1 files changed, 159 insertions, 0 deletions
diff --git a/library/std/src/sys/windows/args.rs b/library/std/src/sys/windows/args.rs
index 3919025b080..c5918103fec 100644
--- a/library/std/src/sys/windows/args.rs
+++ b/library/std/src/sys/windows/args.rs
@@ -8,12 +8,14 @@ mod tests;
 
 use crate::ffi::OsString;
 use crate::fmt;
+use crate::io;
 use crate::marker::PhantomData;
 use crate::num::NonZeroU16;
 use crate::os::windows::prelude::*;
 use crate::path::PathBuf;
 use crate::ptr::NonNull;
 use crate::sys::c;
+use crate::sys::process::ensure_no_nuls;
 use crate::sys::windows::os::current_exe;
 use crate::vec;
 
@@ -234,3 +236,160 @@ impl Iterator for WStrUnits<'_> {
         }
     }
 }
+
+#[derive(Debug)]
+pub(crate) enum Arg {
+    /// Add quotes (if needed)
+    Regular(OsString),
+    /// Append raw string without quoting
+    Raw(OsString),
+}
+
+enum Quote {
+    // Every arg is quoted
+    Always,
+    // Whitespace and empty args are quoted
+    Auto,
+    // Arg appended without any changes (#29494)
+    Never,
+}
+
+pub(crate) fn append_arg(cmd: &mut Vec<u16>, arg: &Arg, force_quotes: bool) -> io::Result<()> {
+    let (arg, quote) = match arg {
+        Arg::Regular(arg) => (arg, if force_quotes { Quote::Always } else { Quote::Auto }),
+        Arg::Raw(arg) => (arg, Quote::Never),
+    };
+
+    // If an argument has 0 characters then we need to quote it to ensure
+    // that it actually gets passed through on the command line or otherwise
+    // it will be dropped entirely when parsed on the other end.
+    ensure_no_nuls(arg)?;
+    let arg_bytes = arg.bytes();
+    let (quote, escape) = match quote {
+        Quote::Always => (true, true),
+        Quote::Auto => {
+            (arg_bytes.iter().any(|c| *c == b' ' || *c == b'\t') || arg_bytes.is_empty(), true)
+        }
+        Quote::Never => (false, false),
+    };
+    if quote {
+        cmd.push('"' as u16);
+    }
+
+    let mut backslashes: usize = 0;
+    for x in arg.encode_wide() {
+        if escape {
+            if x == '\\' as u16 {
+                backslashes += 1;
+            } else {
+                if x == '"' as u16 {
+                    // Add n+1 backslashes to total 2n+1 before internal '"'.
+                    cmd.extend((0..=backslashes).map(|_| '\\' as u16));
+                }
+                backslashes = 0;
+            }
+        }
+        cmd.push(x);
+    }
+
+    if quote {
+        // Add n backslashes to total 2n before ending '"'.
+        cmd.extend((0..backslashes).map(|_| '\\' as u16));
+        cmd.push('"' as u16);
+    }
+    Ok(())
+}
+
+pub(crate) fn make_bat_command_line(
+    script: &[u16],
+    args: &[Arg],
+    force_quotes: bool,
+) -> io::Result<Vec<u16>> {
+    // Set the start of the command line to `cmd.exe /c "`
+    // It is necessary to surround the command in an extra pair of quotes,
+    // hence the trailing quote here. It will be closed after all arguments
+    // have been added.
+    let mut cmd: Vec<u16> = "cmd.exe /c \"".encode_utf16().collect();
+
+    // Push the script name surrounded by its quote pair.
+    cmd.push(b'"' as u16);
+    // Windows file names cannot contain a `"` character or end with `\\`.
+    // If the script name does then return an error.
+    if script.contains(&(b'"' as u16)) || script.last() == Some(&(b'\\' as u16)) {
+        return Err(io::const_io_error!(
+            io::ErrorKind::InvalidInput,
+            "Windows file names may not contain `\"` or end with `\\`"
+        ));
+    }
+    cmd.extend_from_slice(script.strip_suffix(&[0]).unwrap_or(script));
+    cmd.push(b'"' as u16);
+
+    // Append the arguments.
+    // FIXME: This needs tests to ensure that the arguments are properly
+    // reconstructed by the batch script by default.
+    for arg in args {
+        cmd.push(' ' as u16);
+        append_arg(&mut cmd, arg, force_quotes)?;
+    }
+
+    // Close the quote we left opened earlier.
+    cmd.push(b'"' as u16);
+
+    Ok(cmd)
+}
+
+/// Takes a path and tries to return a non-verbatim path.
+///
+/// This is necessary because cmd.exe does not support verbatim paths.
+pub(crate) fn to_user_path(mut path: Vec<u16>) -> io::Result<Vec<u16>> {
+    use crate::ptr;
+    use crate::sys::windows::fill_utf16_buf;
+
+    // UTF-16 encoded code points, used in parsing and building UTF-16 paths.
+    // All of these are in the ASCII range so they can be cast directly to `u16`.
+    const SEP: u16 = b'\\' as _;
+    const QUERY: u16 = b'?' as _;
+    const COLON: u16 = b':' as _;
+    const U: u16 = b'U' as _;
+    const N: u16 = b'N' as _;
+    const C: u16 = b'C' as _;
+
+    // Early return if the path is too long to remove the verbatim prefix.
+    const LEGACY_MAX_PATH: usize = 260;
+    if path.len() > LEGACY_MAX_PATH {
+        return Ok(path);
+    }
+
+    match &path[..] {
+        // `\\?\C:\...` => `C:\...`
+        [SEP, SEP, QUERY, SEP, _, COLON, SEP, ..] => unsafe {
+            let lpfilename = path[4..].as_ptr();
+            fill_utf16_buf(
+                |buffer, size| c::GetFullPathNameW(lpfilename, size, buffer, ptr::null_mut()),
+                |full_path: &[u16]| {
+                    if full_path == &path[4..path.len() - 1] { full_path.into() } else { path }
+                },
+            )
+        },
+        // `\\?\UNC\...` => `\\...`
+        [SEP, SEP, QUERY, SEP, U, N, C, SEP, ..] => unsafe {
+            // Change the `C` in `UNC\` to `\` so we can get a slice that starts with `\\`.
+            path[6] = b'\\' as u16;
+            let lpfilename = path[6..].as_ptr();
+            fill_utf16_buf(
+                |buffer, size| c::GetFullPathNameW(lpfilename, size, buffer, ptr::null_mut()),
+                |full_path: &[u16]| {
+                    if full_path == &path[6..path.len() - 1] {
+                        full_path.into()
+                    } else {
+                        // Restore the 'C' in "UNC".
+                        path[6] = b'C' as u16;
+                        path
+                    }
+                },
+            )
+        },
+        // For everything else, leave the path unchanged.
+        _ => Ok(path),
+    }
+}