tty_char.c

完整的EVRC压缩解压缩算法源码,通过C-C++编译后可以运行!

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/*                                                                   */
/*-------------------------------------------------------------------*/


/*********************************************************************
*   get_tty_state()
*
**********************************************************************/
#include <stdio.h>
#include "typedef.h"
#include "tty.h"
#include "basic_op.h"


#define MAX_CHAR_LEN        72
#define MIN_CHAR_LEN        51
#define BAD_DITS_PER_CHAR   22

Word16 get_tty_char(
    Word16   *tty_char,              /* (o): TTY character               */
    Word16   tty_bit_hist[],         /* (i): TTY bit history buffer      */
    Word16   tty_bit_len_hist[]      /* (i): TTY bit length history buffer */
)
{
    Word16   i;
    Word16   char_len;
    Word16   tmp_tty_char;


    /* Check start bit, stop bit and bit before start bit */
                                                                
    if( sub(tty_bit_hist[MEM_BIT_IDX],LOGIC_0) == 0
        || sub(tty_bit_hist[START_BIT_IDX],LOGIC_0) != 0
        || sub(tty_bit_hist[STOP_BIT_IDX],LOGIC_1) != 0
    )
    {

        return(0);
    }
    else
    {
        tmp_tty_char = 0;                                       
        for( i=STOP_BIT_IDX-1 ; i > START_BIT_IDX ; i-- )
        {
                                                                
            if( sub(tty_bit_hist[i],LOGIC_0) == 0
                || sub(tty_bit_hist[i],LOGIC_1) == 0 )
            {
                tmp_tty_char = shl(tmp_tty_char,1);
                tmp_tty_char = add(tmp_tty_char,tty_bit_hist[i]);
            }
            else
            {

                return(0);
            }
        }
    }

    /* Check the character length */

    char_len = 0;                                               
    for( i= START_BIT_IDX ; i < STOP_BIT_IDX ; i++ )
    {
        char_len = add(char_len,tty_bit_len_hist[i]);
    }

                                                                
    if( sub(char_len,MAX_CHAR_LEN) > 0 )
    {


        return(0);
    }
                                                                
    if( sub(char_len,MIN_CHAR_LEN) < 0 )
    {


        return(0);
    }

    /* Check the total # of bad dits per character */

    if( sub(tty_bit_len_hist[MEM_BIT_IDX],BAD_DITS_PER_CHAR) > 0 )
    {
        tty_bit_hist[MEM_BIT_IDX] = LOGIC_0;                    
        tty_bit_len_hist[MEM_BIT_IDX] = 0;                      


        return(0);
    }

    /*
    *  Update the bit and length buffers, wiping out all of
    *  info that was used to form this character.
    */

    tty_bit_len_hist[MEM_BIT_IDX] = 0;                          

    for( i=0 ; i <= STOP_BIT_IDX ; i++ )
    {
        tty_bit_hist[i] = UNKNOWN;                              
    }

    *tty_char = tmp_tty_char;                                   


    return(1);
}