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use std::io;
use std::iter::repeat;
use crc::{Crc8Reader, Crc16Reader};
use error::{Error, Result, fmt_err};
use input::{Bitstream, ReadExt};
use sample;
use subframe;
#[derive(Clone, Copy)]
enum BlockingStrategy {
Fixed,
Variable,
}
#[derive(Clone, Copy)]
enum BlockTime {
FrameNumber(u32),
SampleNumber(u64),
}
#[derive(Clone, Copy, Debug)]
enum ChannelAssignment {
Independent(u8),
LeftSideStereo,
RightSideStereo,
MidSideStereo,
}
#[derive(Clone, Copy)]
struct FrameHeader {
pub block_time: BlockTime,
pub block_size: u16,
pub sample_rate: Option<u32>,
pub channel_assignment: ChannelAssignment,
pub bits_per_sample: Option<u8>,
}
impl FrameHeader {
pub fn channels(&self) -> u8 {
match self.channel_assignment {
ChannelAssignment::Independent(n) => n,
ChannelAssignment::LeftSideStereo => 2,
ChannelAssignment::RightSideStereo => 2,
ChannelAssignment::MidSideStereo => 2,
}
}
}
fn read_var_length_int<R: io::Read>(input: &mut R) -> Result<u64> {
let first = try!(input.read_u8());
let mut read_additional = 0u8;
let mut mask_data = 0b0111_1111u8;
let mut mask_mark = 0b1000_0000u8;
while first & mask_mark != 0 {
read_additional = read_additional + 1;
mask_data = mask_data >> 1;
mask_mark = mask_mark >> 1;
}
if read_additional > 0 {
if read_additional == 1 {
return fmt_err("invalid variable-length integer");
} else {
read_additional = read_additional - 1;
}
}
let mut result = ((first & mask_data) as u64) << (6 * read_additional);
for i in (0..read_additional as i16).rev() {
let byte = try!(input.read_u8());
if byte & 0b1100_0000 != 0b1000_0000 {
return fmt_err("invalid variable-length integer");
}
result = result | (((byte & 0b0011_1111) as u64) << (6 * i as usize));
}
Ok(result)
}
#[test]
fn verify_read_var_length_int() {
let mut reader = io::Cursor::new(vec![0x24, 0xc2, 0xa2, 0xe2, 0x82, 0xac, 0xf0, 0x90, 0x8d,
0x88, 0xc2, 0x00, 0x80]);
assert_eq!(read_var_length_int(&mut reader).unwrap(), 0x24);
assert_eq!(read_var_length_int(&mut reader).unwrap(), 0xa2);
assert_eq!(read_var_length_int(&mut reader).unwrap(), 0x20ac);
assert_eq!(read_var_length_int(&mut reader).unwrap(), 0x010348);
assert_eq!(read_var_length_int(&mut reader).err().unwrap(),
Error::FormatError("invalid variable-length integer"));
assert_eq!(read_var_length_int(&mut reader).err().unwrap(),
Error::FormatError("invalid variable-length integer"));
}
fn read_frame_header_or_eof<R: io::Read>(input: &mut R) -> Result<Option<FrameHeader>> {
let mut crc_input = Crc8Reader::new(input);
let sync_res_block = match try!(crc_input.read_be_u16_or_eof()) {
None => return Ok(None),
Some(x) => x,
};
let sync_code = sync_res_block & 0b1111_1111_1111_1100;
if sync_code != 0b1111_1111_1111_1000 {
return fmt_err("frame sync code missing");
}
if sync_res_block & 0b0000_0000_0000_0010 != 0 {
return fmt_err("invalid frame header, encountered reserved value");
}
let blocking_strategy = if sync_res_block & 0b0000_0000_0000_0001 == 0 {
BlockingStrategy::Fixed
} else {
BlockingStrategy::Variable
};
let bs_sr = try!(crc_input.read_u8());
let mut block_size = 0u16;
