Add function for synchsafe integers

src/logic/id3/mod.rs

@@ -12,10 +12,22 @@ use std::io::{Read, Seek, SeekFrom};
 use std::ops::Neg;
 
 // https://github.com/polyfloyd/rust-id3/blob/e142ec656bf70a8153f6e5b34a37f26df144c3c1/src/stream/unsynch.rs#L18-L20
-pub(crate) fn decode_u32(n: u32) -> u32 {
+pub(crate) fn unsynch_u32(n: u32) -> u32 {
 	n & 0xFF | (n & 0xFF00) >> 1 | (n & 0xFF_0000) >> 2 | (n & 0xFF00_0000) >> 3
 }
 
+// https://github.com/polyfloyd/rust-id3/blob/e142ec656bf70a8153f6e5b34a37f26df144c3c1/src/stream/unsynch.rs#L9-L15
+pub(crate) fn synch_u32(n: u32) -> Result<u32> {
+	if n > 0x1000_0000 {
+		return Err(LoftyError::TooMuchData);
+	}
+
+	let mut x: u32 = n & 0x7F | (n & 0xFFFF_FF80) << 1;
+	x = x & 0x7FFF | (x & 0xFFFF_8000) << 1;
+	x = x & 0x7F_FFFF | (x & 0xFF80_0000) << 1;
+	Ok(x)
+}
+
 pub(crate) fn find_lyrics3v2<R>(data: &mut R) -> Result<(bool, u32)>
 where
 	R: Read + Seek,

src/logic/id3/v2/frame/header.rs

@@ -50,7 +50,7 @@ where
 	let id_str = std::str::from_utf8(&frame_header[..4]).map_err(|_| LoftyError::BadFrameID)?;
 
 	let (id, size) = if synchsafe {
-		let size = crate::logic::id3::decode_u32(u32::from_be_bytes([
+		let size = crate::logic::id3::unsynch_u32(u32::from_be_bytes([
 			frame_header[4],
 			frame_header[5],
 			frame_header[6],

src/logic/id3/v2/mod.rs

@@ -1,4 +1,4 @@
-use crate::logic::id3::decode_u32;
+use crate::logic::id3::unsynch_u32;
 use crate::Result;
 
 use std::io::{Read, Seek, SeekFrom};
@@ -103,7 +103,7 @@ pub enum Id3v2Frame {
 	EncapsulatedObject,
 	/// When an ID3v2.2 key couldn't be upgraded
 	///
-	/// This **will not** be written. It is up to the user to upgrade and store the key as [`ItemKey::Unknown`](crate::ItemKey::Unknown).
+	/// This **will not** be written. It is up to the user to upgrade and store the key as another variant.
 	Outdated(String),
 }
 
@@ -117,7 +117,7 @@ where
 	data.read_exact(&mut id3_header)?;
 
 	if &id3_header[..3] == b"ID3" {
-		let size = decode_u32(BigEndian::read_u32(&id3_header[6..]));
+		let size = unsynch_u32(BigEndian::read_u32(&id3_header[6..]));
 
 		if read {
 			data.seek(SeekFrom::Current(-10))?;

src/logic/mpeg/read.rs

@@ -1,6 +1,6 @@
 use super::header::{Header, XingHeader};
 use crate::files::MpegFile;
-use crate::logic::id3::decode_u32;
+use crate::logic::id3::unsynch_u32;
 use crate::logic::id3::v2::read::parse_id3v2;
 use crate::{FileProperties, LoftyError, Result};
 
@@ -92,7 +92,7 @@ where
 				let mut remaining_header = [0; 6];
 				data.read_exact(&mut remaining_header)?;
 
-				let size = (decode_u32(BigEndian::read_u32(&remaining_header[2..])) + 10) as usize;
+				let size = (unsynch_u32(BigEndian::read_u32(&remaining_header[2..])) + 10) as usize;
 				data.seek(SeekFrom::Current(-10))?;
 
 				let mut id3v2_read = vec![0; size];

src/types/file.rs

@@ -315,7 +315,7 @@ impl FileType {
 	where
 		R: Read + Seek,
 	{
-		use crate::logic::{id3::decode_u32, mpeg::header::verify_frame_sync};
+		use crate::logic::{id3::unsynch_u32, mpeg::header::verify_frame_sync};
 
 		if data.seek(SeekFrom::End(0))? == 0 {
 			return Err(LoftyError::EmptyFile);
@@ -329,7 +329,7 @@ impl FileType {
 		let ret = match sig.first().unwrap() {
 			77 if sig.starts_with(b"MAC") => Ok(Self::APE),
 			73 if sig.starts_with(b"ID3") => {
-				let size = decode_u32(u32::from_be_bytes(
+				let size = unsynch_u32(u32::from_be_bytes(
 					sig[6..10]
 						.try_into()
 						.map_err(|_| LoftyError::UnknownFormat)?,