improved error handling

src/addrmap.rs

@@ -1,11 +1,11 @@
-use crate::btrfs_structs::{ParseBin, Key, ChunkItem, Leaf, Value, Superblock, LogToPhys};
+use crate::btrfs_structs::{ParseBin, Key, ChunkItem, Leaf, Value, Superblock, LogToPhys, ParseError};
 
 #[derive(Debug)]
 pub struct AddressMap(Vec<(u64,u64,Vec<(u64,u64)>)>);
 
 // TODO: support for internal nodes, multiple devices?
 impl AddressMap {
-	pub fn new(image: &[u8]) -> Result<AddressMap,String> {
+	pub fn new(image: &[u8]) -> Result<AddressMap, ParseError> {
 		let superblock = Superblock::parse(&image[0x10000..])?;
 		let bootstrap_addr = AddressMap::from_superblock(&superblock)?;
 
@@ -36,7 +36,7 @@ impl AddressMap {
 		Ok(AddressMap(addr_map))
 	}
 
-	pub fn from_superblock(superblock: &Superblock) -> Result<AddressMap,String> {
+	pub fn from_superblock(superblock: &Superblock) -> Result<AddressMap, ParseError> {
 		let sys_chunk_array_size = superblock.sys_chunk_array_size;
 		let sys_chunk_array: &[u8] = &superblock.sys_chunk_array;
 		let mut addr_map = Vec::new();

src/btrfs_structs.rs

@@ -390,15 +390,15 @@ impl From<ParseError> for io::Error {
 }
 
 pub trait ParseBin where Self: Sized {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String>;
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError>;
 
-	fn parse(bytes: &[u8]) -> Result<Self, String> {
+	fn parse(bytes: &[u8]) -> Result<Self, ParseError> {
 		Self::parse_len(bytes).map(|x|x.0)
 	}
 }
 
 impl ParseBin for u8 {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		if bytes.len() < 1 {
 			Err("not enough data".into())
 		} else {
@@ -408,7 +408,7 @@ impl ParseBin for u8 {
 }
 
 impl ParseBin for u16 {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		if bytes.len() < 2 {
 			Err("not enough data".into())
 		} else {
@@ -419,7 +419,7 @@ impl ParseBin for u16 {
 }
 
 impl ParseBin for u32 {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		if bytes.len() < 4 {
 			Err("not enough data".into())
 		} else {
@@ -430,7 +430,7 @@ impl ParseBin for u32 {
 }
 
 impl ParseBin for u64 {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		if bytes.len() < 8 {
 			Err("not enough data".into())
 		} else {
@@ -441,7 +441,7 @@ impl ParseBin for u64 {
 }
 
 impl<const N: usize> ParseBin for [u8; N] {
-	fn parse_len(bytes: &[u8]) -> Result<([u8; N], usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<([u8; N], usize), ParseError> {
 		if bytes.len() < N {
 			Err("not enough data".into())
 		} else {
@@ -452,13 +452,13 @@ impl<const N: usize> ParseBin for [u8; N] {
 
 // we use Vec<u8> for "unknown extra data", so just eat up everything
 impl ParseBin for Vec<u8> {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		Ok((Vec::from(bytes), bytes.len()))
 	}
 }
 
 impl ParseBin for CString {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		let mut chars = Vec::from(bytes);
 		chars.push(0);
 		Ok((CString::from_vec_with_nul(chars).unwrap(), bytes.len()))
@@ -484,13 +484,13 @@ impl From<u8> for ItemType {
 }
 
 impl ParseBin for ItemType {
-	fn parse_len(bytes: &[u8]) -> Result<(ItemType, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(ItemType, usize), ParseError> {
 		u8::parse(bytes).map(|x|(ItemType::from(x),1))
 	}
 }
 
 impl ParseBin for Leaf {
-	fn parse_len(bytes: &[u8]) -> Result<(Leaf, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Leaf, usize), ParseError> {
 		if bytes.len() < 0x65 {
 			return Err("not enough data".into());
 		}
@@ -551,7 +551,7 @@ impl ParseBin for Leaf {
 
 // ExtentDataItem needs a custom implementation because it can have inline or external data
 impl ParseBin for ExtentDataItem {
-	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), String> {
+	fn parse_len(bytes: &[u8]) -> Result<(Self, usize), ParseError> {
 		let (header, header_size) = ExtentDataHeader::parse_len(bytes)?;
 		if header.extent_type == 1 { // external extent
 			let (body, body_size) = ExternalExtent::parse_len(&bytes[header_size..])?;

src/main.rs

@@ -21,16 +21,19 @@ fn main() -> Result<(), IOError> {
 	let file = File::open("../image")?;
 	let image = unsafe { Mmap::map(&file)? };
 
-	let addr = AddressMap::new(&image).map_err(|e|IOError::other(e))?;
-	let superblock = Superblock::parse(&image[0x10000..]).map_err(|e|IOError::other(e))?;
+	let addr = AddressMap::new(&image).unwrap();
+	let superblock = Superblock::parse(&image[0x10000..]).unwrap();
 
-	let chunk_root_phys = addr.to_phys(superblock.chunk_root).unwrap() as usize;
-	let root_phys = addr.to_phys(superblock.root).unwrap() as usize;
+	let chunk_root_phys = addr.to_phys(superblock.chunk_root)
+		.ok_or(IOError::other("Chunk root address stored in superblock is invalid"))? as usize;
+	let root_phys = addr.to_phys(superblock.root)
+		.ok_or(IOError::other("Root address stored in superblock is invalid"))? as usize;
 
-	let root_tree_leaf = Leaf::parse(&image[root_phys .. root_phys + NODE_SIZE]).map_err(|e|IOError::other(e))?;
+	let root_tree_leaf = Leaf::parse(&image[root_phys .. root_phys + NODE_SIZE])?;
 
 	let root_key = Key::new(EXTENT_TREE, ItemType::Root, 0);
-	let root = root_tree_leaf.find_key(root_key).unwrap();
+	let root = root_tree_leaf.find_key(root_key)
+		.ok_or(IOError::other("Could not find extent tree in tree of roots"))?;
 
 	let root_addr = if let Value::Root(root_item) = root.value {
 		addr.to_phys(root_item.bytenr)
@@ -38,7 +41,7 @@ fn main() -> Result<(), IOError> {
 		None
 	}.unwrap() as usize;
 
-	let tree_leaf = Leaf::parse(&image[root_addr .. root_addr + NODE_SIZE]).map_err(|e|IOError::other(e))?;
+	let tree_leaf = Leaf::parse(&image[root_addr .. root_addr + NODE_SIZE])?;
 
 	println!("{:#?}", &tree_leaf);