/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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/. */

#ifndef frontend_TokenStream_h
#define frontend_TokenStream_h

/*
 * JS lexical scanner interface.
 */

#include "mozilla/DebugOnly.h"
#include "mozilla/PodOperations.h"

#include <stddef.h>
#include <stdio.h>
#include <stdarg.h>
#include "jscntxt.h"
#include "jsversion.h"
#include "jsopcode.h"
#include "jsprvtd.h"
#include "jspubtd.h"

#include "js/Vector.h"

namespace js {
namespace frontend {

enum TokenKind {
    TOK_ERROR = -1,                /* well-known as the only code < EOF */
    TOK_EOF,                       /* end of file */
    TOK_EOL,                       /* end of line; only returned by peekTokenSameLine() */
    TOK_SEMI,                      /* semicolon */
    TOK_COMMA,                     /* comma operator */
    TOK_HOOK, TOK_COLON,           /* conditional (?:) */
    TOK_INC, TOK_DEC,              /* increment/decrement (++ --) */
    TOK_DOT,                       /* member operator (.) */
    TOK_TRIPLEDOT,                 /* for rest arguments (...) */
    TOK_LB, TOK_RB,                /* left and right brackets */
    TOK_LC, TOK_RC,                /* left and right curlies (braces) */
    TOK_LP, TOK_RP,                /* left and right parentheses */
    TOK_NAME,                      /* identifier */
    TOK_NUMBER,                    /* numeric constant */
    TOK_STRING,                    /* string constant */
    TOK_REGEXP,                    /* RegExp constant */
    TOK_TRUE,                      /* true */
    TOK_FALSE,                     /* false */
    TOK_NULL,                      /* null */
    TOK_THIS,                      /* this */
    TOK_FUNCTION,                  /* function keyword */
    TOK_IF,                        /* if keyword */
    TOK_ELSE,                      /* else keyword */
    TOK_SWITCH,                    /* switch keyword */
    TOK_CASE,                      /* case keyword */
    TOK_DEFAULT,                   /* default keyword */
    TOK_WHILE,                     /* while keyword */
    TOK_DO,                        /* do keyword */
    TOK_FOR,                       /* for keyword */
    TOK_BREAK,                     /* break keyword */
    TOK_CONTINUE,                  /* continue keyword */
    TOK_VAR,                       /* var keyword */
    TOK_CONST,                     /* const keyword */
    TOK_WITH,                      /* with keyword */
    TOK_RETURN,                    /* return keyword */
    TOK_NEW,                       /* new keyword */
    TOK_DELETE,                    /* delete keyword */
    TOK_TRY,                       /* try keyword */
    TOK_CATCH,                     /* catch keyword */
    TOK_FINALLY,                   /* finally keyword */
    TOK_THROW,                     /* throw keyword */
    TOK_DEBUGGER,                  /* debugger keyword */
    TOK_YIELD,                     /* yield from generator function */
    TOK_LET,                       /* let keyword */
    TOK_EXPORT,                    /* export keyword */
    TOK_IMPORT,                    /* import keyword */
    TOK_RESERVED,                  /* reserved keywords */
    TOK_STRICT_RESERVED,           /* reserved keywords in strict mode */

    /*
     * The following token types occupy contiguous ranges to enable easy
     * range-testing.
     */

    /*
     * Binary operators tokens, TOK_OR thru TOK_MOD. These must be in the same
     * order as F(OR) and friends in FOR_EACH_PARSE_NODE_KIND in ParseNode.h.
     */
    TOK_OR,                        /* logical or (||) */
    TOK_BINOP_FIRST = TOK_OR,
    TOK_AND,                       /* logical and (&&) */
    TOK_BITOR,                     /* bitwise-or (|) */
    TOK_BITXOR,                    /* bitwise-xor (^) */
    TOK_BITAND,                    /* bitwise-and (&) */

    /* Equality operation tokens, per TokenKindIsEquality */
    TOK_STRICTEQ,
    TOK_EQUALITY_START = TOK_STRICTEQ,
    TOK_EQ,
    TOK_STRICTNE,
    TOK_NE,
    TOK_EQUALITY_LAST = TOK_NE,