let mut read_8bit_bs = false;
let mut read_16bit_bs = false;
match bs_sr >> 4 {
0b0000 => return fmt_err("invalid frame header, encountered reserved value"),
0b0001 => block_size = 192,
n if 0b0010 <= n && n <= 0b0101 => block_size = 576 * (1 << (n - 2) as usize),
0b0110 => read_8bit_bs = true,
0b0111 => read_16bit_bs = true,
n => block_size = 256 * (1 << (n - 8) as usize),
}
let mut sample_rate = None;
let mut read_8bit_sr = false;
let mut read_16bit_sr = false;
let mut read_16bit_sr_ten = false;
match bs_sr & 0b0000_1111 {
0b0000 => sample_rate = None,
0b0001 => sample_rate = Some(88_200),
0b0010 => sample_rate = Some(176_400),
0b0011 => sample_rate = Some(192_000),
0b0100 => sample_rate = Some(8_000),
0b0101 => sample_rate = Some(16_000),
0b0110 => sample_rate = Some(22_050),
0b0111 => sample_rate = Some(24_000),
0b1000 => sample_rate = Some(32_000),
0b1001 => sample_rate = Some(44_100),
0b1010 => sample_rate = Some(48_000),
0b1011 => sample_rate = Some(96_000),
0b1100 => read_8bit_sr = true,
0b1101 => read_16bit_sr = true,
0b1110 => read_16bit_sr_ten = true,
_ => return fmt_err("invalid frame header"),
}
let chan_bps_res = try!(crc_input.read_u8());
let channel_assignment = match chan_bps_res >> 4 {
n if n < 8 => ChannelAssignment::Independent(n + 1),
0b1000 => ChannelAssignment::LeftSideStereo,
0b1001 => ChannelAssignment::RightSideStereo,
0b1010 => ChannelAssignment::MidSideStereo,
_ => return fmt_err("invalid frame header, encountered reserved value"),
};
let bits_per_sample = match (chan_bps_res & 0b0000_1110) >> 1 {
0b000 => None,
0b001 => Some(8),
0b010 => Some(12),
0b100 => Some(16),
0b101 => Some(20),
0b110 => Some(24),
_ => return fmt_err("invalid frame header, encountered reserved value"),
};
if chan_bps_res & 0b0000_0001 != 0 {
return fmt_err("invalid frame header, encountered reserved value");
}
let block_time = match blocking_strategy {
BlockingStrategy::Variable => {
let sample = try!(read_var_length_int(&mut crc_input));
BlockTime::SampleNumber(sample)
}
BlockingStrategy::Fixed => {
let frame = try!(read_var_length_int(&mut crc_input));
if frame > 0x7fffffff {
return fmt_err("invalid frame header, frame number too large");
}
BlockTime::FrameNumber(frame as u32)
}
};
if read_8bit_bs {
let bs = try!(crc_input.read_u8());
block_size = bs as u16 + 1;
}
if read_16bit_bs {
let bs = try!(crc_input.read_be_u16());
if bs == 0xffff {
return fmt_err("invalid block size, exceeds 65535");
}
block_size = bs + 1;
}
if block_size < 16 {
return fmt_err("invalid block size, must be at least 16");
}
if read_8bit_sr {
let sr = try!(crc_input.read_u8());
sample_rate = Some(sr as u32);
}
if read_16bit_sr {
let sr = try!(crc_input.read_be_u16());
sample_rate = Some(sr as u32);
}
if read_16bit_sr_ten {
let sr_ten = try!(crc_input.read_be_u16());
sample_rate = Some(sr_ten as u32 * 10);
}
let computed_crc = crc_input.crc();
let presumed_crc = try!(crc_input.read_u8());
if computed_crc != presumed_crc {
return fmt_err("frame header CRC mismatch");
}
let frame_header = FrameHeader {
block_time: block_time,
block_size: block_size,
sample_rate: sample_rate,
