From 8e554429e8a9dbb5dba6b8aeca66fc27c0bb5538 Mon Sep 17 00:00:00 2001 From: "Shawn O. Pearce" Date: Sun, 24 Dec 2006 00:45:47 -0500 Subject: [PATCH] Switch git_mmap to use pread. Now that Git depends on pread in index-pack its safe to say we can also depend on it within the git_mmap emulation we activate when NO_MMAP is set. On most systems pread should be slightly faster than an lseek/read/lseek sequence as its one system call vs. three system calls. We also now honor EAGAIN and EINTR error codes from pread and restart the prior read. Signed-off-by: Shawn O. Pearce Signed-off-by: Junio C Hamano --- compat/mmap.c | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/compat/mmap.c b/compat/mmap.c index bb34c7e95..4cfaee313 100644 --- a/compat/mmap.c +++ b/compat/mmap.c @@ -2,17 +2,11 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset) { - int n = 0; - off_t current_offset = lseek(fd, 0, SEEK_CUR); + size_t n = 0; if (start != NULL || !(flags & MAP_PRIVATE)) die("Invalid usage of mmap when built with NO_MMAP"); - if (lseek(fd, offset, SEEK_SET) < 0) { - errno = EINVAL; - return MAP_FAILED; - } - start = xmalloc(length); if (start == NULL) { errno = ENOMEM; @@ -20,14 +14,16 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of } while (n < length) { - int count = read(fd, start+n, length-n); + ssize_t count = pread(fd, (char *)start + n, length - n, offset + n); if (count == 0) { - memset(start+n, 0, length-n); + memset((char *)start+n, 0, length-n); break; } if (count < 0) { + if (errno == EAGAIN || errno == EINTR) + continue; free(start); errno = EACCES; return MAP_FAILED; @@ -36,11 +32,6 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of n += count; } - if (current_offset != lseek(fd, current_offset, SEEK_SET)) { - errno = EINVAL; - return MAP_FAILED; - } - return start; } -- 2.30.2