Source code
Revision control
Copy as Markdown
Other Tools
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
//! This crate implements a prefs file parser.
//!
//! Pref files have the following grammar. Note that there are slight
//! differences between the grammar for a default prefs files and a user prefs
//! file.
//!
//! ```text
//! <pref-file> = <pref>*
//! <pref> = <pref-spec> "(" <pref-name> "," <pref-value> <pref-attrs> ")" ";"
//! <pref-spec> = "user_pref" | "pref" | "sticky_pref" // in default pref files
//! <pref-spec> = "user_pref" // in user pref files
//! <pref-name> = <string-literal>
//! <pref-value> = <string-literal> | "true" | "false" | <int-value>
//! <int-value> = <sign>? <int-literal>
//! <sign> = "+" | "-"
//! <int-literal> = [0-9]+ (and cannot be followed by [A-Za-z_])
//! <string-literal> =
//! A single or double-quoted string, with the following escape sequences
//! allowed: \", \', \\, \n, \r, \xNN, \uNNNN, where \xNN gives a raw byte
//! value that is copied directly into an 8-bit string value, and \uNNNN
//! gives a UTF-16 code unit that is converted to UTF-8 before being copied
//! into an 8-bit string value. \x00 and \u0000 are disallowed because they
//! would cause C++ code handling such strings to misbehave.
//! <pref-attrs> = ("," <pref-attr>)* // in default pref files
//! = <empty> // in user pref files
//! <pref-attr> = "sticky" | "locked" // default pref files only
//! ```
//!
//! Comments can take three forms:
//! - `# Python-style comments`
//! - `// C++ style comments`
//! - `/* C style comments (non-nested) */`
//!
//! Non-end-of-line whitespace chars are `\t`, `\v`, `\f`, and space.
//!
//! End-of-line sequences can take three forms, each of which is considered as
//! a single EOL:
//! - `\n`
//! - `\r` (without subsequent `\n`)
//! - `\r\n`
//!
//! The valid range for `<int-value>` is -2,147,483,648..2,147,483,647. Values
//! outside that range will result in a parse error.
//!
//! A `\0` char is interpreted as the end of the file. The use of this character
//! in a prefs file is not recommended. Within string literals `\x00` or
//! `\u0000` can be used instead.
//!
//! The parser performs error recovery. On a syntax error, it will scan forward
//! to the next `;` token and then continue parsing. If the syntax error occurs
//! in the middle of a token, it will first finish obtaining the current token
//! in an appropriate fashion.
// This parser uses several important optimizations.
//
// - Because "`\0` means EOF" is part of the grammar (see above), EOF is
// representable by a u8. If EOF was represented by an out-of-band value such
// as -1 or 256, we'd have to return a larger type such as `u16` or `i16`
// from `get_char()`.
//
// - When starting a new token, it uses a lookup table with the first char,
// which quickly identifies what kind of token it will be. Furthermore, if
// that token is an unambiguous single-char token (e.g. `(`, `)`, `+`, `,`,
// `-`, `;`), the parser will return the appropriate token kind value at
// minimal cost because the single-char tokens have a uniform representation.
//
// - It has a lookup table that identifies chars in string literals that need
// special handling. This means non-special chars (the common case) can be
// handled with a single test, rather than testing for the multiple special
// cases.
//
// - It pre-scans string literals for special chars. If none are present, it
// bulk copies the string literal into a Vec, which is faster than doing a
// char-by-char copy.
//
// - It reuses Vecs to avoid creating a new one for each string literal.
use std::os::raw::{c_char, c_uchar};
//---------------------------------------------------------------------------
// The public interface
//---------------------------------------------------------------------------
/// Keep this in sync with PrefType in Preferences.cpp.
#[derive(Clone, Copy, Debug, PartialEq)]
#[repr(u8)]
pub enum PrefType {
None,
String,
Int,
Bool,
}
/// Keep this in sync with PrefValueKind in Preferences.h.
#[derive(Clone, Copy, Debug, PartialEq)]
#[repr(u8)]
pub enum PrefValueKind {
Default,
User,
}
/// Keep this in sync with PrefValue in Preferences.cpp.
