streamhandle.c

来自「一个264程序在NS2下面的仿真程序。非常好用」· C语言 代码 · 共 86 行

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include "global.h"

read_bits_result readbits(unsigned char *pt, int bitpos, int length){
  int read,value=0,thisbit,bytepos=0;
  unsigned char byte;
  float potencia;
  read_bits_result result;

  byte = *pt;

  for(read=0;read<length;read++){
    
    potencia = pow(2.0,length-1-read);
    thisbit = (( byte >> 7-bitpos ) & 1) * potencia;
    value = value + thisbit;
    bitpos++;
    if (bitpos == 8){
      bytepos++;
      pt++;
      bitpos = 0;
      byte = *pt;
    }   
  }

  result.value = value;
  result.bytesread = bytepos;
  result.bitpos = bitpos;
   
  return result;
}

read_bits_result uvlc(unsigned char *pt, int bitpos){ 
  int leadingzerobits=0, thisbit, flag, bytepos = 0, length;
  unsigned char byte;
  read_bits_result rbres1,rbres2;
  div_t half;

  byte = *pt;
  flag = 0;

  while(flag == 0) {
  
    thisbit = ( byte >> ( 7 - bitpos)) & 1;
    bitpos++;
    printf(" Byte: %x\tBytepos: %d\tBitpos: %d\tThisbit: %d\n", byte, bytepos,bitpos,thisbit);
    if (thisbit == 0){
      leadingzerobits++;
      if ( bitpos > 7 ){
        bitpos = 0;
        bytepos++; 
        pt++;

        byte = *pt;
      }
    } else {
      flag = 1;
      if (bitpos > 7){       
        bitpos = 0;
        bytepos++;
        pt++;
      }

      printf("Bytepos: %d\tBitpos: %d\tLeading zero bits: %d\n",bytepos,\
	bitpos,leadingzerobits);
      rbres1 = readbits(pt,bitpos,leadingzerobits);
      printf("Read bits value: %d\tNew byte pos: %d\t New bit pos: %d\n",\
	rbres1.value,rbres1.bytesread,rbres1.bitpos);
      length = 1 + 2 * leadingzerobits;
      half = div(length,2);
      rbres2.value = pow(2.0,half.quot) - 1 + rbres1.value;
      rbres2.bytesread = bytepos + rbres1.bytesread;
      rbres2.bitpos = rbres1.bitpos;
      printf("UVLC code: %d\tNew bytes read: %d\tNew bit pos: %d\n",\
	rbres2.value,rbres2.bytesread,rbres2.bitpos);   
    }
  }

  return rbres2;
}