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/* Bitstring library.
* Copyright (C) 2008 Red Hat Inc., Richard W.M. Jones
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version,
* with the OCaml linking exception described in COPYING.LIB.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* $Id: bitstring.ml 146 2008-08-20 16:58:33Z richard.wm.jones $
*/
/* This file contains hand-coded, optimized C implementations of
* certain very frequently used functions.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <byteswap.h>
#include <caml/mlvalues.h>
#include <caml/fail.h>
/* 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)
#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)
/* 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) \
{ \
CAMLparam3(strv, offv, rv); \
type *ptr = (type *) ((void *) String_val (strv) + Int_val (offv)); \
type r; \
r = *ptr; \
swap_##endian(size,r); \
CAMLreturn(caml_copy_int64(r)); \
}
#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)
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