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+//! Defining custom `Reader`s quickly.
+
+use alloc::borrow::Cow;
+use alloc::rc::Rc;
+use alloc::string::String;
+use alloc::sync::Arc;
+use core::fmt::Debug;
+use core::ops::{Deref, Index, Range, RangeFrom, RangeTo};
+use core::slice;
+use core::str;
+use stable_deref_trait::CloneStableDeref;
+
+use crate::endianity::Endianity;
+use crate::read::{Error, Reader, ReaderOffsetId, Result};
+
+/// A reference counted, non-thread-safe slice of bytes and associated
+/// endianity.
+///
+/// ```
+/// # #[cfg(feature = "std")] {
+/// use std::rc::Rc;
+///
+/// let buf = Rc::from(&[1, 2, 3, 4][..]);
+/// let reader = gimli::EndianRcSlice::new(buf, gimli::NativeEndian);
+/// # let _ = reader;
+/// # }
+/// ```
+pub type EndianRcSlice<Endian> = EndianReader<Endian, Rc<[u8]>>;
+
+/// An atomically reference counted, thread-safe slice of bytes and associated
+/// endianity.
+///
+/// ```
+/// # #[cfg(feature = "std")] {
+/// use std::sync::Arc;
+///
+/// let buf = Arc::from(&[1, 2, 3, 4][..]);
+/// let reader = gimli::EndianArcSlice::new(buf, gimli::NativeEndian);
+/// # let _ = reader;
+/// # }
+/// ```
+pub type EndianArcSlice<Endian> = EndianReader<Endian, Arc<[u8]>>;
+
+/// An easy way to define a custom `Reader` implementation with a reference to a
+/// generic buffer of bytes and an associated endianity.
+///
+/// Note that the whole original buffer is kept alive in memory even if there is
+/// only one reader that references only a handful of bytes from that original
+/// buffer. That is, `EndianReader` will not do any copying, moving, or
+/// compacting in order to free up unused regions of the original buffer. If you
+/// require this kind of behavior, it is up to you to implement `Reader`
+/// directly by-hand.
+///
+/// # Example
+///
+/// Say you have an `mmap`ed file that you want to serve as a `gimli::Reader`.
+/// You can wrap that `mmap`ed file up in a `MmapFile` type and use
+/// `EndianReader<Rc<MmapFile>>` or `EndianReader<Arc<MmapFile>>` as readers as
+/// long as `MmapFile` dereferences to the underlying `[u8]` data.
+///
+/// ```
+/// use std::io;
+/// use std::ops::Deref;
+/// use std::path::Path;
+/// use std::slice;
+/// use std::sync::Arc;
+///
+/// /// A type that represents an `mmap`ed file.
+/// #[derive(Debug)]
+/// pub struct MmapFile {
+/// ptr: *const u8,
+/// len: usize,
+/// }
+///
+/// impl MmapFile {
+/// pub fn new(path: &Path) -> io::Result<MmapFile> {
+/// // Call `mmap` and check for errors and all that...
+/// # unimplemented!()
+/// }
+/// }
+///
+/// impl Drop for MmapFile {
+/// fn drop(&mut self) {
+/// // Call `munmap` to clean up after ourselves...
+/// # unimplemented!()
+/// }
+/// }
+///
+/// // And `MmapFile` can deref to a slice of the `mmap`ed region of memory.
+/// impl Deref for MmapFile {
+/// type Target = [u8];
+/// fn deref(&self) -> &[u8] {
+/// unsafe {
+/// slice::from_raw_parts(self.ptr, self.len)
+/// }
+/// }
+/// }
+///
+/// /// A type that represents a shared `mmap`ed file.
+/// #[derive(Debug, Clone)]
+/// pub struct ArcMmapFile(Arc<MmapFile>);
+///
+/// // And `ArcMmapFile` can deref to a slice of the `mmap`ed region of memory.
+/// impl Deref for ArcMmapFile {
+/// type Target = [u8];
+/// fn deref(&self) -> &[u8] {
+/// &self.0
+/// }
+/// }
+///
+/// // These are both valid for any `Rc` or `Arc`.
