DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Implementation

Mercurial (31ec81b5d7bb)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213
/* -*- 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 jsonparser_h
#define jsonparser_h

#include "mozilla/Attributes.h"

#include "ds/IdValuePair.h"
#include "vm/String.h"

namespace js {

class MOZ_STACK_CLASS JSONParser : private AutoGCRooter
{
  public:
    enum ErrorHandling { RaiseError, NoError };

  private:
    /* Data members */

    JSContext * const cx;
    StableCharPtr current;
    const StableCharPtr end;

    Value v;

    const ErrorHandling errorHandling;

    enum Token { String, Number, True, False, Null,
                 ArrayOpen, ArrayClose,
                 ObjectOpen, ObjectClose,
                 Colon, Comma,
                 OOM, Error };

    // State related to the parser's current position. At all points in the
    // parse this keeps track of the stack of arrays and objects which have
    // been started but not finished yet. The actual JS object is not
    // allocated until the literal is closed, so that the result can be sized
    // according to its contents and have its type and shape filled in using
    // caches.

    // State for an array that is currently being parsed. This includes all
    // elements that have been seen so far.
    typedef Vector<Value, 20> ElementVector;

    // State for an object that is currently being parsed. This includes all
    // the key/value pairs that have been seen so far.
    typedef Vector<IdValuePair, 10> PropertyVector;

    // Possible states the parser can be in between values.
    enum ParserState {
        // An array element has just being parsed.
        FinishArrayElement,

        // An object property has just been parsed.
        FinishObjectMember,

        // At the start of the parse, before any values have been processed.
        JSONValue
    };

    // Stack element for an in progress array or object.
    struct StackEntry {
        ElementVector &elements() {
            JS_ASSERT(state == FinishArrayElement);
            return * static_cast<ElementVector *>(vector);
        }

        PropertyVector &properties() {
            JS_ASSERT(state == FinishObjectMember);
            return * static_cast<PropertyVector *>(vector);
        }

        StackEntry(ElementVector *elements)
          : state(FinishArrayElement), vector(elements)
        {}

        StackEntry(PropertyVector *properties)
          : state(FinishObjectMember), vector(properties)
        {}

        ParserState state;

      private:
        void *vector;
    };

    // All in progress arrays and objects being parsed, in order from outermost
    // to innermost.
    Vector<StackEntry, 10> stack;

    // Unused element and property vectors for previous in progress arrays and
    // objects. These vectors are not freed until the end of the parse to avoid
    // unnecessary freeing and allocation.
    Vector<ElementVector*, 5> freeElements;
    Vector<PropertyVector*, 5> freeProperties;

#ifdef DEBUG
    Token lastToken;
#endif

  public:
    /* Public API */

    /* Create a parser for the provided JSON data. */
    JSONParser(JSContext *cx, JS::StableCharPtr data, size_t length,
               ErrorHandling errorHandling = RaiseError)
      : AutoGCRooter(cx, JSONPARSER),
        cx(cx),
        current(data),
        end((data + length).get(), data.get(), length),
        errorHandling(errorHandling),
        stack(cx),
        freeElements(cx),
        freeProperties(cx)
#ifdef DEBUG
      , lastToken(Error)
#endif
    {
        JS_ASSERT(current <= end);
    }

    ~JSONParser();

    /*
     * Parse the JSON data specified at construction time.  If it parses
     * successfully, store the prescribed value in *vp and return true.  If an
     * internal error (e.g. OOM) occurs during parsing, return false.
     * Otherwise, if invalid input was specifed but no internal error occurred,
     * behavior depends upon the error handling specified at construction: if
     * error handling is RaiseError then throw a SyntaxError and return false,
     * otherwise return true and set *vp to |undefined|.  (JSON syntax can't
     * represent |undefined|, so the JSON data couldn't have specified it.)
     */
    bool parse(MutableHandleValue vp);

  private:
    Value numberValue() const {
        JS_ASSERT(lastToken == Number);
        JS_ASSERT(v.isNumber());
        return v;
    }

    Value stringValue() const {
        JS_ASSERT(lastToken == String);
        JS_ASSERT(v.isString());
        return v;
    }

    JSAtom *atomValue() const {
        Value strval = stringValue();
        return &strval.toString()->asAtom();
    }

    Token token(Token t) {
        JS_ASSERT(t != String);
        JS_ASSERT(t != Number);
#ifdef DEBUG
        lastToken = t;
#endif
        return t;
    }

    Token stringToken(JSString *str) {
        this->v = StringValue(str);
#ifdef DEBUG
        lastToken = String;
#endif
        return String;
    }

    Token numberToken(double d) {
        this->v = NumberValue(d);
#ifdef DEBUG
        lastToken = Number;
#endif
        return Number;
    }

    enum StringType { PropertyName, LiteralValue };
    template<StringType ST> Token readString();

    Token readNumber();

    Token advance();
    Token advancePropertyName();
    Token advancePropertyColon();
    Token advanceAfterProperty();
    Token advanceAfterObjectOpen();
    Token advanceAfterArrayElement();

    void error(const char *msg);
    bool errorReturn();

    JSObject *createFinishedObject(PropertyVector &properties);
    bool finishObject(MutableHandleValue vp, PropertyVector &properties);
    bool finishArray(MutableHandleValue vp, ElementVector &elements);

    friend void AutoGCRooter::trace(JSTracer *trc);
    void trace(JSTracer *trc);

  private:
    JSONParser(const JSONParser &other) MOZ_DELETE;
    void operator=(const JSONParser &other) MOZ_DELETE;
};

} /* namespace js */

#endif /* jsonparser_h */