[PATCH v6 2/7] read-cache: clean up casting and byte decoding

[Ben Peart]

This patch does a clean up pass to minimize the casting required to work
with the memory mapped index (mmap).

It also makes the decoding of network byte order more consistent by using
get_be32() where possible.

Signed-off-by: Ben Peart <ben.pe...@microsoft.com>
---
 read-cache.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index 583a4fb1f8..6ba99e2c96 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1650,7 +1650,7 @@ int verify_index_checksum;
 /* Allow fsck to force verification of the cache entry order. */
 int verify_ce_order;
 
-static int verify_hdr(struct cache_header *hdr, unsigned long size)
+static int verify_hdr(const struct cache_header *hdr, unsigned long size)
 {
        git_hash_ctx c;
        unsigned char hash[GIT_MAX_RAWSZ];
@@ -1674,7 +1674,7 @@ static int verify_hdr(struct cache_header *hdr, unsigned 
long size)
 }
 
 static int read_index_extension(struct index_state *istate,
-                               const char *ext, void *data, unsigned long sz)
+                               const char *ext, const char *data, unsigned 
long sz)
 {
        switch (CACHE_EXT(ext)) {
        case CACHE_EXT_TREE:
@@ -1889,8 +1889,8 @@ int do_read_index(struct index_state *istate, const char 
*path, int must_exist)
        int fd, i;
        struct stat st;
        unsigned long src_offset;
-       struct cache_header *hdr;
-       void *mmap;
+       const struct cache_header *hdr;
+       const char *mmap;
        size_t mmap_size;
        const struct cache_entry *previous_ce = NULL;
 
@@ -1918,7 +1918,7 @@ int do_read_index(struct index_state *istate, const char 
*path, int must_exist)
                die_errno("unable to map index file");
        close(fd);
 
-       hdr = mmap;
+       hdr = (const struct cache_header *)mmap;
        if (verify_hdr(hdr, mmap_size) < 0)
                goto unmap;
 
@@ -1943,7 +1943,7 @@ int do_read_index(struct index_state *istate, const char 
*path, int must_exist)
                struct cache_entry *ce;
                unsigned long consumed;
 
-               disk_ce = (struct ondisk_cache_entry *)((char *)mmap + 
src_offset);
+               disk_ce = (struct ondisk_cache_entry *)(mmap + src_offset);
                ce = create_from_disk(istate, disk_ce, &consumed, previous_ce);
                set_index_entry(istate, i, ce);
 
@@ -1961,21 +1961,20 @@ int do_read_index(struct index_state *istate, const 
char *path, int must_exist)
                 * in 4-byte network byte order.
                 */
                uint32_t extsize;
-               memcpy(&extsize, (char *)mmap + src_offset + 4, 4);
-               extsize = ntohl(extsize);
+               extsize = get_be32(mmap + src_offset + 4);
                if (read_index_extension(istate,
-                                        (const char *) mmap + src_offset,
-                                        (char *) mmap + src_offset + 8,
+                                        mmap + src_offset,
+                                        mmap + src_offset + 8,
                                         extsize) < 0)
                        goto unmap;
                src_offset += 8;
                src_offset += extsize;
        }
-       munmap(mmap, mmap_size);
+       munmap((void *)mmap, mmap_size);
        return istate->cache_nr;
 
 unmap:
-       munmap(mmap, mmap_size);
+       munmap((void *)mmap, mmap_size);
        die("index file corrupt");
 }
 
-- 
2.18.0.windows.1