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, 60 insertions, 51 deletions

diff --git a/src/midx.c b/src/midx.c
index cd3c98cef..b8da98986 100644
--- a/src/midx.c
+++ b/src/midx.c
@@ -8,7 +8,7 @@
 #include "midx.h"
 
 #include "array.h"
-#include "buffer.h"
+#include "buf.h"
 #include "filebuf.h"
 #include "futils.h"
 #include "hash.h"
@@ -16,6 +16,7 @@
 #include "pack.h"
 #include "path.h"
 #include "repository.h"
+#include "str.h"
 
 #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
 #define MIDX_VERSION 1
@@ -313,7 +314,7 @@ int git_midx_open(
 	idx = git__calloc(1, sizeof(git_midx_file));
 	GIT_ERROR_CHECK_ALLOC(idx);
 
-	error = git_buf_sets(&idx->filename, path);
+	error = git_str_sets(&idx->filename, path);
 	if (error < 0)
 		return error;
 
@@ -477,7 +478,7 @@ void git_midx_free(git_midx_file *idx)
 	if (!idx)
 		return;
 
-	git_buf_dispose(&idx->filename);
+	git_str_dispose(&idx->filename);
 	git_midx_close(idx);
 	git__free(idx);
 }
@@ -497,14 +498,14 @@ int git_midx_writer_new(
 	git_midx_writer *w = git__calloc(1, sizeof(git_midx_writer));
 	GIT_ERROR_CHECK_ALLOC(w);
 
-	if (git_buf_sets(&w->pack_dir, pack_dir) < 0) {
+	if (git_str_sets(&w->pack_dir, pack_dir) < 0) {
 		git__free(w);
 		return -1;
 	}
 	git_path_squash_slashes(&w->pack_dir);
 
 	if (git_vector_init(&w->packs, 0, packfile__cmp) < 0) {
-		git_buf_dispose(&w->pack_dir);
+		git_str_dispose(&w->pack_dir);
 		git__free(w);
 		return -1;
 	}
@@ -524,7 +525,7 @@ void git_midx_writer_free(git_midx_writer *w)
 	git_vector_foreach (&w->packs, i, p)
 		git_mwindow_put_pack(p);
 	git_vector_free(&w->packs);
-	git_buf_dispose(&w->pack_dir);
+	git_str_dispose(&w->pack_dir);
 	git__free(w);
 }
 
@@ -532,16 +533,16 @@ int git_midx_writer_add(
 		git_midx_writer *w,
 		const char *idx_path)
 {
-	git_buf idx_path_buf = GIT_BUF_INIT;
+	git_str idx_path_buf = GIT_STR_INIT;
 	int error;
 	struct git_pack_file *p;
 
-	error = git_path_prettify(&idx_path_buf, idx_path, git_buf_cstr(&w->pack_dir));
+	error = git_path_prettify(&idx_path_buf, idx_path, git_str_cstr(&w->pack_dir));
 	if (error < 0)
 		return error;
 
-	error = git_mwindow_get_pack(&p, git_buf_cstr(&idx_path_buf));
-	git_buf_dispose(&idx_path_buf);
+	error = git_mwindow_get_pack(&p, git_str_cstr(&idx_path_buf));
+	git_str_dispose(&idx_path_buf);
 	if (error < 0)
 		return error;
 
@@ -613,8 +614,8 @@ static int write_chunk_header(int chunk_id, off64_t offset, midx_write_cb write_
 
 static int midx_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 midx_write_hash_context {
@@ -648,10 +649,10 @@ static int midx_write(
 	uint32_t object_large_offsets_count;
 	uint32_t oid_fanout[256];
 	off64_t offset;
-	git_buf packfile_names = GIT_BUF_INIT,
-		oid_lookup = GIT_BUF_INIT,
-		object_offsets = GIT_BUF_INIT,
-		object_large_offsets = GIT_BUF_INIT;
+	git_str packfile_names = GIT_STR_INIT,
+		oid_lookup = GIT_STR_INIT,
+		object_offsets = GIT_STR_INIT,
+		object_large_offsets = GIT_STR_INIT;
 	git_oid idx_checksum = {{0}};
 	git_midx_entry *entry;
 	object_entry_array_t object_entries_array = GIT_ARRAY_INIT;
@@ -676,34 +677,34 @@ static int midx_write(
 
 	git_vector_sort(&w->packs);
 	git_vector_foreach (&w->packs, i, p) {
-		git_buf relative_index = GIT_BUF_INIT;
+		git_str relative_index = GIT_STR_INIT;
 		struct object_entry_cb_state state = {0};
 		size_t path_len;
 
 		state.pack_index = (uint32_t)i;
 		state.object_entries_array = &object_entries_array;
 
