serialise.js

 /*
  * graphic depictions, a visual workbench for graphs 
  * 
  * Copyright (C) 2016-2018 Matvey Soloviev
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

 /* based on json2.js by Douglas Crockford, which was
  * released into the public domain
  */

(function () {
    "use strict";

    var rx_one = /^[\],:{}\s]*$/;
    var rx_two = /\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g;
    var rx_three = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g;
    var rx_four = /(?:^|:|,)(?:\s*\[)+/g;
    var rx_escapable = /[\\"\u0000-\u001f\u007f-\u009f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;
    var rx_dangerous = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g;

    function f(n) {
        // Format integers to have at least two digits.
        return n < 10
            ? "0" + n
            : n;
    }

    function this_value() {
        return this.valueOf();
    }

    if (typeof Date.prototype.toJSON !== "function") {

        Date.prototype.toJSON = function () {

            return isFinite(this.valueOf())
                ? this.getUTCFullYear() + "-" +
                        f(this.getUTCMonth() + 1) + "-" +
                        f(this.getUTCDate()) + "T" +
                        f(this.getUTCHours()) + ":" +
                        f(this.getUTCMinutes()) + ":" +
                        f(this.getUTCSeconds()) + "Z"
                : null;
        };

        Boolean.prototype.toJSON = this_value;
        Number.prototype.toJSON = this_value;
        String.prototype.toJSON = this_value;
    }

    var gap;
    var indent;
    var meta;
    var rep;


    function quote(string) {

// If the string contains no control characters, no quote characters, and no
// backslash characters, then we can safely slap some quotes around it.
// Otherwise we must also replace the offending characters with safe escape
// sequences.

        rx_escapable.lastIndex = 0;
        return rx_escapable.test(string)
            ? "\"" + string.replace(rx_escapable, function (a) {
                var c = meta[a];
                return typeof c === "string"
                    ? c
                    : "\\u" + ("0000" + a.charCodeAt(0).toString(16)).slice(-4);
            }) + "\""
            : "\"" + string + "\"";
    }


    function str(key, holder) {

// Produce a string from holder[key].

        var i;          // The loop counter.
        var k;          // The member key.
        var v;          // The member value.
        var length;
        var mind = gap;
        var partial;
        var value = holder[key];

// If the value has a toJSON method, call it to obtain a replacement value.

        if (value && typeof value === "object" &&
                typeof value.toJSON === "function") {
            value = value.toJSON(key);
        }

// If we were called with a replacer function, then call the replacer to
// obtain a replacement value.

        if (typeof rep === "function") {
            value = rep.call(holder, key, value);
        }

// What happens next depends on the value's type.

        switch (typeof value) {
        case "string":
            return quote(value);

        case "number":

// JSON numbers must be finite. Encode non-finite numbers as null.

            return isFinite(value)
                ? String(value)
                : "null";

        case "boolean":
        case "null":

// If the value is a boolean or null, convert it to a string. Note:
// typeof null does not produce "null". The case is included here in
// the remote chance that this gets fixed someday.

            return String(value);

// If the type is "function", hope that we have a representation of its source.
// This is not JSON anymore.

        case "function":
            var strep = value.toString();
            if((/\{\s*\[native code\]\s*\}$/).test(strep)) return;
            return value.toString();

// If the type is "object", we might be dealing with an object or an array or
// null.

        case "object":

// Due to a specification blunder in ECMAScript, typeof null is "object",
// so watch out for that case.

            if (!value) {
                return "null";
            }

// Is this a wrapped native object?

            if(typeof value._nativeRendition === "function") {
                return value._nativeRendition();
            }

// Make an array to hold the partial results of stringifying this object value.

            gap += indent;
            partial = [];

// Is the value an array?

            if (Object.prototype.toString.apply(value) === "[object Array]") {

// The value is an array. Stringify every element. Use null as a placeholder
// for non-JSON values.

                length = value.length;
                for (i = 0; i < length; i += 1) {
                    partial[i] = str(i, value) || "null";
                }

// Join all of the elements together, separated with commas, and wrap them in
// brackets.

                v = partial.length === 0
                    ? "[]"
                    : gap
                        ? "[\n" + gap + partial.join(",\n" + gap) + "\n" + mind + "]"
                        : "[" + partial.join(",") + "]";
                gap = mind;
                return v;
            }

// If the replacer is an array, use it to select the members to be stringified.

            if (rep && typeof rep === "object") {
                length = rep.length;
                for (i = 0; i < length; i += 1) {
                    if (typeof rep[i] === "string") {
                        k = rep[i];
                        v = str(k, value);
                        if (v) {
                            partial.push(quote(k) + (
                                gap
                                    ? ": "
                                    : ":"
                            ) + v);
                        }
                    }
                }
            } else {

// Otherwise, iterate through all of the keys in the object.

                for (k in value) {
                    if (Object.prototype.hasOwnProperty.call(value, k)) {
                        v = str(k, value);
                        if (v) {
                            partial.push(quote(k) + (
                                gap
                                    ? ": "
                                    : ":"
                            ) + v);
                        }
                    }
                }
            }

// Join all of the member texts together, separated with commas,
// and wrap them in braces.

            v = partial.length === 0
                ? "{}"
                : gap
                    ? "{\n" + gap + partial.join(",\n" + gap) + "\n" + mind + "}"
                    : "{" + partial.join(",") + "}";
            gap = mind;
            return v;
        }
    }

    meta = {    // table of character substitutions
        "\b": "\\b",
        "\t": "\\t",
        "\n": "\\n",
        "\f": "\\f",
        "\r": "\\r",
        "\"": "\\\"",
        "\\": "\\\\"
    };
    JSON.strong_stringify = function (value, replacer, space) {

// The strong_stringify method takes a value and an optional replacer, and an optional
// space parameter, and returns a JSON text. The replacer can be a function
// that can replace values, or an array of strings that will select the keys.
// A default replacer method can be provided. Use of the space parameter can
// produce text that is more easily readable.
// Unlike JSON.stringify, we (1) save the textual representation of functions, and
// (2) treat wrapped native classes in a special way.

        var i;
        gap = "";
        indent = "";

// If the space parameter is a number, make an indent string containing that
// many spaces.

        if (typeof space === "number") {
            for (i = 0; i < space; i += 1) {
                indent += " ";
            }

// If the space parameter is a string, it will be used as the indent string.

        } else if (typeof space === "string") {
            indent = space;
        }

// If there is a replacer, it must be a function or an array.
// Otherwise, throw an error.

        rep = replacer;
        if (replacer && typeof replacer !== "function" &&
                (typeof replacer !== "object" ||
                typeof replacer.length !== "number")) {
            throw new Error("JSON.stringify");
        }

// Make a fake root object containing our value under the key of "".
// Return the result of stringifying the value.

        return str("", {"": value});
    };

    JSON.strong_parse = function (input) {
        return eval("(" + input + ")");
    };

// Other service functions that really don't belong in JSON.
    JSON.deep_wipe = function (ptr,obj) {
        if(typeof obj === "object") {
            for(var k in obj) {
                if(typeof obj[k] === "object" && typeof obj[k]._nativeRendition === "function" && obj[k].valueOf()==ptr) {
                    obj[k] = undefined;
                } else {
                    JSON.deep_wipe(ptr,obj[k]);
                }
            }
        }
    };

    JSON.import_object = function(target,obj) {
        for(var k in obj) {
            target[k] = obj[k];
        }
    };

}());