WAV File Reader / Writer C++

Audio.cpp

#pragma once

#include "Audio.h"

Audio::Audio(std::string str) {
	if (str.substr(str.size() - 4) != ".wav")
		throw std::invalid_argument("Can only read WAV files!");
	load_wav(str);
}

void Audio::load_wav(std::string str) {
	FILE *fp;
	errno_t err = fopen_s(&fp, str.c_str(), "rb");
	if (err != 0)
		throw std::runtime_error("Error opening file!");

	// Chunk
	fread(type, sizeof(char), 4, fp);
	if (strcmp(type, "RIFF"))
		throw std::runtime_error("Not a RIFF file!");

	fread(&ChunkSize, sizeof(int), 1, fp);
	fread(format, sizeof(char), 4, fp);
	if (strcmp(format, "WAVE"))
		throw std::runtime_error("Not a WAVE format!");

	// 1st Subchunk
	fread(Subchunk1ID, sizeof(char), 4, fp);
	if (strcmp(Subchunk1ID, "fmt "))
		throw std::runtime_error("Missing fmt header!");
	fread(&Subchunk1Size, sizeof(int), 1, fp);
	fread(&AudioFormat, sizeof(short), 1, fp);
	fread(&NumChannels, sizeof(short), 1, fp);
	fread(&SampleRate, sizeof(int), 1, fp);
	fread(&ByteRate, sizeof(int), 1, fp);
	fread(&BlockAlign, sizeof(short), 1, fp);
	fread(&BitsPerSample, sizeof(short), 1, fp);

	// 2nd Subchunk
	fread(Subchunk2ID, sizeof(char), 4, fp);
	if (strcmp(Subchunk2ID, "data")!=0)
		throw std::runtime_error("Missing data header!");
	fread(&Subchunk2Size, sizeof(int), 1, fp);
	// Data

	//Subchunk2Size = NumSamples * NumChannels * BitsPerSample/8
	int NumSamples = Subchunk2Size / (NumChannels*(BitsPerSample / 8));

	data = std::vector<std::pair<short, short> >(NumSamples);
	for (int i = 0; i < NumSamples; i++) {
		fread(&data[i].first, sizeof(short), 1, fp);
		fread(&data[i].second, sizeof(short), 1, fp);
	}
	fclose(fp);
}

void Audio::write_wav(std::string str) {
	FILE *fp;
	fopen_s(&fp, str.c_str(), "wb");

	fwrite(type, sizeof(char), 4, fp);
	fwrite(&ChunkSize, sizeof(int), 1, fp);
	fwrite(format, sizeof(char), 4, fp);

	// 1st Subchunk
	fwrite(Subchunk1ID, sizeof(char), 4, fp);
	fwrite(&Subchunk1Size, sizeof(int), 1, fp);
	fwrite(&AudioFormat, sizeof(short), 1, fp);
	fwrite(&NumChannels, sizeof(short), 1, fp);
	fwrite(&SampleRate, sizeof(int), 1, fp);
	fwrite(&ByteRate, sizeof(int), 1, fp);
	fwrite(&BlockAlign, sizeof(short), 1, fp);
	fwrite(&BitsPerSample, sizeof(short), 1, fp);

	// 2nd Subchunk
	fwrite(Subchunk2ID, sizeof(char), 4, fp);
	fwrite(&Subchunk2Size, sizeof(int), 1, fp);
	
	// Ideally instead of the for loop there would be something like
	// fwrite(&data[0], sizeof(short), data.size(), fp);
	// But I have pairs and they have to be written interchangebly like right,left right,left right,left...

	for (int i = 0; i < data.size(); i++) {
		fwrite(&data[i].first, sizeof(short), 1, fp);
		fwrite(&data[i].second, sizeof(short), 1, fp);
	}
	fclose(fp);
}

Audio.h

#pragma once

//#define _CRT_SECURE_NO_DEPRECATE

#include <vector>
#include <utility>
#include <string>
#include <stdexcept>
#include <iostream>
#include <stdio.h>
#include <cstring>

class Audio {
public:
	// Constructors
	Audio(std::string str);
	Audio() {};

	// Read / Write files
	void load_wav(std::string str);
	void write_wav(std::string str);

	// Get functions
	// Subchunk2Size = NumSamples * NumChannels * BitsPerSample / 8 <==> NumSamples = Subchunk2Size / (NumChannels*(BitsPerSample / 8))
	unsigned get_size() { return data.size(); }
	unsigned get_sample_rate() { return SampleRate; }
	unsigned get_n_channels() { return NumChannels; }

	// Set Functions
	void set_sample_rate(int n) { SampleRate = n; }
	void set_n_channels(int n) { if (n != 1 && n != 2)throw std::invalid_argument("n can only be 1 (MONO) or 2 (STEREO)!"); NumChannels = n; }

	// Overloaded Operators
	std::pair<short, short> &operator[](unsigned i) { return data[i]; }
protected:
	char type[5];
	char format[5];
	char Subchunk1ID[5];
	char Subchunk2ID[5];

	int ChunkSize;
	int Subchunk1Size;
	int SampleRate;
	int ByteRate;
	int Subchunk2Size;

	short AudioFormat;
	short NumChannels;
	short BlockAlign;
	short BitsPerSample;

	// utility
	unsigned NumSamples;

	std::vector<std::pair<short, short> > data;
};

Thanks for reporting those issues. I have fixed the issue with set_n_channels. However, I don't plan to expand this gist any further. It's just some example code - it's not meant to be a library. For a more stable implementation, I would suggest using an audio library for C++.

	memset(format,0,sizeof(format));
	memset(Subchunk1ID,0,sizeof(Subchunk1ID));
	memset(Subchunk2ID,0,sizeof(Subchunk2ID));