SoftFM/AudioOutput.h

#ifndef SOFTFM_AUDIOOUTPUT_H
#define SOFTFM_AUDIOOUTPUT_H

#include <cstdint>
#include <cstdio>
#include <string>
#include <vector>

#include "SoftFM.h"


/** Base class for writing audio data to file or playback. */
class AudioOutput
{
public:

    /** Destructor. */
    virtual ~AudioOutput() { }

    /**
     * Write audio data.
     *
     * Return true on success.
     * Return false if an error occurs.
     */
    virtual bool write(const SampleVector& samples) = 0;

    /** Return the last error, or return an empty string if there is no error. */
    std::string error()
    {
        std::string ret(m_error);
        m_error.clear();
        return ret;
    }

    /** Return true if the stream is OK, return false if there is an error. */
    operator bool() const
    {
        return (!m_zombie) && m_error.empty();
    }

protected:
    /** Constructor. */
    AudioOutput() : m_zombie(false) { }

    /** Encode a list of samples as signed 16-bit little-endian integers. */
    static void samplesToInt16(const SampleVector& samples,
                               std::vector<uint8_t>& bytes);

    std::string m_error;
    bool        m_zombie;

private:
    AudioOutput(const AudioOutput&);            // no copy constructor
    AudioOutput& operator=(const AudioOutput&); // no assignment operator
};


/** Write audio data as raw signed 16-bit little-endian data. */
class RawAudioOutput : public AudioOutput
{
public:

    /**
     * Construct raw audio writer.
     *
     * filename :: file name (including path) or "-" to write to stdout
     */
    RawAudioOutput(const std::string& filename);

    ~RawAudioOutput();
    bool write(const SampleVector& samples);

private:
    int                  m_fd;
    std::vector<uint8_t> m_bytebuf;
};


/** Write audio data as .WAV file. */
class WavAudioOutput : public AudioOutput
{
public:

    /**
     * Construct .WAV writer.
     *
     * filename     :: file name (including path) or "-" to write to stdout
     * samplerate   :: audio sample rate in Hz
     * stereo       :: true if the output stream contains stereo data
     */
    WavAudioOutput(const std::string& filename,
                   unsigned int samplerate,
                   bool stereo);

    ~WavAudioOutput();
    bool write(const SampleVector& samples);

private:

    /** (Re-)Write .WAV header. */
    bool write_header(unsigned int nsamples);

    static void encode_chunk_id(uint8_t * ptr, const char * chunkname);

    template <typename T>
    static void set_value(uint8_t * ptr, T value);

    const unsigned numberOfChannels;
    const unsigned sampleRate;
    FILE *m_stream;
    std::vector<uint8_t> m_bytebuf;
};


/** Write audio data to ALSA device. */
class AlsaAudioOutput : public AudioOutput
{
public:

    /**
     * Construct ALSA output stream.
     *
     * dename       :: ALSA PCM device
     * samplerate   :: audio sample rate in Hz
     * stereo       :: true if the output stream contains stereo data
     */
    AlsaAudioOutput(const std::string& devname,
                    unsigned int samplerate,
                    bool stereo);

    ~AlsaAudioOutput();
    bool write(const SampleVector& samples);

private:
    unsigned int         m_nchannels;
    struct _snd_pcm *    m_pcm;
    std::vector<uint8_t> m_bytebuf;
};

#endif