+/// unsafe impl gimli::StableDeref for ArcMmapFile {}
+/// unsafe impl gimli::CloneStableDeref for ArcMmapFile {}
+///
+/// /// A `gimli::Reader` that is backed by an `mmap`ed file!
+/// pub type MmapFileReader<Endian> = gimli::EndianReader<Endian, ArcMmapFile>;
+/// # fn test(_: &MmapFileReader<gimli::NativeEndian>) { }
+/// ```
+#[derive(Debug, Clone, Copy, Hash)]
+pub struct EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ range: SubRange<T>,
+ endian: Endian,
+}
+
+impl<Endian, T1, T2> PartialEq<EndianReader<Endian, T2>> for EndianReader<Endian, T1>
+where
+ Endian: Endianity,
+ T1: CloneStableDeref<Target = [u8]> + Debug,
+ T2: CloneStableDeref<Target = [u8]> + Debug,
+{
+ fn eq(&self, rhs: &EndianReader<Endian, T2>) -> bool {
+ self.bytes() == rhs.bytes()
+ }
+}
+
+impl<Endian, T> Eq for EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+}
+
+// This is separated out from `EndianReader` so that we can avoid running afoul
+// of borrowck. We need to `read_slice(&mut self, ...) -> &[u8]` and then call
+// `self.endian.read_whatever` on the result. The problem is that the returned
+// slice keeps the `&mut self` borrow active, so we wouldn't be able to access
+// `self.endian`. Splitting the sub-range out from the endian lets us work
+// around this, making it so that only the `self.range` borrow is held active,
+// not all of `self`.
+//
+// This also serves to encapsulate the unsafe code concerning `CloneStableDeref`.
+// The `bytes` member is held so that the bytes live long enough, and the
+// `CloneStableDeref` ensures these bytes never move. The `ptr` and `len`
+// members point inside `bytes`, and are updated during read operations.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+struct SubRange<T>
+where
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ bytes: T,
+ ptr: *const u8,
+ len: usize,
+}
+
+unsafe impl<T> Send for SubRange<T> where T: CloneStableDeref<Target = [u8]> + Debug + Send {}
+
+unsafe impl<T> Sync for SubRange<T> where T: CloneStableDeref<Target = [u8]> + Debug + Sync {}
+
+impl<T> SubRange<T>
+where
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ #[inline]
+ fn new(bytes: T) -> Self {
+ let ptr = bytes.as_ptr();
+ let len = bytes.len();
+ SubRange { bytes, ptr, len }
+ }
+
+ #[inline]
+ fn bytes(&self) -> &[u8] {
+ // Safe because `T` implements `CloneStableDeref`, `bytes` can't be modified,
+ // and all operations that modify `ptr` and `len` ensure they stay in range.
+ unsafe { slice::from_raw_parts(self.ptr, self.len) }
+ }
+
+ #[inline]
+ fn len(&self) -> usize {
+ self.len
+ }
+
+ #[inline]
+ fn truncate(&mut self, len: usize) {
+ assert!(len <= self.len);
+ self.len = len;
+ }
+
+ #[inline]
+ fn skip(&mut self, len: usize) {
+ assert!(len <= self.len);
+ self.ptr = unsafe { self.ptr.add(len) };
+ self.len -= len;
+ }
+
+ #[inline]
+ fn read_slice(&mut self, len: usize) -> Option<&[u8]> {
+ if self.len() < len {
+ None
+ } else {
+ // Same as for `bytes()`.
+ let bytes = unsafe { slice::from_raw_parts(self.ptr, len) };
+ self.skip(len);
+ Some(bytes)
+ }
+ }
+}
+
+impl<Endian, T> EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ /// Construct a new `EndianReader` with the given bytes.
+ #[inline]
+ pub fn new(bytes: T, endian: Endian) -> EndianReader<Endian, T> {
+ EndianReader {
+ range: SubRange::new(bytes),
+ endian,
+ }
+ }
+
+ /// Return a reference to the raw bytes underlying this reader.
+ #[inline]
+ pub fn bytes(&self) -> &[u8] {
+ self.range.bytes()
+ }
+}
+
+/// # Range Methods
+///
+/// Unfortunately, `std::ops::Index` *must* return a reference, so we can't
+/// implement `Index<Range<usize>>` to return a new `EndianReader` the way we
+/// would like to. Instead, we abandon fancy indexing operators and have these
+/// plain old methods.
