Audio.h

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#pragma once
 
#include <cstring>
#include <iostream>
#include <portaudio.h>
#include <vector>
 
namespace FuncDoodle {
    struct AudioData {
        std::vector<float> samples;
        int sampleRate;
        int numChannels;
        size_t cur = 0;
        size_t total = 0;
    };
};  // namespace FuncDoodle

static int paCB(const void* inBuf, void* outBuf, unsigned long framesPerBuf,
    const PaStreamCallbackTimeInfo* timeInfo, PaStreamCallbackFlags statusFlags,
    void* userData) {
    if (!userData) {
        return paAbort;
    }
 
    auto* data = static_cast<FuncDoodle::AudioData*>(userData);
    auto* out = static_cast<float*>(outBuf);
    unsigned long framesLeft = data->total - data->cur;
    unsigned long framesToProcess =
        (framesLeft < framesPerBuf) ? framesLeft : framesPerBuf;
 
    std::memcpy(out, data->samples.data() + (data->cur * data->numChannels),
        framesToProcess * data->numChannels * sizeof(float));
 
    data->cur += framesToProcess;
 
    if (framesToProcess < framesPerBuf) {
        size_t offset = framesToProcess * data->numChannels;
 
        memset(out + offset, 0,
            (framesPerBuf - framesToProcess) * data->numChannels *
                sizeof(float));
 
        return paComplete;
    }
 
    return paContinue;
}