1 files changed, 266 insertions, 0 deletions
diff --git a/library/std/src/sys/windows/args.rs b/library/std/src/sys/windows/args.rs
new file mode 100644
index 00000000000..5fbea2a2910
--- /dev/null
+++ b/library/std/src/sys/windows/args.rs
@@ -0,0 +1,266 @@
+#![allow(dead_code)] // runtime init functions not used during testing
+
+use crate::ffi::OsString;
+use crate::fmt;
+use crate::os::windows::prelude::*;
+use crate::path::PathBuf;
+use crate::slice;
+use crate::sys::c;
+use crate::sys::windows::os::current_exe;
+use crate::vec;
+
+use core::iter;
+
+pub unsafe fn init(_argc: isize, _argv: *const *const u8) {}
+
+pub unsafe fn cleanup() {}
+
+pub fn args() -> Args {
+    unsafe {
+        let lp_cmd_line = c::GetCommandLineW();
+        let parsed_args_list = parse_lp_cmd_line(lp_cmd_line as *const u16, || {
+            current_exe().map(PathBuf::into_os_string).unwrap_or_else(|_| OsString::new())
+        });
+
+        Args { parsed_args_list: parsed_args_list.into_iter() }
+    }
+}
+
+/// Implements the Windows command-line argument parsing algorithm.
+///
+/// Microsoft's documentation for the Windows CLI argument format can be found at
+/// <https://docs.microsoft.com/en-us/previous-versions//17w5ykft(v=vs.85)>.
+///
+/// Windows includes a function to do this in shell32.dll,
+/// but linking with that DLL causes the process to be registered as a GUI application.
+/// GUI applications add a bunch of overhead, even if no windows are drawn. See
+/// <https://randomascii.wordpress.com/2018/12/03/a-not-called-function-can-cause-a-5x-slowdown/>.
+///
+/// This function was tested for equivalence to the shell32.dll implementation in
+/// Windows 10 Pro v1803, using an exhaustive test suite available at
+/// <https://gist.github.com/notriddle/dde431930c392e428055b2dc22e638f5> or
+/// <https://paste.gg/p/anonymous/47d6ed5f5bd549168b1c69c799825223>.
+unsafe fn parse_lp_cmd_line<F: Fn() -> OsString>(
+    lp_cmd_line: *const u16,
+    exe_name: F,
+) -> Vec<OsString> {
+    const BACKSLASH: u16 = '\\' as u16;
+    const QUOTE: u16 = '"' as u16;
+    const TAB: u16 = '\t' as u16;
+    const SPACE: u16 = ' ' as u16;
+    let mut ret_val = Vec::new();
+    if lp_cmd_line.is_null() || *lp_cmd_line == 0 {
+        ret_val.push(exe_name());
+        return ret_val;
+    }
+    let mut cmd_line = {
+        let mut end = 0;
+        while *lp_cmd_line.offset(end) != 0 {
+            end += 1;
+        }
+        slice::from_raw_parts(lp_cmd_line, end as usize)
+    };
+    // The executable name at the beginning is special.
+    cmd_line = match cmd_line[0] {
+        // The executable name ends at the next quote mark,
+        // no matter what.
+        QUOTE => {
+            let args = {
+                let mut cut = cmd_line[1..].splitn(2, |&c| c == QUOTE);
+                if let Some(exe) = cut.next() {
+                    ret_val.push(OsString::from_wide(exe));
+                }
+                cut.next()
+            };
+            if let Some(args) = args {
+                args
+            } else {
+                return ret_val;
+            }
+        }
+        // Implement quirk: when they say whitespace here,
+        // they include the entire ASCII control plane:
+        // "However, if lpCmdLine starts with any amount of whitespace, CommandLineToArgvW
+        // will consider the first argument to be an empty string. Excess whitespace at the
+        // end of lpCmdLine is ignored."
+        0..=SPACE => {
+            ret_val.push(OsString::new());
+            &cmd_line[1..]
+        }
+        // The executable name ends at the next whitespace,
+        // no matter what.