+impl<Endian, T> EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ /// Take the given `start..end` range of the underlying buffer and return a
+ /// new `EndianReader`.
+ ///
+ /// ```
+ /// # #[cfg(feature = "std")] {
+ /// use gimli::{EndianReader, LittleEndian};
+ /// use std::sync::Arc;
+ ///
+ /// let buf = Arc::<[u8]>::from(&[0x01, 0x02, 0x03, 0x04][..]);
+ /// let reader = EndianReader::new(buf.clone(), LittleEndian);
+ /// assert_eq!(reader.range(1..3),
+ /// EndianReader::new(&buf[1..3], LittleEndian));
+ /// # }
+ /// ```
+ ///
+ /// # Panics
+ ///
+ /// Panics if the range is out of bounds.
+ pub fn range(&self, idx: Range<usize>) -> EndianReader<Endian, T> {
+ let mut r = self.clone();
+ r.range.skip(idx.start);
+ r.range.truncate(idx.len());
+ r
+ }
+
+ /// Take the given `start..` range of the underlying buffer and return a new
+ /// `EndianReader`.
+ ///
+ /// ```
+ /// # #[cfg(feature = "std")] {
+ /// use gimli::{EndianReader, LittleEndian};
+ /// use std::sync::Arc;
+ ///
+ /// let buf = Arc::<[u8]>::from(&[0x01, 0x02, 0x03, 0x04][..]);
+ /// let reader = EndianReader::new(buf.clone(), LittleEndian);
+ /// assert_eq!(reader.range_from(2..),
+ /// EndianReader::new(&buf[2..], LittleEndian));
+ /// # }
+ /// ```
+ ///
+ /// # Panics
+ ///
+ /// Panics if the range is out of bounds.
+ pub fn range_from(&self, idx: RangeFrom<usize>) -> EndianReader<Endian, T> {
+ let mut r = self.clone();
+ r.range.skip(idx.start);
+ r
+ }
+
+ /// Take the given `..end` range of the underlying buffer and return a new
+ /// `EndianReader`.
+ ///
+ /// ```
+ /// # #[cfg(feature = "std")] {
+ /// use gimli::{EndianReader, LittleEndian};
+ /// use std::sync::Arc;
+ ///
+ /// let buf = Arc::<[u8]>::from(&[0x01, 0x02, 0x03, 0x04][..]);
+ /// let reader = EndianReader::new(buf.clone(), LittleEndian);
+ /// assert_eq!(reader.range_to(..3),
+ /// EndianReader::new(&buf[..3], LittleEndian));
+ /// # }
+ /// ```
+ ///
+ /// # Panics
+ ///
+ /// Panics if the range is out of bounds.
+ pub fn range_to(&self, idx: RangeTo<usize>) -> EndianReader<Endian, T> {
+ let mut r = self.clone();
+ r.range.truncate(idx.end);
+ r
+ }
+}
+
+impl<Endian, T> Index<usize> for EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ type Output = u8;
+ fn index(&self, idx: usize) -> &Self::Output {
+ &self.bytes()[idx]
+ }
+}
+
+impl<Endian, T> Index<RangeFrom<usize>> for EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ type Output = [u8];
+ fn index(&self, idx: RangeFrom<usize>) -> &Self::Output {
+ &self.bytes()[idx]
+ }
+}
+
+impl<Endian, T> Deref for EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ type Target = [u8];
+ fn deref(&self) -> &Self::Target {
+ self.bytes()
+ }
+}
+
+impl<Endian, T> Reader for EndianReader<Endian, T>
+where
+ Endian: Endianity,
+ T: CloneStableDeref<Target = [u8]> + Debug,
+{
+ type Endian = Endian;
+ type Offset = usize;
+
+ #[inline]
+ fn endian(&self) -> Endian {
+ self.endian
+ }
+
+ #[inline]
+ fn len(&self) -> usize {
+ self.range.len()
+ }
+
+ #[inline]
+ fn empty(&mut self) {
+ self.range.truncate(0);
