4coder/custom/4coder_audio.cpp

////////////////////////////////
// NOTE(allen): Default Mixer Helpers

// TODO(allen): intrinsics wrappers
#include <intrin.h>

function u32
AtomicAddU32AndReturnOriginal(u32 volatile *Value, u32 Addend)
{
    // NOTE(casey): Returns the original value _prior_ to adding
    u32 Result = _InterlockedExchangeAdd((long volatile*)Value, (long)Addend);
    return(Result);
}

function void
def_audio_begin_ticket_mutex(Audio_System *Crunky)
{
    u32 Ticket = AtomicAddU32AndReturnOriginal(&Crunky->ticket, 1);
    while(Ticket != Crunky->serving) {_mm_pause();}
}

function void
def_audio_end_ticket_mutex(Audio_System *Crunky)
{
    AtomicAddU32AndReturnOriginal(&Crunky->serving, 1);
}


////////////////////////////////
// NOTE(allen): Default Mixer

global Audio_System def_audio_system = {};

function void
def_audio_init(void){
    block_zero_struct(&def_audio_system);
    system_set_source_mixer(&def_audio_system, def_audio_mix_sources);
    system_set_destination_mixer(def_audio_mix_destination);
}

function void
def_audio_play_clip(Audio_Clip clip, Audio_Control *control){
    clip.control = control;
    Audio_System *Crunky = &def_audio_system;
    def_audio_begin_ticket_mutex(Crunky);
    if (Crunky->pending_clip_count < ArrayCount(Crunky->pending_clips))
    {
        Crunky->pending_clips[Crunky->pending_clip_count++] = clip;
    }
    def_audio_end_ticket_mutex(Crunky);
}

internal b32
def_audio_is_playing(Audio_Control *control){
    Audio_System *Crunky = &def_audio_system;
    b32 result = (Crunky->generation - control->generation < 2);
    return(result);
}

internal void
def_audio_stop(Audio_Control *control){
    Audio_System *Crunky = &def_audio_system;
    def_audio_begin_ticket_mutex(Crunky);
    
    Audio_Clip *clip = Crunky->playing_clips;
    for(u32 i = 0;
        i < ArrayCount(Crunky->playing_clips);
        i += 1, clip += 1){
        if (clip->control == control){
            clip->at_sample_index = clip->sample_count;
			clip->control = 0;
        }
    }
	control->loop = false;
    
    def_audio_end_ticket_mutex(Crunky);
}

function void
def_audio_mix_sources(void *ctx, f32 *mix_buffer, u32 sample_count){
    Audio_System *Crunky = (Audio_System*)ctx;
    def_audio_begin_ticket_mutex(Crunky);
    // NOTE(casey): Move pending sounds into the playing list
    {
        Crunky->generation += 1;
        u32 PendIndex = 0;
        Audio_Clip *clip = Crunky->playing_clips;
        for(u32 DestIndex = 0;
            (DestIndex < ArrayCount(Crunky->playing_clips)) && (PendIndex < Crunky->pending_clip_count);
            DestIndex += 1, clip += 1)
        {
            if (clip->at_sample_index == clip->sample_count)
            {
                Audio_Control *control = clip->control;
                if (control == 0 || !control->loop){
                    *clip = Crunky->pending_clips[PendIndex++];
                }
            }
        }
        Crunky->pending_clip_count = 0;
    }
    def_audio_end_ticket_mutex(Crunky);
    
    // NOTE(casey): Mix all sounds into the output buffer
    {
        Audio_Clip *clip = Crunky->playing_clips;
        for(u32 SoundIndex = 0;
            SoundIndex < ArrayCount(Crunky->playing_clips);
            SoundIndex += 1, clip += 1)
        {
            // NOTE(allen): Determine starting point
            Audio_Control *control = clip->control;
            if (control != 0 && control->loop && clip->at_sample_index == clip->sample_count){
                clip->at_sample_index = 0;
            }
            u32 base_sample_index = clip->at_sample_index;
            
            // NOTE(casey): Determine how many samples are left to play in this
            // sound (possible none)
            u32 SamplesToMix = clamp_top((clip->sample_count - clip->at_sample_index), sample_count);
            clip->at_sample_index += SamplesToMix;
            
