git-repack --max-pack-size: write_{object,one}() respect pack limit

With --max-pack-size,  generate the appropriate write limit
for each object and check against it before each group of writes.
Update delta usability rules to handle base being in a previously-
written pack.  Inline sha1write_compress() so we know the
exact size of the written data when it needs to be compressed.
Detect and return write "failure".

Signed-off-by: Dana L. How <danahow@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-pack-objects.c

@@ -352,16 +352,31 @@ static void copy_pack_data(struct sha1file *f,
 }
 
 static unsigned long write_object(struct sha1file *f,
-				  struct object_entry *entry)
+				  struct object_entry *entry,
+				  off_t write_offset)
 {
 	unsigned long size;
 	enum object_type type;
 	void *buf;
 	unsigned char header[10];
+	unsigned char dheader[10];
 	unsigned hdrlen;
 	off_t datalen;
 	enum object_type obj_type;
 	int to_reuse = 0;
+	/* write limit if limited packsize and not first object */
+	unsigned long limit = pack_size_limit && nr_written ?
+				pack_size_limit - write_offset : 0;
+				/* no if no delta */
+	int usable_delta =	!entry->delta ? 0 :
+				/* yes if unlimited packfile */
+				!pack_size_limit ? 1 :
+				/* no if base written to previous pack */
+				entry->delta->offset == (off_t)-1 ? 0 :
+				/* otherwise double-check written to this
+				 * pack,  like we do below
+				 */
+				entry->delta->offset ? 1 : 0;
 
 	if (!pack_to_stdout)
 		crc32_begin(f);
@@ -372,7 +387,9 @@ static unsigned long write_object(struct sha1file *f,
 	else if (!entry->in_pack)
 		to_reuse = 0;	/* can't reuse what we don't have */
 	else if (obj_type == OBJ_REF_DELTA || obj_type == OBJ_OFS_DELTA)
-		to_reuse = 1;	/* check_object() decided it for us */
+				/* check_object() decided it for us ... */
+		to_reuse = usable_delta;
+				/* ... but pack split may override that */
 	else if (obj_type != entry->in_pack_type)
 		to_reuse = 0;	/* pack has delta which is unusable */
 	else if (entry->delta)
@@ -383,24 +400,48 @@ static unsigned long write_object(struct sha1file *f,
 				 */
 
 	if (!to_reuse) {
+		z_stream stream;
+		unsigned long maxsize;
+		void *out;
 		buf = read_sha1_file(entry->sha1, &type, &size);
 		if (!buf)
 			die("unable to read %s", sha1_to_hex(entry->sha1));
 		if (size != entry->size)
 			die("object %s size inconsistency (%lu vs %lu)",
 			    sha1_to_hex(entry->sha1), size, entry->size);
-		if (entry->delta) {
+		if (usable_delta) {
 			buf = delta_against(buf, size, entry);
 			size = entry->delta_size;
 			obj_type = (allow_ofs_delta && entry->delta->offset) ?
 				OBJ_OFS_DELTA : OBJ_REF_DELTA;
+		} else {
+			/*
+			 * recover real object type in case
+			 * check_object() wanted to re-use a delta,
+			 * but we couldn't since base was in previous split pack
+			 */
+			obj_type = type;
 		}
+		/* compress the data to store and put compressed length in datalen */
+		memset(&stream, 0, sizeof(stream));
+		deflateInit(&stream, pack_compression_level);
+		maxsize = deflateBound(&stream, size);
+		out = xmalloc(maxsize);
+		/* Compress it */
+		stream.next_in = buf;
+		stream.avail_in = size;
+		stream.next_out = out;
+		stream.avail_out = maxsize;
+		while (deflate(&stream, Z_FINISH) == Z_OK)
+			/* nothing */;
+		deflateEnd(&stream);
+		datalen = stream.total_out;
+		deflateEnd(&stream);
 		/*
 		 * The object header is a byte of 'type' followed by zero or
 		 * more bytes of length.
 		 */
 		hdrlen = encode_header(obj_type, size, header);
-		sha1write(f, header, hdrlen);
 
