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+/* 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
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! 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
+ }
+}