Refactor Windows stdio and remove stdin double buffering
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cc20ed678e
commit
f411852add
2 changed files with 180 additions and 118 deletions
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@ -252,9 +252,9 @@ impl Stdio {
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// should still be unavailable so propagate the
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// INVALID_HANDLE_VALUE.
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Stdio::Inherit => {
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match stdio::get(stdio_id) {
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match stdio::get_handle(stdio_id) {
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Ok(io) => {
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let io = Handle::new(io.handle());
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let io = Handle::new(io);
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let ret = io.duplicate(0, true,
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c::DUPLICATE_SAME_ACCESS);
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io.into_raw();
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@ -1,131 +1,226 @@
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#![unstable(issue = "0", feature = "windows_stdio")]
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use cell::Cell;
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use cmp;
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use io::{self, Cursor};
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use io;
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use ptr;
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use str;
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use sync::Mutex;
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use sys::c;
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use sys::cvt;
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use sys::handle::Handle;
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pub enum Output {
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Console(c::HANDLE),
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Pipe(c::HANDLE),
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}
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// Don't cache handles but get them fresh for every read/write. This allows us to track changes to
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// the value over time (such as if a process calls `SetStdHandle` while it's running). See #40490.
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pub struct Stdin {
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utf8: Mutex<io::Cursor<Vec<u8>>>,
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high_surrogate: Cell<u16>,
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}
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pub struct Stdout;
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pub struct Stderr;
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pub fn get(handle: c::DWORD) -> io::Result<Output> {
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let handle = unsafe { c::GetStdHandle(handle) };
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// Apparently Windows doesn't handle large reads on stdin or writes to stdout/stderr well (see
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// #13304 for details).
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//
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// From MSDN (2011): "The storage for this buffer is allocated from a shared heap for the
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// process that is 64 KB in size. The maximum size of the buffer will depend on heap usage."
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//
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// We choose the cap at 8 KiB because libuv does the same, and it seems to be acceptable so far.
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const MAX_BUFFER_SIZE: usize = 8192;
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// The standard buffer size of BufReader for Stdin should be able to hold 3x more bytes than there
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// are `u16`'s in MAX_BUFFER_SIZE. This ensures the read data can always be completely decoded from
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// UTF-16 to UTF-8.
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pub const STDIN_BUF_SIZE: usize = MAX_BUFFER_SIZE / 2 * 3;
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pub fn get_handle(handle_id: c::DWORD) -> io::Result<c::HANDLE> {
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let handle = unsafe { c::GetStdHandle(handle_id) };
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if handle == c::INVALID_HANDLE_VALUE {
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Err(io::Error::last_os_error())
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} else if handle.is_null() {
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Err(io::Error::from_raw_os_error(c::ERROR_INVALID_HANDLE as i32))
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} else {
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let mut out = 0;
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match unsafe { c::GetConsoleMode(handle, &mut out) } {
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0 => Ok(Output::Pipe(handle)),
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_ => Ok(Output::Console(handle)),
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}
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Ok(handle)
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}
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}
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fn write(handle: c::DWORD, data: &[u8]) -> io::Result<usize> {
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let handle = match get(handle)? {
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Output::Console(c) => c,
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Output::Pipe(p) => {
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let handle = Handle::new(p);
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let ret = handle.write(data);
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handle.into_raw();
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return ret
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}
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};
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fn is_console(handle: c::HANDLE) -> bool {
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// `GetConsoleMode` will return false (0) if this is a pipe (we don't care about the reported
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// mode). This will only detect Windows Console, not other terminals connected to a pipe like
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// MSYS. Which is exactly what we need, as only Windows Console needs a conversion to UTF-16.
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let mut mode = 0;
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unsafe { c::GetConsoleMode(handle, &mut mode) != 0 }
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}
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// As with stdin on windows, stdout often can't handle writes of large
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// sizes. For an example, see #14940. For this reason, don't try to
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// write the entire output buffer on windows.
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fn write(handle_id: c::DWORD, data: &[u8]) -> io::Result<usize> {
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let handle = get_handle(handle_id)?;
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if !is_console(handle) {
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let handle = Handle::new(handle);
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let ret = handle.write(data);
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handle.into_raw(); // Don't close the handle
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return ret;
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}
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// As the console is meant for presenting text, we assume bytes of `data` come from a string
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// and are encoded as UTF-8, which needs to be encoded as UTF-16.
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//
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// For some other references, it appears that this problem has been
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// encountered by others [1] [2]. We choose the number 8K just because
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// libuv does the same.
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//
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// [1]: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1232
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// [2]: http://www.mail-archive.com/log4net-dev@logging.apache.org/msg00661.html
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const OUT_MAX: usize = 8192;
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let len = cmp::min(data.len(), OUT_MAX);
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// If the data is not valid UTF-8 we write out as many bytes as are valid.
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// Only when there are no valid bytes (which will happen on the next call), return an error.
