cfs_tool.c

基于nucleus实时操作系统的webserver源代码

*                                                                       
*       *stream                 Pointer to BIT_FILE structure.   
*                               This structure holds all the     
*                               related to the input file to be  
*                               compressed.                      
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       None
*                                                                       
*************************************************************************/
static VOID CFS_Init_Arithmetic_Decoder(WS_BIT_FILE *stream)
{
    INT i;

    CFS_Code = 0;
    for ( i = 0 ; i < 16 ; i++ )
    {
        CFS_Code <<= 1;
        CFS_Code = (UINT16)(CFS_Code + (CFS_Input_Bit(stream)));
    }
    CFS_Low = 0;
    CFS_High = 0xffff;
}

/************************************************************************
*                                                                       
* FUNCTION                                                              
*                                                                       
*       CFS_Remove_Symbol_From_Stream                                        
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       Just figuring out what the present symbol is                     
*       doesn't remove it from the input bit stream. After               
*       the character has been decoded, this routine has to              
*       be called to remove it from the input stream.                    
*                                                                       
* INPUTS                                                                
*                                                                       
*       *stream                 Pointer to BIT_FILE structure.   
*                               This structure holds all the     
*                               related to the input file to be  
*                               compressed.                      
*       *s                      Pointer to the SYMBOL structure  
*                               that contains the converted      
*                               symbol information.              
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       None
*                                                                       
*************************************************************************/
static VOID CFS_Remove_Symbol_From_Stream(WS_BIT_FILE *stream, WS_SYMBOL *s)
{
    INT32 range;
    
    /*
     * First, the range is expanded to account for the symbol removal.
     */
    range = (INT32)( CFS_High - CFS_Low ) + 1;
    CFS_High = (UINT16)(CFS_Low + (UINT16)((range * s->high_count) / s->scale - 1));
    CFS_Low = (UINT16)(CFS_Low + (UINT16)((range * s->low_count) / s->scale));
    /*
     * Next, any possible bits are shipped out.
     */
    while(1)
    {
    /*
    * If the MSDigits match, the bits will be shifted out.
        */
        if ( ( CFS_High & 0x8000 ) == ( CFS_Low & 0x8000 ) )
        {
        }
        /*
        * Else, if underflow is threatening, shift out the 2nd MSDigit.
        */
        else if ( (CFS_Low & 0x4000) == 0x4000  && (CFS_High & 0x4000) == 0 )
        {
            CFS_Code ^= 0x4000;
            CFS_Low   &= 0x3fff;
            CFS_High  |= 0x4000;
        } else
        /*
        * Otherwise, nothing can be shifted out, so I return.
        */
            return;
        
        CFS_Low <<= 1;
        CFS_High <<= 1;
        CFS_High |= 1;
        CFS_Code <<= 1;
        CFS_Code = (UINT16)(CFS_Code + CFS_Input_Bit(stream));
    }
}

/************************************************************************
*                                                                       
* FUNCTION                                                              
*                                                                       
*       CFS_Open_Output_Bit_File                                                
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       This function initializes the Output Bit File that is to be      
*       compressed or decompressed.                                                                                                     
*                                                                       
* INPUTS                                                                
*                                                                       
*       *bitfile                Pointer to structure that holds all 
*                               information about the file.                        
*       *buf                    Output Bit Buffer to be opened.  
*                                                                       
* OUTPUTS                                                               
*                                                                       
*      None
*                                                                       
*************************************************************************/
static VOID CFS_Open_Output_Bit_File( WS_BIT_FILE * bit_file, CHAR *buf )
{
    bit_file->fstart = buf;
    bit_file->cur_pos = buf;
    bit_file->length = 0;
    bit_file->rack = 0;
    bit_file->mask = 0x80;
    bit_file->pacifier_counter = 0;
}

/************************************************************************
*                                                                       
* FUNCTION                                                              
*                                                                       
*       CFS_Open_Input_Bit_File                                                 
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       This function initializes the Input Bit File that is to be       
*       compressed or decompressed.                                                                                                     
*                                                                       
* INPUTS                                                                
*                                                                       
*       *bitfile                Pointer to structure that        
*                               holds all information about      
*                               the file.                        
*       *buf                    Input Bit Buffer to be opened.   
*       length                  Input Bit Buffer length.         
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       NU_SUCCESS
*                                                                       
*************************************************************************/
static VOID CFS_Open_Input_Bit_File( WS_BIT_FILE *bit_file, CHAR *buf, INT32 length)
{
    bit_file->fstart = buf;
    bit_file->cur_pos = buf;
    bit_file->length = length;
    bit_file->rack = 0;
    bit_file->mask = 0x80;
    bit_file->pacifier_counter = 0;
}

/************************************************************************
*                                                                       
* FUNCTION                                                              
*                                                                       
*       CFS_Close_Output_Bit_File                                               
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       Function that closes the bit file and then flushes the buffer.                                                                
*                                                                       
* INPUTS                                                                
*                                                                       
*       *bitfile                Pointer to structure that holds all 
*                               information about the file.                        
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       None
*                                                                       
*************************************************************************/
static VOID CFS_Close_Output_Bit_File(WS_BIT_FILE *bit_file)
{
    if ( bit_file->mask != 0x80 )
        if ( CFS_Buf_Putc( (unsigned int)bit_file->rack, bit_file ) != bit_file->rack )
            CFS_Fatal_Error( "Fatal error in CFS_Close_Output_Bit_File!\n" );
}

/************************************************************************
*                                                                       
* FUNCTION                                                              
*                                                                       
*       CFS_Output_Bit                                                        
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       Function to output a specific bit into the file stream.          
*                                                                       
* INPUTS                                                                
*                                                                       
*       *bit_file               Pointer to structure that holds all 
*                               information about the file.                        
*       bit                     Bit to be outputted              
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       None
*                                                                       
*************************************************************************/
static VOID CFS_Output_Bit(WS_BIT_FILE *bit_file, INT bit)
{
    if ( bit )
        bit_file->rack |= bit_file->mask;
    bit_file->mask >>= 1;
    if ( bit_file->mask == 0 )
    {
        if ( CFS_Buf_Putc( (unsigned int)bit_file->rack, bit_file ) != bit_file->rack )
            CFS_Fatal_Error( "Fatal error in CFS_Output_Bit!\n" );
        else
            if ( ( bit_file->pacifier_counter++ & CFS_PACIFIER_COUNT ) == 0 );
            /*null statement*/
            bit_file->rack = 0;
            bit_file->mask = 0x80;
    }
}

/************************************************************************
*                                                                       
* FUNCTION                                                              
*                                                                       
*       CFS_Output_Bits                                                       
*                                                                       
* DESCRIPTION                                                           
*