    /* Relational ops (< <= > >=), per TokenKindIsRelational */
    TOK_LT,
    TOK_RELOP_START = TOK_LT,
    TOK_LE,
    TOK_GT,
    TOK_GE,
    TOK_RELOP_LAST = TOK_GE,

    TOK_INSTANCEOF,                /* instanceof keyword */
    TOK_IN,                        /* in keyword */

    /* Shift ops (<< >> >>>), per TokenKindIsShift */
    TOK_LSH,
    TOK_SHIFTOP_START = TOK_LSH,
    TOK_RSH,
    TOK_URSH,
    TOK_SHIFTOP_LAST = TOK_URSH,

    TOK_PLUS,                      /* plus */
    TOK_MINUS,                     /* minus */
    TOK_STAR,                      /* multiply */
    TOK_DIV,                       /* divide */
    TOK_MOD,                       /* modulus */
    TOK_BINOP_LAST = TOK_MOD,

    /* Unary operation tokens */
    TOK_TYPEOF,
    TOK_VOID,
    TOK_NOT,
    TOK_BITNOT,

    TOK_ARROW,                     /* function arrow (=>) */

    /* Assignment ops (= += -= etc.), per TokenKindIsAssignment */
    TOK_ASSIGN,                    /* assignment ops (= += -= etc.) */
    TOK_ASSIGNMENT_START = TOK_ASSIGN,
    TOK_ADDASSIGN,
    TOK_SUBASSIGN,
    TOK_BITORASSIGN,
    TOK_BITXORASSIGN,
    TOK_BITANDASSIGN,
    TOK_LSHASSIGN,
    TOK_RSHASSIGN,
    TOK_URSHASSIGN,
    TOK_MULASSIGN,
    TOK_DIVASSIGN,
    TOK_MODASSIGN,
    TOK_ASSIGNMENT_LAST = TOK_MODASSIGN,

    TOK_LIMIT                      /* domain size */
};

inline bool
TokenKindIsBinaryOp(TokenKind tt)
{
    return TOK_BINOP_FIRST <= tt && tt <= TOK_BINOP_LAST;
}

inline bool
TokenKindIsEquality(TokenKind tt)
{
    return TOK_EQUALITY_START <= tt && tt <= TOK_EQUALITY_LAST;
}

inline bool
TokenKindIsRelational(TokenKind tt)
{
    return TOK_RELOP_START <= tt && tt <= TOK_RELOP_LAST;
}

inline bool
TokenKindIsShift(TokenKind tt)
{
    return TOK_SHIFTOP_START <= tt && tt <= TOK_SHIFTOP_LAST;
}

inline bool
TokenKindIsAssignment(TokenKind tt)
{
    return TOK_ASSIGNMENT_START <= tt && tt <= TOK_ASSIGNMENT_LAST;
}

inline bool
TokenKindIsDecl(TokenKind tt)
{
#if JS_HAS_BLOCK_SCOPE
    return tt == TOK_VAR || tt == TOK_LET;
#else
    return tt == TOK_VAR;
#endif
}

struct TokenPos {
    uint32_t          begin;          /* offset of the token's first char */
    uint32_t          end;            /* offset of 1 past the token's last char */

    TokenPos() : begin(0), end(0) {}
    TokenPos(uint32_t begin, uint32_t end) : begin(begin), end(end) {}

    /* Return a TokenPos that covers left, right, and anything in between. */
    static TokenPos box(const TokenPos &left, const TokenPos &right) {
        JS_ASSERT(left.begin <= left.end);
        JS_ASSERT(left.end <= right.begin);
        JS_ASSERT(right.begin <= right.end);
        return TokenPos(left.begin, right.end);
    }

    bool operator==(const TokenPos& bpos) const {
        return begin == bpos.begin && end == bpos.end;
    }

    bool operator!=(const TokenPos& bpos) const {
        return begin != bpos.begin || end != bpos.end;
    }

    bool operator <(const TokenPos& bpos) const {
        return begin < bpos.begin;
    }

    bool operator <=(const TokenPos& bpos) const {
        return begin <= bpos.begin;
    }

    bool operator >(const TokenPos& bpos) const {
        return !(*this <= bpos);
    }

    bool operator >=(const TokenPos& bpos) const {
        return !(*this < bpos);
    }

