freq.c

来自「Arithmetic coding source code. A very go」· C语言 代码 · 共 30 行

#include <stdio.h>
#include "mytypes.h"
#include "code.h"

void
freq_count(FILE *f, FILE *out_file) {
    #define BUFF_SIZE 4096

    uint block[BUFF_SIZE], b;
    uint n = 0, max_symbol=0;

    uint *A, *p;
 
    allocate(A , uint, MAX_SYMBOL);
    for(p = A ; p < A + MAX_SYMBOL ; p++)
        *p = 0;

    while ((b=fread(block,sizeof(uint),BUFF_SIZE, f)) > 0)
        for(p = block ; p < block + b ; p++) {
            *p = *p + 1; // add one so zeroes work
            CHECK_SYMBOL_RANGE(*p);
            if (A[*p] == 0) n++;
            if (*p > max_symbol) max_symbol = *p;
            A[*p]++;
        }

    fwrite(&max_symbol,sizeof(uint),1,out_file);
    fwrite(A+1,sizeof(uint),max_symbol,out_file);
}