impeg2d_bitstream.c revision aed24eee7ddfc93f1436b0c1679431bd286879b4
1/****************************************************************************** 2 * 3 * Copyright (C) 2015 The Android Open Source Project 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ***************************************************************************** 18 * Originally developed and contributed by Ittiam Systems Pvt. Ltd, Bangalore 19*/ 20/*****************************************************************************/ 21/* */ 22/* File Name : impeg2d_bitstream.c */ 23/* */ 24/* Description : This file contains all the necessary examples to */ 25/* establish a consistent use of Ittiam C coding */ 26/* standards (based on Indian Hill C Standards) */ 27/* */ 28/* List of Functions : <List the functions defined in this file> */ 29/* */ 30/* Issues / Problems : None */ 31/* */ 32/* Revision History : */ 33/* */ 34/* DD MM YYYY Author(s) Changes (Describe the changes made) */ 35/* 10 01 2005 Ittiam Draft */ 36/* */ 37/*****************************************************************************/ 38#include <stdlib.h> 39 40#include "iv_datatypedef.h" 41#include "impeg2_defs.h" 42#include "impeg2_platform_macros.h" 43#include "impeg2_macros.h" 44#include "impeg2d_bitstream.h" 45 46#define BIT(val,bit) (UWORD16)(((val) >> (bit)) & 0x1) 47/****************************************************************************** 48* 49* Function Name : impeg2d_bit_stream_init 50* 51* Description : This is a Bitstream initialising function. 52* Arguments : 53* stream : Pointer to the Bitstream. 54* byteBuf : Address of the buffer 55* size : Size of the buffer in bytes 56* 57* Values Returned : None 58*******************************************************************************/ 59void impeg2d_bit_stream_init(stream_t *ps_stream, 60 UWORD8 *pu1_byte_buf, 61 UWORD32 u4_max_offset) 62{ 63 UWORD8 *pu1_byte_buff; 64 UWORD32 *pu4_word_buf; 65 size_t u4_byte_addr; 66 UWORD32 u4_temp1,u4_temp2; 67 68 /* Set parameters of the stream structure.Associate the structure with 69 the file */ 70 ps_stream->pv_bs_buf = pu1_byte_buf; 71 ps_stream->u4_offset = 0; 72 73 /* Take care of unaligned address and create 74 nearest greater aligned address */ 75 pu1_byte_buff = (UWORD8 *)pu1_byte_buf; 76 u4_byte_addr = (size_t)pu1_byte_buff; 77 78 if((u4_byte_addr & 3) == 1) 79 { 80 u4_temp1 = ((UWORD32)(*pu1_byte_buff++)) << 8; 81 u4_temp1 += ((UWORD32)(*pu1_byte_buff++)) << 16; 82 u4_temp1 += ((UWORD32)(*pu1_byte_buff++)) << 24; 83 84 pu4_word_buf = (UWORD32 *)pu1_byte_buff; 85 86 ps_stream->u4_offset = 8; 87 } 88 else if((u4_byte_addr & 3) == 2) 89 { 90 u4_temp1 = ((UWORD32)(*pu1_byte_buff++)) << 16; 91 u4_temp1 += ((UWORD32)(*pu1_byte_buff++)) << 24; 92 93 pu4_word_buf = (UWORD32 *)pu1_byte_buff; 94 95 ps_stream->u4_offset = 16; 96 } 97 else if((u4_byte_addr & 3) == 3) 98 { 99 u4_temp1 = (((UWORD32)(*pu1_byte_buff++)) << 24); 100 101 pu4_word_buf = (UWORD32 *)pu1_byte_buff; 102 103 ps_stream->u4_offset = 24; 104 } 105 else 106 { 107 pu4_word_buf = (UWORD32 *)pu1_byte_buff; 108 109 u4_temp1 = *pu4_word_buf++; 110 ps_stream->u4_offset = 0; 111 } 112 113 /* convert the endian ness from Little endian to Big endian so that bits 114 are in proper order from MSB to LSB */ 115 CONV_LE_TO_BE(u4_temp2,u4_temp1) 116 117 /* Read One more word for buf nxt */ 118 u4_temp1 = *pu4_word_buf++; 119 ps_stream->u4_buf = u4_temp2; 120 121 CONV_LE_TO_BE(u4_temp2,u4_temp1) 122 123 ps_stream->u4_buf_nxt = u4_temp2; 124 125 ps_stream->pu4_buf_aligned = pu4_word_buf; 126 127 128 ps_stream->u4_max_offset = (u4_max_offset << 3) + ps_stream->u4_offset; 129 130 return; 131} 132 133 134 135/****************************************************************************** 136* 137* Function Name : impeg2d_bit_stream_get_bit 138* 139* Description : This is a Bitstream processing function. It reads the 140* bit currently pointed by the bit pointer in the buffer and 141* advances the pointer by one. 142* Arguments : 143* stream : Pointer to the Bitstream. 