    bool encloses(const TokenPos& pos) const {
        return begin <= pos.begin && pos.end <= end;
    }
};

enum DecimalPoint { NoDecimal = false, HasDecimal = true };

struct Token {
    TokenKind           type;           /* char value or above enumerator */
    TokenPos            pos;            /* token position in file */
    union {
        struct {                        /* name or string literal */
            JSOp        op;             /* operator, for minimal parser */
            union {
              private:
                friend struct Token;
                PropertyName *name;     /* non-numeric atom */
                JSAtom       *atom;     /* potentially-numeric atom */
            } n;
        } s;

      private:
        friend struct Token;
        struct {
            double       value;         /* floating point number */
            DecimalPoint decimalPoint;  /* literal contains . or exponent */
        } number;
        RegExpFlag      reflags;        /* regexp flags, use tokenbuf to access
                                           regexp chars */
    } u;

    /* Mutators */

    /*
     * FIXME: Init type early enough such that all mutators can assert
     *        type-safety.  See bug 697000.
     */

    void setName(JSOp op, PropertyName *name) {
        JS_ASSERT(op == JSOP_NAME);
        JS_ASSERT(!IsPoisonedPtr(name));
        u.s.op = op;
        u.s.n.name = name;
    }

    void setAtom(JSOp op, JSAtom *atom) {
        JS_ASSERT(op == JSOP_STRING);
        JS_ASSERT(!IsPoisonedPtr(atom));
        u.s.op = op;
        u.s.n.atom = atom;
    }

    void setRegExpFlags(js::RegExpFlag flags) {
        JS_ASSERT((flags & AllFlags) == flags);
        u.reflags = flags;
    }

    void setNumber(double n, DecimalPoint decimalPoint) {
        u.number.value = n;
        u.number.decimalPoint = decimalPoint;
    }

    /* Type-safe accessors */

    PropertyName *name() const {
        JS_ASSERT(type == TOK_NAME);
        return u.s.n.name->asPropertyName(); /* poor-man's type verification */
    }

    JSAtom *atom() const {
        JS_ASSERT(type == TOK_STRING);
        return u.s.n.atom;
    }

    js::RegExpFlag regExpFlags() const {
        JS_ASSERT(type == TOK_REGEXP);
        JS_ASSERT((u.reflags & AllFlags) == u.reflags);
        return u.reflags;
    }

    double number() const {
        JS_ASSERT(type == TOK_NUMBER);
        return u.number.value;
    }

    DecimalPoint decimalPoint() const {
        JS_ASSERT(type == TOK_NUMBER);
        return u.number.decimalPoint;
    }
};

#define t_op            u.s.op

enum TokenStreamFlags
{
    TSF_EOF = 0x02,             /* hit end of file */
    TSF_EOL = 0x04,             /* an EOL was hit in whitespace or a multi-line comment */
    TSF_OPERAND = 0x08,         /* looking for operand, not operator */
    TSF_UNEXPECTED_EOF = 0x10,  /* unexpected end of input, i.e. TOK_EOF not at top-level. */
    TSF_KEYWORD_IS_NAME = 0x20, /* Ignore keywords and return TOK_NAME instead to the parser. */
    TSF_DIRTYLINE = 0x40,       /* non-whitespace since start of line */
    TSF_OCTAL_CHAR = 0x80,      /* observed a octal character escape */
    TSF_HAD_ERROR = 0x100,      /* returned TOK_ERROR from getToken */

    /*
     * To handle the hard case of contiguous HTML comments, we want to clear the
     * TSF_DIRTYINPUT flag at the end of each such comment.  But we'd rather not
     * scan for --> within every //-style comment unless we have to.  So we set
     * TSF_IN_HTML_COMMENT when a <!-- is scanned as an HTML begin-comment, and
     * clear it (and TSF_DIRTYINPUT) when we scan --> either on a clean line, or
     * only if (ts->flags & TSF_IN_HTML_COMMENT), in a //-style comment.
     *
     * This still works as before given a malformed comment hiding hack such as:
     *
     *    <script>
     *      <!-- comment hiding hack #1
     *      code goes here
     *      // --> oops, markup for script-unaware browsers goes here!
     *    </script>
     *
     * It does not cope with malformed comment hiding hacks where --> is hidden
     * by C-style comments, or on a dirty line.  Such cases are already broken.
     */
    TSF_IN_HTML_COMMENT = 0x200
};

struct CompileError {
    JSContext *cx;
    JSErrorReport report;
    char *message;
    ErrorArgumentsType argumentsType;
    CompileError(JSContext *cx)
      : cx(cx), message(NULL), argumentsType(ArgumentsAreUnicode)
    {
        mozilla::PodZero(&report);
    }
    ~CompileError();
    void throwError();
};

inline bool
StrictModeFromContext(JSContext *cx)
{
    return cx->hasOption(JSOPTION_STRICT_MODE);
}

