pack-objects: refactor write_object() into helper functions

The function first decides if we want to copy data taken from existing
pack verbatim or we want to encode the data ourselves for the packfile
we are creating and then carries out the decision.  Separate the latter
phase into two helper functions, one for the case the data is reused,
the other for the case the data is produced anew.

A little twist is that it can later turn out that we cannot reuse the
data after we initially decide to do so; in such a case, the "reuse"
helper makes a call to "generate" helper.  It is easier to follow than
the current fallback code that uses "goto" inside a single large
function.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 172 insertions, 150 deletions

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index b2e0940c7a..ccfcbad146 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -200,22 +200,178 @@ static void copy_pack_data(struct sha1file *f,
 }
 
 /* Return 0 if we will bust the pack-size limit */
-static unsigned long write_object(struct sha1file *f,
-				  struct object_entry *entry,
-				  off_t write_offset)
+static unsigned long write_no_reuse_object(struct sha1file *f, struct object_entry *entry,
+					   unsigned long limit, int usable_delta)
 {
-	unsigned long size, limit, datalen;
-	void *buf;
+	unsigned long size, datalen;
 	unsigned char header[10], dheader[10];
 	unsigned hdrlen;
 	enum object_type type;
+	void *buf;
+
+	if (!usable_delta) {
+		buf = read_sha1_file(entry->idx.sha1, &type, &size);
+		if (!buf)
+			die("unable to read %s", sha1_to_hex(entry->idx.sha1));
+		/*
+		 * make sure no cached delta data remains from a
+		 * previous attempt before a pack split occurred.
+		 */
+		free(entry->delta_data);
+		entry->delta_data = NULL;
+		entry->z_delta_size = 0;
+	} else if (entry->delta_data) {
+		size = entry->delta_size;
+		buf = entry->delta_data;
+		entry->delta_data = NULL;
+		type = (allow_ofs_delta && entry->delta->idx.offset) ?
+			OBJ_OFS_DELTA : OBJ_REF_DELTA;
+	} else {
+		buf = get_delta(entry);
+		size = entry->delta_size;
+		type = (allow_ofs_delta && entry->delta->idx.offset) ?
+			OBJ_OFS_DELTA : OBJ_REF_DELTA;
+	}
+
+	if (entry->z_delta_size)
+		datalen = entry->z_delta_size;
+	else
+		datalen = do_compress(&buf, size);
+
+	/*
+	 * The object header is a byte of 'type' followed by zero or
+	 * more bytes of length.
+	 */
+	hdrlen = encode_in_pack_object_header(type, size, header);
+
+	if (type == OBJ_OFS_DELTA) {
+		/*
+		 * Deltas with relative base contain an additional
+		 * encoding of the relative offset for the delta
+		 * base from this object's position in the pack.
+		 */
+		off_t ofs = entry->idx.offset - entry->delta->idx.offset;
+		unsigned pos = sizeof(dheader) - 1;
+		dheader[pos] = ofs & 127;
+		while (ofs >>= 7)
+			dheader[--pos] = 128 | (--ofs & 127);
+		if (limit && hdrlen + sizeof(dheader) - pos + datalen + 20 >= limit) {
+			free(buf);
+			return 0;
+		}
+		sha1write(f, header, hdrlen);
+		sha1write(f, dheader + pos, sizeof(dheader) - pos);
+		hdrlen += sizeof(dheader) - pos;
+	} else if (type == OBJ_REF_DELTA) {