channel_assignment: channel_assignment,
bits_per_sample: bits_per_sample,
};
Ok(Some(frame_header))
}
fn decode_left_side<Sample: sample::WideSample>(buffer: &mut [Sample]) -> Result<()> {
let block_size = buffer.len() / 2;
for i in 0..block_size {
let left = buffer[i];
let side = buffer[i + block_size];
let right = left - side;
buffer[block_size + i] = right;
}
Ok(())
}
#[test]
fn verify_decode_left_side() {
let mut buffer = vec![2i16, 5, 83, 113, 127, -63, -45, -15, 7, 38, 142, 238, 0, -152, -52, -18];
let result = vec![2i16, 5, 83, 113, 127, -63, -45, -15, -5, -33, -59, -125, 127, 89, 7, 3];
decode_left_side(&mut buffer).ok().unwrap();
assert_eq!(buffer, result);
}
fn decode_right_side<Sample: sample::WideSample>(buffer: &mut [Sample]) -> Result<()> {
let block_size = buffer.len() / 2;
for i in 0..block_size {
let side = buffer[i];
let right = buffer[block_size + i];
let left = side + right;
buffer[i] = left;
}
Ok(())
}
#[test]
fn verify_decode_right_side() {
let mut buffer = vec![7i16, 38, 142, 238, 0, -152, -52, -18, -5, -33, -59, -125, 127, 89, 7, 3];
let result = vec![2i16, 5, 83, 113, 127, -63, -45, -15, -5, -33, -59, -125, 127, 89, 7, 3];
decode_right_side(&mut buffer).expect("decoding is wrong");
assert_eq!(buffer, result);
}
fn decode_mid_side<Sample: sample::WideSample>(buffer: &mut [Sample]) -> Result<()> {
let block_size = buffer.len() / 2;
for i in 0..block_size {
let mid = buffer[i];
let side = buffer[i + block_size];
let mid = (mid << 1) | (side & Sample::one());
let left = (mid + side) >> 1;
let right = (mid - side) >> 1;
buffer[i] = left;
buffer[block_size + i] = right;
}
Ok(())
}
#[test]
fn verify_decode_mid_side() {
let mut buffer = vec!(-2i16, -14, 12, -6, 127, 13, -19, -6,
7, 38, 142, 238, 0, -152, -52, -18);
let result = vec!(2i16, 5, 83, 113, 127, -63, -45, -15,
-5, -33, -59, -125, 127, 89, 7, 3);
decode_mid_side(&mut buffer).expect("decoding is wrong");
assert_eq!(buffer, result);
}
pub struct Block<Sample> {
first_sample_number: u64,
block_size: u16,
channels: u8,
buffer: Vec<Sample>,
}
impl<Sample: sample::Sample> Block<Sample> {
fn new(time: u64, bs: u16, buffer: Vec<Sample>) -> Block<Sample> {
Block {
first_sample_number: time,
block_size: bs,
channels: (buffer.len() / bs as usize) as u8,
buffer: buffer,
}
}
pub fn empty() -> Block<Sample> {
Block {
first_sample_number: 0,
block_size: 0,
channels: 0,
buffer: Vec::with_capacity(0),
}
}
pub fn time(&self) -> u64 {
self.first_sample_number
}
pub fn len(&self) -> u16 {
self.block_size
}
pub fn channels(&self) -> u8 {
self.channels
}
pub fn channel(&self, ch: u8) -> &[Sample] {
&self.buffer[ch as usize * self.block_size as usize..(ch as usize + 1) *
self.block_size as usize]
}
pub fn sample(&self, ch: u8, sample: u16) -> Sample {
return self.buffer[ch as usize * self.block_size as usize + sample as usize];
}
pub fn into_buffer(self) -> Vec<Sample> {
return self.buffer;
}
}
#[test]
fn verify_block_sample() {
let block = Block {
first_sample_number: 0,
block_size: 5,
channels: 3,
buffer: vec![2i8, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47],
};
