1 files changed, 71 insertions, 0 deletions
diff --git a/library/std/src/sys/io/is_terminal/windows.rs b/library/std/src/sys/io/is_terminal/windows.rs
new file mode 100644
index 00000000000..3ec18fb47b9
--- /dev/null
+++ b/library/std/src/sys/io/is_terminal/windows.rs
@@ -0,0 +1,71 @@
+use crate::ffi::c_void;
+use crate::mem::size_of;
+use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle};
+use crate::sys::c;
+
+pub fn is_terminal(h: &impl AsHandle) -> bool {
+    handle_is_console(h.as_handle())
+}
+
+fn handle_is_console(handle: BorrowedHandle<'_>) -> bool {
+    // A null handle means the process has no console.
+    if handle.as_raw_handle().is_null() {
+        return false;
+    }
+
+    let mut out = 0;
+    if unsafe { c::GetConsoleMode(handle.as_raw_handle(), &mut out) != 0 } {
+        // False positives aren't possible. If we got a console then we definitely have a console.
+        return true;
+    }
+
+    // Otherwise, we fall back to an msys hack to see if we can detect the presence of a pty.
+    msys_tty_on(handle)
+}
+
+fn msys_tty_on(handle: BorrowedHandle<'_>) -> bool {
+    // Early return if the handle is not a pipe.
+    if unsafe { c::GetFileType(handle.as_raw_handle()) != c::FILE_TYPE_PIPE } {
+        return false;
+    }
+
+    /// Mirrors [`FILE_NAME_INFO`], giving it a fixed length that we can stack
+    /// allocate
+    ///
+    /// [`FILE_NAME_INFO`]: https://learn.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_name_info
+    #[repr(C)]
+    #[allow(non_snake_case)]
+    struct FILE_NAME_INFO {
+        FileNameLength: u32,
+        FileName: [u16; c::MAX_PATH as usize],
+    }
+    let mut name_info = FILE_NAME_INFO { FileNameLength: 0, FileName: [0; c::MAX_PATH as usize] };
+    // Safety: buffer length is fixed.
+    let res = unsafe {
+        c::GetFileInformationByHandleEx(
+            handle.as_raw_handle(),
+            c::FileNameInfo,
+            (&raw mut name_info) as *mut c_void,
+            size_of::<FILE_NAME_INFO>() as u32,
+        )
+    };
+    if res == 0 {
+        return false;
+    }
+
+    // Use `get` because `FileNameLength` can be out of range.
+    let s = match name_info.FileName.get(..name_info.FileNameLength as usize / 2) {
+        None => return false,
+        Some(s) => s,
+    };
+    let name = String::from_utf16_lossy(s);
+    // Get the file name only.
+    let name = name.rsplit('\\').next().unwrap_or(&name);
+    // This checks whether 'pty' exists in the file name, which indicates that
+    // a pseudo-terminal is attached. To mitigate against false positives
+    // (e.g., an actual file name that contains 'pty'), we also require that
+    // the file name begins with either the strings 'msys-' or 'cygwin-'.)
+    let is_msys = name.starts_with("msys-") || name.starts_with("cygwin-");
+    let is_pty = name.contains("-pty");
+    is_msys && is_pty
+}