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use std::convert::TryInto;
pub fn is_jpeg(buf: &[u8]) -> bool {
buf.len() > 2 && buf[0] == 0xFF && buf[1] == 0xD8 && buf[2] == 0xFF
}
pub fn is_jpeg2000(buf: &[u8]) -> bool {
buf.len() > 12
&& buf[0] == 0x0
&& buf[1] == 0x0
&& buf[2] == 0x0
&& buf[3] == 0xC
&& buf[4] == 0x6A
&& buf[5] == 0x50
&& buf[6] == 0x20
&& buf[7] == 0x20
&& buf[8] == 0xD
&& buf[9] == 0xA
&& buf[10] == 0x87
&& buf[11] == 0xA
&& buf[12] == 0x0
}
pub fn is_png(buf: &[u8]) -> bool {
buf.len() > 3 && buf[0] == 0x89 && buf[1] == 0x50 && buf[2] == 0x4E && buf[3] == 0x47
}
pub fn is_gif(buf: &[u8]) -> bool {
buf.len() > 2 && buf[0] == 0x47 && buf[1] == 0x49 && buf[2] == 0x46
}
pub fn is_webp(buf: &[u8]) -> bool {
buf.len() > 11 && buf[8] == 0x57 && buf[9] == 0x45 && buf[10] == 0x42 && buf[11] == 0x50
}
pub fn is_cr2(buf: &[u8]) -> bool {
buf.len() > 9
&& ((buf[0] == 0x49 && buf[1] == 0x49 && buf[2] == 0x2A && buf[3] == 0x0)
|| (buf[0] == 0x4D && buf[1] == 0x4D && buf[2] == 0x0 && buf[3] == 0x2A))
&& buf[8] == 0x43
&& buf[9] == 0x52
&& buf[10] == 0x02
}
pub fn is_tiff(buf: &[u8]) -> bool {
buf.len() > 9
&& ((buf[0] == 0x49 && buf[1] == 0x49 && buf[2] == 0x2A && buf[3] == 0x0)
|| (buf[0] == 0x4D && buf[1] == 0x4D && buf[2] == 0x0 && buf[3] == 0x2A))
&& buf[8] != 0x43
&& buf[9] != 0x52
&& !is_cr2(buf)
}
pub fn is_bmp(buf: &[u8]) -> bool {
buf.len() > 1 && buf[0] == 0x42 && buf[1] == 0x4D
}
pub fn is_jxr(buf: &[u8]) -> bool {
buf.len() > 2 && buf[0] == 0x49 && buf[1] == 0x49 && buf[2] == 0xBC
}
pub fn is_psd(buf: &[u8]) -> bool {
buf.len() > 3 && buf[0] == 0x38 && buf[1] == 0x42 && buf[2] == 0x50 && buf[3] == 0x53
}
pub fn is_ico(buf: &[u8]) -> bool {
buf.len() > 3 && buf[0] == 0x00 && buf[1] == 0x00 && buf[2] == 0x01 && buf[3] == 0x00
}
pub fn is_heif(buf: &[u8]) -> bool {
if buf.is_empty() {
return false;
}
if !is_isobmff(buf) {
return false;
}
if let Some((major, _minor, compatible)) = get_ftyp(buf) {
if major == b"heic" {
return true;
}
if major == b"mif1" || major == b"msf1" {
for b in compatible {
if b == b"heic" {
return true;
}
}
}
}
false
}
pub fn is_avif(buf: &[u8]) -> bool {
if buf.is_empty() {
return false;
}
if !is_isobmff(buf) {
return false;
}
if let Some((major, _minor, compatible)) = get_ftyp(buf) {
if major == b"avif" || major == b"avis" {
return true;
}
for b in compatible {
if b == b"avif" || b == b"avis" {
return true;
}
}
}
false
}
fn is_isobmff(buf: &[u8]) -> bool {
if buf.len() < 16 {
return false;
}
if &buf[4..8] != b"ftyp" {
return false;
}
let ftyp_length = u32::from_be_bytes(buf[0..4].try_into().unwrap()) as usize;
buf.len() >= ftyp_length
}
fn get_ftyp(buf: &[u8]) -> Option<(&[u8], &[u8], impl Iterator<Item = &[u8]>)> {
if buf.len() < 16 {
return None;
}
let ftyp_length = u32::from_be_bytes(buf[0..4].try_into().unwrap()) as usize;
let major = &buf[8..12];
let minor = &buf[12..16];
let compatible = (16..ftyp_length).step_by(4).map(move |i| &buf[i..i + 4]);
Some((major, minor, compatible))
}