+ }
+
+ #[inline]
+ fn truncate(&mut self, len: usize) -> Result<()> {
+ if self.len() < len {
+ Err(Error::UnexpectedEof(self.offset_id()))
+ } else {
+ self.range.truncate(len);
+ Ok(())
+ }
+ }
+
+ #[inline]
+ fn offset_from(&self, base: &EndianReader<Endian, T>) -> usize {
+ let base_ptr = base.bytes().as_ptr() as *const u8 as usize;
+ let ptr = self.bytes().as_ptr() as *const u8 as usize;
+ debug_assert!(base_ptr <= ptr);
+ debug_assert!(ptr + self.bytes().len() <= base_ptr + base.bytes().len());
+ ptr - base_ptr
+ }
+
+ #[inline]
+ fn offset_id(&self) -> ReaderOffsetId {
+ ReaderOffsetId(self.bytes().as_ptr() as u64)
+ }
+
+ #[inline]
+ fn lookup_offset_id(&self, id: ReaderOffsetId) -> Option<Self::Offset> {
+ let id = id.0;
+ let self_id = self.bytes().as_ptr() as u64;
+ let self_len = self.bytes().len() as u64;
+ if id >= self_id && id <= self_id + self_len {
+ Some((id - self_id) as usize)
+ } else {
+ None
+ }
+ }
+
+ #[inline]
+ fn find(&self, byte: u8) -> Result<usize> {
+ self.bytes()
+ .iter()
+ .position(|x| *x == byte)
+ .ok_or_else(|| Error::UnexpectedEof(self.offset_id()))
+ }
+
+ #[inline]
+ fn skip(&mut self, len: usize) -> Result<()> {
+ if self.len() < len {
+ Err(Error::UnexpectedEof(self.offset_id()))
+ } else {
+ self.range.skip(len);
+ Ok(())
+ }
+ }
+
+ #[inline]
+ fn split(&mut self, len: usize) -> Result<Self> {
+ if self.len() < len {
+ Err(Error::UnexpectedEof(self.offset_id()))
+ } else {
+ let mut r = self.clone();
+ r.range.truncate(len);
+ self.range.skip(len);
+ Ok(r)
+ }
+ }
+
+ #[inline]
+ fn to_slice(&self) -> Result<Cow<[u8]>> {
+ Ok(self.bytes().into())
+ }
+
+ #[inline]
+ fn to_string(&self) -> Result<Cow<str>> {
+ match str::from_utf8(self.bytes()) {
+ Ok(s) => Ok(s.into()),
+ _ => Err(Error::BadUtf8),
+ }
+ }
+
+ #[inline]
+ fn to_string_lossy(&self) -> Result<Cow<str>> {
+ Ok(String::from_utf8_lossy(self.bytes()))
+ }
+
+ #[inline]
+ fn read_slice(&mut self, buf: &mut [u8]) -> Result<()> {
+ match self.range.read_slice(buf.len()) {
+ Some(slice) => {
+ buf.copy_from_slice(slice);
+ Ok(())
+ }
+ None => Err(Error::UnexpectedEof(self.offset_id())),
+ }
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use crate::endianity::NativeEndian;
+ use crate::read::Reader;
+
+ fn native_reader<T: CloneStableDeref<Target = [u8]> + Debug>(
+ bytes: T,
+ ) -> EndianReader<NativeEndian, T> {
+ EndianReader::new(bytes, NativeEndian)
+ }
+
+ const BUF: &[u8] = &[1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
+
+ #[test]
+ fn test_reader_split() {
+ let mut reader = native_reader(BUF);
+ let left = reader.split(3).unwrap();
+ assert_eq!(left, native_reader(&BUF[..3]));
+ assert_eq!(reader, native_reader(&BUF[3..]));
+ }
+
+ #[test]
+ fn test_reader_split_out_of_bounds() {
+ let mut reader = native_reader(BUF);
+ assert!(reader.split(30).is_err());
+ }
+
+ #[test]
+ fn bytes_and_len_and_range_and_eq() {
+ let reader = native_reader(BUF);
+ assert_eq!(reader.len(), BUF.len());
+ assert_eq!(reader.bytes(), BUF);
+ assert_eq!(reader, native_reader(BUF));
+
+ let range = reader.range(2..8);