#[repr(C)]
pub union PrefValue {
pub string_val: *const c_char,
pub int_val: i32,
pub bool_val: bool,
}
/// Keep this in sync with PrefsParserPrefFn in Preferences.cpp.
type PrefFn = unsafe extern "C" fn(
pref_name: *const c_char,
pref_type: PrefType,
pref_value_kind: PrefValueKind,
pref_value: PrefValue,
is_sticky: bool,
is_locked: bool,
);
/// Keep this in sync with PrefsParserErrorFn in Preferences.cpp.
type ErrorFn = unsafe extern "C" fn(msg: *const c_char);
/// Parse the contents of a prefs file.
///
/// `buf` is a null-terminated string. `len` is its length, excluding the
/// null terminator.
///
/// `pref_fn` is called once for each successfully parsed pref.
///
/// `error_fn` is called once for each parse error detected.
///
/// Keep this in sync with the prefs_parser_parse() declaration in
/// Preferences.cpp.
#[no_mangle]
pub unsafe extern "C" fn prefs_parser_parse(
path: *const c_char,
kind: PrefValueKind,
buf: *const c_char,
len: usize,
pref_fn: PrefFn,
error_fn: ErrorFn,
) -> bool {
let path = std::ffi::CStr::from_ptr(path)
.to_string_lossy()
.into_owned();
// Make sure `buf` ends in a '\0', and include that in the length, because
// it represents EOF.
let buf = std::slice::from_raw_parts(buf as *const c_uchar, len + 1);
assert!(buf.last() == Some(&EOF));
let mut parser = Parser::new(&path, kind, &buf, pref_fn, error_fn);
parser.parse()
}
//---------------------------------------------------------------------------
// The implementation
//---------------------------------------------------------------------------
#[derive(Clone, Copy, Debug, PartialEq)]
enum Token {
// Unambiguous single-char tokens.
SingleChar(u8),
// Keywords
Pref, // pref
StickyPref, // sticky_pref
UserPref, // user_pref
True, // true
False, // false
Sticky, // sticky
Locked, // locked
// String literal, e.g. '"string"'. The value is stored elsewhere.
String,
// Unsigned integer literal, e.g. '123'. Although libpref uses i32 values,
// any '-' and '+' before an integer literal are treated as separate
// tokens, so these token values are always positive. Furthermore, we
// tokenize int literals as u32 so that 2147483648 (which doesn't fit into
// an i32) can be subsequently negated to -2147483648 (which does fit into
// an i32) if a '-' token precedes it.
Int(u32),
// Malformed token.
Error(&'static str),
// Malformed token at a particular line number. For use when
// Parser::line_num might not be the right line number when the error is
// reported. E.g. if a multi-line string has a bad escape sequence on the
// first line, we don't report the error until the string's end has been
// reached.
ErrorAtLine(&'static str, u32),
}
// We categorize every char by what action should be taken when it appears at
// the start of a new token.
#[derive(Clone, Copy, PartialEq)]
enum CharKind {
// These are ordered by frequency. See the comment in GetToken().
SingleChar, // Unambiguous single-char tokens: [()+,-] or EOF
SpaceNL, // [\t\v\f \n]
Keyword, // [A-Za-z_]
Quote, // ["']
Slash, // /
Digit, // [0-9]
Hash, // #
CR, // \r
Other, // Everything else; invalid except within strings and comments.
