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https://github.com/Serial-ATA/lofty-rs
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MP4: Document AtomReader
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Serial
Alex
parent
ef532557a7
commit
3afe6d251a
2 changed files with 166 additions and 137 deletions
163
lofty/src/mp4/read/atom_reader.rs
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163
lofty/src/mp4/read/atom_reader.rs
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@ -0,0 +1,163 @@
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use crate::config::ParsingMode;
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use crate::error::Result;
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use crate::macros::err;
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use crate::mp4::atom_info::AtomInfo;
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use crate::util::io::SeekStreamLen;
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use std::io::{Read, Seek, SeekFrom};
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use byteorder::{BigEndian, ReadBytesExt};
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/// A reader for an MP4 file
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///
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/// This is a special wrapper around a reader that provides:
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///
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/// * [`Self::next`] to read atoms.
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/// * `read_u*` methods to read integers without needing to specify the endianness.
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/// * Bounds checking on reads and seeks to prevent going outside the file.
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pub(crate) struct AtomReader<R>
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where
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R: Read + Seek,
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{
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reader: R,
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start: u64,
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remaining_size: u64,
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len: u64,
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parse_mode: ParsingMode,
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}
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impl<R> AtomReader<R>
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where
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R: Read + Seek,
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{
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/// Create a new `AtomReader`
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pub(crate) fn new(mut reader: R, parse_mode: ParsingMode) -> Result<Self> {
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let len = reader.stream_len_hack()?;
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Ok(Self {
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reader,
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start: 0,
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remaining_size: len,
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len,
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parse_mode,
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})
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}
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/// Set new bounds for the reader
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///
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/// This is useful when reading an atom such as `moov`, where we only want to read it and its
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/// children. We can read the atom, set the bounds to the atom's length, and then read the children
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/// without worrying about reading past the atom's end.
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pub(crate) fn reset_bounds(&mut self, start_position: u64, len: u64) {
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self.start = start_position;
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self.remaining_size = len;
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self.len = len;
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}
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pub(crate) fn read_u8(&mut self) -> std::io::Result<u8> {
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self.remaining_size = self.remaining_size.saturating_sub(1);
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self.reader.read_u8()
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}
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pub(crate) fn read_u16(&mut self) -> std::io::Result<u16> {
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self.remaining_size = self.remaining_size.saturating_sub(2);
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self.reader.read_u16::<BigEndian>()
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}
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pub(crate) fn read_u24(&mut self) -> std::io::Result<u32> {
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self.remaining_size = self.remaining_size.saturating_sub(3);
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self.reader.read_u24::<BigEndian>()
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}
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pub(crate) fn read_u32(&mut self) -> std::io::Result<u32> {
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self.remaining_size = self.remaining_size.saturating_sub(4);
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self.reader.read_u32::<BigEndian>()
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}
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pub(crate) fn read_u64(&mut self) -> std::io::Result<u64> {
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self.remaining_size = self.remaining_size.saturating_sub(8);
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self.reader.read_u64::<BigEndian>()
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}
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pub(crate) fn read_uint(&mut self, size: usize) -> std::io::Result<u64> {
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self.remaining_size = self.remaining_size.saturating_sub(size as u64);
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self.reader.read_uint::<BigEndian>(size)
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}
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/// Read the next atom in the file
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///
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/// This will leave the reader at the beginning of the atom content.
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pub(crate) fn next(&mut self) -> Result<Option<AtomInfo>> {
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if self.remaining_size == 0 {
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return Ok(None);
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}
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if self.remaining_size < 8 {
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err!(SizeMismatch);
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}
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AtomInfo::read(self, self.remaining_size, self.parse_mode)
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}
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pub(crate) fn into_inner(self) -> R {
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self.reader
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}
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}
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impl<R> Seek for AtomReader<R>
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where
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R: Read + Seek,
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{
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fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
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match pos {
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SeekFrom::Start(s) => {
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if s > self.len {
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self.remaining_size = 0;
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let bound_end = self.start + self.len;
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return self.reader.seek(SeekFrom::Start(bound_end));
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}
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let ret = self.reader.seek(SeekFrom::Start(self.start + s))?;
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self.remaining_size = self.len.saturating_sub(ret);
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Ok(ret)
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},
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SeekFrom::End(s) => {
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if s >= 0 {
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self.remaining_size = 0;
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return self.reader.seek(SeekFrom::Start(self.start + self.len));
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}
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let bound_end = self.start + self.len;
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let relative_seek_count = core::cmp::min(self.len, s.unsigned_abs());
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self.reader.seek(SeekFrom::Start(
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bound_end.saturating_sub(relative_seek_count),
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))
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},
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SeekFrom::Current(s) => {
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if s.is_negative() {
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self.remaining_size = self.remaining_size.saturating_add(s.unsigned_abs());
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} else {
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self.remaining_size = self.remaining_size.saturating_sub(s as u64);
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}
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self.reader.seek(pos)
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},
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}
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}
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}
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impl<R> Read for AtomReader<R>
