utils.js

'use strict';

var support = require('./support');
var base64 = require('./base64');
var nodejsUtils = require('./nodejsUtils');
var setImmediate = require('set-immediate-shim');
var external = require("./external");


/**
 * Convert a string that pass as a "binary string": it should represent a byte
 * array but may have > 255 char codes. Be sure to take only the first byte
 * and returns the byte array.
 * @param {String} str the string to transform.
 * @return {Array|Uint8Array} the string in a binary format.
 */
function string2binary(str) {
    var result = null;
    if (support.uint8array) {
      result = new Uint8Array(str.length);
    } else {
      result = new Array(str.length);
    }
    return stringToArrayLike(str, result);
}

/**
 * Create a new blob with the given content and the given type.
 * @param {String|ArrayBuffer} part the content to put in the blob. DO NOT use
 * an Uint8Array because the stock browser of android 4 won't accept it (it
 * will be silently converted to a string, "[object Uint8Array]").
 *
 * Use only ONE part to build the blob to avoid a memory leak in IE11 / Edge:
 * when a large amount of Array is used to create the Blob, the amount of
 * memory consumed is nearly 100 times the original data amount.
 *
 * @param {String} type the mime type of the blob.
 * @return {Blob} the created blob.
 */
exports.newBlob = function(part, type) {
    exports.checkSupport("blob");

    try {
        // Blob constructor
        return new Blob([part], {
            type: type
        });
    }
    catch (e) {

        try {
            // deprecated, browser only, old way
            var Builder = self.BlobBuilder || self.WebKitBlobBuilder || self.MozBlobBuilder || self.MSBlobBuilder;
            var builder = new Builder();
            builder.append(part);
            return builder.getBlob(type);
        }
        catch (e) {

            // well, fuck ?!
            throw new Error("Bug : can't construct the Blob.");
        }
    }


};
/**
 * The identity function.
 * @param {Object} input the input.
 * @return {Object} the same input.
 */
function identity(input) {
    return input;
}

/**
 * Fill in an array with a string.
 * @param {String} str the string to use.
 * @param {Array|ArrayBuffer|Uint8Array|Buffer} array the array to fill in (will be mutated).
 * @return {Array|ArrayBuffer|Uint8Array|Buffer} the updated array.
 */
function stringToArrayLike(str, array) {
    for (var i = 0; i < str.length; ++i) {
        array[i] = str.charCodeAt(i) & 0xFF;
    }
    return array;
}

/**
 * An helper for the function arrayLikeToString.
 * This contains static information and functions that
 * can be optimized by the browser JIT compiler.
 */
var arrayToStringHelper = {
    /**
     * Transform an array of int into a string, chunk by chunk.
     * See the performances notes on arrayLikeToString.
     * @param {Array|ArrayBuffer|Uint8Array|Buffer} array the array to transform.
     * @param {String} type the type of the array.
     * @param {Integer} chunk the chunk size.
     * @return {String} the resulting string.
     * @throws Error if the chunk is too big for the stack.
     */
    stringifyByChunk: function(array, type, chunk) {
        var result = [], k = 0, len = array.length;
        // shortcut
        if (len <= chunk) {
            return String.fromCharCode.apply(null, array);
        }
        while (k < len) {
            if (type === "array" || type === "nodebuffer") {
                result.push(String.fromCharCode.apply(null, array.slice(k, Math.min(k + chunk, len))));
            }
            else {
                result.push(String.fromCharCode.apply(null, array.subarray(k, Math.min(k + chunk, len))));
            }
            k += chunk;
        }
        return result.join("");
    },
    /**
     * Call String.fromCharCode on every item in the array.
     * This is the naive implementation, which generate A LOT of intermediate string.
     * This should be used when everything else fail.
     * @param {Array|ArrayBuffer|Uint8Array|Buffer} array the array to transform.
     * @return {String} the result.
     */
    stringifyByChar: function(array){
        var resultStr = "";
        for(var i = 0; i < array.length; i++) {
            resultStr += String.fromCharCode(array[i]);
        }
        return resultStr;
    },
    applyCanBeUsed : {
        /**
         * true if the browser accepts to use String.fromCharCode on Uint8Array
         */
        uint8array : (function () {
            try {
                return support.uint8array && String.fromCharCode.apply(null, new Uint8Array(1)).length === 1;
            } catch (e) {
                return false;
            }
        })(),
        /**
         * true if the browser accepts to use String.fromCharCode on nodejs Buffer.
         */
        nodebuffer : (function () {
            try {
                return support.nodebuffer && String.fromCharCode.apply(null, nodejsUtils.allocBuffer(1)).length === 1;
            } catch (e) {
                return false;
            }
        })()
    }
};

