记一次把聊天表情包转成文件再还原的故事

#include <iostream>
#include <fstream>
#include <stdio.h>

int main(){
    FILE * in;
    FILE * out;
    if((in = fopen("xxx.hex", "rb"))==NULL){
        printf("打开输入文件失败\n");
        return -1;
    }
    if((out = fopen("yyy.gif","wb"))==NULL){
        printf("打开输出文件失败\n");
        return -1;
    }

//    fseek(in,0,SET_SEEK);
//    fseek(out,0,SEEK_END);
//    printf("移动到文件头\n");

    char * buf=(char *)malloc(2);
    rewind(out);
    int dec_val;
    char dec_vals[100];  
    int dec_index=0;
    int count=0;
    while((fgets(buf,2,in))!=NULL && count++>=0){
        dec_val = strtol(buf, NULL, 16);   // decimal
        dec_vals[dec_index]=dec_val*16;
        if((fgets(buf,2,in)!=NULL)){// 读第二个8字节
            dec_val = strtol(buf, NULL, 16);   // decimal
            dec_vals[dec_index]+=dec_val;
        }else{
            break;
        }
        dec_index++;
        if(dec_index==100){
            printf("before fwrite, pos=%ld\n", ftell(out));
            fseek(out, 0, SEEK_END);
            fwrite(dec_vals, 1, dec_index, out);
            dec_index=0;
            printf("after fwrite, pos=%ld\n", ftell(out));
        }
    }
    fwrite(dec_vals, 1, dec_index, out);

    fclose(in);
    fclose(out);
    return 1;
}