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let len = cmp::min(data.len(), MAX_BUFFER_SIZE);
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let utf8 = match str::from_utf8(&data[..len]) {
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Ok(s) => s,
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Err(ref e) if e.valid_up_to() == 0 => return Err(invalid_encoding()),
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Err(ref e) if e.valid_up_to() == 0 => {
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return Err(io::Error::new(io::ErrorKind::InvalidData,
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"Windows stdio in console mode does not support non-UTF-8 byte sequences; \
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see https://github.com/rust-lang/rust/issues/23344"))
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},
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Err(e) => str::from_utf8(&data[..e.valid_up_to()]).unwrap(),
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};
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let utf16 = utf8.encode_utf16().collect::<Vec<u16>>();
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let mut written = write_u16s(handle, &utf16)?;
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// Figure out how many bytes of as UTF-8 were written away as UTF-16.
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if written >= utf16.len() {
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Ok(utf8.len())
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} else {
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// Make sure we didn't end up writing only half of a surrogate pair (even though the chance
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// is tiny). Because it is not possible for user code to re-slice `data` in such a way that
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// a missing surrogate can be produced (and also because of the UTF-8 validation above),
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// write the missing surrogate out now.
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// Buffering it would mean we have to lie about the number of bytes written.
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let first_char_remaining = utf16[written];
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if first_char_remaining >= 0xDCEE && first_char_remaining <= 0xDFFF { // low surrogate
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// We just hope this works, and give up otherwise
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let _ = write_u16s(handle, &utf16[written..written]);
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written += 1;
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}
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// Calculate the number of bytes of `utf8` that were actually written.
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let mut count = 0;
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for ch in utf16[..written].iter() {
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count += match ch {
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0x0000 ..= 0x007F => 1,
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0x0080 ..= 0x07FF => 2,
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0xDCEE ..= 0xDFFF => 1, // Low surrogate. We already counted 3 bytes for the other.
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_ => 3,
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};
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}
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Ok(count)
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}
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}
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fn write_u16s(handle: c::HANDLE, data: &[u16]) -> io::Result<usize> {
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let mut written = 0;
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cvt(unsafe {
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c::WriteConsoleW(handle,
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utf16.as_ptr() as c::LPCVOID,
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utf16.len() as u32,
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data.as_ptr() as c::LPCVOID,
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data.len() as u32,
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&mut written,
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ptr::null_mut())
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})?;
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// FIXME if this only partially writes the utf16 buffer then we need to
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// figure out how many bytes of `data` were actually written
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assert_eq!(written as usize, utf16.len());
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Ok(utf8.len())
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Ok(written as usize)
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}
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impl Stdin {
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pub fn new() -> io::Result<Stdin> {
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Ok(Stdin {
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utf8: Mutex::new(Cursor::new(Vec::new())),
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})
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Ok(Stdin { high_surrogate: Cell::new(0) })
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}
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pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
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let handle = match get(c::STD_INPUT_HANDLE)? {
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Output::Console(c) => c,
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Output::Pipe(p) => {
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let handle = Handle::new(p);
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let ret = handle.read(buf);
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handle.into_raw();
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return ret
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}
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};
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let mut utf8 = self.utf8.lock().unwrap();
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// Read more if the buffer is empty
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if utf8.position() as usize == utf8.get_ref().len() {
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let mut utf16 = vec![0u16; 0x1000];
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let mut num = 0;
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let mut input_control = readconsole_input_control(CTRL_Z_MASK);
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cvt(unsafe {
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c::ReadConsoleW(handle,
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utf16.as_mut_ptr() as c::LPVOID,
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utf16.len() as u32,
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&mut num,
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&mut input_control as c::PCONSOLE_READCONSOLE_CONTROL)
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})?;
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utf16.truncate(num as usize);
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// FIXME: what to do about this data that has already been read?
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let mut data = match String::from_utf16(&utf16) {
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Ok(utf8) => utf8.into_bytes(),
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Err(..) => return Err(invalid_encoding()),
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};
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if let Some(&last_byte) = data.last() {
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if last_byte == CTRL_Z {
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data.pop();
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}
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}
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*utf8 = Cursor::new(data);
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let handle = get_handle(c::STD_INPUT_HANDLE)?;
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if !is_console(handle) {
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let handle = Handle::new(handle);
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let ret = handle.read(buf);
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handle.into_raw(); // Don't close the handle
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return ret;
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}
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// MemReader shouldn't error here since we just filled it
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utf8.read(buf)
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if buf.len() == 0 {
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return Ok(0);
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} else if buf.len() < 4 {
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return Err(io::Error::new(io::ErrorKind::InvalidInput,
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"Windows stdin in console mode does not support a buffer too small to; \
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guarantee holding one arbitrary UTF-8 character (4 bytes)"))
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}
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let mut utf16_buf = [0u16; MAX_BUFFER_SIZE / 2];
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// In the worst case, an UTF-8 string can take 3 bytes for every `u16` of an UTF-16. So
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// we can read at most a third of `buf.len()` chars and uphold the guarantee no data gets
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// lost.
