index-pack: smarter memory usage when appending objects

In the same spirit as commit 9892bebafe, let's avoid allocating the full
buffer for the deflated data in write_compressed() in order to write it.
Let's deflate and write the data in chunks instead to reduce memory
usage.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-index-pack.c b/builtin-index-pack.c
index 4308abb60e8cf750f3c3a38c2100f910b0bcbdf9..7f3208457567642cf5fa474a0dc3194ca0f808e8 100644 (file)
--- a/builtin-index-pack.c
+++ b/builtin-index-pack.c
@@ -669,25 +669,25 @@ static void parse_pack_objects(unsigned char *sha1)
 static int write_compressed(struct sha1file *f, void *in, unsigned int size)
 {
        z_stream stream;
-       unsigned long maxsize;
-       void *out;
+       int status;
+       unsigned char outbuf[4096];
 
        memset(&stream, 0, sizeof(stream));
        deflateInit(&stream, zlib_compression_level);
-       maxsize = deflateBound(&stream, size);
-       out = xmalloc(maxsize);
-
-       /* Compress it */
        stream.next_in = in;
        stream.avail_in = size;
-       stream.next_out = out;
-       stream.avail_out = maxsize;
-       while (deflate(&stream, Z_FINISH) == Z_OK);
-       deflateEnd(&stream);
 
+       do {
+               stream.next_out = outbuf;
+               stream.avail_out = sizeof(outbuf);
+               status = deflate(&stream, Z_FINISH);
+               sha1write(f, outbuf, sizeof(outbuf) - stream.avail_out);
+       } while (status == Z_OK);
+
+       if (status != Z_STREAM_END)
+               die("unable to deflate appended object (%d)", status);
        size = stream.total_out;
-       sha1write(f, out, size);
-       free(out);
+       deflateEnd(&stream);
        return size;
 }