}
const C_SINGL: CharKind = CharKind::SingleChar;
const C_SPCNL: CharKind = CharKind::SpaceNL;
const C_KEYWD: CharKind = CharKind::Keyword;
const C_QUOTE: CharKind = CharKind::Quote;
const C_SLASH: CharKind = CharKind::Slash;
const C_DIGIT: CharKind = CharKind::Digit;
const C_HASH_: CharKind = CharKind::Hash;
const C_CR___: CharKind = CharKind::CR;
const C______: CharKind = CharKind::Other;
#[rustfmt::skip]
const CHAR_KINDS: [CharKind; 256] = [
/* 0 1 2 3 4 5 6 7 8 9 */
/* 0+ */ C_SINGL, C______, C______, C______, C______, C______, C______, C______, C______, C_SPCNL,
/* 10+ */ C_SPCNL, C_SPCNL, C_SPCNL, C_CR___, C______, C______, C______, C______, C______, C______,
/* 20+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 30+ */ C______, C______, C_SPCNL, C______, C_QUOTE, C_HASH_, C______, C______, C______, C_QUOTE,
/* 40+ */ C_SINGL, C_SINGL, C______, C_SINGL, C_SINGL, C_SINGL, C______, C_SLASH, C_DIGIT, C_DIGIT,
/* 50+ */ C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C______, C_SINGL,
/* 60+ */ C______, C______, C______, C______, C______, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD,
/* 70+ */ C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD,
/* 80+ */ C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD,
/* 90+ */ C_KEYWD, C______, C______, C______, C______, C_KEYWD, C______, C_KEYWD, C_KEYWD, C_KEYWD,
/* 100+ */ C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD,
/* 110+ */ C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD, C_KEYWD,
/* 120+ */ C_KEYWD, C_KEYWD, C_KEYWD, C______, C______, C______, C______, C______, C______, C______,
/* 130+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 140+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 150+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 160+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 170+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 180+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 190+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 200+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 210+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 220+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 230+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 240+ */ C______, C______, C______, C______, C______, C______, C______, C______, C______, C______,
/* 250+ */ C______, C______, C______, C______, C______, C______
];
const _______: bool = false;
#[rustfmt::skip]
const SPECIAL_STRING_CHARS: [bool; 256] = [
/* 0 1 2 3 4 5 6 7 8 9 */
/* 0+ */ true, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 10+ */ true, _______, _______, true, _______, _______, _______, _______, _______, _______,
/* 20+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 30+ */ _______, _______, _______, _______, true, _______, _______, _______, _______, true,
/* 40+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 50+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 60+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 70+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 80+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 90+ */ _______, _______, true, _______, _______, _______, _______, _______, _______, _______,
/* 100+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 110+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 120+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 130+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 140+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 150+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 160+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 170+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 180+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 190+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 200+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 210+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 220+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 230+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 240+ */ _______, _______, _______, _______, _______, _______, _______, _______, _______, _______,
/* 250+ */ _______, _______, _______, _______, _______, _______
];
struct KeywordInfo {
string: &'static [u8],
token: Token,
}
const KEYWORD_INFOS: [KeywordInfo; 7] = [
// These are ordered by frequency.
KeywordInfo {
string: b"pref",
token: Token::Pref,
},
KeywordInfo {
string: b"true",
token: Token::True,
},
KeywordInfo {
string: b"false",
token: Token::False,
},
KeywordInfo {
string: b"user_pref",
token: Token::UserPref,
},
KeywordInfo {
string: b"sticky",
token: Token::Sticky,
},
KeywordInfo {
string: b"locked",
token: Token::Locked,
},
KeywordInfo {
string: b"sticky_pref",
token: Token::StickyPref,
},
];
struct Parser<'t> {
path: &'t str, // Path to the file being parsed. Used in error messages.
kind: PrefValueKind, // Default prefs file or user prefs file?
buf: &'t [u8], // Text being parsed.
i: usize, // Index of next char to be read.
line_num: u32, // Current line number within the text.
pref_fn: PrefFn, // Callback for processing each pref.
error_fn: ErrorFn, // Callback for parse errors.
has_errors: bool, // Have we encountered errors?
}
// As described above, we use 0 to represent EOF.
const EOF: u8 = b'\0';
impl<'t> Parser<'t> {
fn new(
path: &'t str,
kind: PrefValueKind,
buf: &'t [u8],
pref_fn: PrefFn,
error_fn: ErrorFn,
) -> Parser<'t> {
// Make sure these tables take up 1 byte per entry.
assert!(std::mem::size_of_val(&CHAR_KINDS) == 256);
assert!(std::mem::size_of_val(&SPECIAL_STRING_CHARS) == 256);
Parser {
path: path,
kind: kind,
buf: buf,
i: 0,
line_num: 1,
pref_fn: pref_fn,
error_fn: error_fn,
has_errors: false,
}
}
fn parse(&mut self) -> bool {
// These are reused, because allocating a new Vec for every string is slow.
