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Add support for mmaps with nonzero offset values. Needs testing.

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This commit is contained in:
Nick Mathewson 2010-10-25 12:10:10 -04:00
parent e72afae068
commit c2d9884a6a
1 changed files with 22 additions and 10 deletions
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32
buffer.c
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@ -2617,13 +2617,25 @@ evbuffer_file_segment_new(
#if defined(_EVENT_HAVE_MMAP)
/* TODO: Implement an mmap-alike for windows. */
if (!(flags & EVBUF_FS_DISABLE_MMAP)) {
/* some mmap implementations require offset to be a multiple of
* the page size. most users of this api, are likely to use 0
* so mapping everything is not likely to be a problem.
* TODO(niels): determine page size and round offset to that
* page size to avoid mapping too much memory.
*/
void *mapped = mmap(NULL, length + offset, PROT_READ,
off_t offset_rounded = 0, offset_leftover = 0;
void *mapped;
if (offset) {
/* mmap implementations don't generally like us
* to have an offset that isn't a round */
#ifdef SC_PAGE_SIZE
long page_size = sysconf(SC_PAGE_SIZE);
#elif defined(_SC_PAGE_SIZE)
long page_size = sysconf(_SC_PAGE_SIZE);
#else
long page_size = 1;
#endif
if (page_size == -1)
goto err;
offset_leftover = offset % page_size;
offset_rounded = offset - offset_leftover;
}
mapped = mmap(NULL, length + offset_leftover,
PROT_READ,
#ifdef MAP_NOCACHE
MAP_NOCACHE | /* ??? */
#endif
@ -2631,14 +2643,14 @@ evbuffer_file_segment_new(
MAP_FILE |
#endif
MAP_PRIVATE,
fd, 0);
fd, offset_rounded);
if (mapped == MAP_FAILED) {
event_warn("%s: mmap(%d, %d, %zu) failed",
__func__, fd, 0, (size_t)(offset + length));
} else {
seg->mapping = mapped;
seg->contents = ((char*)mapped)+offset;
seg->offset = offset;
seg->contents = (char*)mapped+offset_leftover;
seg->offset = 0;
seg->type = EVBUF_FS_MMAP;
goto done;
}