1use crate::{
2 util::{read_u16, read_u32, Endian},
3 ImageResult, ImageSize,
4};
5use std::io::{BufRead, Seek, SeekFrom};
6
7pub fn size<R: BufRead + Seek>(reader: &mut R) -> ImageResult<ImageSize> {
8 // skip the IFF header
9 reader.seek(SeekFrom::Start(12))?;
10
11 let mut chunk_id = [0; 4];
12
13 loop {
14 reader.read_exact(&mut chunk_id)?;
15 let chunk_length = read_u32(reader, &Endian::Big)? as i64;
16
17 if &chunk_id == b"BMHD" {
18 return Ok(ImageSize {
19 width: read_u16(reader, &Endian::Big)? as usize,
20 height: read_u16(reader, &Endian::Big)? as usize,
21 });
22 }
23
24 // the BMHD chunk must occur before the BODY chunk
25 if &chunk_id == b"BODY" {
26 return Err(crate::ImageError::CorruptedImage);
27 }
28
29 // skip over the chunk; chunks of odd length have a padding byte
30 reader.seek(SeekFrom::Current(chunk_length + chunk_length % 2))?;
31 }
32}
33
34pub fn matches(header: &[u8]) -> bool {
35 header.len() >= 12
36 && &header[0..4] == b"FORM"
37 && (&header[8..12] == b"ILBM" || &header[8..12] == b"PBM ")
38}
39