mirror of
https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs.git
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153 lines
4.3 KiB
Rust
153 lines
4.3 KiB
Rust
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// Copyright (C) 2020 Matthew Waters <matthew@centricular.com>
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this library; if not, write to the
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// Free Software Foundation, Inc., 51 Franklin Street, Suite 500,
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// Boston, MA 02110-1335, USA.
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use byteorder::{BigEndian, ByteOrder};
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use std::fmt;
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#[allow(clippy::enum_variant_names)]
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#[derive(Debug, Clone, Copy)]
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pub enum ParseErrorCode {
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WrongLength,
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WrongMagicSequence,
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WrongLayout,
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}
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#[derive(Debug, Clone)]
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pub struct ParseError {
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pub code: ParseErrorCode,
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pub byte: usize,
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pub msg: String,
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}
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pub fn extract_cdp(mut data: &[u8]) -> Result<&[u8], ParseError> {
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/* logic from ccconverter */
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let data_len = data.len();
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if data.len() < 11 {
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return Err(ParseError {
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code: ParseErrorCode::WrongLength,
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byte: data_len - data.len(),
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msg: format!(
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"cdp packet too short {}. expected at least {}",
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data.len(),
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11
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),
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});
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}
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if 0x9669 != BigEndian::read_u16(&data[..2]) {
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return Err(ParseError {
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code: ParseErrorCode::WrongMagicSequence,
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byte: data_len - data.len(),
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msg: String::from("cdp packet does not have initial magic bytes of 0x9669"),
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});
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}
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data = &data[2..];
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if (data[0] as usize) != data_len {
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return Err(ParseError {
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code: ParseErrorCode::WrongLength,
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byte: data_len - data.len(),
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msg: format!(
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"advertised cdp packet length {} does not match length of data {}",
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data[0], data_len
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),
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});
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}
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data = &data[1..];
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/* skip framerate value */
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data = &data[1..];
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let flags = data[0];
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data = &data[1..];
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if flags & 0x40 == 0 {
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/* no cc_data */
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return Ok(&[]);
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}
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/* skip sequence counter */
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data = &data[2..];
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/* timecode present? */
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if flags & 0x80 == 0x80 {
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if data.len() < 5 {
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return Err(ParseError {
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code: ParseErrorCode::WrongLength,
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byte: data_len - data.len(),
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msg: String::from(
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"cdp packet signals a timecode but is not large enough to contain a timecode",
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),
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});
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}
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data = &data[5..];
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}
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/* cc_data */
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if data.len() < 2 {
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return Err(ParseError {
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code: ParseErrorCode::WrongLength,
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byte: data_len - data.len(),
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msg: String::from(
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"cdp packet signals cc_data but is not large enough to contain cc_data",
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),
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});
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}
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if data[0] != 0x72 {
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return Err(ParseError {
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code: ParseErrorCode::WrongMagicSequence,
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byte: data_len - data.len(),
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msg: String::from("ccp is missing start code 0x72"),
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});
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}
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data = &data[1..];
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let cc_count = data[0];
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data = &data[1..];
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if cc_count & 0xe0 != 0xe0 {
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return Err(ParseError {
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code: ParseErrorCode::WrongMagicSequence,
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byte: data_len - data.len(),
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msg: format!("reserved bits are not 0xe0, found {:02x}", cc_count & 0xe0),
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});
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}
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let cc_count = cc_count & 0x1f;
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let len = 3 * cc_count as usize;
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if len > data.len() {
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return Err(ParseError {
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code: ParseErrorCode::WrongLength,
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byte: data_len - data.len(),
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msg: String::from("cc_data length extends past the end of the cdp packet"),
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});
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}
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/* TODO: validate checksum */
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Ok(&data[..len])
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}
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impl fmt::Display for ParseError {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "{:?} at byte {}: {}", self.code, self.byte, self.msg)
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}
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}
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impl std::error::Error for ParseError {}
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