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-rw-r--r--read-cache.c21
1 files changed, 19 insertions, 2 deletions
diff --git a/read-cache.c b/read-cache.c
index 5453694..2ee96bc 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -216,8 +216,25 @@ int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
int fd;
fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
- if (fd < 0)
- return (errno == EEXIST) ? 0 : -1;
+ if (fd < 0) {
+ void *map;
+ static int error(const char * string);
+
+ if (errno != EEXIST)
+ return -1;
+#ifndef COLLISION_CHECK
+ fd = open(filename, O_RDONLY);
+ if (fd < 0)
+ return -1;
+ map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+ if (map == MAP_FAILED)
+ return -1;
+ if (memcmp(buf, map, size))
+ return error("SHA1 collision detected!"
+ " This is bad, bad, BAD!\a\n");
+#endif
+ return 0;
+ }
write(fd, buf, size);
close(fd);
return 0;