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|
//! Reading the initial STREAMINFO block from a FLAC file,
//! as documented in its
//! [specification](https://xiph.org/flac/format.html#stream).
//!
extern crate bitstream_io;
use bitstream_io::{BigEndian, BitRead, BitReader, FromBitStream};
use std::num::NonZero;
#[derive(Debug, PartialEq, Eq)]
struct BlockHeader {
last_block: bool, // 1 bit
block_type: u8, // 7 bits
block_size: u32, // 24 bits
}
impl FromBitStream for BlockHeader {
type Error = std::io::Error;
fn from_reader<R: BitRead + ?Sized>(r: &mut R) -> std::io::Result<Self> {
Ok(Self {
last_block: r.read_bit()?,
block_type: r.read::<7, _>()?,
block_size: r.read::<24, _>()?,
})
}
}
#[derive(Debug, PartialEq, Eq)]
struct Streaminfo {
minimum_block_size: u16, // 16 bits
maximum_block_size: u16, // 16 bits
minimum_frame_size: u32, // 24 bits
maximum_frame_size: u32, // 24 bits
sample_rate: u32, // 20 bits
channels: NonZero<u8>, // 3 bits
bits_per_sample: NonZero<u8>, // 5 bits
total_samples: u64, // 36 bits
md5: [u8; 16], // 16 bytes
}
impl FromBitStream for Streaminfo {
type Error = std::io::Error;
fn from_reader<R: BitRead + ?Sized>(r: &mut R) -> std::io::Result<Self> {
Ok(Self {
minimum_block_size: r.read_to()?,
maximum_block_size: r.read_to()?,
minimum_frame_size: r.read::<24, _>()?,
maximum_frame_size: r.read::<24, _>()?,
sample_rate: r.read::<20, _>()?,
channels: r.read::<3, _>()?,
bits_per_sample: r.read::<5, _>()?,
total_samples: r.read::<36, _>()?,
md5: r.read_to()?,
})
}
}
#[derive(Debug, PartialEq, Eq)]
struct VorbisComment {
vendor: String,
comment: Vec<String>,
}
impl FromBitStream for VorbisComment {
type Error = Box<dyn std::error::Error>;
fn from_reader<R: BitRead + ?Sized>(r: &mut R) -> Result<Self, Self::Error> {
use bitstream_io::LE;
fn read_entry<R: BitRead + ?Sized>(
r: &mut R,
) -> Result<String, Box<dyn std::error::Error>> {
use std::convert::TryInto;
let size = r.read_as_to::<LE, u32>()?.try_into()?;
Ok(String::from_utf8(r.read_to_vec(size)?)?)
}
Ok(Self {
vendor: read_entry(r)?,
comment: (0..r.read_as_to::<LE, u32>()?)
.map(|_| read_entry(r))
.collect::<Result<Vec<_>, _>>()?,
})
}
}
fn main() {
// test FLAC file data
let flac = include_bytes!("data/metadata-only.flac");
let mut reader = BitReader::endian(flac.as_slice(), BigEndian);
// stream marker
assert_eq!(&reader.read_to::<[u8; 4]>().unwrap(), b"fLaC");
// metadata block header
assert_eq!(
reader.parse::<BlockHeader>().unwrap(),
BlockHeader {
last_block: false,
block_type: 0,
block_size: 34
}
);
// STREAMINFO block
assert_eq!(
dbg!(reader.parse::<Streaminfo>().unwrap()),
Streaminfo {
minimum_block_size: 4096,
maximum_block_size: 4096,
minimum_frame_size: 1542,
maximum_frame_size: 8546,
sample_rate: 44100,
channels: NonZero::new(2).unwrap(),
bits_per_sample: NonZero::new(16).unwrap(),
total_samples: 304844,
md5: *b"\xFA\xF2\x69\x2F\xFD\xEC\x2D\x5B\x30\x01\x76\xB4\x62\x88\x7D\x92",
}
);
// metadata block header
assert_eq!(
dbg!(reader.parse::<BlockHeader>().unwrap()),
BlockHeader {
last_block: false,
block_type: 4,
block_size: 122
}
);
// VORBIS_COMMENT block
assert_eq!(
dbg!(reader.parse::<VorbisComment>().unwrap()),
VorbisComment {
vendor: "reference libFLAC 1.1.4 20070213".to_string(),
comment: vec![
"title=2ch 44100 16bit".to_string(),
"album=Test Album".to_string(),
"artist=Assorted".to_string(),
"tracknumber=1".to_string(),
],
}
);
}
|