-		error = git_buf_sets(&relative_index, p->pack_name);
+		error = git_str_sets(&relative_index, p->pack_name);
 		if (error < 0)
 			goto cleanup;
-		error = git_path_make_relative(&relative_index, git_buf_cstr(&w->pack_dir));
+		error = git_path_make_relative(&relative_index, git_str_cstr(&w->pack_dir));
 		if (error < 0) {
-			git_buf_dispose(&relative_index);
+			git_str_dispose(&relative_index);
 			goto cleanup;
 		}
-		path_len = git_buf_len(&relative_index);
-		if (path_len <= strlen(".pack") || git__suffixcmp(git_buf_cstr(&relative_index), ".pack") != 0) {
-			git_buf_dispose(&relative_index);
+		path_len = git_str_len(&relative_index);
+		if (path_len <= strlen(".pack") || git__suffixcmp(git_str_cstr(&relative_index), ".pack") != 0) {
+			git_str_dispose(&relative_index);
 			git_error_set(GIT_ERROR_INVALID, "invalid packfile name: '%s'", p->pack_name);
 			error = -1;
 			goto cleanup;
 		}
 		path_len -= strlen(".pack");
 
-		git_buf_put(&packfile_names, git_buf_cstr(&relative_index), path_len);
-		git_buf_puts(&packfile_names, ".idx");
-		git_buf_putc(&packfile_names, '\0');
-		git_buf_dispose(&relative_index);
+		git_str_put(&packfile_names, git_str_cstr(&relative_index), path_len);
+		git_str_puts(&packfile_names, ".idx");
+		git_str_putc(&packfile_names, '\0');
+		git_str_dispose(&relative_index);
 
 		error = git_pack_foreach_entry_offset(p, object_entry__cb, &state);
 		if (error < 0)
@@ -723,8 +724,8 @@ static int midx_write(
 	git_vector_uniq(&object_entries, NULL);
 
 	/* Pad the packfile names so it is a multiple of four. */
-	while (git_buf_len(&packfile_names) & 3)
-		git_buf_putc(&packfile_names, '\0');
+	while (git_str_len(&packfile_names) & 3)
+		git_str_putc(&packfile_names, '\0');
 
 	/* Fill the OID Fanout table. */
 	oid_fanout_count = 0;
@@ -737,7 +738,7 @@ static int midx_write(
 
 	/* Fill the OID Lookup table. */
 	git_vector_foreach (&object_entries, i, entry) {
-		error = git_buf_put(&oid_lookup, (const char *)&entry->sha1, sizeof(entry->sha1));
+		error = git_str_put(&oid_lookup, (const char *)&entry->sha1, sizeof(entry->sha1));
 		if (error < 0)
 			goto cleanup;
 	}
@@ -748,7 +749,7 @@ static int midx_write(
 		uint32_t word;
 
 		word = htonl((uint32_t)entry->pack_index);
-		error = git_buf_put(&object_offsets, (const char *)&word, sizeof(word));
+		error = git_str_put(&object_offsets, (const char *)&word, sizeof(word));
 		if (error < 0)
 			goto cleanup;
 		if (entry->offset >= 0x80000000l) {
@@ -759,7 +760,7 @@ static int midx_write(
 			word = htonl((uint32_t)entry->offset & 0x7fffffffu);
 		}
 