            // NOTE(casey): Load the volume out of the control if there is one,
            // and if there is, update the generation and sample index so
            // external controllers can take action
            f32 LeftVol = clip->channel_volume[0];
            f32 RightVol = clip->channel_volume[1];
            if(SamplesToMix && control != 0)
            {
                LeftVol *= control->channel_volume[0];
                RightVol *= control->channel_volume[1];
                control->generation = Crunky->generation;
                control->last_played_sample_index = clip->at_sample_index;
            }
            
            // NOTE(casey): Mix samples
            for(u32 SampleIndex = 0;
                SampleIndex < SamplesToMix;
                ++SampleIndex)
            {
                u32 src_index = 2*(base_sample_index + SampleIndex);
                f32 Left  = LeftVol *(f32)clip->samples[src_index + 0];
                f32 Right = RightVol*(f32)clip->samples[src_index + 1];
                
                u32 dst_index = 2*SampleIndex;
                mix_buffer[dst_index + 0] += Left;
                mix_buffer[dst_index + 1] += Right;
            }
        }
    }
}

function void
def_audio_mix_destination(i16 *dst, f32 *src, u32 sample_count){
    u32 opl = sample_count*2;
    for(u32 i = 0; i < opl; i += 1){
        f32 sample = src[i];
        f32 sat_sample = clamp(-32768.f, sample, 32767.f);
        dst[i] = (i16)sat_sample;
    }
}


////////////////////////////////
// NOTE(allen): Loading Clip

#if !defined(FCODER_SKIP_WAV)
#define FCODER_SKIP_WAV
#pragma pack(push, 1)
struct wave_fmt_data
{
    u16 wFormatTag;
    u16 wChannels;
    u32 dwSamplesPerSec;
    u32 dwAvgBytesPerSec;
    u16 wBlockAlign;
    u16 wBitsPerSample;
};

struct riff_header
{
    u32 ID;
    u32 DataSize;
};
#pragma pack(pop)
#endif

function Audio_Clip
audio_clip_from_wav_data(String_Const_u8 data){
    Audio_Clip Result = {};
    
    if (data.size >= 4 && *(u32 *)data.str == *(u32 *)"RIFF"){
        // NOTE(casey): This ROM is in WAV format
        
        riff_header *RootHeader = (riff_header *)data.str;
        
        wave_fmt_data *Format = 0;
        u32 SampleDataSize = 0;
        i16 *Samples = 0;
        
        u32 At = sizeof(riff_header);
        u32 LastAt = At + ((RootHeader->DataSize + 1) & ~1);
        if ((*(u32 *)(data.str + At) == *(u32 *)"WAVE") &&
            (LastAt <= data.size)){
            At += sizeof(u32);
            while (At < LastAt){
                riff_header *Header = (riff_header *)(data.str + At);
                u32 DataAt = At + sizeof(riff_header);
                u32 EndAt = DataAt + ((Header->DataSize + 1) & ~1);
                if(EndAt <= data.size)
                {
                    void *Data = (data.str + DataAt);
                    if(Header->ID == *(u32 *)"fmt ")
                    {
                        Format = (wave_fmt_data *)Data;
                    }
                    else if(Header->ID == *(u32 *)"data")
                    {
                        SampleDataSize = Header->DataSize;
                        Samples = (i16 *)Data;
                    }
                }
                
                At = EndAt;
            }
        }
        
        if (Format &&
            Samples &&
            (Format->wFormatTag == 1) &&
            (Format->wChannels == 2) &&
            (Format->wBitsPerSample == 16) &&
            (Format->dwSamplesPerSec == 48000)){
            for (u32 i = 0; i < 2; i += 1){
                Result.channel_volume[i] = 1.f;
            }
            Result.sample_count = SampleDataSize / (Format->wChannels*Format->wBitsPerSample/8);
            Result.samples = (i16 *)Samples;
        }
		else{
			// TODO(casey): This is where you would output an error - to 4coder somehow?
		}
    }
	else{
		// TODO(casey): This is where you would output an error - to 4coder somehow?
	}
    
    return(Result);
}

#include <stdlib.h>

function Audio_Clip
audio_clip_from_wav_file_name(char *file_name){
    String_Const_u8 data = {};
    FILE *file = fopen(file_name, "rb");
    if (file != 0){
        fseek(file, 0, SEEK_END);
        data.size = ftell(file);
        data.str = (u8*)malloc(data.size);
        if (data.str != 0 && data.size > 0){
            fseek(file, 0, SEEK_SET);
            fread(data.str, data.size, 1, file);
        }
        fclose(file);
    }
    
    Audio_Clip result = audio_clip_from_wav_data(data);
    return(result);
}