read_wav.cpp

//
//    openSAM: open source SAM emulator for X Plane
//
//    Copyright (C) 2024, 2025, 2026  Holger Teutsch
//
//    This library is free software; you can redistribute it and/or
//    modify it under the terms of the GNU Lesser General Public
//    License as published by the Free Software Foundation; either
//    version 2.1 of the License, or (at your option) any later version.
//
//    This library is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//    Lesser General Public License for more details.
//
//    You should have received a copy of the GNU Lesser General Public
//    License along with this library; if not, write to the Free Software
//    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
//    USA
//

#include <cstdlib>
#include <cstdio>
#include <cstring>

#include "samjw.h"
#include "log_msg.h"

struct WAV_FORMAT {
    short format;
    short num_channels;
    int sample_rate;
    int byte_rate;
    short block_align;
    short bits_per_sample;
};

struct CHUNK_HEADER {
    char id[4];
    unsigned int size;
};

struct WAV_HEADER {
    CHUNK_HEADER riffheader;
    char wav[4];
    CHUNK_HEADER fmtheader;
    WAV_FORMAT fmt;
};

//
// A super simple wav file reader. I don't know and don't care whether it reads any other
// file than the ones supplied here.
//
void ReadWav(const std::string& fname, Sound& sound) {
    sound = {};

    FILE* f = fopen(fname.c_str(), "rb");
    if (NULL == f) {
        LogMsg("can't open wav %s", fname.c_str());
        return;
    }

    WAV_HEADER header;
    CHUNK_HEADER chunk;

    if (1 != fread(&header, sizeof(header), 1, f)) {
        LogMsg("can't read header");
        fclose(f);
        return;
    }

    if (memcmp(header.riffheader.id, "RIFF", 4) || memcmp(header.wav, "WAVE", 4) ||
        memcmp(header.fmtheader.id, "fmt ", 4) || header.fmtheader.size < sizeof(WAV_FORMAT)) {
        LogMsg("wav invalid header");
        fclose(f);
        return;
    }

    fseek(f, header.fmtheader.size - sizeof(WAV_FORMAT), SEEK_CUR);

    // loop over chunks and find first data chunk
    while (1 == fread(&chunk, sizeof(chunk), 1, f)) {
        printf("chunk '%s' %d\n", chunk.id, chunk.size);
        if (0 == memcmp(chunk.id, "data", 4)) {
            void* data = malloc(chunk.size);
            if (NULL == data) {
                LogMsg("Can't malloc data for wav file");
                fclose(f);
                return;
            }

            if (1 != fread(data, chunk.size, 1, f)) {
                LogMsg("error reading wav file");
                fclose(f);
                free(data);
                return;
            }

            fclose(f);

            sound.data = data;
            sound.size = chunk.size;
            sound.sample_rate = header.fmt.sample_rate;
            sound.num_channels = header.fmt.num_channels;
            return;
        } else
            fseek(f, chunk.size, SEEK_CUR);  // skip over chunk
    }

    fclose(f);
    LogMsg("can't find data chunk in %s", fname.c_str());
    return;
}