let mut name_str = Vec::with_capacity(128); // For pref names.
let mut value_str = Vec::with_capacity(512); // For string pref values.
let mut none_str = Vec::with_capacity(0); // For tokens that shouldn't be strings.
let mut token = self.get_token(&mut none_str);
// At the top of the loop we already have a token. In a valid input
// this will be either the first token of a new pref, or EOF.
loop {
// <pref-spec>
let (pref_value_kind, mut is_sticky) = match token {
Token::Pref if self.kind == PrefValueKind::Default => {
(PrefValueKind::Default, false)
}
Token::StickyPref if self.kind == PrefValueKind::Default => {
(PrefValueKind::Default, true)
}
Token::UserPref => (PrefValueKind::User, false),
Token::SingleChar(EOF) => return !self.has_errors,
_ => {
token = self.error_and_recover(
token,
if self.kind == PrefValueKind::Default {
"expected pref specifier at start of pref definition"
} else {
"expected 'user_pref' at start of pref definition"
},
);
continue;
}
};
// "("
token = self.get_token(&mut none_str);
if token != Token::SingleChar(b'(') {
token = self.error_and_recover(token, "expected '(' after pref specifier");
continue;
}
// <pref-name>
token = self.get_token(&mut name_str);
let pref_name = if token == Token::String {
&name_str
} else {
token = self.error_and_recover(token, "expected pref name after '('");
continue;
};
// ","
token = self.get_token(&mut none_str);
if token != Token::SingleChar(b',') {
token = self.error_and_recover(token, "expected ',' after pref name");
continue;
}
// <pref-value>
token = self.get_token(&mut value_str);
let (pref_type, pref_value) = match token {
Token::True => (PrefType::Bool, PrefValue { bool_val: true }),
Token::False => (PrefType::Bool, PrefValue { bool_val: false }),
Token::String => (
PrefType::String,
PrefValue {
string_val: value_str.as_ptr() as *const c_char,
},
),
Token::Int(u) => {
// Accept u <= 2147483647; anything larger will overflow i32.
if u <= std::i32::MAX as u32 {
(PrefType::Int, PrefValue { int_val: u as i32 })
} else {
token =
self.error_and_recover(Token::Error("integer literal overflowed"), "");
continue;
}
}
Token::SingleChar(b'-') => {
token = self.get_token(&mut none_str);
if let Token::Int(u) = token {
// Accept u <= 2147483648; anything larger will overflow i32 once negated.
if u <= std::i32::MAX as u32 {
(
PrefType::Int,
PrefValue {
int_val: -(u as i32),
},
)
} else if u == std::i32::MAX as u32 + 1 {
(
PrefType::Int,
PrefValue {
int_val: std::i32::MIN,
},
)
} else {
token = self
.error_and_recover(Token::Error("integer literal overflowed"), "");
continue;
}
} else {
token = self.error_and_recover(token, "expected integer literal after '-'");
continue;
}
}
Token::SingleChar(b'+') => {
token = self.get_token(&mut none_str);
if let Token::Int(u) = token {
// Accept u <= 2147483647; anything larger will overflow i32.
