* certain very frequently used functions.
*/
+#include <config.h>
+
#include <stdio.h>
#include <stdlib.h>
+#include <stdint.h>
+#include <byteswap.h>
+#include <string.h>
#include <caml/mlvalues.h>
#include <caml/fail.h>
-/* Return a mask of 0-31 bits wide. */
-CAMLprim value
-ocaml_bitstring_I_mask (value bitsv)
-{
- int bits = Int_val (bitsv);
-
- if (bits <= 31)
- return Val_int ((1 << bits) - 1);
- else
- caml_invalid_argument ("Bitstring.I.mask");
-}
+/* Fastpath functions. These are used in the common case for reading
+ * ints where the following conditions are known to be true:
+ * (a) the int size is a whole number of bytes (eg. 16, 24, 32, etc bits)
+ * (b) the access in the match is byte-aligned
+ * (c) the access in the underlying bitstring is byte-aligned
+ *
+ * These functions are all "noalloc" meaning they must not perform
+ * any OCaml allocations. For this reason, when the function returns
+ * an int32 or int64, the OCaml code passes in the pre-allocated pointer
+ * to the return value.
+ *
+ * The final offset in the string is calculated by the OCaml (caller)
+ * code. All we need to do is to read the string+offset and byteswap,
+ * sign-extend as necessary.
+ *
+ * There is one function for every combination of:
+ * (i) int size: 16, 32, 64 bits
+ * (ii) endian: bigendian, littleendian, nativeendian
+ * (iii) signed and unsigned
+ *
+ * XXX Future work: Expand this to 24, 40, 48, 56 bits. This
+ * requires some extra work because sign-extension won't "just happen".
+ */
+
+#ifdef WORDS_BIGENDIAN
+#define swap_be(size,v)
+#define swap_le(size,v) v = bswap_##size (v)
+#define swap_ne(size,v)
+#else
+#define swap_be(size,v) v = bswap_##size (v)
+#define swap_le(size,v)
+#define swap_ne(size,v)
+#endif
+
+#define fastpath1(size,endian,signed,type) \
+ CAMLprim value \
+ ocaml_bitstring_extract_fastpath_int##size##_##endian##_##signed \
+ (value strv, value offv) \
+ { \
+ type *ptr = (type *) ((void *) String_val (strv) + Int_val (offv)); \
+ type r; \
+ memcpy(&r, ptr, sizeof(r)); \
+ swap_##endian(size,r); \
+ return Val_int (r); \
+ }
+
+fastpath1(16,be,unsigned,uint16_t)
+fastpath1(16,le,unsigned,uint16_t)
+fastpath1(16,ne,unsigned,uint16_t)
+fastpath1(16,be,signed,int16_t)
+fastpath1(16,le,signed,int16_t)
+fastpath1(16,ne,signed,int16_t)
+
+#define fastpath2(size,endian,signed,type,rval) \
+ CAMLprim value \
+ ocaml_bitstring_extract_fastpath_int##size##_##endian##_##signed \
+ (value strv, value offv, value rv) \
+ { \
+ type *ptr = (type *) ((void *) String_val (strv) + Int_val (offv)); \
+ type r; \
+ memcpy(&r, ptr, sizeof(r)); \
+ swap_##endian(size,r); \
+ rval(rv) = r; \
+ return rv; \
+ }
+
+fastpath2(32,be,unsigned,uint32_t,Int32_val)
+fastpath2(32,le,unsigned,uint32_t,Int32_val)
+fastpath2(32,ne,unsigned,uint32_t,Int32_val)
+fastpath2(32,be,signed,int32_t,Int32_val)
+fastpath2(32,le,signed,int32_t,Int32_val)
+fastpath2(32,ne,signed,int32_t,Int32_val)
+
+/* Special care needs to be taken on ARCH_ALIGN_INT64 platforms
+ (hppa and sparc in Debian). */
+
+#ifdef ARCH_ALIGN_INT64
+#include <caml/memory.h>
+#include <caml/alloc.h>
+#define fastpath3(size,endian,signed,type,rval) \
+ CAMLprim value \
+ ocaml_bitstring_extract_fastpath_int##size##_##endian##_##signed \
+ (value strv, value offv, value rv) \
+ { \
+ type *ptr = (type *) ((void *) String_val (strv) + Int_val (offv)); \
+ type r; \
+ memcpy(&r, ptr, sizeof(r)); \
+ swap_##endian(size,r); \
+ memcpy(Data_custom_val(rv), &r, sizeof(r)); \
+ return rv; \
+ }
+
+#else
+#define fastpath3 fastpath2
+#endif
+
+fastpath3(64,be,unsigned,uint64_t,Int64_val)
+fastpath3(64,le,unsigned,uint64_t,Int64_val)
+fastpath3(64,ne,unsigned,uint64_t,Int64_val)
+fastpath3(64,be,signed,int64_t,Int64_val)
+fastpath3(64,le,signed,int64_t,Int64_val)
+fastpath3(64,ne,signed,int64_t,Int64_val)
git.annexia.org / ocaml-bitstring.git / blobdiff