// Ideally, tokenizing would be entirely independent of context.  But the
// strict mode flag, which is in SharedContext, affects tokenizing, and
// TokenStream needs to see it.
//
// This class is a tiny back-channel from TokenStream to the strict mode flag
// that avoids exposing the rest of SharedContext to TokenStream.
//
class StrictModeGetter {
  public:
    virtual bool strictMode() = 0;
};

// TokenStream is the lexical scanner for Javascript source text.
//
// It takes a buffer of jschars and linearly scans it into |Token|s.
// Internally the class uses a four element circular buffer |tokens| of
// |Token|s. As an index for |tokens|, the member |cursor| points to the
// current token.
// Calls to getToken() increase |cursor| by one and return the new current
// token. If a TokenStream was just created, the current token is initialized
// with random data (i.e. not initialized). It is therefore important that
// either of the first four member functions listed below is called first.
// The circular buffer lets us go back up to two tokens from the last
// scanned token. Internally, the relative number of backward steps that were
// taken (via ungetToken()) after the last token was scanned is stored in
// |lookahead|.
//
// The following table lists in which situations it is safe to call each listed
// function. No checks are made by the functions in non-debug builds.
//
// Function Name     | Precondition; changes to |lookahead|
// ------------------+---------------------------------------------------------
// getToken          | none; if |lookahead > 0| then |lookahead--|
// peekToken         | none; none
// peekTokenSameLine | none; none
// matchToken        | none; if |lookahead > 0| and the match succeeds then
//                   |       |lookahead--|
// consumeKnownToken | none; if |lookahead > 0| then |lookahead--|
// ungetToken        | 0 <= |lookahead| <= |maxLookahead - 1|; |lookahead++|
//
// The behavior of the token scanning process (see getTokenInternal()) can be
// modified by calling one of the first four above listed member functions with
// an optional argument of type TokenStreamFlags. The two flags that do
// influence the scanning process are TSF_OPERAND and TSF_KEYWORD_IS_NAME.
// However, they will be ignored unless |lookahead == 0| holds.
// Due to constraints of the grammar, this turns out not to be a problem in
// practice. See the mozilla.dev.tech.js-engine.internals thread entitled 'Bug
// in the scanner?' for more details (https://groups.google.com/forum/?
// fromgroups=#!topic/mozilla.dev.tech.js-engine.internals/2JLH5jRcr7E).
//
// The methods seek() and tell() allow to rescan from a previous visited
// location of the buffer.
class MOZ_STACK_CLASS TokenStream
{
    /* Unicode separators that are treated as line terminators, in addition to \n, \r */
    enum {
        LINE_SEPARATOR = 0x2028,
        PARA_SEPARATOR = 0x2029
    };

    static const size_t ntokens = 4;                /* 1 current + 2 lookahead, rounded
                                                       to power of 2 to avoid divmod by 3 */
    static const unsigned maxLookahead = 2;
    static const unsigned ntokensMask = ntokens - 1;

  public:
    typedef Vector<jschar, 32> CharBuffer;

    TokenStream(JSContext *cx, const CompileOptions &options,
                const jschar *base, size_t length, StrictModeGetter *smg,
                AutoKeepAtoms& keepAtoms);

    ~TokenStream();

