Re: First cut at git port to Cygwin

From

Linus Torvalds <torvalds@osdl.org>

Date

Oct 8, 2005, 16:11 UTC

Message-ID

<Pine.LNX.4.64.0510080900510.31407@g5.osdl.org>

In-Reply-To

<20051007213952.GA8821@steel.home>

On Fri, 7 Oct 2005, Alex Riesen wrote:

> 
> Make read_cache copy the index into memory, to improve portability on
> other OS's which have mmap too, tend to use it less commonly.

I really think that you should just get rid of the mmap.

So I'd suggest something like this instead.

Totally untested, of course.

		Linus

----

diff --git a/read-cache.c b/read-cache.c
--- a/read-cache.c
+++ b/read-cache.c
@@ -454,13 +454,39 @@ static int verify_hdr(struct cache_heade
 	return 0;
 }
 
+static void *map_index_file(int fd, size_t size)
+{
+	void *map;
+#ifdef NO_MMAP
+	map = malloc(size);
+	if (!map)
+		die("Unable to allocate index file mapping");
+	if (read(fd, map, size) != size)
+		die("Unable to read %z bytes from inde
+#else
+	map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+	if (map == MAP_FAILED)
+		die("index file mmap failed (%s)", strerror(errno));
+#endif
+	return map;
+}
+
+static void unmap_index_file(void *map, size_t size)
+{
+#ifdef NO_MMAP
+	free(map);
+#else
+	munmap(map, size);
+#endif
+}
+
 int read_cache(void)
 {
 	int fd, i;
 	struct stat st;
 	unsigned long size, offset;
-	void *map;
 	struct cache_header *hdr;
+	void *map;
 
 	errno = EBUSY;
 	if (active_cache)
@@ -475,16 +501,15 @@ int read_cache(void)
 	}
 
 	size = 0; // avoid gcc warning
-	map = MAP_FAILED;
-	if (!fstat(fd, &st)) {
-		size = st.st_size;
-		errno = EINVAL;
-		if (size >= sizeof(struct cache_header) + 20)
-			map = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-	}
+	if (fstat(fd, &st))
+		die("unable to fstat index file");
+
+	size = st.st_size;
+	errno = EINVAL;
+	if (size < sizeof(struct cache_header) + 20)
+		goto corrupt;
+	map = map_index_file(fd, size);
 	close(fd);
-	if (map == MAP_FAILED)
-		die("index file mmap failed (%s)", strerror(errno));
 
 	hdr = map;
 	if (verify_hdr(hdr, size) < 0)
@@ -503,8 +528,9 @@ int read_cache(void)
 	return active_nr;
 
 unmap:
-	munmap(map, size);
+	unmap_index_file(map, size);
 	errno = EINVAL;
+corrupt:
 	die("index file corrupt");
 }