suaveplan/packages/media/audio/audio-decode-wav/tests/fixtures/build-wav.ts

/**
 * Programmatic WAV fixture builders used by the test suite. No binary files
 * are checked in — every fixture is generated deterministically from
 * primitives at test time. Each builder returns a `Uint8Array` ready to be
 * fed to `decodeWav` or `createWavStreamDecoder`.
 */

export interface BuildWavInput {
    readonly sampleRate: number;
    readonly channels: number;
    readonly bitsPerSample: number;
    readonly samplesPerChannel: number;
    /** `1` for integer PCM, `3` for IEEE float PCM. */
    readonly formatCode: 1 | 3;
    /** Per-channel sample generator. Defaults to silence. */
    readonly sampler?: (channel: number, index: number) => number;
}

/** Build a well-formed RIFF/WAVE byte buffer. */
export function buildWav(input: BuildWavInput): Uint8Array {
    const {
        sampleRate,
        channels,
        bitsPerSample,
        samplesPerChannel,
        formatCode,
        sampler = () => 0,
    } = input;
    const bytesPerSample = bitsPerSample / 8;
    const dataBytes = samplesPerChannel * channels * bytesPerSample;
    const headerBytes = 44;
    const buffer = new Uint8Array(headerBytes + dataBytes);
    const dv = new DataView(buffer.buffer);
    writeAscii(buffer, 0, "RIFF");
    dv.setUint32(4, headerBytes - 8 + dataBytes, true);
    writeAscii(buffer, 8, "WAVE");
    writeAscii(buffer, 12, "fmt ");
    dv.setUint32(16, 16, true);
    dv.setUint16(20, formatCode, true);
    dv.setUint16(22, channels, true);
    dv.setUint32(24, sampleRate, true);
    dv.setUint32(28, sampleRate * channels * bytesPerSample, true);
    dv.setUint16(32, channels * bytesPerSample, true);
    dv.setUint16(34, bitsPerSample, true);
    writeAscii(buffer, 36, "data");
    dv.setUint32(40, dataBytes, true);
    let p = headerBytes;
    for (let i = 0; i < samplesPerChannel; i++) {
        for (let c = 0; c < channels; c++) {
            const v = sampler(c, i);
            p += writeSample(dv, p, v, bitsPerSample, formatCode);
        }
    }
    return buffer;
}

function writeAscii(b: Uint8Array, off: number, s: string): void {
    for (let i = 0; i < s.length; i++) b[off + i] = s.charCodeAt(i);
}

function writeSample(
    dv: DataView,
    pos: number,
    value: number,
    bits: number,
    fmt: 1 | 3
): number {
    if (fmt === 3) {
        if (bits === 32) {
            dv.setFloat32(pos, value, true);
            return 4;
        }
        dv.setFloat64(pos, value, true);
        return 8;
    }
    if (bits === 16) {
        const clipped = clip(value);
        const v = Math.round(clipped < 0 ? clipped * 32768 : clipped * 32767);
        dv.setInt16(pos, v, true);
        return 2;
    }
    if (bits === 24) {
        const clipped = clip(value);
        const v = Math.round(
            clipped < 0 ? clipped * 8388608 : clipped * 8388607
        );
        dv.setUint8(pos, v & 0xff);
        dv.setUint8(pos + 1, (v >> 8) & 0xff);
        dv.setUint8(pos + 2, (v >> 16) & 0xff);
        return 3;
    }
    const clipped = clip(value);
    const v = Math.round(
        clipped < 0 ? clipped * 2147483648 : clipped * 2147483647
    );
    dv.setInt32(pos, v, true);
    return 4;
}

function clip(v: number): number {
    if (v > 1) return 1;
    if (v < -1) return -1;
    return v;
}

/** Build an A-law WAV header — the body is silence; we only verify rejection. */
export function buildAlawWav(): Uint8Array {
    const dataBytes = 32;
    const buffer = new Uint8Array(44 + dataBytes);
    const dv = new DataView(buffer.buffer);
    writeAscii(buffer, 0, "RIFF");
    dv.setUint32(4, 36 + dataBytes, true);
    writeAscii(buffer, 8, "WAVE");
    writeAscii(buffer, 12, "fmt ");
    dv.setUint32(16, 16, true);
    dv.setUint16(20, 6, true); // A-law format code
    dv.setUint16(22, 1, true);
    dv.setUint32(24, 8000, true);
    dv.setUint32(28, 8000, true);
    dv.setUint16(32, 1, true);
    dv.setUint16(34, 8, true);
    writeAscii(buffer, 36, "data");
    dv.setUint32(40, dataBytes, true);
    return buffer;
}

/** Build a WAV whose `data` chunk declares double the bytes present. */
export function buildTruncatedWav(): Uint8Array {
    const real = buildWav({
        sampleRate: 8000,
        channels: 1,
        bitsPerSample: 16,
        samplesPerChannel: 100,
        formatCode: 1,
    });
    const dv = new DataView(real.buffer);
    const declared = dv.getUint32(40, true);
    dv.setUint32(40, declared * 2, true);
    return real;
}

/** Build a buffer whose first 4 bytes are zeroed (no RIFF magic). */
export function buildCorruptHeaderWav(): Uint8Array {
    const real = buildWav({
        sampleRate: 8000,
        channels: 1,
        bitsPerSample: 16,
        samplesPerChannel: 8,
        formatCode: 1,
    });
    real[0] = 0;
    real[1] = 0;
    real[2] = 0;
    real[3] = 0;
    return real;
}