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|
use std::io::Cursor;
use crate::{Codec, Error};
use hound::{self, Sample, SampleFormat, WavReader, WavSamples, WavWriter};
use itertools::{Chunk, Itertools};
use num_traits::{FromBytes, ToBytes};
/// A Least-Significant Bit (LSB) Codec for WAV files. Stores 1 bit of payload data in each sample
/// of a WAV file. Supported sample formats are 8, 16, and 32-bit PCM, and 32-bit float.
pub struct LsbCodec;
impl Codec for LsbCodec {
fn encode(&self, carrier: &[u8], payload: &[u8]) -> Result<Vec<u8>, crate::Error> {
if let Ok(mut reader) = hound::WavReader::new(Cursor::new(carrier)) {
let mut encoded = vec![];
{
let mut writer = WavWriter::new(Cursor::new(&mut encoded), reader.spec()).unwrap();
match reader.spec().sample_format {
hound::SampleFormat::Float => {
encode::<f32, 4>(payload, &mut reader, &mut writer);
}
hound::SampleFormat::Int => {
match reader.spec().bits_per_sample {
8 => {
encode::<i8, 1>(payload, &mut reader, &mut writer);
}
16 => {
encode::<i16, 2>(payload, &mut reader, &mut writer);
}
32 => {
encode::<i32, 4>(payload, &mut reader, &mut writer);
}
_ => return Err(Error::DataInvalid(
"Provided WAV data has an unsupported number of bits per sample."
.into(),
)),
}
}
}
writer.flush().unwrap();
}
Ok(encoded)
} else {
Err(Error::DataInvalid(
"Could not create WAV reader from provided data".into(),
))
}
}
fn decode(&self, encoded: &[u8]) -> Result<(Vec<u8>, Vec<u8>), crate::Error> {
if let Ok(mut reader) = hound::WavReader::new(Cursor::new(encoded)) {
let decoded = match reader.spec().sample_format {
SampleFormat::Float => decode::<f32, 4>(&mut reader)?,
SampleFormat::Int => match reader.spec().bits_per_sample {
8 => decode::<i8, 1>(&mut reader)?,
16 => decode::<i16, 2>(&mut reader)?,
32 => decode::<i32, 4>(&mut reader)?,
_ => return Err(Error::DataNotEncoded),
},
};
Ok((encoded.to_vec(), decoded))
} else {
Err(Error::DataInvalid(
"Could not create WAV reader from provided data".into(),
))
}
}
}
fn encode<T, const N: usize>(
payload: &[u8],
reader: &mut WavReader<Cursor<&[u8]>>,
writer: &mut WavWriter<Cursor<&mut Vec<u8>>>,
) where
T: Sample + ToBytes<Bytes = [u8; N]> + FromBytes<Bytes = [u8; N]>,
{
let payload_len = ((payload.len() + size_of::<u32>()) as u32).to_le_bytes();
let mut payload_iter = payload_len.iter().chain(payload.iter());
for sample_chunk in &reader.samples::<T>().chunks(8) {
match payload_iter.next() {
Some(payload_byte) => {
encode_byte(writer, *payload_byte, sample_chunk);
}
None => {
for sample in sample_chunk {
writer.write_sample(sample.unwrap()).unwrap();
}
}
}
}
}
fn encode_byte<T, const N: usize>(
writer: &mut WavWriter<Cursor<&mut Vec<u8>>>,
payload_byte: u8,
sample_chunk: Chunk<WavSamples<Cursor<&[u8]>, T>>,
) where
T: Sample + ToBytes<Bytes = [u8; N]> + FromBytes<Bytes = [u8; N]>,
{
for (i, sample) in sample_chunk.enumerate() {
let sample = sample.unwrap();
let mut sample_bytes = sample.to_le_bytes();
let payload_bit = (payload_byte >> (7 - i)) & 0b0000_0001;
sample_bytes[1] &= 0b1111_1110;
sample_bytes[1] |= payload_bit;
writer
.write_sample(T::from_le_bytes(&sample_bytes))
.unwrap();
}
}
fn decode<T, const N: usize>(reader: &mut WavReader<Cursor<&[u8]>>) -> Result<Vec<u8>, Error>
where
T: Sample + ToBytes<Bytes = [u8; N]> + FromBytes<Bytes = [u8; N]>,
{
let mut decoded = vec![];
let mut length_bytes = [0_u8; 4];
for (i, sample_chunk) in reader
.samples::<T>()
.take(8 * 4)
.chunks(8)
.into_iter()
.enumerate()
{
for (j, sample) in sample_chunk.enumerate() {
let sample = sample.unwrap();
let sample_bytes = sample.to_le_bytes();
let payload_bit = (sample_bytes[1] & 0b0000_0001) << (7 - j);
length_bytes[i] |= payload_bit;
}
}
let payload_length = u32::from_le_bytes(length_bytes) as usize - size_of::<u32>();
if payload_length > reader.samples::<T>().len() {
return Err(Error::DataNotEncoded);
}
for sample_chunk in &reader.samples::<T>().chunks(8) {
let mut byte = 0_u8;
for (i, sample) in sample_chunk.enumerate() {
let sample = sample.unwrap();
let sample_bytes = sample.to_le_bytes();
let payload_bit = (sample_bytes[1] & 0b0000_0001) << (7 - i);
byte |= payload_bit;
}
decoded.push(byte);
if decoded.len() >= payload_length {
break;
}
}
Ok(decoded)
}
|
