kithara-decode 0.0.1-alpha1

Synchronous audio decoding via Symphonia with PCM output
Documentation 
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#![allow(non_upper_case_globals)]

use super::ffi::{AudioFormatFlags, AudioFormatID, OSStatus};

pub(crate) struct Consts;

impl Consts {
    /// AAC always decodes 1024 samples per packet (SBR spectral bands
    /// use the same packet boundary).
    pub(crate) const AAC_FRAMES_PER_PACKET: u32 = 1024;
    pub(crate) const BITS_PER_F32_SAMPLE: u32 = 32;
    pub(crate) const BYTES_PER_F32_SAMPLE: u32 = 4;
    /// Bytes prepended to STREAMINFO in the Apple FLAC magic cookie:
    /// 4 bytes `"fLaC"` marker + 4 bytes `METADATA_BLOCK_HEADER`.
    pub(crate) const FLAC_COOKIE_PREFIX_LEN: usize = 8;
    /// Size of the FLAC STREAMINFO metadata block body (fixed by spec).
    pub(crate) const FLAC_STREAMINFO_LEN: usize = 34;
    pub(crate) const kAudioConverterDecompressionMagicCookie: u32 = 0x646d_6763;
    pub(crate) const kAudioConverterErr_NoDataNow: OSStatus = 0x2164_6174;
    /// `'prim'` — codec-reported `AudioConverterPrimeInfo` (encoder
    /// priming + trailing padding in PCM frames). Available after the
    /// converter has consumed at least one input packet.
    pub(crate) const kAudioConverterPrimeInfo: u32 = 0x7072_696d;
    /// `'caff'` — Core Audio Format file-type hint.
    pub(crate) const kAudioFileCAFType: u32 = 0x6361_6666;
    /// `'m4af'` — M4A (ALAC / AAC) file-type hint.
    pub(crate) const kAudioFileM4AType: u32 = 0x6d34_6166;
    /// `'MPG3'` — MPEG-1/2 Layer 3 file-type hint.
    pub(crate) const kAudioFileMP3Type: u32 = 0x4d50_4733;
    /// `'pcnt'` — total audio data packet count.
    pub(crate) const kAudioFilePropertyAudioDataPacketCount: u32 = 0x7063_6e74;
    /// `'dfmt'` — ASBD of the file's canonical audio data format.
    pub(crate) const kAudioFilePropertyDataFormat: u32 = 0x6466_6d74;
    /// `'mgic'` — codec-specific magic cookie (ALAC, ESDS-wrapped AAC).
    pub(crate) const kAudioFilePropertyMagicCookieData: u32 = 0x6d67_6963;
    /// `'psze'` — maximum audio packet size in bytes.
    pub(crate) const kAudioFilePropertyMaximumPacketSize: u32 = 0x7073_7a65;
    /// `'WAVE'` — RIFF WAV file-type hint for `AudioFileOpenWithCallbacks`.
    pub(crate) const kAudioFileWAVEType: u32 = 0x5741_5645;
    /// `'alac'` — Apple Lossless Audio Codec input format ID.
    pub(crate) const kAudioFormatAppleLossless: AudioFormatID = 0x616c_6163;
    pub(crate) const kAudioFormatFLAC: AudioFormatID = 0x666c_6163;
    pub(crate) const kAudioFormatFlagIsFloat: AudioFormatFlags = 1 << 0;
    pub(crate) const kAudioFormatFlagIsPacked: AudioFormatFlags = 1 << 3;
    pub(crate) const kAudioFormatFlagsNativeFloatPacked: AudioFormatFlags =
        Self::kAudioFormatFlagIsFloat | Self::kAudioFormatFlagIsPacked;
    pub(crate) const kAudioFormatLinearPCM: AudioFormatID = 0x6c70_636d;
    /// `'aac '` — MPEG-4 AAC LC input format ID.
    pub(crate) const kAudioFormatMPEG4AAC: AudioFormatID = 0x6161_6320;
    /// `'aach'` — MPEG-4 HE-AAC (LC + SBR). Decodes to 2x the encoded
    /// sample rate; AudioConverter handles the upsampling once it reads
    /// the AudioSpecificConfig cookie. Frames per *encoded* packet stay
    /// at 1024 (the SBR layer doubles output frames per packet).
    pub(crate) const kAudioFormatMPEG4AAC_HE: AudioFormatID = 0x6161_6368;
    /// `'aacp'` — MPEG-4 HE-AAC v2 (LC + SBR + Parametric Stereo).
    /// Same input/output frame ratio as HE-AAC v1; PS reconstructs the
    /// stereo image from a mono base + side parameters at decode time.
    pub(crate) const kAudioFormatMPEG4AAC_HE_V2: AudioFormatID = 0x6161_6370;
    /// `'.mp3'` — MPEG-1/2 Layer 3 input format ID.
    pub(crate) const kAudioFormatMPEGLayer3: AudioFormatID = 0x2e6d_7033;
    pub(crate) const noErr: OSStatus = 0;
}

/// Decode a `FourCC`-style `OSStatus` into an ASCII tag when possible.
pub(crate) fn os_status_to_string(status: OSStatus) -> String {
    if status == Consts::noErr {
        return "noErr".to_string();
    }
    let bytes = status.to_be_bytes();
    if bytes.iter().all(|&b| b.is_ascii_graphic() || b == b' ') {
        let s: String = bytes.iter().map(|&b| b as char).collect();
        format!("'{}' ({})", s, status)
    } else {
        format!("{}", status)
    }
}

#[cfg(test)]
mod tests {
    use kithara_test_utils::kithara;

    use super::*;

    #[kithara::test]
    fn test_os_status_to_string() {
        assert_eq!(os_status_to_string(Consts::noErr), "noErr");
        assert!(os_status_to_string(0x7768_743f).contains("wht?"));
    }
}