144* 145* Values Returned : The bit read(0/1) 146*******************************************************************************/ 147INLINE UWORD8 impeg2d_bit_stream_get_bit(stream_t *ps_stream) 148{ 149 UWORD32 u4_bit,u4_offset,u4_temp; 150 UWORD32 u4_curr_bit; 151 152 u4_offset = ps_stream->u4_offset; 153 u4_curr_bit = u4_offset & 0x1F; 154 u4_bit = ps_stream->u4_buf; 155 156 /* Move the current bit read from the current word to the 157 least significant bit positions of 'c'.*/ 158 u4_bit >>= BITS_IN_INT - u4_curr_bit - 1; 159 160 u4_offset++; 161 162 /* If the last bit of the last word of the buffer has been read update 163 the currrent buf with next, and read next buf from bit stream buffer */ 164 if (u4_curr_bit == 31) 165 { 166 ps_stream->u4_buf = ps_stream->u4_buf_nxt; 167 u4_temp = *(ps_stream->pu4_buf_aligned)++; 168 169 CONV_LE_TO_BE(ps_stream->u4_buf_nxt,u4_temp) 170 } 171 ps_stream->u4_offset = u4_offset; 172 173 return (u4_bit & 0x1); 174} 175/****************************************************************************** 176* 177* Function Name : impeg2d_bit_stream_flush 178* 179* Description : This is a Bitstream processing function. It 180* advances the bit and byte pointers appropriately 181* 182* Arguments : 183* ctxt : Pointer to the Bitstream. 184* numBits : No of bits to be read 185* 186* Values Returned : None 187*******************************************************************************/ 188INLINE void impeg2d_bit_stream_flush(void* pv_ctxt, UWORD32 u4_no_of_bits) 189{ 190 stream_t *ps_stream = (stream_t *)pv_ctxt; 191 192 FLUSH_BITS(ps_stream->u4_offset,ps_stream->u4_buf,ps_stream->u4_buf_nxt,u4_no_of_bits,ps_stream->pu4_buf_aligned) 193 return; 194} 195/****************************************************************************** 196* 197* Function Name : impeg2d_bit_stream_flush_to_byte_boundary 198* 199* Description : This is a Bitstream processing function.It advances 200* the bit and byte pointers to next byte boundary 201* 202* Arguments : 203* stream : Pointer to the Bitstream. 204* NoOfBits : No of bits to be read 205* 206* Values Returned : The bits read (upto 32 bits maximum) starting from the 207* least significant bit and going towards most significant 208* bit in the order of their occurence. 209*******************************************************************************/ 210INLINE void impeg2d_bit_stream_flush_to_byte_boundary(void* pv_ctxt) 211{ 212 UWORD8 u1_bit_offset; 213 stream_t *ps_stream = (stream_t *)pv_ctxt; 214 215 u1_bit_offset = (ps_stream->u4_offset) & 0x7; 216 217 218 /* if it is not byte aligned make it byte aligned*/ 219 if(u1_bit_offset != 0) 220 { 221 impeg2d_bit_stream_flush(ps_stream,(8 - u1_bit_offset)); 222 } 223 224 225 226} 227 228 229/****************************************************************************** 230* 231* Function Name : ibits_next 232* 233* Description : This is a Bitstream processing function.It gets the 234* specified number of bits from the buffer without 235* altering the current pointers. It is used mainly to 236* check for some specific pattern of bits like start 237* code. This is equivalent to next_bits() function 238* defined in MPEG-4 Visual Standard Definition of functions 239* 240* Arguments : 241* ctxt : Pointer to the Bitstream. 