    /* Accessors. */
    JSContext *getContext() const { return cx; }
    bool onCurrentLine(const TokenPos &pos) const { return srcCoords.isOnThisLine(pos.end, lineno); }
    const Token &currentToken() const { return tokens[cursor]; }
    bool isCurrentTokenType(TokenKind type) const {
        return currentToken().type == type;
    }
    bool isCurrentTokenType(TokenKind type1, TokenKind type2) const {
        TokenKind type = currentToken().type;
        return type == type1 || type == type2;
    }
    const CharBuffer &getTokenbuf() const { return tokenbuf; }
    const char *getFilename() const { return filename; }
    unsigned getLineno() const { return lineno; }
    unsigned getColumn() const { return userbuf.addressOfNextRawChar() - linebase - 1; }
    JSVersion versionNumber() const { return VersionNumber(version); }
    JSVersion versionWithFlags() const { return version; }
    bool hadError() const { return !!(flags & TSF_HAD_ERROR); }

    bool isCurrentTokenEquality() const {
        return TokenKindIsEquality(currentToken().type);
    }

    bool isCurrentTokenRelational() const {
        return TokenKindIsRelational(currentToken().type);
    }

    bool isCurrentTokenShift() const {
        return TokenKindIsShift(currentToken().type);
    }

    bool isCurrentTokenAssignment() const {
        return TokenKindIsAssignment(currentToken().type);
    }

    /* Flag methods. */
    void setUnexpectedEOF(bool enabled = true) { setFlag(enabled, TSF_UNEXPECTED_EOF); }

    bool isUnexpectedEOF() const { return !!(flags & TSF_UNEXPECTED_EOF); }
    bool isEOF() const { return !!(flags & TSF_EOF); }
    bool sawOctalEscape() const { return !!(flags & TSF_OCTAL_CHAR); }

    // TokenStream-specific error reporters.
    bool reportError(unsigned errorNumber, ...);
    bool reportWarning(unsigned errorNumber, ...);

    // General-purpose error reporters.  You should avoid calling these
    // directly, and instead use the more succinct alternatives (e.g.
    // reportError()) in TokenStream, Parser, and BytecodeEmitter.
    bool reportCompileErrorNumberVA(uint32_t offset, unsigned flags, unsigned errorNumber,
                                    va_list args);
    bool reportStrictModeErrorNumberVA(uint32_t offset, bool strictMode, unsigned errorNumber,
                                       va_list args);
    bool reportStrictWarningErrorNumberVA(uint32_t offset, unsigned errorNumber,
                                          va_list args);

    // asm.js reporter
    void reportAsmJSError(uint32_t offset, unsigned errorNumber, ...);

  private:
    // These are private because they should only be called by the tokenizer
    // while tokenizing not by, for example, BytecodeEmitter.
    bool reportStrictModeError(unsigned errorNumber, ...);
    bool strictMode() const { return strictModeGetter && strictModeGetter->strictMode(); }

    void onError();
    static JSAtom *atomize(JSContext *cx, CharBuffer &cb);
    bool putIdentInTokenbuf(const jschar *identStart);

    /*
     * Enables flags in the associated tokenstream for the object lifetime.
     * Useful for lexically-scoped flag toggles.
     */
    class Flagger {
        TokenStream * const parent;
        unsigned       flags;
      public:
        Flagger(TokenStream *parent, unsigned withFlags) : parent(parent), flags(withFlags) {
            parent->flags |= flags;
        }

        ~Flagger() { parent->flags &= ~flags; }
    };
    friend class Flagger;

    void setFlag(bool enabled, TokenStreamFlags flag) {
        if (enabled)
            flags |= flag;
        else
            flags &= ~flag;
    }

  public:
    /*
     * Get the next token from the stream, make it the current token, and
     * return its kind.
     */
    TokenKind getToken() {
        /* Check for a pushed-back token resulting from mismatching lookahead. */
        if (lookahead != 0) {
            lookahead--;
            cursor = (cursor + 1) & ntokensMask;
            TokenKind tt = currentToken().type;
            JS_ASSERT(tt != TOK_EOL);
            return tt;
        }

        return getTokenInternal();
    }

    /* Similar, but also sets flags. */
    TokenKind getToken(unsigned withFlags) {
        Flagger flagger(this, withFlags);
        return getToken();
    }

    /*
     * Push the last scanned token back into the stream.
     */
    void ungetToken() {
        JS_ASSERT(lookahead < maxLookahead);
        lookahead++;
        cursor = (cursor - 1) & ntokensMask;
    }

    TokenKind peekToken() {
        if (lookahead != 0)
            return tokens[(cursor + 1) & ntokensMask].type;
        TokenKind tt = getTokenInternal();
        ungetToken();
        return tt;
    }

