pack-objects: use streaming interface for reading large loose blobs

git usually streams large blobs directly to packs. But there are cases
where git can create large loose blobs (unpack-objects or hash-object
over pipe). Or they can come from other git implementations.
core.bigfilethreshold can also be lowered down and introduce a new
wave of large loose blobs.

Use streaming interface to read/compress/write these blobs in one
go. Fall back to normal way if somehow streaming interface cannot be
used.

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

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index ccfcbad14647eff80131cd99c22a18f13016b4af..f3348208d89a4fbeb3ae9f79376d7d21a8f9015c 100644 (file)
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -16,6 +16,7 @@
 #include "list-objects.h"
 #include "progress.h"
 #include "refs.h"
+#include "streaming.h"
 #include "thread-utils.h"
 
 static const char *pack_usage[] = {
@@ -150,6 +151,46 @@ static unsigned long do_compress(void **pptr, unsigned long size)
        return stream.total_out;
 }
 
+static unsigned long write_large_blob_data(struct git_istream *st, struct sha1file *f,
+                                          const unsigned char *sha1)
+{
+       git_zstream stream;
+       unsigned char ibuf[1024 * 16];
+       unsigned char obuf[1024 * 16];
+       unsigned long olen = 0;
+
+       memset(&stream, 0, sizeof(stream));
+       git_deflate_init(&stream, pack_compression_level);
+
+       for (;;) {
+               ssize_t readlen;
+               int zret = Z_OK;
+               readlen = read_istream(st, ibuf, sizeof(ibuf));
+               if (readlen == -1)
+                       die(_("unable to read %s"), sha1_to_hex(sha1));
+
+               stream.next_in = ibuf;
+               stream.avail_in = readlen;
+               while ((stream.avail_in || readlen == 0) &&
+                      (zret == Z_OK || zret == Z_BUF_ERROR)) {
+                       stream.next_out = obuf;
+                       stream.avail_out = sizeof(obuf);
+                       zret = git_deflate(&stream, readlen ? 0 : Z_FINISH);
+                       sha1write(f, obuf, stream.next_out - obuf);
+                       olen += stream.next_out - obuf;
+               }
+               if (stream.avail_in)
+                       die(_("deflate error (%d)"), zret);
+               if (readlen == 0) {
+                       if (zret != Z_STREAM_END)
+                               die(_("deflate error (%d)"), zret);
+                       break;
+               }
+       }
+       git_deflate_end(&stream);
+       return olen;
+}
+
 /*
  * we are going to reuse the existing object data as is.  make
  * sure it is not corrupt.
@@ -208,11 +249,18 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
        unsigned hdrlen;
        enum object_type type;
        void *buf;
+       struct git_istream *st = NULL;
 
        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));
+               if (entry->type == OBJ_BLOB &&
+                   entry->size > big_file_threshold &&
+                   (st = open_istream(entry->idx.sha1, &type, &size, NULL)) != NULL)
+                       buf = NULL;
+               else {
+                       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.
@@ -233,7 +281,9 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
                        OBJ_OFS_DELTA : OBJ_REF_DELTA;
        }
 
-       if (entry->z_delta_size)
+       if (st) /* large blob case, just assume we don't compress well */
+               datalen = size;
+       else if (entry->z_delta_size)
                datalen = entry->z_delta_size;
        else
                datalen = do_compress(&buf, size);
@@ -256,6 +306,8 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
                while (ofs >>= 7)
                        dheader[--pos] = 128 | (--ofs & 127);
                if (limit && hdrlen + sizeof(dheader) - pos + datalen + 20 >= limit) {
+                       if (st)
+                               close_istream(st);
                        free(buf);
                        return 0;
                }
@@ -268,6 +320,8 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
                 * an additional 20 bytes for the base sha1.
                 */
                if (limit && hdrlen + 20 + datalen + 20 >= limit) {
+                       if (st)
+                               close_istream(st);
                        free(buf);
                        return 0;
                }
@@ -276,13 +330,20 @@ static unsigned long write_no_reuse_object(struct sha1file *f, struct object_ent
                hdrlen += 20;
        } else {
                if (limit && hdrlen + datalen + 20 >= limit) {
+                       if (st)
+                               close_istream(st);
                        free(buf);
                        return 0;
                }
                sha1write(f, header, hdrlen);
        }
-       sha1write(f, buf, datalen);
-       free(buf);
+       if (st) {
+               datalen = write_large_blob_data(st, f, entry->idx.sha1);
+               close_istream(st);
+       } else {
+               sha1write(f, buf, datalen);
+               free(buf);
+       }
 
        return hdrlen + datalen;
 }

diff --git a/t/t1050-large.sh b/t/t1050-large.sh
index 55ed955ceffee9184b5822054697f58e7d0ef6a4..313889b5b4d9b52dc68d64cde3587d41f57c1340 100755 (executable)
--- a/t/t1050-large.sh
+++ b/t/t1050-large.sh
@@ -134,6 +134,18 @@ test_expect_success 'repack' '
        git repack -ad
 '
 
+test_expect_success 'pack-objects with large loose object' '
+       SHA1=`git hash-object huge` &&
+       test_create_repo loose &&
+       echo $SHA1 | git pack-objects --stdout |
+               GIT_ALLOC_LIMIT=0 GIT_DIR=loose/.git git unpack-objects &&
+       echo $SHA1 | GIT_DIR=loose/.git git pack-objects pack &&
+       test_create_repo packed &&
+       mv pack-* packed/.git/objects/pack &&
+       GIT_DIR=packed/.git git cat-file blob $SHA1 >actual &&
+       cmp huge actual
+'
+
 test_expect_success 'tar achiving' '
        git archive --format=tar HEAD >/dev/null
 '