| use super::{BorrowedBuf, BufWriter, ErrorKind, Read, Result, Write, DEFAULT_BUF_SIZE}; |
| use crate::mem::MaybeUninit; |
| |
| /// Copies the entire contents of a reader into a writer. |
| /// |
| /// This function will continuously read data from `reader` and then |
| /// write it into `writer` in a streaming fashion until `reader` |
| /// returns EOF. |
| /// |
| /// On success, the total number of bytes that were copied from |
| /// `reader` to `writer` is returned. |
| /// |
| /// If you’re wanting to copy the contents of one file to another and you’re |
| /// working with filesystem paths, see the [`fs::copy`] function. |
| /// |
| /// [`fs::copy`]: crate::fs::copy |
| /// |
| /// # Errors |
| /// |
| /// This function will return an error immediately if any call to [`read`] or |
| /// [`write`] returns an error. All instances of [`ErrorKind::Interrupted`] are |
| /// handled by this function and the underlying operation is retried. |
| /// |
| /// [`read`]: Read::read |
| /// [`write`]: Write::write |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::io; |
| /// |
| /// fn main() -> io::Result<()> { |
| /// let mut reader: &[u8] = b"hello"; |
| /// let mut writer: Vec<u8> = vec![]; |
| /// |
| /// io::copy(&mut reader, &mut writer)?; |
| /// |
| /// assert_eq!(&b"hello"[..], &writer[..]); |
| /// Ok(()) |
| /// } |
| /// ``` |
| /// |
| /// # Platform-specific behavior |
| /// |
| /// On Linux (including Android), this function uses `copy_file_range(2)`, |
| /// `sendfile(2)` or `splice(2)` syscalls to move data directly between file |
| /// descriptors if possible. |
| /// |
| /// Note that platform-specific behavior [may change in the future][changes]. |
| /// |
| /// [changes]: crate::io#platform-specific-behavior |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64> |
| where |
| R: Read, |
| W: Write, |
| { |
| cfg_if::cfg_if! { |
| if #[cfg(any(target_os = "linux", target_os = "android"))] { |
| crate::sys::kernel_copy::copy_spec(reader, writer) |
| } else { |
| generic_copy(reader, writer) |
| } |
| } |
| } |
| |
| /// The userspace read-write-loop implementation of `io::copy` that is used when |
| /// OS-specific specializations for copy offloading are not available or not applicable. |
| pub(crate) fn generic_copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64> |
| where |
| R: Read, |
| W: Write, |
| { |
| BufferedCopySpec::copy_to(reader, writer) |
| } |
| |
| /// Specialization of the read-write loop that either uses a stack buffer |
| /// or reuses the internal buffer of a BufWriter |
| trait BufferedCopySpec: Write { |
| fn copy_to<R: Read + ?Sized>(reader: &mut R, writer: &mut Self) -> Result<u64>; |
| } |
| |
| impl<W: Write + ?Sized> BufferedCopySpec for W { |
| default fn copy_to<R: Read + ?Sized>(reader: &mut R, writer: &mut Self) -> Result<u64> { |
| stack_buffer_copy(reader, writer) |
| } |
| } |
| |
| impl<I: Write> BufferedCopySpec for BufWriter<I> { |
| fn copy_to<R: Read + ?Sized>(reader: &mut R, writer: &mut Self) -> Result<u64> { |
| if writer.capacity() < DEFAULT_BUF_SIZE { |
| return stack_buffer_copy(reader, writer); |
| } |
| |
| let mut len = 0; |
| let mut init = 0; |
| |
| loop { |
| let buf = writer.buffer_mut(); |
| let mut read_buf: BorrowedBuf<'_> = buf.spare_capacity_mut().into(); |
| |
| unsafe { |
| // SAFETY: init is either 0 or the init_len from the previous iteration. |
| read_buf.set_init(init); |
| } |
| |
| if read_buf.capacity() >= DEFAULT_BUF_SIZE { |
| let mut cursor = read_buf.unfilled(); |
| match reader.read_buf(cursor.reborrow()) { |
| Ok(()) => { |
| let bytes_read = cursor.written(); |
| |
| if bytes_read == 0 { |
| return Ok(len); |
| } |
| |
| init = read_buf.init_len() - bytes_read; |
| len += bytes_read as u64; |
| |
| // SAFETY: BorrowedBuf guarantees all of its filled bytes are init |
| unsafe { buf.set_len(buf.len() + bytes_read) }; |
| |
| // Read again if the buffer still has enough capacity, as BufWriter itself would do |
| // This will occur if the reader returns short reads |
| } |
| Err(ref e) if e.kind() == ErrorKind::Interrupted => {} |
| Err(e) => return Err(e), |
| } |
| } else { |
| writer.flush_buf()?; |
| init = 0; |
| } |
| } |
| } |
| } |
| |
| fn stack_buffer_copy<R: Read + ?Sized, W: Write + ?Sized>( |
| reader: &mut R, |
| writer: &mut W, |
| ) -> Result<u64> { |
| let buf: &mut [_] = &mut [MaybeUninit::uninit(); DEFAULT_BUF_SIZE]; |
| let mut buf: BorrowedBuf<'_> = buf.into(); |
| |
| let mut len = 0; |
| |
| loop { |
| match reader.read_buf(buf.unfilled()) { |
| Ok(()) => {} |
| Err(e) if e.kind() == ErrorKind::Interrupted => continue, |
| Err(e) => return Err(e), |
| }; |
| |
| if buf.filled().is_empty() { |
| break; |
| } |
| |
| len += buf.filled().len() as u64; |
| writer.write_all(buf.filled())?; |
| buf.clear(); |
| } |
| |
| Ok(len) |
| } |