Move RustPython vendored and helper code into its own crate (#3171)

crates/ruff_rustpython/src/vendor/bytes.rs

@@ -0,0 +1,68 @@
+//! Vendored from [bytes.rs in rustpython-common](https://github.com/RustPython/RustPython/blob/1d8269fb729c91fc56064e975172d3a11bd62d07/common/src/bytes.rs).
+//! The only changes we make are to remove dead code and make the default quote
+//! type configurable.
+
+use crate::vendor;
+use crate::vendor::str::Quote;
+
+pub fn repr(b: &[u8], quote: Quote) -> String {
+    repr_with(b, &[], "", quote)
+}
+
+pub fn repr_with(b: &[u8], prefixes: &[&str], suffix: &str, quote: Quote) -> String {
+    use std::fmt::Write;
+
+    let mut out_len = 0usize;
+    let mut squote = 0;
+    let mut dquote = 0;
+
+    for &ch in b {
+        let incr = match ch {
+            b'\'' => {
+                squote += 1;
+                1
+            }
+            b'"' => {
+                dquote += 1;
+                1
+            }
+            b'\\' | b'\t' | b'\r' | b'\n' => 2,
+            0x20..=0x7e => 1,
+            _ => 4, // \xHH
+        };
+        // TODO: OverflowError
+        out_len = out_len.checked_add(incr).unwrap();
+    }
+
+    let (quote, num_escaped_quotes) = vendor::str::choose_quotes_for_repr(squote, dquote, quote);
+    // we'll be adding backslashes in front of the existing inner quotes
+    out_len += num_escaped_quotes;
+
+    // 3 is for b prefix + outer quotes
+    out_len += 3 + prefixes.iter().map(|s| s.len()).sum::<usize>() + suffix.len();
+
+    let mut res = String::with_capacity(out_len);
+    res.extend(prefixes.iter().copied());
+    res.push('b');
+    res.push(quote);
+    for &ch in b {
+        match ch {
+            b'\t' => res.push_str("\\t"),
+            b'\n' => res.push_str("\\n"),
+            b'\r' => res.push_str("\\r"),
+            // printable ascii range
+            0x20..=0x7e => {
+                let ch = ch as char;
+                if ch == quote || ch == '\\' {
+                    res.push('\\');
+                }
+                res.push(ch);
+            }
+            _ => write!(res, "\\x{ch:02x}").unwrap(),
+        }
+    }
+    res.push(quote);
+    res.push_str(suffix);
+
+    res
+}