Read .wav audio file format and save the raw data

gistfile1.c

/* 
 * Copyright (c) 2015 lalawue
 * 
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the MIT license. See LICENSE for details.
 */

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

static char* _read_file(const char* fileName) {
   FILE *fp = fopen(fileName, "rb");
   assert( fp );
   fseek(fp, 0, SEEK_END);
   long len = ftell(fp);
   char *data = (char*)malloc(len+1);
   assert(data);
   memset(data, 0, len+1);
   rewind(fp);
   fread(data, 1, len, fp);
   fclose(fp);
   return data;
}

int _is_chunk(char *b, char *s) {
   int i;
   for (i=0; i<strlen(s); i++)
      if (b[i] != s[i]) return 0;
   return 1;
}

unsigned int _to_dword(char *buf) {
   return *(unsigned int*)buf;
}

unsigned short _to_word(char *buf) {
   return *(unsigned short*)buf;
}

void _dump_buf(char *buf) {
   int i;
   for (i=0; i<32; i++) {
      if (i && (i%16==0)) {
         printf("\n");
      }
      printf("%02x ", buf[i]);
   }
   printf("\n");
}

void _save_file(char *fname, char *buf, int buf_len) {
   FILE *fp = fopen(fname, "wb");
   if (fp) {
      fwrite(buf, 1, buf_len, fp);
      fclose(fp);
   }
}

int main(int argc, char *argv[]) {
   if (argc < 3) {
      printf("%s wav_file save_file\n", argv[0]);
      return 0;
   }
   char *buf = _read_file(argv[1]);
   unsigned int size = 0;
   if (_is_chunk(buf, "RIFF")) {
      buf += 4;
      size = _to_dword(buf);
      buf += 4;
      printf("RIFF:%d\n", size);
   } else assert(0);
   if (_is_chunk(buf, "WAVE")) {
      buf += 4;
   } else assert(0);
   if (_is_chunk(buf, "fmt ")) {
      buf += 4;
      size = _to_dword(buf);
      buf += 4;
      printf("fmt :%d\n", size);
      /*  */
      printf("formatTag:%d\n", _to_word(buf));
      buf += 2;
      printf("channels:%d\n", _to_word(buf));
      buf += 2;
      printf("samplePerSec:%d\n", _to_dword(buf));
      buf += 4;
      printf("AvgBytePerSec:%d\n", _to_dword(buf));
      buf += 4;
      printf("BlockAlign:%d\n", _to_dword(buf));
      buf += 2;
      printf("BytePerSample:%d\n", _to_dword(buf));
      buf += 2;
      if (size == 18) {
         buf += 2;         
      }
   } else assert(0);
   if (_is_chunk(buf, "LIST")) {
      buf += 4;
      size = _to_dword(buf);
      buf += 4;
      printf("list :%d\n", size);
      buf += size;
   } else assert(0);
   if (_is_chunk(buf, "data")) {
      buf += 4;
      size = _to_dword(buf);
      buf += 4;
      printf("data :%d\n", size);
      _save_file(argv[2], buf, size);
   } else assert(0);
   return 0;
}