if u <= std::i32::MAX as u32 {
(PrefType::Int, PrefValue { int_val: u as i32 })
} else {
token = self
.error_and_recover(Token::Error("integer literal overflowed"), "");
continue;
}
} else {
token = self.error_and_recover(token, "expected integer literal after '+'");
continue;
}
}
_ => {
token = self.error_and_recover(token, "expected pref value after ','");
continue;
}
};
// ("," <pref-attr>)* // default pref files only
let mut is_locked = false;
let mut has_attrs = false;
if self.kind == PrefValueKind::Default {
let ok = loop {
// ","
token = self.get_token(&mut none_str);
if token != Token::SingleChar(b',') {
break true;
}
// <pref-attr>
token = self.get_token(&mut none_str);
match token {
Token::Sticky => is_sticky = true,
Token::Locked => is_locked = true,
_ => {
token =
self.error_and_recover(token, "expected pref attribute after ','");
break false;
}
}
has_attrs = true;
};
if !ok {
continue;
}
} else {
token = self.get_token(&mut none_str);
}
// ")"
if token != Token::SingleChar(b')') {
let expected_msg = if self.kind == PrefValueKind::Default {
if has_attrs {
"expected ',' or ')' after pref attribute"
} else {
"expected ',' or ')' after pref value"
}
} else {
"expected ')' after pref value"
};
token = self.error_and_recover(token, expected_msg);
continue;
}
// ";"
token = self.get_token(&mut none_str);
if token != Token::SingleChar(b';') {
token = self.error_and_recover(token, "expected ';' after ')'");
continue;
}
unsafe {
(self.pref_fn)(
pref_name.as_ptr() as *const c_char,
pref_type,
pref_value_kind,
pref_value,
is_sticky,
is_locked,
)
};
token = self.get_token(&mut none_str);
}
}
fn error_and_recover(&mut self, token: Token, msg: &str) -> Token {
self.has_errors = true;
// If `token` is a Token::{Error,ErrorAtLine}, it's a lexing error and
// the error message is within `token`. Otherwise, it's a parsing error
// and the error message is in `msg`.
let (msg, line_num) = match token {
Token::Error(token_msg) => (token_msg, self.line_num),
Token::ErrorAtLine(token_msg, line_num) => (token_msg, line_num),
_ => (msg, self.line_num),
};
let msg = format!("{}:{}: prefs parse error: {}", self.path, line_num, msg);
let msg = std::ffi::CString::new(msg).unwrap();
unsafe { (self.error_fn)(msg.as_ptr() as *const c_char) };
// "Panic-mode" recovery: consume tokens until one of the following
// occurs.
// - We hit a semicolon, whereupon we return the following token.
// - We hit EOF, whereupon we return EOF.
//
// For this to work, if the lexing functions hit EOF in an error case
// they must unget it so we can safely reget it here.
//
// If the starting token (passed in above) is EOF we must not get
// another token otherwise we will read past the end of `self.buf`.
let mut dummy_str = Vec::with_capacity(128);
let mut token = token;
loop {
match token {
Token::SingleChar(b';') => return self.get_token(&mut dummy_str),
Token::SingleChar(EOF) => return token,
_ => {}
}
token = self.get_token(&mut dummy_str);
}
}
#[inline(always)]
fn get_char(&mut self) -> u8 {
// We do the bounds check ourselves so we can return EOF on failure.
// (Although the buffer is guaranteed to end in an EOF char, we might
// go one char past that, whereupon we must return EOF again.)
if self.i < self.buf.len() {
let c = unsafe { *self.buf.get_unchecked(self.i) };
self.i += 1;
c
} else {
debug_assert!(self.i == self.buf.len());
EOF
}
}
// This function skips the bounds check in optimized builds. Using it at
// the hottest two call sites gives a ~15% parsing speed boost.
#[inline(always)]
unsafe fn get_char_unchecked(&mut self) -> u8 {
debug_assert!(self.i < self.buf.len());
let c = *self.buf.get_unchecked(self.i);
self.i += 1;
c
}
#[inline(always)]
fn unget_char(&mut self) {
debug_assert!(self.i > 0);
self.i -= 1;
}
#[inline(always)]
fn match_char(&mut self, c: u8) -> bool {
if self.buf[self.i] == c {
self.i += 1;
return true;
}
false
}
#[inline(always)]
fn match_single_line_comment(&mut self) {
loop {
// To reach here, the previous char must have been '/' (if this is
// the first loop iteration) or non-special (if this is the second
// or subsequent iteration), and assertions elsewhere ensure that
// there must be at least one subsequent char after those chars
// (the '\0' for EOF).
let c = unsafe { self.get_char_unchecked() };
// All the special chars have value <= b'\r'.
if c > b'\r' {
continue;
}
match c {
b'\n' => {
self.line_num += 1;
break;
}
b'\r' => {
self.line_num += 1;
self.match_char(b'\n');
break;
}
EOF => {
break;
}
_ => continue,
}
}
}
// Returns false if we hit EOF without closing the comment.
