创建输出文件时更改 .wav 文件头中的字节

Question

我正在尝试更改 .wav 文件 header 中与文件大小相对应的字节，即第 4 个和第 40 个字节。目前，我正在将整个 header 复制到缓冲区，尝试在那里编辑它，然后将其写入目标文件，但它似乎不起作用。

int main(int argc, char * argv []){

    int delay = atoi(argv[1]);
    FILE * source = fopen(argv[2], "rb");
    FILE * destination = fopen(argv[3], "wb");

    void * header = malloc(44); // size of a wav file header
    fread(header, sizeof(header), 1, source);

    // my attempt at changing the 4nd and 40th bytes
    sizeptr1 = (unsigned int *)(header + 4);
    sizeptr2 = (unsigned int *)(header + 40);
    *sizeptr1 = *sizeptr1 + delay;
    *sizeptr2 = *sizeptr2 + delay
    fwrite(header, sizeof(header), 1, destination);

    return 0;
}

更改这些字节并将新 header 写入输出文件的最有效方法是什么？

Answer 1

如果您确定要更改哪些字节，则字节数组是最简单的。例如，第 4 个字节位于 buffer[3]。

#include <stdio.h>
#include <stdlib.h>

#define BUFFSIZE    1024
#define HEADSIZE    44

int main(int argc, char * argv []) {
    int delay;
    size_t bytes;
    FILE * source = NULL;
    FILE * destination = NULL;
    unsigned char buffer[BUFFSIZE];

    if (argc < 4) return 0;         // check enough args
    delay = atoi(argv[1]);
    if (NULL == (source = fopen(argv[2], "rb")))
        return 0;
    if (NULL == (destination = fopen(argv[3], "wb")))
        return 0;

    // copy & alter buffer
    if (HEADSIZE != fread(buffer, 1, HEADSIZE, source))
        return 0;
    buffer[4] = delay;
    buffer[40] = delay;
    if (HEADSIZE != fwrite(buffer, 1, HEADSIZE, destination))
        return 0;

    // copy rest of file
    while ((bytes = fread(buffer, 1, BUFFSIZE, source)) != 0) {
        if (bytes != fwrite(buffer, 1, bytes, destination))
            return 0;
    }
    if (0 == fclose(destination))
        printf("Success\n");
    fclose (source);
    return 0;
}