use crate::Error;
use proc_macro2::{Delimiter, Ident, Literal, Span, TokenStream, TokenTree};
use std::char;
macro_rules! unexpected_content {
() => {
"expected one of: byte string literal, string literal, identifier"
};
}
pub(crate) fn parse_input(mut input: TokenStream) -> Result<(Vec<u8>, Span), Error> {
loop {
let mut tokens = input.into_iter();
let token = match tokens.next() {
Some(token) => token,
None => {
return Err(Error(
Span::call_site(),
concat!("unexpected end of input, ", unexpected_content!()),
))
}
};
let span = token.span();
let result = match token {
// Unwrap any empty group which may be created from macro expansion.
TokenTree::Group(group) if group.delimiter() == Delimiter::None => Err(group),
TokenTree::Literal(literal) => match parse_literal(literal) {
Ok(result) => Ok(result),
Err(msg) => return Err(Error(span, msg)),
},
TokenTree::Ident(ident) => Ok(parse_ident(ident)),
_ => return Err(Error(span, unexpected_content!())),
};
if let Some(token) = tokens.next() {
return Err(Error(token.span(), "unexpected token"));
}
match result {
Ok(result) => return Ok((result, span)),
Err(group) => input = group.stream(),
}
}
}
fn parse_literal(literal: Literal) -> Result<Vec<u8>, &'static str> {
let s = literal.to_string();
let s = s.as_bytes();
match s[0] {
b'"' => Ok(parse_cooked_content(s)),
b'r' => Ok(parse_raw_content(&s[1..])),
b'b' => match s[1] {
b'"' => Ok(parse_cooked_content(&s[1..])),
b'r' => Ok(parse_raw_content(&s[2..])),
_ => Err(unexpected_content!()),
},
_ => Err(unexpected_content!()),
}
}
fn all_pounds(bytes: &[u8]) -> bool {
bytes.iter().all(|b| *b == b'#')
}
/// Parses raw string / bytes content after `r` prefix.
fn parse_raw_content(s: &[u8]) -> Vec<u8> {
let q_start = s.iter().position(|b| *b == b'"').unwrap();
let q_end = s.iter().rposition(|b| *b == b'"').unwrap();
assert!(all_pounds(&s[0..q_start]));
assert!(all_pounds(&s[q_end + 1..q_end + q_start + 1]));
Vec::from(&s[q_start + 1..q_end])
}
/// Parses the cooked string / bytes content within quotes.
fn parse_cooked_content(mut s: &[u8]) -> Vec<u8> {
s = &s[1..s.iter().rposition(|b| *b == b'"').unwrap()];
let mut result = Vec::new();
while !s.is_empty() {
match s[0] {
b'\\' => {}
b'\r' => {
assert_eq!(s[1], b'\n');
result.push(b'\n');
s = &s[2..];
continue;
}
b => {
result.push(b);
s = &s[1..];
continue;
}
}
let b = s[1];
s = &s[2..];
match b {
b'x' => {
let (b, rest) = backslash_x(s);
result.push(b);
s = rest;
}
b'u' => {
let (c, rest) = backslash_u(s);
result.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes());
s = rest;
}
b'n' => result.push(b'\n'),
b'r' => result.push(b'\r'),
b't' => result.push(b'\t'),
b'\\' => result.push(b'\\'),
b'0' => result.push(b'\0'),
b'\'' => result.push(b'\''),
b'"' => result.push(b'"'),
b'\r' | b'\n' => {
let next = s.iter().position(|b| {
let ch = char::from_u32(u32::from(*b)).unwrap();
!ch.is_whitespace()
});
match next {
Some(pos) => s = &s[pos..],
None => s = b"",
}
}
b => panic!("unexpected byte {:?} after \\", b),
}
}
result
}
fn backslash_x(s: &[u8]) -> (u8, &[u8]) {
let ch = hex_to_u8(s[0]) * 0x10 + hex_to_u8(s[1]);
(ch, &s[2..])
}
fn hex_to_u8(b: u8) -> u8 {
match b {
b'0'..=b'9' => b - b'0',
b'a'..=b'f' => b - b'a' + 10,
b'A'..=b'F' => b - b'A' + 10,
_ => unreachable!("unexpected non-hex character {:?} after \\x", b),
}
}
fn backslash_u(s: &[u8]) -> (char, &[u8]) {
assert_eq!(s[0], b'{');
let end = s[1..].iter().position(|b| *b == b'}').unwrap();
let mut ch = 0;
for b in &s[1..=end] {
ch *= 0x10;
ch += u32::from(hex_to_u8(*b));
}
(char::from_u32(ch).unwrap(), &s[end + 2..])
}
fn parse_ident(ident: Ident) -> Vec<u8> {
ident.to_string().into_bytes()
}
#[cfg(test)]
mod tests {
use super::*;
use std::str::FromStr;
// Tests below were modified from
//
https://github.com/dtolnay/syn/blob/cd5fdc0f530f822446fccaf831669cd0cf4a0fc9/tests/test_lit.rs
fn lit(s: &str) -> Vec<u8> {
match TokenStream::from_str(s)
.unwrap()
.into_iter()
.next()
.unwrap()
{
TokenTree::Literal(lit) => parse_literal(lit).unwrap(),
_ => panic!(),
}
}
#[test]
fn strings() {
#[track_caller]
fn test_string(s: &str, value: &[u8]) {
assert_eq!(lit(s), value);
}
test_string("\"a\"", b"a");
test_string("\"\\n\"", b"\n");
test_string("\"\\r\"", b"\r");
test_string("\"\\t\"", b"\t");
test_string("\"��\"", b"\xf0\x9f\x90\x95"); // NOTE: This is an emoji
test_string("\"\\\"\"", b"\"");
test_string("\"'\"", b"'");
test_string("\"\"", b"");
test_string("\"\\u{1F415}\"", b"\xf0\x9f\x90\x95");
test_string(
"\"contains\nnewlines\\\nescaped newlines\"",
b"contains\nnewlinesescaped newlines",
);
test_string("r\"raw\nstring\\\nhere\"", b"raw\nstring\\\nhere");
test_string("\"...\"q", b"...");
test_string("r\"...\"q", b"...");
test_string("r##\"...\"##q", b"...");
}
#[test]
fn byte_strings() {
#[track_caller]
fn test_byte_string(s: &str, value: &[u8]) {
assert_eq!(lit(s), value);
}
test_byte_string("b\"a\"", b"a");
test_byte_string("b\"\\n\"", b"\n");
test_byte_string("b\"\\r\"", b"\r");
test_byte_string("b\"\\t\"", b"\t");
test_byte_string("b\"\\\"\"", b"\"");
test_byte_string("b\"'\"", b"'");
test_byte_string("b\"\"", b"");
test_byte_string(
"b\"contains\nnewlines\\\nescaped newlines\"",
b"contains\nnewlinesescaped newlines",
);
test_byte_string("br\"raw\nstring\\\nhere\"", b"raw\nstring\\\nhere");
test_byte_string("b\"...\"q", b"...");
test_byte_string("br\"...\"q", b"...");
test_byte_string("br##\"...\"##q", b"...");
}
}