    TokenKind peekToken(unsigned withFlags) {
        Flagger flagger(this, withFlags);
        return peekToken();
    }

    TokenKind peekTokenSameLine(unsigned withFlags = 0) {
        if (!onCurrentLine(currentToken().pos))
            return TOK_EOL;

        if (lookahead != 0)
            return tokens[(cursor + 1) & ntokensMask].type;

        /*
         * This is the only place TOK_EOL is produced.  No token with TOK_EOL
         * is created, just a TOK_EOL TokenKind is returned.
         */
        flags &= ~TSF_EOL;
        TokenKind tt = getToken(withFlags);
        if (flags & TSF_EOL) {
            tt = TOK_EOL;
            flags &= ~TSF_EOL;
        }
        ungetToken();
        return tt;
    }

    /*
     * Get the next token from the stream if its kind is |tt|.
     */
    bool matchToken(TokenKind tt) {
        if (getToken() == tt)
            return true;
        ungetToken();
        return false;
    }

    bool matchToken(TokenKind tt, unsigned withFlags) {
        Flagger flagger(this, withFlags);
        return matchToken(tt);
    }

    void consumeKnownToken(TokenKind tt) {
        JS_ALWAYS_TRUE(matchToken(tt));
    }

    class MOZ_STACK_CLASS Position {
      public:
        /*
         * The Token fields may contain pointers to atoms, so for correct
         * rooting we must ensure collection of atoms is disabled while objects
         * of this class are live.  Do this by requiring a dummy AutoKeepAtoms
         * reference in the constructor.
         *
         * This class is explicity ignored by the analysis, so don't add any
         * more pointers to GC things here!
         */
        Position(AutoKeepAtoms&) { }
      private:
        Position(const Position&) MOZ_DELETE;
        friend class TokenStream;
        const jschar *buf;
        unsigned flags;
        unsigned lineno;
        const jschar *linebase;
        const jschar *prevLinebase;
        Token currentToken;
        unsigned lookahead;
        Token lookaheadTokens[maxLookahead];
    };

    void advance(size_t position);
    void tell(Position *);
    void seek(const Position &pos);
    void seek(const Position &pos, const TokenStream &other);
    void positionAfterLastFunctionKeyword(Position &pos);

    size_t positionToOffset(const Position &pos) const {
        return pos.buf - userbuf.base();
    }

    bool hasSourceMap() const {
        return sourceMap != NULL;
    }

    /*
     * Give up responsibility for managing the sourceMap filename's memory.
     */
    jschar *releaseSourceMap() {
        JS_ASSERT(hasSourceMap());
        jschar *sm = sourceMap;
        sourceMap = NULL;
        return sm;
    }

    /*
     * If the name at s[0:length] is not a keyword in this version, return
     * true with *ttp and *topp unchanged.
     *
     * If it is a reserved word in this version and strictness mode, and thus
     * can't be present in correct code, report a SyntaxError and return false.
     *
     * If it is a keyword, like "if", the behavior depends on ttp/topp. If ttp
     * and topp are null, report a SyntaxError ("if is a reserved identifier")
     * and return false. If ttp and topp are non-null, return true with the
     * keyword's TokenKind in *ttp and its JSOp in *topp.
     *
     * ttp and topp must be either both null or both non-null.
     */
    bool checkForKeyword(const jschar *s, size_t length, TokenKind *ttp, JSOp *topp);