242* numBits : No of bits to be read 243* 244* Values Returned : The bits read (upto 32 bits maximum) starting from the 245* least significant bit and going towards most significant 246* bit in the order of their occurence. 247*******************************************************************************/ 248INLINE UWORD32 impeg2d_bit_stream_nxt( stream_t *ps_stream, WORD32 i4_no_of_bits) 249{ 250 UWORD32 u4_bits,u4_offset,u4_temp; 251 UWORD8 u4_bit_ptr; 252 253 ASSERT(i4_no_of_bits > 0); 254 255 u4_offset = ps_stream->u4_offset; 256 u4_bit_ptr = u4_offset & 0x1F; 257 u4_bits = ps_stream->u4_buf << u4_bit_ptr; 258 259 u4_bit_ptr += i4_no_of_bits; 260 if(32 < u4_bit_ptr) 261 { 262 /* Read bits from the next word if necessary */ 263 u4_temp = ps_stream->u4_buf_nxt; 264 u4_bit_ptr &= (BITS_IN_INT - 1); 265 266 u4_temp = (u4_temp >> (BITS_IN_INT - u4_bit_ptr)); 267 268 /* u4_temp consists of bits,if any that had to be read from the next word 269 of the buffer.The bits read from both the words are concatenated and 270 moved to the least significant positions of 'u4_bits'*/ 271 u4_bits = (u4_bits >> (32 - i4_no_of_bits)) | u4_temp; 272 } 273 else 274 { 275 u4_bits = (u4_bits >> (32 - i4_no_of_bits)); 276 } 277 278 return (u4_bits); 279} 280/****************************************************************************** 281* 282* Function Name : impeg2d_bit_stream_get 283* 284* Description : This is a Bitstream processing function. It reads a 285* specified number of bits from the current bit 286* position and advances the bit and byte pointers 287* appropriately 288* Arguments : 289* ctxt : Pointer to the Bitstream. 290* numBits : No of bits to be read 291* 292* Values Returned : The bits read (upto 32 bits maximum) starting from the 293* least significant bit and going towards most significant 294* bit in the order of their occurence. 295*******************************************************************************/ 296 297INLINE UWORD32 impeg2d_bit_stream_get(void* pv_ctxt, UWORD32 u4_num_bits) 298{ 299 UWORD32 u4_next_bits = impeg2d_bit_stream_nxt(pv_ctxt, u4_num_bits); 300 impeg2d_bit_stream_flush(pv_ctxt, u4_num_bits); 301 return(u4_next_bits); 302} 303 304 305 306/****************************************************************************** 307* 308* Function Name : impeg2d_bit_stream_num_bits_read 309* 310* Description : This is a Bitstream processing function. It reads a 311* specified number of bits from the current bit 312* position and advances the bit and byte pointers 313* appropriately 314* Arguments : 315* ctxt : Pointer to the Bitstream. 316* numBits : No of bits to be read 317* 318* Values Returned : The bits read (upto 16 bits maximum) starting from the 319* least significant bit and going towards most significant 320* bit in the order of their occurence. 321*******************************************************************************/ 322INLINE UWORD32 impeg2d_bit_stream_num_bits_read(void* pv_ctxt) 323{ 324 stream_t *u4_no_of_bitsstream = (stream_t *)pv_ctxt; 325 size_t u4_temp; 326 UWORD32 u4_bits_read; 327 u4_temp = (size_t)(u4_no_of_bitsstream->pv_bs_buf); 328 u4_temp &= 0x3; 329 u4_bits_read = (u4_no_of_bitsstream->u4_offset - (u4_temp << 3)); 330 331 return(u4_bits_read); 332 333} 334 335 336