[PATCH v3 2/5] archive-zip: use strbuf for ZIP directory

["René Scharfe" <l.s.r@web.de>]

Keep the ZIP central director, which is written after all archive
entries, in a strbuf instead of a custom-managed buffer.  It contains
binary data, so we can't (and don't want to) use the full range of
strbuf functions and we don't need the terminating NUL, but the result
is shorter and simpler code.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 archive-zip.c | 36 +++++++++++-------------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

diff --git a/archive-zip.c b/archive-zip.c
index b429a8d974..a6fac59602 100644
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -11,16 +11,14 @@
 static int zip_date;
 static int zip_time;
 
-static unsigned char *zip_dir;
-static unsigned int zip_dir_size;
+/* We only care about the "buf" part here. */
+static struct strbuf zip_dir;
 
 static unsigned int zip_offset;
-static unsigned int zip_dir_offset;
 static uint64_t zip_dir_entries;
 
 static unsigned int max_creator_version;
 
-#define ZIP_DIRECTORY_MIN_SIZE	(1024 * 1024)
 #define ZIP_STREAM	(1 <<  3)
 #define ZIP_UTF8	(1 << 11)
 
@@ -268,7 +266,6 @@ static int write_zip_entry(struct archiver_args *args,
 	unsigned long attr2;
 	unsigned long compressed_size;
 	unsigned long crc;
-	unsigned long direntsize;
 	int method;
 	unsigned char *out;
 	void *deflated = NULL;
@@ -356,13 +353,6 @@ static int write_zip_entry(struct archiver_args *args,
 	extra.flags[0] = 1;	/* just mtime */
 	copy_le32(extra.mtime, args->time);
 
-	/* make sure we have enough free space in the dictionary */
-	direntsize = ZIP_DIR_HEADER_SIZE + pathlen + ZIP_EXTRA_MTIME_SIZE;
-	while (zip_dir_size < zip_dir_offset + direntsize) {
-		zip_dir_size += ZIP_DIRECTORY_MIN_SIZE;
-		zip_dir = xrealloc(zip_dir, zip_dir_size);
-	}
-
 	copy_le32(dirent.magic, 0x02014b50);
 	copy_le16(dirent.creator_version, creator_version);
 	copy_le16(dirent.version, 10);
@@ -486,12 +476,9 @@ static int write_zip_entry(struct archiver_args *args,
 
 	copy_le16(dirent.attr1, !is_binary);
 
-	memcpy(zip_dir + zip_dir_offset, &dirent, ZIP_DIR_HEADER_SIZE);
-	zip_dir_offset += ZIP_DIR_HEADER_SIZE;
-	memcpy(zip_dir + zip_dir_offset, path, pathlen);
-	zip_dir_offset += pathlen;
-	memcpy(zip_dir + zip_dir_offset, &extra, ZIP_EXTRA_MTIME_SIZE);
-	zip_dir_offset += ZIP_EXTRA_MTIME_SIZE;
+	strbuf_add(&zip_dir, &dirent, ZIP_DIR_HEADER_SIZE);
+	strbuf_add(&zip_dir, path, pathlen);
+	strbuf_add(&zip_dir, &extra, ZIP_EXTRA_MTIME_SIZE);
 	zip_dir_entries++;
 
 	return 0;
@@ -510,12 +497,12 @@ static void write_zip64_trailer(void)
 	copy_le32(trailer64.directory_start_disk, 0);
 	copy_le64(trailer64.entries_on_this_disk, zip_dir_entries);
 	copy_le64(trailer64.entries, zip_dir_entries);
-	copy_le64(trailer64.size, zip_dir_offset);
+	copy_le64(trailer64.size, zip_dir.len);
 	copy_le64(trailer64.offset, zip_offset);
 
 	copy_le32(locator64.magic, 0x07064b50);
 	copy_le32(locator64.disk, 0);
-	copy_le64(locator64.offset, zip_offset + zip_dir_offset);
+	copy_le64(locator64.offset, zip_offset + zip_dir.len);
 	copy_le32(locator64.number_of_disks, 1);
 
 	write_or_die(1, &trailer64, ZIP64_DIR_TRAILER_SIZE);
@@ -533,11 +520,11 @@ static void write_zip_trailer(const unsigned char *sha1)
 	copy_le16_clamp(trailer.entries_on_this_disk, zip_dir_entries,
 			&clamped);
 	copy_le16_clamp(trailer.entries, zip_dir_entries, &clamped);
-	copy_le32(trailer.size, zip_dir_offset);
+	copy_le32(trailer.size, zip_dir.len);
 	copy_le32(trailer.offset, zip_offset);
 	copy_le16(trailer.comment_length, sha1 ? GIT_SHA1_HEXSZ : 0);
 
-	write_or_die(1, zip_dir, zip_dir_offset);
+	write_or_die(1, zip_dir.buf, zip_dir.len);
 	if (clamped)
 		write_zip64_trailer();
 	write_or_die(1, &trailer, ZIP_DIR_TRAILER_SIZE);
@@ -568,14 +555,13 @@ static int write_zip_archive(const struct archiver *ar,
 
 	dos_time(&args->time, &zip_date, &zip_time);
 
-	zip_dir = xmalloc(ZIP_DIRECTORY_MIN_SIZE);
-	zip_dir_size = ZIP_DIRECTORY_MIN_SIZE;
+	strbuf_init(&zip_dir, 0);
 
 	err = write_archive_entries(args, write_zip_entry);
 	if (!err)
 		write_zip_trailer(args->commit_sha1);
 
-	free(zip_dir);
+	strbuf_release(&zip_dir);
 
 	return err;
 }
-- 
2.12.2