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228 lines
7.3 KiB
C
228 lines
7.3 KiB
C
#include "config.h"
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#include "getbits.h"
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/* Defined in gstgetbits_i386.s */
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extern unsigned long _gst_get1bit_i386(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_getbits_i386(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_getbits_fast_i386(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_showbits_i386(gst_getbits_t *gb, unsigned long bits);
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extern void _gst_flushbits_i386(gst_getbits_t *gb, unsigned long bits);
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extern void _gst_getbits_back_i386(gst_getbits_t *gb, unsigned long bits);
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/* Defined in gstgetbits_generic.c */
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extern unsigned long _gst_getbits_int_cb(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_get1bit_int(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_getbits_int(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_getbits_fast_int(gst_getbits_t *gb, unsigned long bits);
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extern unsigned long _gst_showbits_int(gst_getbits_t *gb, unsigned long bits);
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extern void _gst_flushbits_int(gst_getbits_t *gb, unsigned long bits);
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extern void _gst_getbits_back_int(gst_getbits_t *gb, unsigned long bits);
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unsigned long gst_getbits_nBitMask[] = {
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0x00000000, 0x80000000, 0xc0000000, 0xe0000000,
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0xf0000000, 0xf8000000, 0xfc000000, 0xfe000000,
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0xff000000, 0xff800000, 0xffc00000, 0xffe00000,
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0xfff00000, 0xfff80000, 0xfffc0000, 0xfffe0000,
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0xffff0000, 0xffff8000, 0xffffc000, 0xffffe000,
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0xfffff000, 0xfffff800, 0xfffffc00, 0xfffffe00,
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0xffffff00, 0xffffff80, 0xffffffc0, 0xffffffe0,
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0xfffffff0, 0xfffffff8, 0xfffffffc, 0xfffffffe};
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unsigned long _getbits_masks[] = {
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0x00000000,
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0x00000001, 0x00000003, 0x00000007, 0x0000000f,
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0x0000001f, 0x0000003f, 0x0000007f, 0x000000ff,
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0x000001ff, 0x000003ff, 0x000007ff, 0x00000fff,
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0x00001fff, 0x00003fff, 0x00007fff, 0x0000ffff,
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0x0001ffff, 0x0003ffff, 0x0007ffff, 0x000fffff,
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0x001fffff, 0x003fffff, 0x007fffff, 0x00ffffff,
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0x01ffffff, 0x03ffffff, 0x07ffffff, 0x0fffffff,
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0x1fffffff, 0x3fffffff, 0x7fffffff, 0xffffffff,
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};
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#ifdef HAVE_LIBMMX
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unsigned long _getbits_64_minus_index[] = {
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64,63,62,61,60,59,58,57,56,55,54,53,52,51,50,49,48,47,46,45,44,43,42,41,
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40,39,38,37,36,35,34,33,32,31,30,29,28,27,26,25,24,23,22,21,20,19,18,17,
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16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1 };
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/* this routine taken from Intel AppNote AP-527:
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"Using MMX[tm] Instructions to Get Bits From a Data Stream"
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written in C with libmmx to *closely* mimic Intel's ASM implementation
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this isn't as cycle-efficient, due to the simple fact that I must call
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emms() at the end. all state must be kept in *gb, not in registers */
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unsigned long _gst_getbits_mmx(gst_getbits_t *gb,unsigned long bits) {
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signed long remaining;
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unsigned long result;
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/* NOTE: this is a code-size optimization Intel seems to have missed!