 		if (obj_type == OBJ_OFS_DELTA) {
 			/*
@@ -409,21 +450,41 @@ static unsigned long write_object(struct sha1file *f,
 			 * base from this object's position in the pack.
 			 */
 			off_t ofs = entry->offset - entry->delta->offset;
-			unsigned pos = sizeof(header) - 1;
+			unsigned pos = sizeof(dheader) - 1;
-			header[pos] = ofs & 127;
+			dheader[pos] = ofs & 127;
 			while (ofs >>= 7)
-				header[--pos] = 128 | (--ofs & 127);
+				dheader[--pos] = 128 | (--ofs & 127);
-			sha1write(f, header + pos, sizeof(header) - pos);
+			if (limit && hdrlen + sizeof(dheader) - pos + datalen + 20 >= limit) {
-			hdrlen += sizeof(header) - pos;
+				free(out);
+				free(buf);
+				return 0;
+			}
+			sha1write(f, header, hdrlen);
+			sha1write(f, dheader + pos, sizeof(dheader) - pos);
+			hdrlen += sizeof(dheader) - pos;
 		} else if (obj_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(out);
+				free(buf);
+				return 0;
+			}
+			sha1write(f, header, hdrlen);
 			sha1write(f, entry->delta->sha1, 20);
 			hdrlen += 20;
+		} else {
+			if (limit && hdrlen + datalen + 20 >= limit) {
+				free(out);
+				free(buf);
+				return 0;
+			}
+			sha1write(f, header, hdrlen);
 		}
-		datalen = sha1write_compressed(f, buf, size, pack_compression_level);
+		sha1write(f, out, datalen);
+		free(out);
 		free(buf);
 	}
 	else {
@@ -438,20 +499,6 @@ static unsigned long write_object(struct sha1file *f,
 			reused_delta++;
 		}
 		hdrlen = encode_header(obj_type, entry->size, header);
-		sha1write(f, header, hdrlen);
-		if (obj_type == OBJ_OFS_DELTA) {
-			off_t ofs = entry->offset - entry->delta->offset;
-			unsigned pos = sizeof(header) - 1;
-			header[pos] = ofs & 127;
-			while (ofs >>= 7)
-				header[--pos] = 128 | (--ofs & 127);
-			sha1write(f, header + pos, sizeof(header) - pos);
-			hdrlen += sizeof(header) - pos;
-		} else if (obj_type == OBJ_REF_DELTA) {
-			sha1write(f, entry->delta->sha1, 20);
-			hdrlen += 20;
-		}
-
 		offset = entry->in_pack_offset;
 		revidx = find_packed_object(p, offset);
 		datalen = revidx[1].offset - offset;
@@ -460,6 +507,29 @@ static unsigned long write_object(struct sha1file *f,
 			die("bad packed object CRC for %s", sha1_to_hex(entry->sha1));
 		offset += entry->in_pack_header_size;
 		datalen -= entry->in_pack_header_size;
+		if (obj_type == OBJ_OFS_DELTA) {
+			off_t ofs = entry->offset - entry->delta->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)
+				return 0;
+			sha1write(f, header, hdrlen);
+			sha1write(f, dheader + pos, sizeof(dheader) - pos);
+			hdrlen += sizeof(dheader) - pos;
+		} else if (obj_type == OBJ_REF_DELTA) {
+			if (limit && hdrlen + 20 + datalen + 20 >= limit)
+				return 0;
+			sha1write(f, header, hdrlen);
+			sha1write(f, entry->delta->sha1, 20);
+			hdrlen += 20;
+		} else {
+			if (limit && hdrlen + datalen + 20 >= limit)
+				return 0;
+			sha1write(f, header, hdrlen);
+		}
+
 		if (!pack_to_stdout && p->index_version == 1 &&
 		    check_pack_inflate(p, &w_curs, offset, datalen, entry->size))
 			die("corrupt packed object for %s", sha1_to_hex(entry->sha1));
@@ -467,7 +537,7 @@ static unsigned long write_object(struct sha1file *f,
 		unuse_pack(&w_curs);
 		reused++;
 	}
-	if (entry->delta)
+	if (usable_delta)
 		written_delta++;
 	written++;
 	if (!pack_to_stdout)
@@ -486,11 +556,18 @@ static off_t write_one(struct sha1file *f,
 		return offset;
 
 	/* if we are deltified, write out base object first. */
-	if (e->delta)
+	if (e->delta) {
 		offset = write_one(f, e->delta, offset);
+		if (!offset)
+			return 0;
+	}
 
 	e->offset = offset;
-	size = write_object(f, e);
+	size = write_object(f, e, offset);
+	if (!size) {
+		e->offset = 0;
+		return 0;
+	}
 
 	/* make sure off_t is sufficiently large not to wrap */
 	if (offset > offset + size)