+		/*
+		 * Deltas with a base reference contain
+		 * an additional 20 bytes for the base sha1.
+		 */
+		if (limit && hdrlen + 20 + datalen + 20 >= limit) {
+			free(buf);
+			return 0;
+		}
+		sha1write(f, header, hdrlen);
+		sha1write(f, entry->delta->idx.sha1, 20);
+		hdrlen += 20;
+	} else {
+		if (limit && hdrlen + datalen + 20 >= limit) {
+			free(buf);
+			return 0;
+		}
+		sha1write(f, header, hdrlen);
+	}
+	sha1write(f, buf, datalen);
+	free(buf);
+
+	return hdrlen + datalen;
+}
+
+/* Return 0 if we will bust the pack-size limit */
+static unsigned long write_reuse_object(struct sha1file *f, struct object_entry *entry,
+					unsigned long limit, int usable_delta)
+{
+	struct packed_git *p = entry->in_pack;
+	struct pack_window *w_curs = NULL;
+	struct revindex_entry *revidx;
+	off_t offset;
+	enum object_type type = entry->type;
+	unsigned long datalen;
+	unsigned char header[10], dheader[10];
+	unsigned hdrlen;
+
+	if (entry->delta)
+		type = (allow_ofs_delta && entry->delta->idx.offset) ?
+			OBJ_OFS_DELTA : OBJ_REF_DELTA;
+	hdrlen = encode_in_pack_object_header(type, entry->size, header);
+
+	offset = entry->in_pack_offset;
+	revidx = find_pack_revindex(p, offset);
+	datalen = revidx[1].offset - offset;
+	if (!pack_to_stdout && p->index_version > 1 &&
+	    check_pack_crc(p, &w_curs, offset, datalen, revidx->nr)) {
+		error("bad packed object CRC for %s", sha1_to_hex(entry->idx.sha1));
+		unuse_pack(&w_curs);
+		return write_no_reuse_object(f, entry, limit, usable_delta);
+	}
+
+	offset += entry->in_pack_header_size;
+	datalen -= entry->in_pack_header_size;
+
+	if (!pack_to_stdout && p->index_version == 1 &&
+	    check_pack_inflate(p, &w_curs, offset, datalen, entry->size)) {
+		error("corrupt packed object for %s", sha1_to_hex(entry->idx.sha1));
+		unuse_pack(&w_curs);
+		return write_no_reuse_object(f, entry, limit, usable_delta);
+	}
+
+	if (type == OBJ_OFS_DELTA) {
+		off_t ofs = entry->idx.offset - entry->delta->idx.offset;
+		unsigned pos = sizeof(dheader) - 1;
+		dheader[pos] = ofs & 127;
+		while (ofs >>= 7)
+			dheader[--pos] = 128 | (--ofs & 127);
+		if (limit && hdrlen + sizeof(dheader) - pos + datalen + 20 >= limit) {
+			unuse_pack(&w_curs);
+			return 0;
+		}
+		sha1write(f, header, hdrlen);
+		sha1write(f, dheader + pos, sizeof(dheader) - pos);
+		hdrlen += sizeof(dheader) - pos;
+		reused_delta++;
+	} else if (type == OBJ_REF_DELTA) {
+		if (limit && hdrlen + 20 + datalen + 20 >= limit) {
+			unuse_pack(&w_curs);
+			return 0;
+		}
+		sha1write(f, header, hdrlen);
+		sha1write(f, entry->delta->idx.sha1, 20);
+		hdrlen += 20;
+		reused_delta++;
+	} else {
+		if (limit && hdrlen + datalen + 20 >= limit) {
+			unuse_pack(&w_curs);
+			return 0;
+		}
+		sha1write(f, header, hdrlen);
+	}
+	copy_pack_data(f, p, &w_curs, offset, datalen);
+	unuse_pack(&w_curs);
+	reused++;
+	return hdrlen + datalen;
+}
+
+/* Return 0 if we will bust the pack-size limit */
+static unsigned long write_object(struct sha1file *f,
+				  struct object_entry *entry,
+				  off_t write_offset)
+{
+	unsigned long limit, len;
 	int usable_delta, to_reuse;
 
