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extern crate bitstream_io;
// Writing the initial STREAMINFO block to a FLAC file,
// as documented in its
// [specification](https://xiph.org/flac/format.html#stream).
use bitstream_io::{
BigEndian, BitWrite, BitWriter, ByteWrite, ByteWriter, LittleEndian, ToBitStream,
};
use std::convert::TryInto;
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 ToBitStream for BlockHeader {
type Error = std::io::Error;
fn to_writer<W: BitWrite + ?Sized>(&self, w: &mut W) -> std::io::Result<()> {
w.write_bit(self.last_block)?;
w.write::<7, _>(self.block_type)?;
w.write::<24, _>(self.block_size)
}
}
#[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 ToBitStream for Streaminfo {
type Error = std::io::Error;
fn to_writer<W: BitWrite + ?Sized>(&self, w: &mut W) -> std::io::Result<()> {
w.write_from(self.minimum_block_size)?;
w.write_from(self.maximum_block_size)?;
w.write::<24, _>(self.minimum_frame_size)?;
w.write::<24, _>(self.maximum_frame_size)?;
w.write::<20, _>(self.sample_rate)?;
w.write::<3, _>(self.channels)?;
w.write::<5, _>(self.bits_per_sample)?;
w.write::<36, _>(self.total_samples)?;
w.write_bytes(&self.md5)
}
}
#[derive(Debug, PartialEq, Eq)]
struct VorbisComment {
vendor: String,
comment: Vec<String>,
}
impl VorbisComment {
fn len(&self) -> usize {
4 + self.vendor.len() + 4 + self.comment.iter().map(|c| 4 + c.len()).sum::<usize>()
}
fn write<W: std::io::Write>(&self, w: &mut ByteWriter<W, LittleEndian>) -> std::io::Result<()> {
use std::convert::TryInto;
fn write_entry<W: std::io::Write>(
w: &mut ByteWriter<W, LittleEndian>,
s: &str,
) -> std::io::Result<()> {
w.write::<u32>(s.len().try_into().unwrap())?;
w.write_bytes(s.as_bytes())
}
write_entry(w, &self.vendor)?;
w.write::<u32>(self.comment.len().try_into().unwrap())?;
self.comment.iter().try_for_each(|s| write_entry(w, s))
}
}
fn main() {
let mut flac: Vec<u8> = Vec::new();
let mut writer = BitWriter::endian(&mut flac, BigEndian);
// stream marker
writer.write_bytes(b"fLaC").unwrap();
// metadata block header
writer
.build(&BlockHeader {
last_block: false,
block_type: 0,
block_size: 34,
})
.unwrap();
// STREAMINFO block
writer
.build(&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",
})
.unwrap();
let comment = 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(),
],
};
// metadata block header
writer
.build(&BlockHeader {
last_block: false,
block_type: 4,
block_size: comment.len().try_into().unwrap(),
})
.unwrap();
// VORBIS_COMMENT block (little endian)
comment
.write(&mut ByteWriter::new(writer.writer().unwrap()))
.unwrap();
assert_eq!(flac, include_bytes!("data/metadata-only.flac"));
}
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