static git_cvar_map map_crlf[] = {
+		{GIT_CVAR_FALSE, NULL, GIT_AUTO_CRLF_FALSE},
+		{GIT_CVAR_TRUE, NULL, GIT_AUTO_CRLF_TRUE},
+		{GIT_CVAR_STRING, "input", GIT_AUTO_CRLF_INPUT}
+	};
+
+	git_config *config;
+	int error;
+
+	if (repo->filter_options.loaded)
+		return GIT_SUCCESS;
+
+	repo->filter_options.eol = GIT_EOL_DEFAULT;
+	repo->filter_options.auto_crlf = GIT_AUTO_CRLF_DEFAULT;
+
+	error = git_repository_config__weakptr(&config, repo);
+	if (error < GIT_SUCCESS)
+		return error;
+
+	error = git_config_get_mapped(
+		config, "core.eol", map_eol, ARRAY_SIZE(map_eol), &repo->filter_options.eol);
+
+	if (error < GIT_SUCCESS && error != GIT_ENOTFOUND)
+		return error;
+
+	error = git_config_get_mapped(
+		config, "core.auto_crlf", map_crlf, ARRAY_SIZE(map_crlf), &repo->filter_options.auto_crlf);
+
+	if (error < GIT_SUCCESS && error != GIT_ENOTFOUND)
+		return error;
+
+	repo->filter_options.loaded = 1;
+	return 0;
+}
+
+int git_filters_load(git_vector *filters, git_repository *repo, const char *path, int mode)
 {
 	int error;
-	git_filter *crlf_filter = NULL;
 
-	error = git_filter__load_settings(repo);
+	/* Make sure that the relevant settings from `gitconfig` have been
+	 * cached on the repository struct to speed things up */
+	error = load_repository_settings(repo);
 	if (error < GIT_SUCCESS)
 		return error;
 
 	if (mode == GIT_FILTER_TO_ODB) {
-		error = git_filter__crlf_to_odb(&crlf_filter, repo, path);
+		/* Load the CRLF cleanup filter when writing to the ODB */
+		error = git_filter_add__crlf_to_odb(filters, repo, path);
 		if (error < GIT_SUCCESS)
 			return error;
-
-		if (crlf_filter != NULL)
-			git_vector_insert(filters, crlf_filter);
-
 	} else {
 		return git__throw(GIT_ENOTIMPLEMENTED,
 			"Worktree filters are not implemented yet");
 	}
 
-	return 0;
+	return (int)filters->length;
 }
 
-void git_filter__free(git_vector *filters)
+void git_filters_free(git_vector *filters)
 {
 	size_t i;
 	git_filter *filter;
@@ -124,7 +166,7 @@ void git_filter__free(git_vector *filters)
 	git_vector_free(filters);
 }
 
-int git_filter__apply(git_buf *dest, git_buf *source, git_vector *filters)
+int git_filters_apply(git_buf *dest, git_buf *source, git_vector *filters)
 {
 	unsigned int src, dst, i;
 	git_buf *dbuffer[2];
@@ -134,6 +176,11 @@ int git_filter__apply(git_buf *dest, git_buf *source, git_vector *filters)
 
 	src = 0;
 
+	if (source->size == 0) {
+		git_buf_clear(dest);
+		return GIT_SUCCESS;
+	}
+
 	/* Pre-grow the destination buffer to more or less the size
 	 * we expect it to have */
 	if (git_buf_grow(dest, source->size) < 0)
@@ -167,46 +214,3 @@ int git_filter__apply(git_buf *dest, git_buf *source, git_vector *filters)
 	return GIT_SUCCESS;
 }
 