    // This class maps a userbuf offset (which is 0-indexed) to a line number
    // (which is 1-indexed) and a column index (which is 0-indexed).
    class SourceCoords
    {
        // For a given buffer holding source code, |lineStartOffsets_| has one
        // element per line of source code, plus one sentinel element.  Each
        // non-sentinel element holds the buffer offset for the start of the
        // corresponding line of source code.  For this example script:
        //
        // 1  // xyz            [line starts at offset 0]
        // 2  var x;            [line starts at offset 7]
        // 3                    [line starts at offset 14]
        // 4  var y;            [line starts at offset 15]
        //
        // |lineStartOffsets_| is:
        //
        //   [0, 7, 14, 15, MAX_PTR]
        //
        // To convert a "line number" to a "line index" (i.e. an index into
        // |lineStartOffsets_|), subtract |initialLineNum_|.  E.g. line 3's
        // line index is (3 - initialLineNum_), which is 2.  Therefore
        // lineStartOffsets_[2] holds the buffer offset for the start of line 3,
        // which is 14.  (Note that |initialLineNum_| is often 1, but not
        // always.)
        //
        // The first element is always 0, and the last element is always the
        // MAX_PTR sentinel.
        //
        // offset-to-line/column lookups are O(log n) in the worst case (binary
        // search), but in practice they're heavily clustered and we do better
        // than that by using the previous lookup's result (lastLineIndex_) as
        // a starting point.
        //
        // Checking if an offset lies within a particular line number
        // (isOnThisLine()) is O(1).
        //
        Vector<uint32_t, 128> lineStartOffsets_;
        uint32_t            initialLineNum_;

        // This is mutable because it's modified on every search, but that fact
        // isn't visible outside this class.
        mutable uint32_t    lastLineIndex_;

        uint32_t lineIndexOf(uint32_t offset) const;

        static const uint32_t MAX_PTR = UINT32_MAX;

        uint32_t lineIndexToNum(uint32_t lineIndex) const { return lineIndex + initialLineNum_; }
        uint32_t lineNumToIndex(uint32_t lineNum)   const { return lineNum   - initialLineNum_; }

      public:
        SourceCoords(JSContext *cx, uint32_t ln);

        void add(uint32_t lineNum, uint32_t lineStartOffset);
        void fill(const SourceCoords &other);

        bool isOnThisLine(uint32_t offset, uint32_t lineNum) const {
            uint32_t lineIndex = lineNumToIndex(lineNum);
            JS_ASSERT(lineIndex + 1 < lineStartOffsets_.length());  // +1 due to sentinel
            return lineStartOffsets_[lineIndex] <= offset &&
                   offset < lineStartOffsets_[lineIndex + 1];
        }

        uint32_t lineNum(uint32_t offset) const;
        uint32_t columnIndex(uint32_t offset) const;
        void lineNumAndColumnIndex(uint32_t offset, uint32_t *lineNum, uint32_t *columnIndex) const;
    };

    SourceCoords srcCoords;

  private:
    /*
     * This is the low-level interface to the JS source code buffer.  It just
     * gets raw chars, basically.  TokenStreams functions are layered on top
     * and do some extra stuff like converting all EOL sequences to '\n',
     * tracking the line number, and setting the TSF_EOF flag.  (The "raw" in
     * "raw chars" refers to the lack of EOL sequence normalization.)
     */
    class TokenBuf {
      public:
        TokenBuf(JSContext *cx, const jschar *buf, size_t length)
          : base_(buf), limit_(buf + length), ptr(buf),
            skipBase(cx, &base_), skipLimit(cx, &limit_), skipPtr(cx, &ptr)
        { }

        bool hasRawChars() const {
            return ptr < limit_;
        }

        bool atStart() const {
            return ptr == base_;
        }

        const jschar *base() const {
            return base_;
        }

        const jschar *limit() const {
            return limit_;
        }

        jschar getRawChar() {
            return *ptr++;      /* this will NULL-crash if poisoned */
        }

        jschar peekRawChar() const {
            return *ptr;        /* this will NULL-crash if poisoned */
        }

        bool matchRawChar(jschar c) {
            if (*ptr == c) {    /* this will NULL-crash if poisoned */
                ptr++;
                return true;
            }
            return false;
        }

        bool matchRawCharBackwards(jschar c) {
            JS_ASSERT(ptr);     /* make sure haven't been poisoned */
            if (*(ptr - 1) == c) {
                ptr--;
                return true;
            }
            return false;
        }

        void ungetRawChar() {
            JS_ASSERT(ptr);     /* make sure haven't been poisoned */
            ptr--;
        }

        const jschar *addressOfNextRawChar(bool allowPoisoned = false) const {
            JS_ASSERT_IF(!allowPoisoned, ptr);     /* make sure haven't been poisoned */
            return ptr;
        }

        /* Use this with caution! */
        void setAddressOfNextRawChar(const jschar *a, bool allowPoisoned = false) {
            JS_ASSERT_IF(!allowPoisoned, a);
            ptr = a;
        }

