str: introduce `git_str` for internal, `git_buf` is externalethomson/gitstr

libgit2 has two distinct requirements that were previously solved by
`git_buf`.  We require:

1. A general purpose string class that provides a number of utility APIs
   for manipulating data (eg, concatenating, truncating, etc).
2. A structure that we can use to return strings to callers that they
   can take ownership of.

By using a single class (`git_buf`) for both of these purposes, we have
confused the API to the point that refactorings are difficult and
reasoning about correctness is also difficult.

Move the utility class `git_buf` to be called `git_str`: this represents
its general purpose, as an internal string buffer class.  The name also
is an homage to Junio Hamano ("gitstr").

The public API remains `git_buf`, and has a much smaller footprint.  It
is generally only used as an "out" param with strict requirements that
follow the documentation.  (Exceptions exist for some legacy APIs to
avoid breaking callers unnecessarily.)

Utility functions exist to convert a user-specified `git_buf` to a
`git_str` so that we can call internal functions, then converting it
back again.

1 files changed, 47 insertions, 38 deletions

diff --git a/src/commit_graph.c b/src/commit_graph.c
index df760b5f8..f9a4bd2b2 100644
--- a/src/commit_graph.c
+++ b/src/commit_graph.c
@@ -8,6 +8,7 @@
 #include "commit_graph.h"
 
 #include "array.h"
+#include "buf.h"
 #include "filebuf.h"
 #include "futils.h"
 #include "hash.h"
@@ -308,12 +309,12 @@ int git_commit_graph_new(git_commit_graph **cgraph_out, const char *objects_dir,
 	cgraph = git__calloc(1, sizeof(git_commit_graph));
 	GIT_ERROR_CHECK_ALLOC(cgraph);
 
-	error = git_buf_joinpath(&cgraph->filename, objects_dir, "info/commit-graph");
+	error = git_str_joinpath(&cgraph->filename, objects_dir, "info/commit-graph");
 	if (error < 0)
 		goto error;
 
 	if (open_file) {
-		error = git_commit_graph_file_open(&cgraph->file, git_buf_cstr(&cgraph->filename));
+		error = git_commit_graph_file_open(&cgraph->file, git_str_cstr(&cgraph->filename));
 		if (error < 0)
 			goto error;
 		cgraph->checked = 1;
@@ -387,7 +388,7 @@ int git_commit_graph_get_file(git_commit_graph_file **file_out, git_commit_graph
 		cgraph->checked = 1;
 
 		/* Best effort */
-		error = git_commit_graph_file_open(&result, git_buf_cstr(&cgraph->filename));
+		error = git_commit_graph_file_open(&result, git_str_cstr(&cgraph->filename));
 
 		if (error < 0)
 			return error;
@@ -407,7 +408,7 @@ void git_commit_graph_refresh(git_commit_graph *cgraph)
 		return;
 
 	if (cgraph->file
-	    && git_commit_graph_file_needs_refresh(cgraph->file, git_buf_cstr(&cgraph->filename))) {
+	    && git_commit_graph_file_needs_refresh(cgraph->file, git_str_cstr(&cgraph->filename))) {
 		/* We just free the commit graph. The next time it is requested, it will be
 		 * re-loaded. */
 		git_commit_graph_file_free(cgraph->file);
@@ -597,7 +598,7 @@ void git_commit_graph_free(git_commit_graph *cgraph)
 	if (!cgraph)
 		return;
 
-	git_buf_dispose(&cgraph->filename);
+	git_str_dispose(&cgraph->filename);
 	git_commit_graph_file_free(cgraph->file);
 	git__free(cgraph);
 }
@@ -623,13 +624,13 @@ int git_commit_graph_writer_new(git_commit_graph_writer **out, const char *objec
 	git_commit_graph_writer *w = git__calloc(1, sizeof(git_commit_graph_writer));
 	GIT_ERROR_CHECK_ALLOC(w);
 
-	if (git_buf_sets(&w->objects_info_dir, objects_info_dir) < 0) {
+	if (git_str_sets(&w->objects_info_dir, objects_info_dir) < 0) {
 		git__free(w);
 		return -1;
 	}
 
 	if (git_vector_init(&w->commits, 0, packed_commit__cmp) < 0) {
-		git_buf_dispose(&w->objects_info_dir);
+		git_str_dispose(&w->objects_info_dir);
 		git__free(w);
 		return -1;
 	}
@@ -649,7 +650,7 @@ void git_commit_graph_writer_free(git_commit_graph_writer *w)
 	git_vector_foreach (&w->commits, i, packed_commit)
 		packed_commit_free(packed_commit);
 	git_vector_free(&w->commits);
-	git_buf_dispose(&w->objects_info_dir);
+	git_str_dispose(&w->objects_info_dir);
 	git__free(w);
 }
 