-int git_filter__load_settings(git_repository *repo)
-{
-	static git_cvar_map map_eol[] = {
-		{GIT_CVAR_FALSE, NULL, GIT_EOL_UNSET},
-		{GIT_CVAR_STRING, "lf", GIT_EOL_LF},
-		{GIT_CVAR_STRING, "crlf", GIT_EOL_CRLF},
-		{GIT_CVAR_STRING, "native", GIT_EOL_NATIVE}
-	};
-
-	static git_cvar_map map_crlf[] = {
-		{GIT_CVAR_FALSE, NULL, GIT_AUTO_CRLF_FALSE},
-		{GIT_CVAR_TRUE, NULL, GIT_AUTO_CRLF_TRUE},
-		{GIT_CVAR_STRING, "input", GIT_AUTO_CRLF_INPUT}
-	};
-
-	git_config *config;
-	int error;
-
-	if (repo->filter_options.loaded)
-		return GIT_SUCCESS;
-
-	repo->filter_options.eol = GIT_EOL_DEFAULT;
-	repo->filter_options.auto_crlf = GIT_AUTO_CRLF_DEFAULT;
-
-	error = git_repository_config__weakptr(&config, repo);
-	if (error < GIT_SUCCESS)
-		return error;
-
-	error = git_config_get_mapped(
-		config, "core.eol", map_eol, ARRAY_SIZE(map_eol), &repo->filter_options.eol);
-
-	if (error < GIT_SUCCESS && error != GIT_ENOTFOUND)
-		return error;
-
-	error = git_config_get_mapped(
-		config, "core.auto_crlf", map_crlf, ARRAY_SIZE(map_crlf), &repo->filter_options.auto_crlf);
-
-	if (error < GIT_SUCCESS && error != GIT_ENOTFOUND)
-		return error;
-
-	repo->filter_options.loaded = 1;
-	return 0;
-}
diff --git a/src/filter.h b/src/filter.h
index 0cf92bd1d..601be1836 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -60,19 +60,81 @@ typedef struct {
 	unsigned int printable, nonprintable;
 } git_text_stats;
 
-extern int git_filter__load_settings(git_repository *repo);
-extern int git_filter__load_for_file(git_vector *filters, git_repository *repo, const char *full_path, int mode);
-extern void git_filter__free(git_vector *filters);
-extern int git_filter__apply(git_buf *dest, git_buf *source, git_vector *filters);
+/*
+ * FILTER API
+ */
+
+/*
+ * For any given path in the working directory, fill the `filters`
+ * array with the relevant filters that need to be applied.
+ *
+ * Mode is either `GIT_FILTER_TO_WORKTREE` if you need to load the
+ * filters that will be used when checking out a file to the working
+ * directory, or `GIT_FILTER_TO_ODB` for the filters used when writing
+ * a file to the ODB.
+ *
+ * @param filters Vector where to store all the loaded filters
+ * @param repo Repository object that contains `path`
+ * @param path Relative path of the file to be filtered
+ * @param mode Filtering direction (WT->ODB or ODB->WT)
+ * @return the number of filters loaded for the file (0 if the file
+ *	doesn't need filtering), or a negative error code
+ */
+extern int git_filters_load(git_vector *filters, git_repository *repo, const char *path, int mode);
+
+/*
+ * Apply one or more filters to a file.
+ *
+ * The file must have been loaded as a `git_buf` object. Both the `source`
+ * and `dest` buffers are owned by the caller and must be freed once
+ * they are no longer needed.
+ *
+ * NOTE: Because of the double-buffering schema, the `source` buffer that contains
+ * the original file may be tampered once the filtering is complete. Regardless, 
+ * the `dest` buffer will always contain the final result of the filtering
+ *
+ * @param dest Buffer to store the result of the filtering
+ * @param source Buffer containing the document to filter
+ * @param filters A non-empty vector of filters as supplied by `git_filters_load`
+ * @return GIT_SUCCESS on success, an error code otherwise
+ */
+extern int git_filters_apply(git_buf *dest, git_buf *source, git_vector *filters);
+
+/*
+ * Free the `filters` array generated by `git_filters_load`.
+ *
+ * Note that this frees both the array and its contents. The array will
+ * be clean/reusable after this call.
+ *
+ * @param filters A filters array as supplied by `git_filters_load`
+ */
+extern void git_filters_free(git_vector *filters);
+
+/*
+ * Available filters
+ */
 
-/* Gather stats for a piece of text */
-extern void git_text__stat(git_text_stats *stats, const git_buf *text);
+/* Strip CRLF, from Worktree to ODB */
+extern int git_filter_add__crlf_to_odb(git_vector *filters, git_repository *repo, const char *path);
 
-/* Heuristics on a set of text stats to check whether it's binary
- * text or not */
-extern int git_text__is_binary(git_text_stats *stats);
 
-/* Available filters */
-extern int git_filter__crlf_to_odb(git_filter **filter_out, git_repository *repo, const char *path);
+/*
+ * PLAINTEXT API
+ */
+
+/*
+ * Gather stats for a piece of text
+ *
+ * Fill the `stats` structure with information on the number of
+ * unreadable characters, carriage returns, etc, so it can be
+ * used in heuristics.
+ */
+extern void git_text_gather_stats(git_text_stats *stats, const git_buf *text);
+
+/*
+ * Process `git_text_stats` data generated by `git_text_stat` to see
+ * if it qualifies as a binary file
+ */
+extern int git_text_is_binary(git_text_stats *stats);
 
 #endif