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where
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R: Read + Seek,
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{
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fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
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if self.remaining_size == 0 {
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return Ok(0);
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}
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let r = self.reader.read(buf)?;
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self.remaining_size = self.remaining_size.saturating_sub(r as u64);
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Ok(r)
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}
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}
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@ -1,3 +1,5 @@
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mod atom_reader;
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use super::atom_info::{AtomIdent, AtomInfo};
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use super::moov::Moov;
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use super::properties::Mp4Properties;
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@ -12,143 +14,7 @@ use std::io::{Read, Seek, SeekFrom};
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use byteorder::{BigEndian, ReadBytesExt};
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pub(super) struct AtomReader<R>
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where
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R: Read + Seek,
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{
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reader: R,
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start: u64,
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remaining_size: u64,
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len: u64,
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parse_mode: ParsingMode,
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}
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impl<R> AtomReader<R>
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where
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R: Read + Seek,
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{
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pub(super) fn new(mut reader: R, parse_mode: ParsingMode) -> Result<Self> {
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let len = reader.stream_len_hack()?;
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Ok(Self {
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reader,
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start: 0,
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remaining_size: len,
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len,
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parse_mode,
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})
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}
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pub(super) fn reset_bounds(&mut self, start_position: u64, len: u64) {
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self.start = start_position;
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self.remaining_size = len;
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self.len = len;
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}
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pub(super) fn read_u8(&mut self) -> std::io::Result<u8> {
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self.remaining_size = self.remaining_size.saturating_sub(1);
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self.reader.read_u8()
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}
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pub(super) fn read_u16(&mut self) -> std::io::Result<u16> {
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self.remaining_size = self.remaining_size.saturating_sub(2);
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self.reader.read_u16::<BigEndian>()
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}
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pub(super) fn read_u24(&mut self) -> std::io::Result<u32> {
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self.remaining_size = self.remaining_size.saturating_sub(3);
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self.reader.read_u24::<BigEndian>()
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}
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pub(super) fn read_u32(&mut self) -> std::io::Result<u32> {
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self.remaining_size = self.remaining_size.saturating_sub(4);
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self.reader.read_u32::<BigEndian>()
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}
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pub(super) fn read_u64(&mut self) -> std::io::Result<u64> {
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self.remaining_size = self.remaining_size.saturating_sub(8);
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self.reader.read_u64::<BigEndian>()
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}
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pub(super) fn read_uint(&mut self, size: usize) -> std::io::Result<u64> {
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self.remaining_size = self.remaining_size.saturating_sub(size as u64);
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self.reader.read_uint::<BigEndian>(size)
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}
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pub(super) fn next(&mut self) -> Result<Option<AtomInfo>> {
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if self.remaining_size == 0 {
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return Ok(None);
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}
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if self.remaining_size < 8 {
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err!(SizeMismatch);
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}
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AtomInfo::read(self, self.remaining_size, self.parse_mode)
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}
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pub(super) fn into_inner(self) -> R {
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self.reader
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}
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}
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impl<R> Seek for AtomReader<R>
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where
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R: Read + Seek,
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{
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fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
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match pos {
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SeekFrom::Start(s) => {
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if s > self.len {
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self.remaining_size = 0;
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let bound_end = self.start + self.len;
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return self.reader.seek(SeekFrom::Start(bound_end));
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}
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let ret = self.reader.seek(SeekFrom::Start(self.start + s))?;
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self.remaining_size = self.len.saturating_sub(ret);
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Ok(ret)
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},
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SeekFrom::End(s) => {
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if s >= 0 {
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self.remaining_size = 0;
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return self.reader.seek(SeekFrom::Start(self.start + self.len));
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}
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let bound_end = self.start + self.len;
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let relative_seek_count = core::cmp::min(self.len, s.unsigned_abs());
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self.reader.seek(SeekFrom::Start(
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bound_end.saturating_sub(relative_seek_count),
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))
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},
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SeekFrom::Current(s) => {
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if s.is_negative() {
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self.remaining_size = self.remaining_size.saturating_add(s.unsigned_abs());
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} else {
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self.remaining_size = self.remaining_size.saturating_sub(s as u64);
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}
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self.reader.seek(pos)
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},
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}
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}
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}
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impl<R> Read for AtomReader<R>
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where
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R: Read + Seek,
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{
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fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
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if self.remaining_size == 0 {
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return Ok(0);
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}
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let r = self.reader.read(buf)?;
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self.remaining_size = self.remaining_size.saturating_sub(r as u64);
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Ok(r)
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}
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}
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pub(super) use atom_reader::AtomReader;
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pub(in crate::mp4) fn verify_mp4<R>(reader: &mut AtomReader<R>) -> Result<String>
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where
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