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let amount = cmp::min(buf.len() / 3, utf16_buf.len());
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let read = self.read_u16s_fixup_surrogates(handle, &mut utf16_buf, amount)?;
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let utf16 = &utf16_buf[..read];
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// FIXME: it would be nice if we could directly decode into the buffer instead of doing an
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// allocation.
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let data = match String::from_utf16(&utf16) {
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Ok(utf8) => utf8.into_bytes(),
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Err(..) => {
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// We can't really do any better than forget all data and return an error.
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return Err(io::Error::new(io::ErrorKind::InvalidData,
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"Windows stdin in console mode does not support non-UTF-16 input; \
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encountered unpaired surrogate"))
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},
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};
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buf.copy_from_slice(&data);
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Ok(data.len())
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}
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// We assume that if the last `u16` is an unpaired surrogate they got sliced apart by our
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// buffer size, and keep it around for the next read hoping to put them together.
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// This is a best effort, and may not work if we are not the only reader on Stdin.
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pub fn read_u16s_fixup_surrogates(&self, handle: c::HANDLE, buf: &mut [u16], mut amount: usize)
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-> io::Result<usize>
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{
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// Insert possibly remaining unpaired surrogate from last read.
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let mut start = 0;
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if self.high_surrogate.get() != 0 {
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buf[0] = self.high_surrogate.replace(0);
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start = 1;
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if amount == 1 {
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// Special case: `Stdin::read` guarantees we can always read at least one new `u16`
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// and combine it with an unpaired surrogate, because the UTF-8 buffer is at least
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// 4 bytes.
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amount = 2;
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}
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}
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let mut amount = read_u16s(handle, &mut buf[start..amount])? + start;
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if amount > 0 {
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let last_char = buf[amount - 1];
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if last_char >= 0xD800 && last_char <= 0xDBFF { // high surrogate
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self.high_surrogate.set(last_char);
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amount -= 1;
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}
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}
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Ok(amount)
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}
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}
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fn read_u16s(handle: c::HANDLE, buf: &mut [u16]) -> io::Result<usize> {
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// Configure the `pInputControl` parameter to not only return on `\r\n` but also Ctrl-Z, the
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// traditional DOS method to indicate end of character stream / user input (SUB).
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// See #38274 and https://stackoverflow.com/questions/43836040/win-api-readconsole.
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const CTRL_Z: u16 = 0x1A;
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const CTRL_Z_MASK: c::ULONG = 1 << CTRL_Z;
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let mut input_control = c::CONSOLE_READCONSOLE_CONTROL {
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nLength: ::mem::size_of::<c::CONSOLE_READCONSOLE_CONTROL>() as c::ULONG,
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nInitialChars: 0,
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dwCtrlWakeupMask: CTRL_Z_MASK,
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dwControlKeyState: 0,
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};
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let mut amount = 0;
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cvt(unsafe {
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c::ReadConsoleW(handle,
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buf.as_mut_ptr() as c::LPVOID,
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buf.len() as u32,
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&mut amount,
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&mut input_control as c::PCONSOLE_READCONSOLE_CONTROL)
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})?;
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if amount > 0 && buf[amount as usize - 1] == CTRL_Z {
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amount -= 1;
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}
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Ok(amount as usize)
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}
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impl Stdout {
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@ -156,43 +251,10 @@ impl Stderr {
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}
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}
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impl Output {
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pub fn handle(&self) -> c::HANDLE {
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match *self {
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Output::Console(c) => c,
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Output::Pipe(c) => c,
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}
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}
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}
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fn invalid_encoding() -> io::Error {
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io::Error::new(io::ErrorKind::InvalidData,
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"Windows stdio in console mode does not support non-UTF-8 byte sequences; \
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see https://github.com/rust-lang/rust/issues/23344")
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}
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fn readconsole_input_control(wakeup_mask: c::ULONG) -> c::CONSOLE_READCONSOLE_CONTROL {
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c::CONSOLE_READCONSOLE_CONTROL {
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nLength: ::mem::size_of::<c::CONSOLE_READCONSOLE_CONTROL>() as c::ULONG,
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nInitialChars: 0,
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dwCtrlWakeupMask: wakeup_mask,
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dwControlKeyState: 0,
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}
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}
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const CTRL_Z: u8 = 0x1A;
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const CTRL_Z_MASK: c::ULONG = 0x4000000; //1 << 0x1A
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pub fn is_ebadf(err: &io::Error) -> bool {
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err.raw_os_error() == Some(c::ERROR_INVALID_HANDLE as i32)
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}
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// The default buffer capacity is 64k, but apparently windows
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// doesn't like 64k reads on stdin. See #13304 for details, but the
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// idea is that on windows we use a slightly smaller buffer that's
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// been seen to be acceptable.
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pub const STDIN_BUF_SIZE: usize = 8 * 1024;
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pub fn panic_output() -> Option<impl io::Write> {
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io::stderr_raw().ok()
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}
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