pub mod io {
pub use bitcoin::io::*;
- #[cfg(not(feature = "std"))] pub use core2::io::Seek;
- #[cfg(not(feature = "std"))] pub use core2::io::SeekFrom;
+ /// The `Seek` trait provides a cursor which can be moved within a stream of
+ /// bytes.
+ ///
+ /// The stream typically has a fixed size, allowing seeking relative to either
+ /// end or the current offset.
+ ///
+ /// # Examples
+ ///
+ /// [`File`]s implement `Seek`:
+ ///
+ /// [`File`]: crate::fs::File
+ ///
+ /// ```no_run
+ /// use std::io;
+ /// use std::io::prelude::*;
+ /// use std::fs::File;
+ /// use std::io::SeekFrom;
+ ///
+ /// fn main() -> io::Result<()> {
+ /// let mut f = File::open("foo.txt")?;
+ ///
+ /// // move the cursor 42 bytes from the start of the file
+ /// f.seek(SeekFrom::Start(42))?;
+ /// Ok(())
+ /// }
+ /// ```
+ pub trait Seek {
+ /// Seek to an offset, in bytes, in a stream.
+ ///
+ /// A seek beyond the end of a stream is allowed, but behavior is defined
+ /// by the implementation.
+ ///
+ /// If the seek operation completed successfully,
+ /// this method returns the new position from the start of the stream.
+ /// That position can be used later with [`SeekFrom::Start`].
+ ///
+ /// # Errors
+ ///
+ /// Seeking to a negative offset is considered an error.
+ fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
+ }
+
+ /// Enumeration of possible methods to seek within an I/O object.
+ ///
+ /// It is used by the [`Seek`] trait.
+ #[derive(Copy, PartialEq, Eq, Clone, Debug)]
+ pub enum SeekFrom {
+ /// Sets the offset to the provided number of bytes.
+ Start(u64),
+
+ /// Sets the offset to the size of this object plus the specified number of
+ /// bytes.
+ ///
+ /// It is possible to seek beyond the end of an object, but it's an error to
+ /// seek before byte 0.
+ End(i64),
+
+ /// Sets the offset to the current position plus the specified number of
+ /// bytes.
+ ///
+ /// It is possible to seek beyond the end of an object, but it's an error to
+ /// seek before byte 0.
+ Current(i64),
+ }
+
+ #[derive(Clone, Debug, Default, Eq, PartialEq)]
+ pub struct Cursor<T> {
+ inner: T,
+ pos: u64,
+ }
+
+ impl<T> Cursor<T> {
+ /// Creates a new cursor wrapping the provided underlying in-memory buffer.
+ ///
+ /// Cursor initial position is `0` even if underlying buffer (e.g., [`Vec`])
+ /// is not empty. So writing to cursor starts with overwriting [`Vec`]
+ /// content, not with appending to it.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use bitcoin::io::Cursor;
+ ///
+ /// let buff = Cursor::new(Vec::new());
+ /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+ /// # force_inference(&buff);
+ /// ```
+ pub fn new(inner: T) -> Cursor<T> {
+ Cursor { pos: 0, inner }
+ }
+
+ /// Consumes this cursor, returning the underlying value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use bitcoin::io::Cursor;
+ ///
+ /// let buff = Cursor::new(Vec::new());
+ /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+ /// # force_inference(&buff);
+ ///
+ /// let vec = buff.into_inner();
+ /// ```
+ pub fn into_inner(self) -> T {
+ self.inner
+ }
+
+ /// Gets a reference to the underlying value in this cursor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use bitcoin::io::Cursor;
+ ///
+ /// let buff = Cursor::new(Vec::new());
+ /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+ /// # force_inference(&buff);
+ ///
+ /// let reference = buff.get_ref();
+ /// ```
+ pub fn get_ref(&self) -> &T {
+ &self.inner
+ }
+
+ /// Gets a mutable reference to the underlying value in this cursor.
+ ///
+ /// Care should be taken to avoid modifying the internal I/O state of the
+ /// underlying value as it may corrupt this cursor's position.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use bitcoin::io::Cursor;
+ ///
+ /// let mut buff = Cursor::new(Vec::new());
+ /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
+ /// # force_inference(&buff);
+ ///
+ /// let reference = buff.get_mut();
+ /// ```
+ pub fn get_mut(&mut self) -> &mut T {
+ &mut self.inner
+ }
+
+ /// Returns the current position of this cursor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use core2::io::{Cursor, Seek, SeekFrom};
+ /// use std::io::prelude::*;
+ ///
+ /// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
+ ///
+ /// assert_eq!(buff.position(), 0);
+ ///
+ /// buff.seek(SeekFrom::Current(2)).unwrap();
+ /// assert_eq!(buff.position(), 2);
+ ///
+ /// buff.seek(SeekFrom::Current(-1)).unwrap();
+ /// assert_eq!(buff.position(), 1);
+ /// ```
+ pub fn position(&self) -> u64 {
+ self.pos
+ }
+
+ /// Sets the position of this cursor.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use core2::io::Cursor;
+ ///
+ /// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
+ ///
+ /// assert_eq!(buff.position(), 0);
+ ///
+ /// buff.set_position(2);
+ /// assert_eq!(buff.position(), 2);
+ ///
+ /// buff.set_position(4);
+ /// assert_eq!(buff.position(), 4);
+ /// ```
+ pub fn set_position(&mut self, pos: u64) {
+ self.pos = pos;
+ }
+ }
- #[cfg(feature = "std")] pub use std::io::Seek;
- #[cfg(feature = "std")] pub use std::io::SeekFrom;
+ impl<T> Seek for Cursor<T>
+ where
+ T: AsRef<[u8]>,
+ {
+ fn seek(&mut self, style: SeekFrom) -> Result<u64> {
+ let (base_pos, offset) = match style {
+ SeekFrom::Start(n) => {
+ self.pos = n;
+ return Ok(n);
+ }
+ SeekFrom::End(n) => (self.inner.as_ref().len() as u64, n),
+ SeekFrom::Current(n) => (self.pos, n),
+ };
+ let new_pos = if offset >= 0 {
+ base_pos.checked_add(offset as u64)
+ } else {
+ base_pos.checked_sub((offset.wrapping_neg()) as u64)
+ };
+ match new_pos {
+ Some(n) => {
+ self.pos = n;
+ Ok(self.pos)
+ }
+ None => Err(Error::new(
+ ErrorKind::InvalidInput,
+ "invalid seek to a negative or overflowing position",
+ )),
+ }
+ }
+ }
+
+ impl<T> Read for Cursor<T>
+ where
+ T: AsRef<[u8]>,
+ {
+ fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
+ let n = Read::read(&mut self.fill_buf()?, buf)?;
+ self.pos += n as u64;
+ Ok(n)
+ }
+
+ fn read_exact(&mut self, buf: &mut [u8]) -> Result<()> {
+ let n = buf.len();
+ Read::read_exact(&mut self.fill_buf()?, buf)?;
+ self.pos += n as u64;
+ Ok(())
+ }
+ }
+
+ impl<T> BufRead for Cursor<T>
+ where
+ T: AsRef<[u8]>,
+ {
+ fn fill_buf(&mut self) -> Result<&[u8]> {
+ let amt = core::cmp::min(self.pos, self.inner.as_ref().len() as u64);
+ Ok(&self.inner.as_ref()[(amt as usize)..])
+ }
+ fn consume(&mut self, amt: usize) {
+ self.pos += amt as u64;
+ }
+ }
}
// #[cfg(feature = "std")]
projects / rust-lightning / commitdiff