@@ -931,8 +932,8 @@ static int write_chunk_header(
 
 static int commit_graph_write_buf(const char *buf, size_t size, void *data)
 {
-	git_buf *b = (git_buf *)data;
-	return git_buf_put(b, buf, size);
+	git_str *b = (git_str *)data;
+	return git_str_put(b, buf, size);
 }
 
 struct commit_graph_write_hash_context {
@@ -971,8 +972,8 @@ static int commit_graph_write(
 	uint32_t extra_edge_list_count;
 	uint32_t oid_fanout[256];
 	off64_t offset;
-	git_buf oid_lookup = GIT_BUF_INIT, commit_data = GIT_BUF_INIT,
-		extra_edge_list = GIT_BUF_INIT;
+	git_str oid_lookup = GIT_STR_INIT, commit_data = GIT_STR_INIT,
+		extra_edge_list = GIT_STR_INIT;
 	git_oid cgraph_checksum = {{0}};
 	git_hash_ctx ctx;
 	struct commit_graph_write_hash_context hash_cb_data = {0};
@@ -1011,7 +1012,7 @@ static int commit_graph_write(
 
 	/* Fill the OID Lookup table. */
 	git_vector_foreach (&w->commits, i, packed_commit) {
-		error = git_buf_put(&oid_lookup,
+		error = git_str_put(&oid_lookup,
 			(const char *)&packed_commit->sha1, sizeof(git_oid));
 		if (error < 0)
 			goto cleanup;
@@ -1026,7 +1027,7 @@ static int commit_graph_write(
 		size_t *packed_index;
 		unsigned int parentcount = (unsigned int)git_array_size(packed_commit->parents);
 
-		error = git_buf_put(&commit_data,
+		error = git_str_put(&commit_data,
 				(const char *)&packed_commit->tree_oid,
 				sizeof(git_oid));
 		if (error < 0)
@@ -1038,7 +1039,7 @@ static int commit_graph_write(
 			packed_index = git_array_get(packed_commit->parent_indices, 0);
 			word = htonl((uint32_t)*packed_index);
 		}
-		error = git_buf_put(&commit_data, (const char *)&word, sizeof(word));
+		error = git_str_put(&commit_data, (const char *)&word, sizeof(word));
 		if (error < 0)
 			goto cleanup;
 
@@ -1050,7 +1051,7 @@ static int commit_graph_write(
 		} else {
 			word = htonl(0x80000000u | extra_edge_list_count);
 		}
-		error = git_buf_put(&commit_data, (const char *)&word, sizeof(word));
+		error = git_str_put(&commit_data, (const char *)&word, sizeof(word));
 		if (error < 0)
 			goto cleanup;
 
@@ -1061,7 +1062,7 @@ static int commit_graph_write(
 					packed_commit->parent_indices, parent_i);
 				word = htonl((uint32_t)(*packed_index | (parent_i + 1 == parentcount ? 0x80000000u : 0)));
 
-				error = git_buf_put(&extra_edge_list,
+				error = git_str_put(&extra_edge_list,
 						(const char *)&word,
 						sizeof(word));
 				if (error < 0)
@@ -1075,18 +1076,18 @@ static int commit_graph_write(
 		if (generation > GIT_COMMIT_GRAPH_GENERATION_NUMBER_MAX)
 			generation = GIT_COMMIT_GRAPH_GENERATION_NUMBER_MAX;
 		word = ntohl((uint32_t)((generation << 2) | ((commit_time >> 32ull) & 0x3ull)));
-		error = git_buf_put(&commit_data, (const char *)&word, sizeof(word));
+		error = git_str_put(&commit_data, (const char *)&word, sizeof(word));
 		if (error < 0)
 			goto cleanup;
 		word = ntohl((uint32_t)(commit_time & 0xffffffffull));
-		error = git_buf_put(&commit_data, (const char *)&word, sizeof(word));
+		error = git_str_put(&commit_data, (const char *)&word, sizeof(word));
 		if (error < 0)
 			goto cleanup;
 	}
 