fn match_multi_line_comment(&mut self) -> bool {
loop {
match self.get_char() {
b'*' => {
if self.match_char(b'/') {
return true;
}
}
b'\n' => {
self.line_num += 1;
}
b'\r' => {
self.line_num += 1;
self.match_char(b'\n');
}
EOF => return false,
_ => continue,
}
}
}
fn match_hex_digits(&mut self, ndigits: i32) -> Option<u16> {
debug_assert!(ndigits == 2 || ndigits == 4);
let mut value: u16 = 0;
for _ in 0..ndigits {
value = value << 4;
match self.get_char() {
c @ b'0'..=b'9' => value += (c - b'0') as u16,
c @ b'A'..=b'F' => value += (c - b'A') as u16 + 10,
c @ b'a'..=b'f' => value += (c - b'a') as u16 + 10,
_ => {
self.unget_char();
return None;
}
}
}
Some(value)
}
#[inline(always)]
fn char_kind(c: u8) -> CharKind {
// Use get_unchecked() because a u8 index cannot exceed this table's
// bounds.
unsafe { *CHAR_KINDS.get_unchecked(c as usize) }
}
#[inline(always)]
fn is_special_string_char(c: u8) -> bool {
// Use get_unchecked() because a u8 index cannot exceed this table's
// bounds.
unsafe { *SPECIAL_STRING_CHARS.get_unchecked(c as usize) }
}
// If the obtained Token has a value, it is put within the Token, unless
// it's a string, in which case it's put in `str_buf`. This avoids
// allocating a new Vec for every string, which is slow.
fn get_token(&mut self, str_buf: &mut Vec<u8>) -> Token {
loop {
// Note: the following tests are ordered by frequency when parsing
// greprefs.js:
// - SingleChar 36.7%
// - SpaceNL 27.7% (14.9% for spaces, 12.8% for NL)
// - Keyword 13.4%
// - Quote 11.4%
// - Slash 8.1%
// - Digit 2.7%
// - Hash, CR, Other 0.0%
let c = self.get_char();
match Parser::char_kind(c) {
CharKind::SingleChar => {
return Token::SingleChar(c);
}
CharKind::SpaceNL => {
// It's slightly faster to combine the handling of the
// space chars with NL than to handle them separately; we
// have an extra test for this case, but one fewer test for
// all the subsequent CharKinds.
if c == b'\n' {
self.line_num += 1;
}
continue;
}
CharKind::Keyword => {
let start = self.i - 1;
loop {
let c = self.get_char();
if Parser::char_kind(c) != CharKind::Keyword {
self.unget_char();
break;
}
}
for info in KEYWORD_INFOS.iter() {
if &self.buf[start..self.i] == info.string {
return info.token;
}
}
return Token::Error("unknown keyword");
}
CharKind::Quote => {
return self.get_string_token(c, str_buf);
}
CharKind::Slash => {
match self.get_char() {
b'/' => {
self.match_single_line_comment();
}
b'*' => {
if !self.match_multi_line_comment() {
return Token::Error("unterminated /* comment");
}
}
c @ _ => {
if c == b'\n' || c == b'\r' {
// Unget the newline char; the outer loop will
// reget it and adjust self.line_num
// appropriately.
self.unget_char();
}
return Token::Error("expected '/' or '*' after '/'");
}
}
continue;
}
CharKind::Digit => {
let mut value = Some((c - b'0') as u32);
loop {
let c = self.get_char();
match Parser::char_kind(c) {
CharKind::Digit => {
fn add_digit(value: Option<u32>, c: u8) -> Option<u32> {
value?.checked_mul(10)?.checked_add((c - b'0') as u32)
}
value = add_digit(value, c);
}
CharKind::Keyword => {
// Reject things like "123foo". Error recovery
// will retokenize from "foo" onward.
self.unget_char();
return Token::Error("unexpected character in integer literal");
}
_ => {
self.unget_char();
break;
}
}
}
return match value {
Some(v) => Token::Int(v),
None => Token::Error("integer literal overflowed"),
};
}
CharKind::Hash => {
self.match_single_line_comment();
continue;
}
CharKind::CR => {
self.match_char(b'\n');
self.line_num += 1;
continue;
}
// Error recovery will retokenize from the next character.