-		error = git_buf_put(&object_offsets, (const char *)&word, sizeof(word));
+		error = git_str_put(&object_offsets, (const char *)&word, sizeof(word));
 		if (error < 0)
 			goto cleanup;
 	}
@@ -767,7 +768,7 @@ static int midx_write(
 	/* Write the header. */
 	hdr.packfiles = htonl((uint32_t)git_vector_length(&w->packs));
 	hdr.chunks = 4;
-	if (git_buf_len(&object_large_offsets) > 0)
+	if (git_str_len(&object_large_offsets) > 0)
 		hdr.chunks++;
 	error = write_cb((const char *)&hdr, sizeof(hdr), cb_data);
 	if (error < 0)
@@ -778,7 +779,7 @@ static int midx_write(
 	error = write_chunk_header(MIDX_PACKFILE_NAMES_ID, offset, write_cb, cb_data);
 	if (error < 0)
 		goto cleanup;
-	offset += git_buf_len(&packfile_names);
+	offset += git_str_len(&packfile_names);
 	error = write_chunk_header(MIDX_OID_FANOUT_ID, offset, write_cb, cb_data);
 	if (error < 0)
 		goto cleanup;
@@ -786,35 +787,35 @@ static int midx_write(
 	error = write_chunk_header(MIDX_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(MIDX_OBJECT_OFFSETS_ID, offset, write_cb, cb_data);
 	if (error < 0)
 		goto cleanup;
-	offset += git_buf_len(&object_offsets);
-	if (git_buf_len(&object_large_offsets) > 0) {
+	offset += git_str_len(&object_offsets);
+	if (git_str_len(&object_large_offsets) > 0) {
 		error = write_chunk_header(MIDX_OBJECT_LARGE_OFFSETS_ID, offset, write_cb, cb_data);
 		if (error < 0)
 			goto cleanup;
-		offset += git_buf_len(&object_large_offsets);
+		offset += git_str_len(&object_large_offsets);
 	}
 	error = write_chunk_header(0, offset, write_cb, cb_data);
 	if (error < 0)
 		goto cleanup;
 
 	/* Write all the chunks. */
-	error = write_cb(git_buf_cstr(&packfile_names), git_buf_len(&packfile_names), cb_data);
+	error = write_cb(git_str_cstr(&packfile_names), git_str_len(&packfile_names), cb_data);
 	if (error < 0)
 		goto cleanup;
 	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(&object_offsets), git_buf_len(&object_offsets), cb_data);
+	error = write_cb(git_str_cstr(&object_offsets), git_str_len(&object_offsets), cb_data);
 	if (error < 0)
 		goto cleanup;
-	error = write_cb(git_buf_cstr(&object_large_offsets), git_buf_len(&object_large_offsets), cb_data);
+	error = write_cb(git_str_cstr(&object_large_offsets), git_str_len(&object_large_offsets), cb_data);
 	if (error < 0)
 		goto cleanup;
 
@@ -829,10 +830,10 @@ static int midx_write(
 cleanup:
 	git_array_clear(object_entries_array);
 	git_vector_free(&object_entries);
-	git_buf_dispose(&packfile_names);
-	git_buf_dispose(&oid_lookup);
-	git_buf_dispose(&object_offsets);
-	git_buf_dispose(&object_large_offsets);
+	git_str_dispose(&packfile_names);
+	git_str_dispose(&oid_lookup);
+	git_str_dispose(&object_offsets);
+	git_str_dispose(&object_large_offsets);
 	git_hash_ctx_cleanup(&ctx);
 	return error;
 }
@@ -848,17 +849,17 @@ int git_midx_writer_commit(
 {
 	int error;
 	int filebuf_flags = GIT_FILEBUF_DO_NOT_BUFFER;
-	git_buf midx_path = GIT_BUF_INIT;
+	git_str midx_path = GIT_STR_INIT;
 	git_filebuf output = GIT_FILEBUF_INIT;
 
-	error = git_buf_joinpath(&midx_path, git_buf_cstr(&w->pack_dir), "multi-pack-index");
+	error = git_str_joinpath(&midx_path, git_str_cstr(&w->pack_dir), "multi-pack-index");
 	if (error < 0)
 		return error;
 
 	if (git_repository__fsync_gitdir)
 		filebuf_flags |= GIT_FILEBUF_FSYNC;
-	error = git_filebuf_open(&output, git_buf_cstr(&midx_path), filebuf_flags, 0644);
-	git_buf_dispose(&midx_path);
+	error = git_filebuf_open(&output, git_str_cstr(&midx_path), filebuf_flags, 0644);
+	git_str_dispose(&midx_path);
 	if (error < 0)
 		return error;
 
@@ -875,5 +876,13 @@ int git_midx_writer_dump(
 		git_buf *midx,
 		git_midx_writer *w)
 {
-	return midx_write(w, midx_write_buf, midx);
+	git_str str = GIT_STR_INIT;
+	int error;
+
+	if ((error = git_buf_tostr(&str, midx)) < 0 ||
+	    (error = midx_write(w, midx_write_buf, &str)) == 0)
+		error = git_buf_fromstr(midx, &str);
+
+	git_str_dispose(&str);
+	return error;
 }