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according to the MMX Programmer's Reference Manual, Chapter 5,
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neither movd nor movq have any effect on the flags. that means you
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can put them before the sub and jl in their code, which I've done
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symbolically in this C code. gcc is probably going to lose horribly,
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I'll do an inline asm version later. I've a point to prove ;-) */
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/* find the right shift value, put it in mm3 */
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movd_m2r(_getbits_64_minus_index[bits],mm3);
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/* load the current quadword into mm0 */
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movq_m2r(gb->qword,mm0);
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/* copy it to mm2 */
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movq_r2r(mm0,mm2);
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remaining = gb->bits - bits;
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if (remaining <= 0) {
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unsigned long dword1,dword2;
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/* shift the pointer by 64 bits (8 bytes) */
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gb->ptr += 8;
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/* add 64 to bits remaining, to bring it positive */
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remaining += 64;
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/* grab the first 32 bits from the buffer and swap them around */
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dword1 = swab32(*(gb->ptr-8));
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/* grab the second 32 bits, swap */
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dword2 = swab32(*(gb->ptr-4));
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/* put second dword in mm4 */
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movd_m2r(dword2,mm4);
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/* shift mm2 over to make room for new bits */
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psrlq_r2r(mm3,mm2);
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/* put first dword in mm1 */
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movd_m2r(dword1,mm1);
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/* shift second dword up 32 bits */
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psrlq_i2r(32,mm4);
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/* put the shift counter in mm3 */
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movd_m2r(remaining,mm3);
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/* combine the swapped data in mm4 */
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por_r2r(mm1,mm4);
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/* save off the bits in mm4 to mm0 */
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movq_r2r(mm4,mm0);
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/* get the new low-order bits in mm4, shifted by 'mm3' */
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psrlq_r2r(mm3,mm4);
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/* save off new remaining bits */
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gb->bits = remaining;
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/* combine bits into mm2 */
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por_r2r(mm2,mm4);
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/* save off the result */
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movd_r2m(mm2,result);
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/* get rid of the bits we just read */
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psllq_r2r(mm1,mm0);
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/* save off mm0 */
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movq_r2m(mm0,gb->qword);
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/* finished with MMX */
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emms();
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/* we have what we came for */
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return(result);
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} else {
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/* load the number of bits requested into mm1 */
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movd_m2r(bits,mm1);
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/* shift the quadword in mm2 by 'mm3' bits */
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psrlq_r2r(mm3,mm2);
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/* update the number of valid bits */
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gb->bits = remaining;
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/* save off the remaining bits */
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movd_r2m(mm2,result);
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/* discard those bits in mm0 */
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psllq_r2r(mm1,mm0);
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/* save off mm0 */
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movq_r2m(mm0,gb->qword);
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/* finished with MMX */
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emms();
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/* we have what we came for */
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return(result);
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}
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}
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#endif /* HAVE_LIBMMX */
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unsigned long _gst_getbyte(gst_getbits_t *gb, unsigned long bits) {
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return *gb->ptr++;
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}
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/* initialize the getbits structure with the proper getbits func */
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void gst_getbits_init(gst_getbits_t *gb, GstGetbitsCallback callback, void *data) {
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gb->ptr = NULL;
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gb->bits = 0;
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gb->callback = callback;
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gb->data = data;
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#ifdef HAVE_LIBMMX
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if (1) {
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gb->getbits = _gst_getbits_mmx;
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/* gb->backbits = _gst_getbits_back_mmx; */
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/* gb->backbytes = _gst_getbits_byteback_mmx; */
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/* printf("gstgetbits: using MMX optimized versions\n"); */
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} else
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#endif /* HAVE_LIBMMX */
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{
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if (gb->callback) {
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gb->getbits = _gst_getbits_int_cb;
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gb->showbits = _gst_showbits_int;
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gb->flushbits = _gst_flushbits_int;
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gb->backbits = _gst_getbits_back_int;
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/* printf("gstgetbits: using callback versions\n"); */
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}
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else {
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#ifdef HAVE_CPU_I386
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gb->get1bit = _gst_get1bit_i386;
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gb->getbits = _gst_getbits_i386;
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gb->getbits_fast = _gst_getbits_fast_i386;
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gb->getbyte = _gst_getbyte;
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gb->show1bit = _gst_showbits_i386;
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gb->showbits = _gst_showbits_i386;
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gb->flushbits = _gst_flushbits_i386;
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gb->backbits = _gst_getbits_back_i386;
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/* printf("gstgetbits: using i386 optimized versions\n"); */
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#else
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gb->get1bit = _gst_get1bit_int;
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gb->getbits = _gst_getbits_int;
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gb->getbits_fast = _gst_getbits_fast_int;
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gb->getbyte = _gst_getbyte;
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gb->show1bit = _gst_showbits_int;
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gb->showbits = _gst_showbits_int;
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gb->flushbits = _gst_flushbits_int;
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gb->backbits = _gst_getbits_back_int;
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/* printf("gstgetbits: using normal versions\n"); */
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#endif
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}
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}
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}
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/* set up the getbits structure with a new buffer */
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void gst_getbits_newbuf(gst_getbits_t *gb,unsigned char *buffer, unsigned long len) {
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gb->ptr = buffer;
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gb->endptr = buffer+len;
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gb->bits = 0;
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#ifdef HAVE_LIBMMX
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/* gb->qword = 0; */
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#endif /* HAVE_LIBMMX */
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}
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static gboolean
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plugin_init (GModule *module, GstPlugin *plugin)
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{
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gst_plugin_set_longname (plugin, "Accelerated routines for getting bits from a data stream");
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return TRUE;
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}
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GstPluginDesc plugin_desc = {
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GST_VERSION_MAJOR,
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GST_VERSION_MINOR,
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"gstgetbits",
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plugin_init
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};
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