FLAC: Fix writing in files with no metadata

CHANGELOG.md

@@ -58,6 +58,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Don't error on empty `SYLT` strings ([issue](https://github.com/Serial-ATA/lofty-rs/issues/563)) ([PR](https://github.com/Serial-ATA/lofty-rs/pull/564))
 - **Vorbis Comments**: Parse `TRACKNUMBER` with respect to `ParseOptions::implicit_conversions` ([issue](https://github.com/Serial-ATA/lofty-rs/issues/540)) ([PR](https://github.com/Serial-ATA/lofty-rs/issues/542))
 - **APE**: Fix disc number removal/writing ([issue](https://github.com/Serial-ATA/lofty-rs/issues/545)) ([PR](https://github.com/Serial-ATA/lofty-rs/pull/546))
+- **FLAC**: Fix corruption of files with no metadata blocks ([issue](https://github.com/Serial-ATA/lofty-rs/issues/549)) ([PR](https://github.com/Serial-ATA/lofty-rs/pull/583))
 
 ### Removed
 

lofty/src/flac/block.rs

@@ -1,11 +1,12 @@
 #![allow(dead_code)]
 
 use crate::error::Result;
-use crate::macros::try_vec;
+use crate::macros::{err, try_vec};
+use crate::picture::{Picture, PictureInformation};
 
-use std::io::{Read, Seek, SeekFrom};
+use std::io::{Cursor, Read, Seek, SeekFrom, Write};
 
-use byteorder::{BigEndian, ReadBytesExt};
+use byteorder::{BigEndian, LittleEndian, ReadBytesExt, WriteBytesExt};
 
 pub(in crate::flac) const BLOCK_ID_STREAMINFO: u8 = 0;
 pub(in crate::flac) const BLOCK_ID_PADDING: u8 = 1;
@@ -16,7 +17,6 @@ pub(in crate::flac) const BLOCK_ID_PICTURE: u8 = 6;
 const BLOCK_HEADER_SIZE: u64 = 4;
 
 pub(crate) struct Block {
-	pub(super) byte: u8,
 	pub(super) ty: u8,
 	pub(super) last: bool,
 	pub(crate) content: Vec<u8>,
@@ -25,6 +25,9 @@ pub(crate) struct Block {
 }
 
 impl Block {
+	pub(super) const BLOCK_HEADER_SIZE: usize = 4;
+	pub(super) const MAX_CONTENT_SIZE: u32 = 16_777_215;
+
 	pub(crate) fn read<R, P>(data: &mut R, mut predicate: P) -> Result<Self>
 	where
 		R: Read + Seek,
@@ -51,12 +54,88 @@ impl Block {
 		let end = start + u64::from(size) + BLOCK_HEADER_SIZE;
 
 		Ok(Self {
-			byte,
 			ty,
 			last,
 			content,
 			start,
 			end,
 		})
 	}
+
+	pub fn len(&self) -> u32 {
+		(Self::BLOCK_HEADER_SIZE as u32) + self.content.len() as u32
+	}
+
+	pub(super) fn new_padding(size: usize) -> Result<Self> {
+		let block_size = core::cmp::min(size, Self::MAX_CONTENT_SIZE as usize);
+		let content = try_vec![0; block_size];
+		Ok(Self {
+			ty: BLOCK_ID_PADDING,
+			last: false,
+			content,
+			start: 0,
+			end: 0,
+		})
+	}
+
+	pub(super) fn new_picture(picture: &Picture, info: PictureInformation) -> Result<Self> {
+		let picture_data = picture.as_flac_bytes(info, false);
+		if picture_data.len() > Self::MAX_CONTENT_SIZE as usize {
+			err!(TooMuchData);
+		}
+
+		Ok(Self {
+			ty: BLOCK_ID_PICTURE,
+			last: false,
+			content: picture_data,
+			start: 0,
+			end: 0,
+		})
+	}
+
+	pub(super) fn new_comments<'a>(
+		vendor: &str,
+		items: &mut impl Iterator<Item = (&'a str, &'a str)>,
+	) -> Result<Self> {
+		let mut comments = Cursor::new(Vec::new());
+
+		comments.write_u32::<LittleEndian>(vendor.len() as u32)?;
+		comments.write_all(vendor.as_bytes())?;
+
+		let item_count_pos = comments.stream_position()?;
+		let mut count = 0;
+
+		comments.write_u32::<LittleEndian>(count)?;
+
+		crate::ogg::write::create_comments(&mut comments, &mut count, items)?;
+
+		if comments.get_ref().len() > Block::MAX_CONTENT_SIZE as usize {
+			err!(TooMuchData);
+		}
+
+		comments.seek(SeekFrom::Start(item_count_pos))?;
+		comments.write_u32::<LittleEndian>(count)?;
+
+		Ok(Self {
+			ty: BLOCK_ID_VORBIS_COMMENTS,
+			last: false,
+			content: comments.into_inner(),
+			start: 0,
+			end: 0,
+		})
+	}
+
+	pub(super) fn write_to<W>(&self, writer: &mut W) -> Result<usize>
+	where
+		W: Write,
+	{
+		let block_content_size =
+			core::cmp::min(self.content.len(), Self::MAX_CONTENT_SIZE as usize);
+
+		writer.write_u8((self.ty & 0x7F) | u8::from(self.last) << 7)?;
+		writer.write_u24::<BigEndian>(block_content_size as u32)?;
+		writer.write_all(&self.content)?;
+
+		Ok(Self::BLOCK_HEADER_SIZE + self.content.len())
+	}
 }