 	/* Write the header. */
 	hdr.chunks = 3;
-	if (git_buf_len(&extra_edge_list) > 0)
+	if (git_str_len(&extra_edge_list) > 0)
 		hdr.chunks++;
 	error = write_cb((const char *)&hdr, sizeof(hdr), cb_data);
 	if (error < 0)
@@ -1101,17 +1102,17 @@ static int commit_graph_write(
 	error = write_chunk_header(COMMIT_GRAPH_OID_LOOKUP_ID, offset, write_cb, cb_data);
 	if (error < 0)
 		goto cleanup;
-	offset += git_buf_len(&oid_lookup);
+	offset += git_str_len(&oid_lookup);
 	error = write_chunk_header(COMMIT_GRAPH_COMMIT_DATA_ID, offset, write_cb, cb_data);
 	if (error < 0)
 		goto cleanup;
-	offset += git_buf_len(&commit_data);
-	if (git_buf_len(&extra_edge_list) > 0) {
+	offset += git_str_len(&commit_data);
+	if (git_str_len(&extra_edge_list) > 0) {
 		error = write_chunk_header(
 				COMMIT_GRAPH_EXTRA_EDGE_LIST_ID, offset, write_cb, cb_data);
 		if (error < 0)
 			goto cleanup;
-		offset += git_buf_len(&extra_edge_list);
+		offset += git_str_len(&extra_edge_list);
 	}
 	error = write_chunk_header(0, offset, write_cb, cb_data);
 	if (error < 0)
@@ -1121,13 +1122,13 @@ static int commit_graph_write(
 	error = write_cb((const char *)oid_fanout, sizeof(oid_fanout), cb_data);
 	if (error < 0)
 		goto cleanup;
-	error = write_cb(git_buf_cstr(&oid_lookup), git_buf_len(&oid_lookup), cb_data);
+	error = write_cb(git_str_cstr(&oid_lookup), git_str_len(&oid_lookup), cb_data);
 	if (error < 0)
 		goto cleanup;
-	error = write_cb(git_buf_cstr(&commit_data), git_buf_len(&commit_data), cb_data);
+	error = write_cb(git_str_cstr(&commit_data), git_str_len(&commit_data), cb_data);
 	if (error < 0)
 		goto cleanup;
-	error = write_cb(git_buf_cstr(&extra_edge_list), git_buf_len(&extra_edge_list), cb_data);
+	error = write_cb(git_str_cstr(&extra_edge_list), git_str_len(&extra_edge_list), cb_data);
 	if (error < 0)
 		goto cleanup;
 
@@ -1140,9 +1141,9 @@ static int commit_graph_write(
 		goto cleanup;
 
 cleanup:
-	git_buf_dispose(&oid_lookup);
-	git_buf_dispose(&commit_data);
-	git_buf_dispose(&extra_edge_list);
+	git_str_dispose(&oid_lookup);
+	git_str_dispose(&commit_data);
+	git_str_dispose(&extra_edge_list);
 	git_hash_ctx_cleanup(&ctx);
 	return error;
 }
@@ -1171,21 +1172,21 @@ int git_commit_graph_writer_commit(
 {
 	int error;
 	int filebuf_flags = GIT_FILEBUF_DO_NOT_BUFFER;
-	git_buf commit_graph_path = GIT_BUF_INIT;
+	git_str commit_graph_path = GIT_STR_INIT;
 	git_filebuf output = GIT_FILEBUF_INIT;
 
 	/* TODO: support options and fill in defaults. */
 	GIT_UNUSED(opts);
 
-	error = git_buf_joinpath(
-			&commit_graph_path, git_buf_cstr(&w->objects_info_dir), "commit-graph");
+	error = git_str_joinpath(
+			&commit_graph_path, git_str_cstr(&w->objects_info_dir), "commit-graph");
 	if (error < 0)
 		return error;
 
 	if (git_repository__fsync_gitdir)
 		filebuf_flags |= GIT_FILEBUF_FSYNC;
-	error = git_filebuf_open(&output, git_buf_cstr(&commit_graph_path), filebuf_flags, 0644);
-	git_buf_dispose(&commit_graph_path);
+	error = git_filebuf_open(&output, git_str_cstr(&commit_graph_path), filebuf_flags, 0644);
+	git_str_dispose(&commit_graph_path);
 	if (error < 0)
 		return error;
 
@@ -1199,9 +1200,17 @@ int git_commit_graph_writer_commit(
 }
 
 int git_commit_graph_writer_dump(
-		git_buf *cgraph,
-		git_commit_graph_writer *w,
-		git_commit_graph_writer_options *opts)
+	git_buf *cgraph,
+	git_commit_graph_writer *w,
+	git_commit_graph_writer_options *opts)
+{
+	GIT_BUF_WRAP_PRIVATE(cgraph, git_commit_graph__writer_dump, w, opts);
+}
+
+int git_commit_graph__writer_dump(
+	git_str *cgraph,
+	git_commit_graph_writer *w,
+	git_commit_graph_writer_options *opts)
 {
 	/* TODO: support options. */
 	GIT_UNUSED(opts);