8e554429e8
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 <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
44 lines
748 B
C
44 lines
748 B
C
#include "../git-compat-util.h"
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void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
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{
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size_t n = 0;
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if (start != NULL || !(flags & MAP_PRIVATE))
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die("Invalid usage of mmap when built with NO_MMAP");
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start = xmalloc(length);
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if (start == NULL) {
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errno = ENOMEM;
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return MAP_FAILED;
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}
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while (n < length) {
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ssize_t count = pread(fd, (char *)start + n, length - n, offset + n);
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if (count == 0) {
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memset((char *)start+n, 0, length-n);
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break;
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}
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if (count < 0) {
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if (errno == EAGAIN || errno == EINTR)
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continue;
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free(start);
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errno = EACCES;
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return MAP_FAILED;
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}
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n += count;
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}
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return start;
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}
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int git_munmap(void *start, size_t length)
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{
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free(start);
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return 0;
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}
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