#ifdef DEBUG
        /* Poison the TokenBuf so it cannot be accessed again. */
        void poison() {
            ptr = NULL;
        }
#endif

        static bool isRawEOLChar(int32_t c) {
            return (c == '\n' || c == '\r' || c == LINE_SEPARATOR || c == PARA_SEPARATOR);
        }

        // Finds the next EOL, but stops once 'max' jschars have been scanned
        // (*including* the starting jschar).
        const jschar *findEOLMax(const jschar *p, size_t max);

      private:
        const jschar *base_;            /* base of buffer */
        const jschar *limit_;           /* limit for quick bounds check */
        const jschar *ptr;              /* next char to get */

        // We are not yet moving strings
        SkipRoot skipBase, skipLimit, skipPtr;
    };

    TokenKind getTokenInternal();     /* doesn't check for pushback or error flag. */

    int32_t getChar();
    int32_t getCharIgnoreEOL();
    void ungetChar(int32_t c);
    void ungetCharIgnoreEOL(int32_t c);
    Token *newToken(ptrdiff_t adjust);
    bool peekUnicodeEscape(int32_t *c);
    bool matchUnicodeEscapeIdStart(int32_t *c);
    bool matchUnicodeEscapeIdent(int32_t *c);
    bool peekChars(int n, jschar *cp);
    bool getSourceMappingURL(bool isMultiline, bool shouldWarnDeprecated);

    // |expect| cannot be an EOL char.
    bool matchChar(int32_t expect) {
        MOZ_ASSERT(!TokenBuf::isRawEOLChar(expect));
        return JS_LIKELY(userbuf.hasRawChars()) &&
               userbuf.matchRawChar(expect);
    }

    void consumeKnownChar(int32_t expect) {
        mozilla::DebugOnly<int32_t> c = getChar();
        JS_ASSERT(c == expect);
    }

    int32_t peekChar() {
        int32_t c = getChar();
        ungetChar(c);
        return c;
    }

    void skipChars(int n) {
        while (--n >= 0)
            getChar();
    }

    void updateLineInfoForEOL();
    void updateFlagsForEOL();

    Token               tokens[ntokens];/* circular token buffer */
    unsigned            cursor;         /* index of last parsed token */
    unsigned            lookahead;      /* count of lookahead tokens */
    unsigned            lineno;         /* current line number */
    unsigned            flags;          /* flags -- see above */
    const jschar        *linebase;      /* start of current line;  points into userbuf */
    const jschar        *prevLinebase;  /* start of previous line;  NULL if on the first line */
    TokenBuf            userbuf;        /* user input buffer */
    const char          *filename;      /* input filename or null */
    jschar              *sourceMap;     /* source map's filename or null */
    void                *listenerTSData;/* listener data for this TokenStream */
    CharBuffer          tokenbuf;       /* current token string buffer */
    int8_t              oneCharTokens[128];  /* table of one-char tokens */
    bool                maybeEOL[256];       /* probabilistic EOL lookup table */
    bool                maybeStrSpecial[256];/* speeds up string scanning */
    JSVersion           version;        /* (i.e. to identify keywords) */
    JSContext           *const cx;
    JSPrincipals        *const originPrincipals;
    StrictModeGetter    *strictModeGetter; /* used to test for strict mode */
    Position            lastFunctionKeyword; /* used as a starting point for reparsing strict functions */

    /*
     * The tokens array stores pointers to JSAtoms. These are rooted by the
     * atoms table using AutoKeepAtoms in the Parser. This SkipRoot tells the
     * exact rooting analysis to ignore the atoms in the tokens array.
     */
    SkipRoot            tokenSkip;

    // Bug 846011
    SkipRoot            linebaseSkip;
    SkipRoot            prevLinebaseSkip;
};

/*
 * Steal one JSREPORT_* bit (see jsapi.h) to tell that arguments to the error
 * message have const jschar* type, not const char*.
 */
#define JSREPORT_UC 0x100

} /* namespace frontend */
} /* namespace js */

extern JS_FRIEND_API(int)
js_fgets(char *buf, int size, FILE *file);

#ifdef DEBUG
extern const char *
TokenKindToString(js::frontend::TokenKind tt);
#endif

#endif /* frontend_TokenStream_h */