_ => return Token::Error("unexpected character"),
}
}
}
fn string_error_token(&self, token: &mut Token, msg: &'static str) {
// We only want to capture the first tokenization error within a string.
if *token == Token::String {
*token = Token::ErrorAtLine(msg, self.line_num);
}
}
// Always inline this because it has a single call site.
#[inline(always)]
fn get_string_token(&mut self, quote_char: u8, str_buf: &mut Vec<u8>) -> Token {
// First scan through the string to see if it contains any chars that
// need special handling.
let start = self.i;
let has_special_chars = loop {
// To reach here, the previous char must have been a quote
// (quote_char), and assertions elsewhere ensure that there must be
// at least one subsequent char (the '\0' for EOF).
let c = unsafe { self.get_char_unchecked() };
if Parser::is_special_string_char(c) {
break c != quote_char;
}
};
// Clear str_buf's contents without changing its capacity.
str_buf.clear();
// If there are no special chars (the common case), we can bulk copy it
// to str_buf. This is a lot faster than the char-by-char loop below.
if !has_special_chars {
str_buf.extend(&self.buf[start..self.i - 1]);
str_buf.push(b'\0');
return Token::String;
}
// There were special chars. Re-scan the string, filling in str_buf one
// char at a time.
//
// On error, we change `token` to an error token and then keep going to
// the end of the string literal. `str_buf` won't be used in that case.
self.i = start;
let mut token = Token::String;
loop {
let c = self.get_char();
let c2 = if !Parser::is_special_string_char(c) {
c
} else if c == quote_char {
break;
} else if c == b'\\' {
match self.get_char() {
b'\"' => b'\"',
b'\'' => b'\'',
b'\\' => b'\\',
b'n' => b'\n',
b'r' => b'\r',
b'x' => {
if let Some(value) = self.match_hex_digits(2) {
debug_assert!(value <= 0xff);
if value != 0 {
value as u8
} else {
self.string_error_token(&mut token, "\\x00 is not allowed");
continue;
}
} else {
self.string_error_token(&mut token, "malformed \\x escape sequence");
continue;
}
}
b'u' => {
if let Some(value) = self.match_hex_digits(4) {
let mut utf16 = vec![value];
if 0xd800 == (0xfc00 & value) {
// High surrogate value. Look for the low surrogate value.
if self.match_char(b'\\') && self.match_char(b'u') {
if let Some(lo) = self.match_hex_digits(4) {
if 0xdc00 == (0xfc00 & lo) {
// Found a valid low surrogate.
utf16.push(lo);
} else {
self.string_error_token(
&mut token,
"invalid low surrogate after high surrogate",
);
continue;
}
}
}
if utf16.len() != 2 {
self.string_error_token(
&mut token,
"expected low surrogate after high surrogate",
);
continue;
}
} else if 0xdc00 == (0xfc00 & value) {
// Unaccompanied low surrogate value.
self.string_error_token(
&mut token,
"expected high surrogate before low surrogate",
);
continue;
} else if value == 0 {
self.string_error_token(&mut token, "\\u0000 is not allowed");
continue;
}
// Insert the UTF-16 sequence as UTF-8.
let utf8 = String::from_utf16(&utf16).unwrap();
str_buf.extend(utf8.as_bytes());
} else {
self.string_error_token(&mut token, "malformed \\u escape sequence");
continue;
}
continue; // We don't want to str_buf.push(c2) below.
}
c @ _ => {
if c == b'\n' || c == b'\r' {
// Unget the newline char; the outer loop will
// reget it and adjust self.line_num appropriately.
self.unget_char();
}
self.string_error_token(
&mut token,
"unexpected escape sequence character after '\\'",
);
continue;
}
}
} else if c == b'\n' {
self.line_num += 1;
c
} else if c == b'\r' {
self.line_num += 1;
if self.match_char(b'\n') {
str_buf.push(b'\r');
b'\n'
} else {
c
}
} else if c == EOF {
self.string_error_token(&mut token, "unterminated string literal");
break;
} else {
// This case is only hit for the non-closing quote char.
debug_assert!((c == b'\'' || c == b'\"') && c != quote_char);
c
};
str_buf.push(c2);
}
str_buf.push(b'\0');
token
}
}