packing.c

PA1688网络电话机全部源程序

    
   /****************************************************************** 
    
       iLBC Speech Coder ANSI-C Source Code 
    
       packing.c  
    
       Copyright (c) 2001, 
       Global IP Sound AB. 
       All rights reserved. 
    
   ******************************************************************/ 
    
   #include <math.h> 
   #include <stdlib.h> 
    
   #include "iLBC_define.h" 
   #include "constants.h" 
   #include "helpfun.h" 
   #include "string.h" 
    
   /*----------------------------------------------------------------* 
    *  splitting an integer into first most significant bits and  
    *  remaining least significant bits 
    *---------------------------------------------------------------*/ 
    
   void packsplit( 
       int *index,                 /* (i) the value to split */ 
       int *firstpart,             /* (o) the value specified by most  
                                          significant bits */ 
       int *rest,                  /* (o) the value specified by least  
                                          significant bits */ 
       int bitno_firstpart,    /* (i) number of bits in most  
                                          significant part */ 
       int bitno_total             /* (i) number of bits in full range  
                                          of value */ 
   ){ 
       int bitno_rest = bitno_total-bitno_firstpart; 
     
    
    
    
       *firstpart = *index>>(bitno_rest); 
       *rest = *index-(*firstpart<<(bitno_rest)); 
   } 
    
   /*----------------------------------------------------------------* 
    *  combining a value corresponding to msb's with a value  
    *  corresponding to lsb's 
    *---------------------------------------------------------------*/ 
    
   void packcombine(  
       int *index,                 /* (i/o) the msb value in the  
                                          combined value out */ 
       int rest,                   /* (i) the lsb value */ 
       int bitno_rest              /* (i) the number of bits in the  
                                          lsb part */ 
   ){ 
       *index = *index<<bitno_rest; 
       *index += rest; 
   } 
    
   /*----------------------------------------------------------------* 
    *  packing of bits into bitstream, i.e., vector of bytes 
    *---------------------------------------------------------------*/ 
    
   void dopack(  
       unsigned char **bitstream,  /* (i/o) on entrance pointer to place  
                                          in bitstream to pack new data,  
                                          on exit pointer to place in  
                                          bitstream to pack future  
                                          data */ 
       int index,                  /* (i) the value to pack */ 
       int bitno,                  /* (i) the number of bits that the  
                                          value will fit within */ 
       int *pos                /* (i/o) write position in the  
                                          current byte */ 
   ){ 
       int posLeft; 
        
       /* Clear the bits before starting in a new byte */ 
        
       if ((*pos)==0) { 
           **bitstream=0; 
       } 
    
       while (bitno>0) { 
            
           /* Jump to the next byte if end of this byte is reached*/ 
            
           if (*pos==8) { 
               *pos=0; 
               (*bitstream)++; 
               **bitstream=0; 
     
    
    
           } 
    
           posLeft=8-(*pos); 
    
           /* Insert index into the bitstream */ 
            
           if (bitno <= posLeft) { 
               **bitstream |= (unsigned char)(index<<(posLeft-bitno)); 
               *pos+=bitno; 
               bitno=0; 
           } else { 
               **bitstream |= (unsigned char)(index>>(bitno-posLeft)); 
                
               *pos=8; 
               index-=((index>>(bitno-posLeft))<<(bitno-posLeft)); 
                
               bitno-=posLeft; 
           } 
       } 
   } 
    
   /*----------------------------------------------------------------* 
    *  unpacking of bits from bitstream, i.e., vector of bytes 
    *---------------------------------------------------------------*/ 
    
   void unpack(  
       unsigned char **bitstream,  /* (i/o) on entrance pointer to  
                                          place in bitstream to  
                                          unpack new data from, on  
                                          exit pointer to place in  
                                          bitstream to unpack future  
                                          data from */ 
       int *index,                 /* (o) resulting value */ 
       int bitno,                  /* (i) number of bits used to  
                                          represent the value */ 
       int *pos                /* (i/o) read position in the  
                                          current byte */ 
   ){ 
       int BitsLeft; 
    
       *index=0; 
    
       while (bitno>0) { 
            
           /* move forward in bitstream when the end of the  
              byte is reached */ 
            
           if (*pos==8) { 
               *pos=0; 
               (*bitstream)++; 
           } 
    
           BitsLeft=8-(*pos); 
     
    
    
    
           /* Extract bits to index */ 
            
           if (BitsLeft>=bitno) { 
               *index+=((((**bitstream)<<(*pos)) & 0xFF)>>(8-bitno)); 
                
               *pos+=bitno; 
               bitno=0; 
           } else { 
                
               if ((8-bitno)>0) { 
                   *index+=((((**bitstream)<<(*pos)) & 0xFF)>> 
                       (8-bitno)); 
                   *pos=8; 
               } else { 
                   *index+=(((int)(((**bitstream)<<(*pos)) & 0xFF))<< 
                       (bitno-8)); 
                   *pos=8; 
               } 
               bitno-=BitsLeft; 
           } 
       } 
   }