+/* 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; \
+ r = *ptr; \
+ 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)
+
+/* XXX This probably doesn't work on ARCH_ALIGN_INT64 platforms. */
+
+#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; \
+ r = *ptr; \
+ 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)
+
+fastpath2(64,be,unsigned,uint64_t,Int64_val)
+fastpath2(64,le,unsigned,uint64_t,Int64_val)
+fastpath2(64,ne,unsigned,uint64_t,Int64_val)
+fastpath2(64,be,signed,int64_t,Int64_val)
+fastpath2(64,le,signed,int64_t,Int64_val)
+fastpath2(64,ne,signed,int64_t,Int64_val)