ID3v2: Expose {synch_u32, unsynch_u32}

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **A proc macro for file creation**:
   - With the new `lofty_attr` crate, file creation has been simplified significantly.
     It is available for both internal and external usage.
+- **ID3v2**: Exposed internal functions `id3::v2::util::{synch_u32, unsynch_u32}`
 
 ### Changed
 - **TaggedFile**: `tag{_mut}` no longer takes a reference to `TagType`

src/file.rs

@@ -699,7 +699,7 @@ impl FileType {
 
 	// TODO: APE tags in the beginning of the file
 	pub(crate) fn from_buffer_inner(buf: &[u8]) -> (Option<Self>, Option<u32>) {
-		use crate::id3::v2::unsynch_u32;
+		use crate::id3::v2::util::unsynch_u32;
 
 		// Start out with an empty return: (File type, id3 size)
 		// Only one can be set

src/id3/v2/frame/header.rs

@@ -80,7 +80,7 @@ where
 
 	// unsynch the frame size if necessary
 	if synchsafe {
-		size = crate::id3::v2::unsynch_u32(size);
+		size = crate::id3::v2::util::unsynch_u32(size);
 	}
 
 	let frame_id = FrameID::new(id_str)?;

src/id3/v2/mod.rs

@@ -8,10 +8,11 @@
 //! * [Frame]
 
 mod flags;
-pub(crate) mod util;
+pub mod util;
 
 use crate::error::{ID3v2Error, ID3v2ErrorKind, Result};
 use crate::macros::err;
+use util::unsynch_u32;
 
 use std::io::Read;
 
@@ -66,24 +67,6 @@ pub enum ID3v2Version {
 	V4,
 }
 
-// https://github.com/polyfloyd/rust-id3/blob/e142ec656bf70a8153f6e5b34a37f26df144c3c1/src/stream/unsynch.rs#L18-L20
-pub(crate) fn unsynch_u32(n: u32) -> u32 {
-	n & 0xFF | (n & 0xFF00) >> 1 | (n & 0xFF_0000) >> 2 | (n & 0xFF00_0000) >> 3
-}
-
-#[cfg(feature = "id3v2")]
-// 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 {
-		err!(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)
-}
-
 #[derive(Copy, Clone)]
 pub(crate) struct ID3v2Header {
 	#[cfg(feature = "id3v2")]

src/id3/v2/util/mod.rs

@@ -1,53 +1,84 @@
+//! Utilities for working with ID3v2 tags
+
 pub(crate) mod text_utils;
-#[cfg(feature = "id3v2")]
-pub(crate) mod upgrade;
 
-#[cfg(feature = "id3v2")]
-use crate::error::{ID3v2Error, ID3v2ErrorKind, Result};
+cfg_if::cfg_if! {
+	if #[cfg(feature = "id3v2")] {
+		pub(crate) mod upgrade;
 
-#[cfg(feature = "id3v2")]
-pub(in crate::id3::v2) fn unsynch_content(content: &[u8]) -> Result<Vec<u8>> {
-	let mut unsynch_content = Vec::new();
+		use crate::error::{ID3v2Error, ID3v2ErrorKind, Result};
 
-	let mut discard = false;
+		pub(in crate::id3::v2) fn unsynch_content(content: &[u8]) -> Result<Vec<u8>> {
+			let mut unsynch_content = Vec::new();
 
-	let mut i = 0;
-	let mut next = 0;
-	let content_len = content.len();
+			let mut discard = false;
 
-	// Check for (0xFF, 0x00, 0x00), replace with (0xFF, 0x00)
-	while i < content_len && next < content_len {
-		// Verify the next byte is less than 0xE0 (0b111xxxxx)
-		// Then remove the next byte if it is a zero
-		if discard {
-			if content[next] >= 0xE0 {
-				return Err(ID3v2Error::new(ID3v2ErrorKind::Other(
-					"Encountered an invalid unsynchronisation",
-				))
-				.into());
-			}
+			let mut i = 0;
+			let mut next = 0;
+			let content_len = content.len();
+
+			// Check for (0xFF, 0x00, 0x00), replace with (0xFF, 0x00)
+			while i < content_len && next < content_len {
+				// Verify the next byte is less than 0xE0 (0b111xxxxx)
+				// Then remove the next byte if it is a zero
+				if discard {
+					if content[next] >= 0xE0 {
+						return Err(ID3v2Error::new(ID3v2ErrorKind::Other(
+							"Encountered an invalid unsynchronisation",
+						))
+						.into());
+					}
+
+					if content[next] == 0 {
+						discard = false;
+						next += 1;
+
+						continue;
+					}
+				}
 
-			if content[next] == 0 {
 				discard = false;
+
+				unsynch_content.push(content[next]);
+
+				if content[next] == 0xFF {
+					discard = true
+				}
+
+				i += 1;
 				next += 1;
-
-				continue;
 			}
+
+			Ok(unsynch_content)
 		}
 
-		discard = false;
+		/// Create a synchsafe integer
+		///
+		/// See [`FrameFlags::unsynchronisation`](crate::id3::v2::FrameFlags::unsynchronisation) for an explanation.
+		///
+		/// # Errors
+		///
+		/// `n` doesn't fit in 28 bits
+		// https://github.com/polyfloyd/rust-id3/blob/e142ec656bf70a8153f6e5b34a37f26df144c3c1/src/stream/unsynch.rs#L9-L15
+		pub fn synch_u32(n: u32) -> Result<u32> {
+			if n > 0x1000_0000 {
+				crate::macros::err!(TooMuchData);
+			}
 
-		unsynch_content.push(content[next]);
-
-		if content[next] == 0xFF {
-			discard = true
+			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)
 		}
-
-		i += 1;
-		next += 1;
 	}
+}
 
-	Ok(unsynch_content)
+/// Unsynchronise a synchsafe integer
+///
+/// See [`FrameFlags::unsynchronisation`](crate::id3::v2::FrameFlags::unsynchronisation) for an explanation.
+// https://github.com/polyfloyd/rust-id3/blob/e142ec656bf70a8153f6e5b34a37f26df144c3c1/src/stream/unsynch.rs#L18-L20
+pub fn unsynch_u32(n: u32) -> u32 {
+	n & 0xFF | (n & 0xFF00) >> 1 | (n & 0xFF_0000) >> 2 | (n & 0xFF00_0000) >> 3
 }
 
 #[cfg(test)]

src/id3/v2/write/frame.rs

@@ -1,6 +1,6 @@
 use crate::error::{ID3v2Error, ID3v2ErrorKind, Result};
 use crate::id3::v2::frame::{FrameFlags, FrameRef, FrameValue};
-use crate::id3::v2::synch_u32;
+use crate::id3::v2::util::synch_u32;
 
 use std::io::Write;
 

src/id3/v2/write/mod.rs

@@ -6,8 +6,8 @@ use crate::error::Result;
 use crate::file::FileType;
 use crate::id3::find_id3v2;
 use crate::id3::v2::frame::FrameRef;
-use crate::id3::v2::synch_u32;
 use crate::id3::v2::tag::Id3v2TagRef;
+use crate::id3::v2::util::synch_u32;
 use crate::macros::err;
 use crate::probe::Probe;