+        _ => {
+            let args = {
+                let mut cut = cmd_line.splitn(2, |&c| c > 0 && c <= SPACE);
+                if let Some(exe) = cut.next() {
+                    ret_val.push(OsString::from_wide(exe));
+                }
+                cut.next()
+            };
+            if let Some(args) = args {
+                args
+            } else {
+                return ret_val;
+            }
+        }
+    };
+    let mut cur = Vec::new();
+    let mut in_quotes = false;
+    let mut was_in_quotes = false;
+    let mut backslash_count: usize = 0;
+    for &c in cmd_line {
+        match c {
+            // backslash
+            BACKSLASH => {
+                backslash_count += 1;
+                was_in_quotes = false;
+            }
+            QUOTE if backslash_count % 2 == 0 => {
+                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count / 2));
+                backslash_count = 0;
+                if was_in_quotes {
+                    cur.push('"' as u16);
+                    was_in_quotes = false;
+                } else {
+                    was_in_quotes = in_quotes;
+                    in_quotes = !in_quotes;
+                }
+            }
+            QUOTE if backslash_count % 2 != 0 => {
+                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count / 2));
+                backslash_count = 0;
+                was_in_quotes = false;
+                cur.push(b'"' as u16);
+            }
+            SPACE | TAB if !in_quotes => {
+                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count));
+                if !cur.is_empty() || was_in_quotes {
+                    ret_val.push(OsString::from_wide(&cur[..]));
+                    cur.truncate(0);
+                }
+                backslash_count = 0;
+                was_in_quotes = false;
+            }
+            _ => {
+                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count));
+                backslash_count = 0;
+                was_in_quotes = false;
+                cur.push(c);
+            }
+        }
+    }
+    cur.extend(iter::repeat(b'\\' as u16).take(backslash_count));
+    // include empty quoted strings at the end of the arguments list
+    if !cur.is_empty() || was_in_quotes || in_quotes {
+        ret_val.push(OsString::from_wide(&cur[..]));
+    }
+    ret_val
+}
+
+pub struct Args {
+    parsed_args_list: vec::IntoIter<OsString>,
+}
+
+pub struct ArgsInnerDebug<'a> {
+    args: &'a Args,
+}
+
+impl<'a> fmt::Debug for ArgsInnerDebug<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.args.parsed_args_list.as_slice().fmt(f)
+    }
+}
+
+impl Args {
+    pub fn inner_debug(&self) -> ArgsInnerDebug<'_> {
+        ArgsInnerDebug { args: self }
+    }
+}
+
+impl Iterator for Args {
+    type Item = OsString;
+    fn next(&mut self) -> Option<OsString> {
+        self.parsed_args_list.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.parsed_args_list.size_hint()
+    }
+}
+
+impl DoubleEndedIterator for Args {
+    fn next_back(&mut self) -> Option<OsString> {
+        self.parsed_args_list.next_back()
+    }
+}
+
+impl ExactSizeIterator for Args {
+    fn len(&self) -> usize {
+        self.parsed_args_list.len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::ffi::OsString;
+    use crate::sys::windows::args::*;
+
+    fn chk(string: &str, parts: &[&str]) {
+        let mut wide: Vec<u16> = OsString::from(string).encode_wide().collect();
+        wide.push(0);
+        let parsed = unsafe {
+            parse_lp_cmd_line(wide.as_ptr() as *const u16, || OsString::from("TEST.EXE"))
+        };
+        let expected: Vec<OsString> = parts.iter().map(|k| OsString::from(k)).collect();
+        assert_eq!(parsed.as_slice(), expected.as_slice());
+    }
+
+    #[test]
+    fn empty() {
+        chk("", &["TEST.EXE"]);
+        chk("\0", &["TEST.EXE"]);
+    }
+
+    #[test]
+    fn single_words() {
+        chk("EXE one_word", &["EXE", "one_word"]);
+        chk("EXE a", &["EXE", "a"]);
+        chk("EXE 😅", &["EXE", "😅"]);
+        chk("EXE 😅🤦", &["EXE", "😅🤦"]);
+    }
+
+    #[test]
+    fn official_examples() {
+        chk(r#"EXE "abc" d e"#, &["EXE", "abc", "d", "e"]);
+        chk(r#"EXE a\\\b d"e f"g h"#, &["EXE", r#"a\\\b"#, "de fg", "h"]);
+        chk(r#"EXE a\\\"b c d"#, &["EXE", r#"a\"b"#, "c", "d"]);
+        chk(r#"EXE a\\\\"b c" d e"#, &["EXE", r#"a\\b c"#, "d", "e"]);
+    }
+
+    #[test]
+    fn whitespace_behavior() {
+        chk(r#" test"#, &["", "test"]);
+        chk(r#"  test"#, &["", "test"]);
+        chk(r#" test test2"#, &["", "test", "test2"]);
+        chk(r#" test  test2"#, &["", "test", "test2"]);
+        chk(r#"test test2 "#, &["test", "test2"]);
+        chk(r#"test  test2 "#, &["test", "test2"]);
+        chk(r#"test "#, &["test"]);
+    }
+
+    #[test]
+    fn genius_quotes() {
+        chk(r#"EXE "" """#, &["EXE", "", ""]);
+        chk(r#"EXE "" """"#, &["EXE", "", "\""]);
+        chk(
+            r#"EXE "this is """all""" in the same argument""#,
+            &["EXE", "this is \"all\" in the same argument"],
+        );
+        chk(r#"EXE "a"""#, &["EXE", "a\""]);
+        chk(r#"EXE "a"" a"#, &["EXE", "a\"", "a"]);
+        // quotes cannot be escaped in command names
+        chk(r#""EXE" check"#, &["EXE", "check"]);
+        chk(r#""EXE check""#, &["EXE check"]);
+        chk(r#""EXE """for""" check"#, &["EXE ", r#"for""#, "check"]);
+        chk(r#""EXE \"for\" check"#, &[r#"EXE \"#, r#"for""#, "check"]);
+    }
+}