ewah: support platforms that require aligned reads
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>
diff --git a/ewah/ewah_io.c b/ewah/ewah_io.c
index aed0da6..4a7fae6 100644
--- a/ewah/ewah_io.c
+++ b/ewah/ewah_io.c
@@ -112,23 +112,38 @@
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 = ntohl(*read32++);
- self->buffer_size = self->alloc_size = ntohl(*read32++);
+ self->bit_size = get_be32(ptr);
+ ptr += sizeof(uint32_t);
+
+ self->buffer_size = self->alloc_size = get_be32(ptr);
+ ptr += sizeof(uint32_t);
+
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);
}
