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// Module for parsing ISO Base Media Format aka video/mp4 streams.

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at https://mozilla.org/MPL/2.0/.

/// Basic ISO box structure.
pub struct Mp4BoxHeader {
    /// Four character box type
pub name: u32,
    /// Size of the box in bytes
pub size: u64,
    /// Offset to the start of the contained data (or header size).
pub offset: u64,
}

/// File type box 'ftyp'.
pub struct Mp4FileTypeBox {
    name: u32,
    size: u64,
    major_brand: u32,
    minor_version: u32,
    compatible_brands: Vec<u32>,
}

extern crate byteorder;
use byteorder::{BigEndian, ReadBytesExt};
use std::io::{Result, Seek, SeekFrom};

/// Parse a box out of a data buffer.
pub fn read_box_header<T: ReadBytesExt>(src: &mut T) -> Option<Mp4BoxHeader> {
    let tmp_size = src.read_u32::<BigEndian>().unwrap();
    let name = src.read_u32::<BigEndian>().unwrap();
    let size = match tmp_size {
        1 => src.read_u64::<BigEndian>().unwrap(),
        _ => tmp_size as u64,
    };
    assert!(size >= 8);
    if tmp_size == 1 {
        assert!(size >= 16);
    }
    let offset = match tmp_size {
        1 => 4 + 4 + 8,
        _ => 4 + 4,
    };
    assert!(offset <= size);
    Some(Mp4BoxHeader{
        name: name,
        size: size,
        offset: offset,
    })
}

/// Skip over the contents of a box.
pub fn skip_box_content<T: ReadBytesExt + std::io::Seek>
  (src: &mut T, header: &Mp4BoxHeader)
  -> std::io::Result<u64>
{
    src.seek(SeekFrom::Current((header.size - header.offset) as i64))
}

/// Parse an ftype box.
pub fn read_ftyp<T: ReadBytesExt>(src: &mut T) -> Option<Mp4FileTypeBox> {
    let head = read_box_header(src).unwrap();
    let major = src.read_u32::<BigEndian>().unwrap();
    let minor = src.read_u32::<BigEndian>().unwrap();
    let brand_count = (head.size - 8 - 8) /4;
    let mut brands = Vec::new();
    for _ in 0..brand_count {
        brands.push(src.read_u32::<BigEndian>().unwrap());
    }
    Some(Mp4FileTypeBox{
        name: head.name,
        size: head.size,
        major_brand: major,
        minor_version: minor,
        compatible_brands: brands,
    })
}

/// Split a u32 box type into a [u8].
fn u32_to_vec(x: u32) -> Vec<u8> {
    vec!((x >> 24 & 0xffu32) as u8,
         (x >> 16 & 0xffu32) as u8,
         (x >>  8 & 0xffu32) as u8,
         (x & 0xffu32) as u8)
}

use std::fmt;
impl fmt::Display for Mp4BoxHeader {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let name_bytes = u32_to_vec(self.name);
        let name = String::from_utf8_lossy(&name_bytes);
        write!(f, "'{}' {} bytes", name, self.size)
    }
}

impl fmt::Display for Mp4FileTypeBox {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let name_bytes = u32_to_vec(self.name);
        let name = String::from_utf8_lossy(&name_bytes);
        let brand_bytes = u32_to_vec(self.major_brand);
        let brand = String::from_utf8_lossy(&brand_bytes);
        write!(f, "'{}' {} bytes '{}' v{}", name, self.size,
            brand, self.minor_version)
    }
}

#[test]
fn test_read_box_header() {
    use std::io::Cursor;
    use std::io::Write;
    let mut test: Vec<u8> = vec![0, 0, 0, 8];  // minimal box length
    write!(&mut test, "test").unwrap(); // box type
    let mut stream = Cursor::new(test);
    let parsed = read_box_header(&mut stream).unwrap();
    assert_eq!(parsed.name, 1952805748);
    assert_eq!(parsed.size, 8);
    println!("box {}", parsed);
}


#[test]
fn test_read_box_header_long() {
    use std::io::Cursor;
    let mut test: Vec<u8> = vec![0, 0, 0, 1]; // long box extension code
    test.extend("long".to_string().into_bytes()); // box type
    test.extend(vec![0, 0, 0, 0, 0, 0, 16, 0]); // 64 bit size
    // Skip generating box content.
    let mut stream = Cursor::new(test);
    let parsed = read_box_header(&mut stream).unwrap();
    assert_eq!(parsed.name, 1819242087);
    assert_eq!(parsed.size, 4096);
    println!("box {}", parsed);
}

#[test]
fn test_read_ftyp() {
    use std::io::Cursor;
    use std::io::Write;
    let mut test: Vec<u8> = vec![0, 0, 0, 24]; // size
    write!(&mut test, "ftyp").unwrap(); // type
    write!(&mut test, "mp42").unwrap(); // major brand
    test.extend(vec![0, 0, 0, 0]);      // minor version
    write!(&mut test, "isom").unwrap(); // compatible brands...
    write!(&mut test, "mp42").unwrap();
    assert_eq!(test.len(), 24);

    let mut stream = Cursor::new(test);
    let parsed = read_ftyp(&mut stream).unwrap();
    assert_eq!(parsed.name, 1718909296);
    assert_eq!(parsed.size, 24);
    assert_eq!(parsed.major_brand, 1836069938);
    assert_eq!(parsed.minor_version, 0);
    assert_eq!(parsed.compatible_brands.len(), 2);
    println!("box {}", parsed);
}