push.default doc: explain simple after upstream

diff --git a/sha1_file.c b/sha1_file.c
index 4f06a0e450359744528d3b125fb09eacebf1eb4a..ad314f08b9abd9a16b410483f9a9629ce59345cf 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -19,6 +19,7 @@
 #include "pack-revindex.h"
 #include "sha1-lookup.h"
 #include "bulk-checkin.h"
+#include "streaming.h"
 
 #ifndef O_NOATIME
 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
@@ -1146,10 +1147,47 @@ static const struct packed_git *has_packed_and_bad(const unsigned char *sha1)
        return NULL;
 }
 
-int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
+/*
+ * With an in-core object data in "map", rehash it to make sure the
+ * object name actually matches "sha1" to detect object corruption.
+ * With "map" == NULL, try reading the object named with "sha1" using
+ * the streaming interface and rehash it to do the same.
+ */
+int check_sha1_signature(const unsigned char *sha1, void *map,
+                        unsigned long size, const char *type)
 {
        unsigned char real_sha1[20];
-       hash_sha1_file(map, size, type, real_sha1);
+       enum object_type obj_type;
+       struct git_istream *st;
+       git_SHA_CTX c;
+       char hdr[32];
+       int hdrlen;
+
+       if (map) {
+               hash_sha1_file(map, size, type, real_sha1);
+               return hashcmp(sha1, real_sha1) ? -1 : 0;
+       }
+
+       st = open_istream(sha1, &obj_type, &size, NULL);
+       if (!st)
+               return -1;
+
+       /* Generate the header */
+       hdrlen = sprintf(hdr, "%s %lu", typename(obj_type), size) + 1;
+
+       /* Sha1.. */
+       git_SHA1_Init(&c);
+       git_SHA1_Update(&c, hdr, hdrlen);
+       for (;;) {
+               char buf[1024 * 16];
+               ssize_t readlen = read_istream(st, buf, sizeof(buf));
+
+               if (!readlen)
+                       break;
+               git_SHA1_Update(&c, buf, readlen);
+       }
+       git_SHA1_Final(real_sha1, &c);
+       close_istream(st);
        return hashcmp(sha1, real_sha1) ? -1 : 0;
 }