 	if (!pack_to_stdout)
 		crc32_begin(f);
 
-	type = entry->type;
-
 	/* apply size limit if limited packsize and not first object */
 	if (!pack_size_limit || !nr_written)
 		limit = 0;
@@ -243,11 +399,11 @@ static unsigned long write_object(struct sha1file *f,
 		to_reuse = 0;	/* explicit */
 	else if (!entry->in_pack)
 		to_reuse = 0;	/* can't reuse what we don't have */
-	else if (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA)
+	else if (entry->type == OBJ_REF_DELTA || entry->type == OBJ_OFS_DELTA)
 				/* check_object() decided it for us ... */
 		to_reuse = usable_delta;
 				/* ... but pack split may override that */
-	else if (type != entry->in_pack_type)
+	else if (entry->type != entry->in_pack_type)
 		to_reuse = 0;	/* pack has delta which is unusable */
 	else if (entry->delta)
 		to_reuse = 0;	/* we want to pack afresh */
@@ -256,153 +412,19 @@ static unsigned long write_object(struct sha1file *f,
 				 * and we do not need to deltify it.
 				 */
 
-	if (!to_reuse) {
-		no_reuse:
-		if (!usable_delta) {
-			buf = read_sha1_file(entry->idx.sha1, &type, &size);
-			if (!buf)
-				die("unable to read %s", sha1_to_hex(entry->idx.sha1));
-			/*
-			 * make sure no cached delta data remains from a
-			 * previous attempt before a pack split occurred.
-			 */
-			free(entry->delta_data);
-			entry->delta_data = NULL;
-			entry->z_delta_size = 0;
-		} else if (entry->delta_data) {
-			size = entry->delta_size;
-			buf = entry->delta_data;
-			entry->delta_data = NULL;
-			type = (allow_ofs_delta && entry->delta->idx.offset) ?
-				OBJ_OFS_DELTA : OBJ_REF_DELTA;
-		} else {
-			buf = get_delta(entry);
-			size = entry->delta_size;
-			type = (allow_ofs_delta && entry->delta->idx.offset) ?
-				OBJ_OFS_DELTA : OBJ_REF_DELTA;
-		}
-
-		if (entry->z_delta_size)
-			datalen = entry->z_delta_size;
-		else
-			datalen = do_compress(&buf, size);
-
-		/*
-		 * The object header is a byte of 'type' followed by zero or
-		 * more bytes of length.
-		 */
-		hdrlen = encode_in_pack_object_header(type, size, header);
-
-		if (type == OBJ_OFS_DELTA) {
-			/*
-			 * Deltas with relative base contain an additional
-			 * encoding of the relative offset for the delta
-			 * base from this object's position in the pack.
-			 */
-			off_t ofs = entry->idx.offset - entry->delta->idx.offset;
-			unsigned pos = sizeof(dheader) - 1;
-			dheader[pos] = ofs & 127;
-			while (ofs >>= 7)
-				dheader[--pos] = 128 | (--ofs & 127);
-			if (limit && hdrlen + sizeof(dheader) - pos + datalen + 20 >= limit) {
-				free(buf);
-				return 0;
-			}
-			sha1write(f, header, hdrlen);
-			sha1write(f, dheader + pos, sizeof(dheader) - pos);
-			hdrlen += sizeof(dheader) - pos;
-		} else if (type == OBJ_REF_DELTA) {
-			/*
-			 * Deltas with a base reference contain
-			 * an additional 20 bytes for the base sha1.
-			 */
-			if (limit && hdrlen + 20 + datalen + 20 >= limit) {
-				free(buf);
-				return 0;
-			}
-			sha1write(f, header, hdrlen);
-			sha1write(f, entry->delta->idx.sha1, 20);
-			hdrlen += 20;
-		} else {
-			if (limit && hdrlen + datalen + 20 >= limit) {
-				free(buf);
-				return 0;
-			}
-			sha1write(f, header, hdrlen);
-		}
-		sha1write(f, buf, datalen);
-		free(buf);
-	}
-	else {
-		struct packed_git *p = entry->in_pack;
-		struct pack_window *w_curs = NULL;
-		struct revindex_entry *revidx;
-		off_t offset;
-
-		if (entry->delta)
-			type = (allow_ofs_delta && entry->delta->idx.offset) ?
-				OBJ_OFS_DELTA : OBJ_REF_DELTA;
-		hdrlen = encode_in_pack_object_header(type, entry->size, header);
-
-		offset = entry->in_pack_offset;
-		revidx = find_pack_revindex(p, offset);
-		datalen = revidx[1].offset - offset;
-		if (!pack_to_stdout && p->index_version > 1 &&
-		    check_pack_crc(p, &w_curs, offset, datalen, revidx->nr)) {
-			error("bad packed object CRC for %s", sha1_to_hex(entry->idx.sha1));
-			unuse_pack(&w_curs);
-			goto no_reuse;
-		}
-
-		offset += entry->in_pack_header_size;
-		datalen -= entry->in_pack_header_size;
-		if (!pack_to_stdout && p->index_version == 1 &&
-		    check_pack_inflate(p, &w_curs, offset, datalen, entry->size)) {
-			error("corrupt packed object for %s", sha1_to_hex(entry->idx.sha1));
-			unuse_pack(&w_curs);
-			goto no_reuse;
-		}
+	if (!to_reuse)
+		len = write_no_reuse_object(f, entry, limit, usable_delta);
+	else
+		len = write_reuse_object(f, entry, limit, usable_delta);
+	if (!len)
+		return 0;
 
-		if (type == OBJ_OFS_DELTA) {
-			off_t ofs = entry->idx.offset - entry->delta->idx.offset;
-			unsigned pos = sizeof(dheader) - 1;
-			dheader[pos] = ofs & 127;
-			while (ofs >>= 7)
-				dheader[--pos] = 128 | (--ofs & 127);
-			if (limit && hdrlen + sizeof(dheader) - pos + datalen + 20 >= limit) {
-				unuse_pack(&w_curs);
-				return 0;
-			}
-			sha1write(f, header, hdrlen);
-			sha1write(f, dheader + pos, sizeof(dheader) - pos);
-			hdrlen += sizeof(dheader) - pos;
-			reused_delta++;
-		} else if (type == OBJ_REF_DELTA) {
-			if (limit && hdrlen + 20 + datalen + 20 >= limit) {
-				unuse_pack(&w_curs);
-				return 0;
-			}
-			sha1write(f, header, hdrlen);
-			sha1write(f, entry->delta->idx.sha1, 20);
-			hdrlen += 20;
-			reused_delta++;
-		} else {
-			if (limit && hdrlen + datalen + 20 >= limit) {
-				unuse_pack(&w_curs);
-				return 0;
-			}
-			sha1write(f, header, hdrlen);
-		}
-		copy_pack_data(f, p, &w_curs, offset, datalen);
-		unuse_pack(&w_curs);
-		reused++;
-	}
 	if (usable_delta)
 		written_delta++;
 	written++;
 	if (!pack_to_stdout)
 		entry->idx.crc32 = crc32_end(f);
-	return hdrlen + datalen;
+	return len;
 }
 
 enum write_one_status {