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ewah: support platforms that require aligned reads

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The caller may hand us an unaligned buffer (e.g., because it
is an mmap of a file with many ewah bitmaps). On some
platforms (like SPARC) this can cause a bus error. We can
fix it with a combination of get_be32 and moving the data
into an aligned buffer (which we would do anyway, but we can
move it before fixing the endianness).

Signed-off-by: Vicent Marti <tanoku@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Vicent Marti 2014-01-23 16:27:52 -05:00 committed by Junio C Hamano
parent c3d8da571f
commit a201c20b41
1 changed files with 24 additions and 9 deletions
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33
ewah/ewah_io.c
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@ -112,23 +112,38 @@ int ewah_serialize(struct ewah_bitmap *self, int fd)
int ewah_read_mmap(struct ewah_bitmap *self, void *map, size_t len)
{
uint32_t *read32 = map;
eword_t *read64;
size_t i;
uint8_t *ptr = map;
self->bit_size = get_be32(ptr);
ptr += sizeof(uint32_t);
self->buffer_size = self->alloc_size = get_be32(ptr);
ptr += sizeof(uint32_t);
self->bit_size = ntohl(*read32++);
self->buffer_size = self->alloc_size = ntohl(*read32++);
self->buffer = ewah_realloc(self->buffer,
self->alloc_size * sizeof(eword_t));
if (!self->buffer)
return -1;
for (i = 0, read64 = (void *)read32; i < self->buffer_size; ++i)
self->buffer[i] = ntohll(*read64++);
/*
* Copy the raw data for the bitmap as a whole chunk;
* if we're in a little-endian platform, we'll perform
* the endianness conversion in a separate pass to ensure
* we're loading 8-byte aligned words.
*/
memcpy(self->buffer, ptr, self->buffer_size * sizeof(uint64_t));
ptr += self->buffer_size * sizeof(uint64_t);
read32 = (void *)read64;
self->rlw = self->buffer + ntohl(*read32++);
#if __BYTE_ORDER != __BIG_ENDIAN
{
size_t i;
for (i = 0; i < self->buffer_size; ++i)
self->buffer[i] = ntohll(self->buffer[i]);
}
#endif
self->rlw = self->buffer + get_be32(ptr);
return (3 * 4) + (self->buffer_size * 8);
}