add encoder function arg

rewriter/src/main.rs

@@ -1,5 +1,6 @@
 #![allow(clippy::print_stdout)]
 use std::{
+    borrow::Cow,
     env,
     path::Path,
     str::{from_utf8, FromStr},
@@ -15,6 +16,91 @@ use url::Url;
 // run `cargo run -p oxc_parser --example visitor`
 // or `cargo watch -x "run -p oxc_parser --example visitor"`
 
+/// Percent-encodes every byte except alphanumerics and `-`, `_`, `.`, `~`. Assumes UTF-8 encoding.
+///
+/// Call `.into_owned()` if you need a `String`
+#[inline(always)]
+#[must_use]
+pub fn encode(data: &str) -> Cow<'_, str> {
+    encode_binary(data.as_bytes())
+}
+
+/// Percent-encodes every byte except alphanumerics and `-`, `_`, `.`, `~`.
+#[inline]
+#[must_use]
+pub fn encode_binary(data: &[u8]) -> Cow<'_, str> {
+    // add maybe extra capacity, but try not to exceed allocator's bucket size
+    let mut escaped = String::new();
+    let _ = escaped.try_reserve(data.len() | 15);
+    let unmodified = append_string(data, &mut escaped, true);
+    if unmodified {
+        return Cow::Borrowed(unsafe {
+            // encode_into has checked it's ASCII
+            std::str::from_utf8_unchecked(data)
+        });
+    }
+    Cow::Owned(escaped)
+}
+
+fn append_string(data: &[u8], escaped: &mut String, may_skip: bool) -> bool {
+    encode_into(data, may_skip, |s| {
+        escaped.push_str(s);
+        Ok::<_, std::convert::Infallible>(())
+    })
+    .unwrap()
+}
+
+fn encode_into<E>(
+    mut data: &[u8],
+    may_skip_write: bool,
+    mut push_str: impl FnMut(&str) -> Result<(), E>,
+) -> Result<bool, E> {
+    let mut pushed = false;
+    loop {
+        // Fast path to skip over safe chars at the beginning of the remaining string
+        let ascii_len = data.iter()
+            .take_while(|&&c| matches!(c, b'0'..=b'9' | b'A'..=b'Z' | b'a'..=b'z' |  b'-' | b'.' | b'_' | b'~')).count();
+
+        let (safe, rest) = if ascii_len >= data.len() {
+            if !pushed && may_skip_write {
+                return Ok(true);
+            }
+            (data, &[][..]) // redundatnt to optimize out a panic in split_at
+        } else {
+            data.split_at(ascii_len)
+        };
+        pushed = true;
+        if !safe.is_empty() {
+            push_str(unsafe { std::str::from_utf8_unchecked(safe) })?;
+        }
+        if rest.is_empty() {
+            break;
+        }
+
+        match rest.split_first() {
+            Some((byte, rest)) => {
+                let enc = &[b'%', to_hex_digit(byte >> 4), to_hex_digit(byte & 15)];
+                push_str(unsafe { std::str::from_utf8_unchecked(enc) })?;
+                data = rest;
+            }
+            None => break,
+        };
+    }
+    Ok(false)
+}
+
+#[inline]
+fn to_hex_digit(digit: u8) -> u8 {
+    match digit {
+        0..=9 => b'0' + digit,
+        10..=255 => b'A' - 10 + digit,
+    }
+}
+
+fn encode_string(s: String) -> String {
+    encode(&s).to_string()
+}
+
 fn main() -> std::io::Result<()> {
     let name = env::args().nth(1).unwrap_or_else(|| "test.js".to_string());
     let path = Path::new(&name);
@@ -25,7 +111,8 @@ fn main() -> std::io::Result<()> {
         from_utf8(
             rewrite(
                 &source_text,
-                Url::from_str("https://google.com/glorngle/si.js").unwrap()
+                Url::from_str("https://google.com/glorngle/si.js").unwrap(),
+                Box::new(encode_string)
             )
             .as_slice()
         )