assert_eq!(block.sample(0, 2), 5);
assert_eq!(block.sample(1, 3), 23);
assert_eq!(block.sample(2, 4), 47);
}
pub struct FrameReader<R: io::Read, Sample: sample::Sample> {
input: R,
wide_buffer: Vec<Sample::Wide>,
}
pub type FrameResult<Sample> = Result<Option<Block<Sample>>>;
macro_rules! ensure_buffer_len {
($buffer: expr, $new_len: expr, $zero: expr) => {
if $buffer.len() < $new_len {
if $buffer.capacity() < $new_len {
$buffer = Vec::with_capacity($new_len);
}
let len = $buffer.len();
$buffer.extend(repeat($zero).take($new_len - len));
} else {
$buffer.truncate($new_len);
}
}
}
impl<R: io::Read, Sample: sample::Sample> FrameReader<R, Sample> {
pub fn new(input: R) -> FrameReader<R, Sample> {
FrameReader {
input: input,
wide_buffer: Vec::new(),
}
}
pub fn read_next_or_eof(&mut self, mut buffer: Vec<Sample>) -> FrameResult<Sample> {
use std::mem::size_of;
let mut crc_input = Crc16Reader::new(&mut self.input);
let header = match try!(read_frame_header_or_eof(&mut crc_input)) {
None => return Ok(None),
Some(h) => h,
};
let total_samples = header.channels() as usize * header.block_size as usize;
ensure_buffer_len!(buffer, total_samples, Sample::zero());
ensure_buffer_len!(self.wide_buffer, total_samples,
<Sample::Wide as sample::WideSample>::zero());
let bps = header.bits_per_sample.unwrap();
debug_assert!(bps as usize <= size_of::<Sample>() * 8);
{
let mut bitstream = Bitstream::new(&mut crc_input);
let bs = header.block_size as usize;
match header.channel_assignment {
ChannelAssignment::Independent(n_ch) => {
for ch in 0..n_ch as usize {
try!(subframe::decode(&mut bitstream,
bps,
&mut self.wide_buffer[ch * bs..(ch + 1) * bs]));
}
}
ChannelAssignment::LeftSideStereo => {
try!(subframe::decode(&mut bitstream, bps, &mut self.wide_buffer[..bs]));
try!(subframe::decode(&mut bitstream,
bps + 1,
&mut self.wide_buffer[bs..bs * 2]));
try!(decode_left_side(&mut self.wide_buffer[..bs * 2]));
}
ChannelAssignment::RightSideStereo => {
try!(subframe::decode(&mut bitstream, bps + 1, &mut self.wide_buffer[..bs]));
try!(subframe::decode(&mut bitstream, bps, &mut self.wide_buffer[bs..bs * 2]));
try!(decode_right_side(&mut self.wide_buffer[..bs * 2]));
}
ChannelAssignment::MidSideStereo => {
try!(subframe::decode(&mut bitstream, bps, &mut self.wide_buffer[..bs]));
try!(subframe::decode(&mut bitstream,
bps + 1,
&mut self.wide_buffer[bs..bs * 2]));
try!(decode_mid_side(&mut self.wide_buffer[..bs * 2]));
}
}
}
{
let n = header.block_size as usize * header.channels() as usize;
let wide_iter = self.wide_buffer[..n].iter();
let dest_iter = buffer[..n].iter_mut();
for (&src, dest) in wide_iter.zip(dest_iter) {
let narrow = Sample::from_wide(src).ok_or(Error::TooWide);
*dest = try!(narrow);
}
}
let computed_crc = crc_input.crc();
let presumed_crc = try!(crc_input.read_be_u16());
if computed_crc != presumed_crc {
return fmt_err("frame CRC mismatch");
}
let time = match header.block_time {
BlockTime::FrameNumber(fnr) => header.block_size as u64 * fnr as u64,
BlockTime::SampleNumber(snr) => snr,
};
let block = Block::new(time, header.block_size, buffer);
Ok(Some(block))
}
}