#include "../SoundBlaster.h"

#include <go32.h>

SoundBlaster soundblaster;

void soundblasterIsr() {
    soundblaster.onInterrupt();
}

SoundBlaster::SoundBlaster() {
    // Allocate twice the amount needed and select one half depending on whether it crosses a 64k boundary
    _dmaBuffer.size = (SB_DMA_BUFFER_SIZE + 15) >> (4-1);
    _go32_dpmi_allocate_dos_memory(&_dmaBuffer);

    auto physFirst = (_dmaBuffer.rm_segment << 4) + _dmaBuffer.rm_offset;
    auto physSecond = physFirst + SB_DMA_BUFFER_SIZE;
    auto pageFirst = physFirst >> 16;
    auto pageSecond = physSecond >> 16;

    if (pageFirst == pageSecond) {
        // Use first half
        _buffers = reinterpret_cast<decltype(_buffers)>(physFirst);
        _dmaPage = pageFirst;
        _dmaOffset = physFirst & 0xFFFF;
    } else {
        // Use second half
        _buffers = reinterpret_cast<decltype(_buffers)>(physSecond);
        _dmaPage = pageSecond;
        _dmaOffset = physSecond & 0xFFFF;
    }
}

SoundBlaster::~SoundBlaster() {
    _go32_dpmi_free_dos_memory(&_dmaBuffer);
}

void SoundBlaster::onInterrupt() {
    // No data available - should not happen, but let's force generate a block
    if (_nextBufferReadIndex == _nextBufferWriteIndex) {
        generateSamples();
    }

    dosmemput(_buffers, SB_BUFFER_SIZE, (_dmaBuffer.rm_segment << 4) + _nextBufferReadIndex * SB_BUFFER_SIZE);
    _nextBufferReadIndex = (_nextBufferReadIndex + 1) & 3;
}