Reverse .wav file in C, any error in there? - c

Question

I've been making the program from CS50'x about reversing the .WAV files. Seems to work fine, however the cs50's check finds an error. Don't know where it is, the code seems to be alright and there I can't find any problem.
I tried to change 'i' - iterator in for-loop but when set as = infile_size - block_size the file won't be converted / reversed.
My code below:
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include "wav.h"
int check_format(WAVHEADER header);
int get_block_size(WAVHEADER header);
int main(int argc, char *argv[])
{
// Ensure proper usage
// TODO #1
// check if command-line arguments = argv[0], argv[1], argv[2] = 3 in sum
if (argc != 3)
{
if (argc < 3)
{
printf("not enough command-line args\n");
}
else
{
printf("too much command-line args\n");
}
return 1;
}
// remember filenames
char *infile = argv[1];
char *outfile = argv[2];
// open input file for reading
FILE *inptr = fopen(infile, "r");
if (inptr == NULL)
{
printf("could not open the infile\n");
return 1;
}
// read header into an array
WAVHEADER header;
fread(&header, sizeof(header), 1, inptr);
// use check_format to ensure WAV format
check_format(header);
// open output file for writing
FILE *outptr = fopen(outfile, "w");
if (outptr == NULL)
{
printf("couldn't open the outfile\n");
fclose(inptr);
return 1;
}
// write header to file
fwrite(&header, sizeof(header), 1, outptr);
// use get_block_size to calculate size of block
int block_size = get_block_size(header);
printf("block_size: %i\n", block_size);
if (block_size < 0)
{
printf("block_size with no size\n");
return 1;
}
// write reversed audio to file
// 1. declare an array to store each block of audio
char *buffer = malloc(block_size * sizeof(char));
if (buffer == NULL)
{
printf("no memory location");
return 1;
}
// get the size of the input file
fseek(inptr, 0, SEEK_END);
long int infile_size = ftell(inptr);
printf("file_size: %li\n", infile_size);
// iterate through the input file audio data
for (long int i = infile_size; i >= 0; i -= block_size)
{
// move the file indicator to the start
fseek(inptr, i, SEEK_SET);
// read from inptr each size
fread(buffer, sizeof(char), block_size, inptr);
// write in outfile
fwrite(buffer, sizeof(char), block_size, outptr);
}
// free
free(buffer);
// close files:
fclose(inptr);
fclose(outptr);
}
int check_format(WAVHEADER header)
{
// TODO #4
if (header.format[0] == 'W' && header.format[1] == 'A' && header.format[2] == 'V' && header.format[3] == 'E')
{
printf("This is the type .wav\n");
return 0;
}
else
{
printf("File is not the type .wav\n");
return 1;
}
}
int get_block_size(WAVHEADER header)
{
// TODO #7
// check if channels are mono or audio
if (header.numChannels == 1 || header.numChannels == 2)
{
int block_size;
block_size = header.numChannels * (header.bitsPerSample / 8);
return block_size;
}
else
{
printf("Not supported\n");
return 1;
}
}
Thanks in advance!