1use super::{BorrowedBuf, BufReader, BufWriter, DEFAULT_BUF_SIZE, Read, Result, Write};
2use crate::alloc::Allocator;
3use crate::cmp;
4use crate::collections::VecDeque;
5use crate::io::IoSlice;
6use crate::mem::MaybeUninit;
7
8#[cfg(test)]
9mod tests;
10
11#[stable(feature = "rust1", since = "1.0.0")]
61pub fn copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
62where
63 R: Read,
64 W: Write,
65{
66 cfg_if::cfg_if! {
67 if #[cfg(any(target_os = "linux", target_os = "android"))] {
68 crate::sys::kernel_copy::copy_spec(reader, writer)
69 } else {
70 generic_copy(reader, writer)
71 }
72 }
73}
74
75pub(crate) fn generic_copy<R: ?Sized, W: ?Sized>(reader: &mut R, writer: &mut W) -> Result<u64>
78where
79 R: Read,
80 W: Write,
81{
82 let read_buf = BufferedReaderSpec::buffer_size(reader);
83 let write_buf = BufferedWriterSpec::buffer_size(writer);
84
85 if read_buf >= DEFAULT_BUF_SIZE && read_buf >= write_buf {
86 return BufferedReaderSpec::copy_to(reader, writer);
87 }
88
89 BufferedWriterSpec::copy_from(writer, reader)
90}
91
92trait BufferedReaderSpec {
96 fn buffer_size(&self) -> usize;
97
98 fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64>;
99}
100
101impl<T> BufferedReaderSpec for T
102where
103 Self: Read,
104 T: ?Sized,
105{
106 #[inline]
107 default fn buffer_size(&self) -> usize {
108 0
109 }
110
111 default fn copy_to(&mut self, _to: &mut (impl Write + ?Sized)) -> Result<u64> {
112 unreachable!("only called from specializations")
113 }
114}
115
116impl BufferedReaderSpec for &[u8] {
117 fn buffer_size(&self) -> usize {
118 usize::MAX
121 }
122
123 fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
124 let len = self.len();
125 to.write_all(self)?;
126 *self = &self[len..];
127 Ok(len as u64)
128 }
129}
130
131impl<A: Allocator> BufferedReaderSpec for VecDeque<u8, A> {
132 fn buffer_size(&self) -> usize {
133 usize::MAX
136 }
137
138 fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
139 let len = self.len();
140 let (front, back) = self.as_slices();
141 let bufs = &mut [IoSlice::new(front), IoSlice::new(back)];
142 to.write_all_vectored(bufs)?;
143 self.clear();
144 Ok(len as u64)
145 }
146}
147
148impl<I> BufferedReaderSpec for BufReader<I>
149where
150 Self: Read,
151 I: ?Sized,
152{
153 fn buffer_size(&self) -> usize {
154 self.capacity()
155 }
156
157 fn copy_to(&mut self, to: &mut (impl Write + ?Sized)) -> Result<u64> {
158 let mut len = 0;
159
160 loop {
161 match self.read(&mut []) {
166 Ok(_) => {}
167 Err(e) if e.is_interrupted() => continue,
168 Err(e) => return Err(e),
169 }
170 let buf = self.buffer();
171 if self.buffer().len() == 0 {
172 return Ok(len);
173 }
174
175 to.write_all(buf)?;
181 len += buf.len() as u64;
182 self.discard_buffer();
183 }
184 }
185}
186
187trait BufferedWriterSpec: Write {
190 fn buffer_size(&self) -> usize;
191
192 fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64>;
193}
194
195impl<W: Write + ?Sized> BufferedWriterSpec for W {
196 #[inline]
197 default fn buffer_size(&self) -> usize {
198 0
199 }
200
201 default fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
202 stack_buffer_copy(reader, self)
203 }
204}
205
206impl<I: Write + ?Sized> BufferedWriterSpec for BufWriter<I> {
207 fn buffer_size(&self) -> usize {
208 self.capacity()
209 }
210
211 fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
212 if self.capacity() < DEFAULT_BUF_SIZE {
213 return stack_buffer_copy(reader, self);
214 }
215
216 let mut len = 0;
217 let mut init = 0;
218
219 loop {
220 let buf = self.buffer_mut();
221 let mut read_buf: BorrowedBuf<'_> = buf.spare_capacity_mut().into();
222
223 unsafe {
224 read_buf.set_init(init);
226 }
227
228 if read_buf.capacity() >= DEFAULT_BUF_SIZE {
229 let mut cursor = read_buf.unfilled();
230 match reader.read_buf(cursor.reborrow()) {
231 Ok(()) => {
232 let bytes_read = cursor.written();
233
234 if bytes_read == 0 {
235 return Ok(len);
236 }
237
238 init = read_buf.init_len() - bytes_read;
239 len += bytes_read as u64;
240
241 unsafe { buf.set_len(buf.len() + bytes_read) };
243
244 }
247 Err(ref e) if e.is_interrupted() => {}
248 Err(e) => return Err(e),
249 }
250 } else {
251 self.flush_buf()?;
252 init = 0;
253 }
254 }
255 }
256}
257
258impl BufferedWriterSpec for Vec<u8> {
259 fn buffer_size(&self) -> usize {
260 cmp::max(DEFAULT_BUF_SIZE, self.capacity() - self.len())
261 }
262
263 fn copy_from<R: Read + ?Sized>(&mut self, reader: &mut R) -> Result<u64> {
264 reader.read_to_end(self).map(|bytes| u64::try_from(bytes).expect("usize overflowed u64"))
265 }
266}
267
268pub fn stack_buffer_copy<R: Read + ?Sized, W: Write + ?Sized>(
269 reader: &mut R,
270 writer: &mut W,
271) -> Result<u64> {
272 let buf: &mut [_] = &mut [MaybeUninit::uninit(); DEFAULT_BUF_SIZE];
273 let mut buf: BorrowedBuf<'_> = buf.into();
274
275 let mut len = 0;
276
277 loop {
278 match reader.read_buf(buf.unfilled()) {
279 Ok(()) => {}
280 Err(e) if e.is_interrupted() => continue,
281 Err(e) => return Err(e),
282 };
283
284 if buf.filled().is_empty() {
285 break;
286 }
287
288 len += buf.filled().len() as u64;
289 writer.write_all(buf.filled())?;
290 buf.clear();
291 }
292
293 Ok(len)
294}