+ let buf_range = &BUF[2..8];
+ assert_eq!(range.len(), buf_range.len());
+ assert_eq!(range.bytes(), buf_range);
+ assert_ne!(range, native_reader(BUF));
+ assert_eq!(range, native_reader(buf_range));
+
+ let range_from = range.range_from(1..);
+ let buf_range_from = &buf_range[1..];
+ assert_eq!(range_from.len(), buf_range_from.len());
+ assert_eq!(range_from.bytes(), buf_range_from);
+ assert_ne!(range_from, native_reader(BUF));
+ assert_eq!(range_from, native_reader(buf_range_from));
+
+ let range_to = range_from.range_to(..4);
+ let buf_range_to = &buf_range_from[..4];
+ assert_eq!(range_to.len(), buf_range_to.len());
+ assert_eq!(range_to.bytes(), buf_range_to);
+ assert_ne!(range_to, native_reader(BUF));
+ assert_eq!(range_to, native_reader(buf_range_to));
+ }
+
+ #[test]
+ fn find() {
+ let mut reader = native_reader(BUF);
+ reader.skip(2).unwrap();
+ assert_eq!(
+ reader.find(5),
+ Ok(BUF[2..].iter().position(|x| *x == 5).unwrap())
+ );
+ }
+
+ #[test]
+ fn indexing() {
+ let mut reader = native_reader(BUF);
+ reader.skip(2).unwrap();
+ assert_eq!(reader[0], BUF[2]);
+ }
+
+ #[test]
+ #[should_panic]
+ fn indexing_out_of_bounds() {
+ let mut reader = native_reader(BUF);
+ reader.skip(2).unwrap();
+ let _ = reader[900];
+ }
+
+ #[test]
+ fn endian() {
+ let reader = native_reader(BUF);
+ assert_eq!(reader.endian(), NativeEndian);
+ }
+
+ #[test]
+ fn empty() {
+ let mut reader = native_reader(BUF);
+ assert!(!reader.is_empty());
+ reader.empty();
+ assert!(reader.is_empty());
+ assert!(reader.bytes().is_empty());
+ }
+
+ #[test]
+ fn truncate() {
+ let reader = native_reader(BUF);
+ let mut reader = reader.range(2..8);
+ reader.truncate(2).unwrap();
+ assert_eq!(reader.bytes(), &BUF[2..4]);
+ }
+
+ #[test]
+ fn offset_from() {
+ let reader = native_reader(BUF);
+ let sub = reader.range(2..8);
+ assert_eq!(sub.offset_from(&reader), 2);
+ }
+
+ #[test]
+ fn skip() {
+ let mut reader = native_reader(BUF);
+ reader.skip(2).unwrap();
+ assert_eq!(reader.bytes(), &BUF[2..]);
+ }
+
+ #[test]
+ fn to_slice() {
+ assert_eq!(
+ native_reader(BUF).range(2..5).to_slice(),
+ Ok(Cow::from(&BUF[2..5]))
+ );
+ }
+
+ #[test]
+ fn to_string_ok() {
+ let buf = b"hello, world!";
+ let reader = native_reader(&buf[..]);
+ let reader = reader.range_from(7..);
+ assert_eq!(reader.to_string(), Ok(Cow::from("world!")));
+ }
+
+ // The rocket emoji (🚀 = [0xf0, 0x9f, 0x9a, 0x80]) but rotated left by one
+ // to make it invalid UTF-8.
+ const BAD_UTF8: &[u8] = &[0x9f, 0x9a, 0x80, 0xf0];
+
+ #[test]
+ fn to_string_err() {
+ let reader = native_reader(BAD_UTF8);
+ assert!(reader.to_string().is_err());
+ }
+
+ #[test]
+ fn to_string_lossy() {
+ let reader = native_reader(BAD_UTF8);
+ assert_eq!(reader.to_string_lossy(), Ok(Cow::from("����")));
+ }
+
+ #[test]
+ fn read_u8_array() {
+ let mut reader = native_reader(BAD_UTF8);
+ reader.skip(1).unwrap();
+ let arr: [u8; 2] = reader.read_u8_array().unwrap();
+ assert_eq!(arr, &BAD_UTF8[1..3]);
+ assert_eq!(reader.bytes(), &BAD_UTF8[3..]);
+ }
+}
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