/**
 * Transform an array-like object to a string.
 * @param {Array|ArrayBuffer|Uint8Array|Buffer} array the array to transform.
 * @return {String} the result.
 */
function arrayLikeToString(array) {
    // Performances notes :
    // --------------------
    // String.fromCharCode.apply(null, array) is the fastest, see
    // see http://jsperf.com/converting-a-uint8array-to-a-string/2
    // but the stack is limited (and we can get huge arrays !).
    //
    // result += String.fromCharCode(array[i]); generate too many strings !
    //
    // This code is inspired by http://jsperf.com/arraybuffer-to-string-apply-performance/2
    // TODO : we now have workers that split the work. Do we still need that ?
    var chunk = 65536,
        type = exports.getTypeOf(array),
        canUseApply = true;
    if (type === "uint8array") {
        canUseApply = arrayToStringHelper.applyCanBeUsed.uint8array;
    } else if (type === "nodebuffer") {
        canUseApply = arrayToStringHelper.applyCanBeUsed.nodebuffer;
    }

    if (canUseApply) {
        while (chunk > 1) {
            try {
                return arrayToStringHelper.stringifyByChunk(array, type, chunk);
            } catch (e) {
                chunk = Math.floor(chunk / 2);
            }
        }
    }

    // no apply or chunk error : slow and painful algorithm
    // default browser on android 4.*
    return arrayToStringHelper.stringifyByChar(array);
}

exports.applyFromCharCode = arrayLikeToString;


/**
 * Copy the data from an array-like to an other array-like.
 * @param {Array|ArrayBuffer|Uint8Array|Buffer} arrayFrom the origin array.
 * @param {Array|ArrayBuffer|Uint8Array|Buffer} arrayTo the destination array which will be mutated.
 * @return {Array|ArrayBuffer|Uint8Array|Buffer} the updated destination array.
 */
function arrayLikeToArrayLike(arrayFrom, arrayTo) {
    for (var i = 0; i < arrayFrom.length; i++) {
        arrayTo[i] = arrayFrom[i];
    }
    return arrayTo;
}

// a matrix containing functions to transform everything into everything.
var transform = {};

// string to ?
transform["string"] = {
    "string": identity,
    "array": function(input) {
        return stringToArrayLike(input, new Array(input.length));
    },
    "arraybuffer": function(input) {
        return transform["string"]["uint8array"](input).buffer;
    },
    "uint8array": function(input) {
        return stringToArrayLike(input, new Uint8Array(input.length));
    },
    "nodebuffer": function(input) {
        return stringToArrayLike(input, nodejsUtils.allocBuffer(input.length));
    }
};

// array to ?
transform["array"] = {
    "string": arrayLikeToString,
    "array": identity,
    "arraybuffer": function(input) {
        return (new Uint8Array(input)).buffer;
    },
    "uint8array": function(input) {
        return new Uint8Array(input);
    },
    "nodebuffer": function(input) {
        return nodejsUtils.newBufferFrom(input);
    }
};

// arraybuffer to ?
transform["arraybuffer"] = {
    "string": function(input) {
        return arrayLikeToString(new Uint8Array(input));
    },
    "array": function(input) {
        return arrayLikeToArrayLike(new Uint8Array(input), new Array(input.byteLength));
    },
    "arraybuffer": identity,
    "uint8array": function(input) {
        return new Uint8Array(input);
    },
    "nodebuffer": function(input) {
        return nodejsUtils.newBufferFrom(new Uint8Array(input));
    }
};

// uint8array to ?
transform["uint8array"] = {
    "string": arrayLikeToString,
    "array": function(input) {
        return arrayLikeToArrayLike(input, new Array(input.length));
    },
    "arraybuffer": function(input) {
        return input.buffer;
    },
    "uint8array": identity,
    "nodebuffer": function(input) {
        return nodejsUtils.newBufferFrom(input);
    }
};

// nodebuffer to ?
transform["nodebuffer"] = {
    "string": arrayLikeToString,
    "array": function(input) {
        return arrayLikeToArrayLike(input, new Array(input.length));
    },
    "arraybuffer": function(input) {
        return transform["nodebuffer"]["uint8array"](input).buffer;
    },
    "uint8array": function(input) {
        return arrayLikeToArrayLike(input, new Uint8Array(input.length));
    },
    "nodebuffer": identity
};

/**
 * Transform an input into any type.
 * The supported output type are : string, array, uint8array, arraybuffer, nodebuffer.
 * If no output type is specified, the unmodified input will be returned.
 * @param {String} outputType the output type.
 * @param {String|Array|ArrayBuffer|Uint8Array|Buffer} input the input to convert.
 * @throws {Error} an Error if the browser doesn't support the requested output type.
 */
exports.transformTo = function(outputType, input) {
    if (!input) {
        // undefined, null, etc
        // an empty string won't harm.
        input = "";
    }
    if (!outputType) {
        return input;
    }
    exports.checkSupport(outputType);
    var inputType = exports.getTypeOf(input);
    var result = transform[inputType][outputType](input);
    return result;
};

/**
 * Return the type of the input.
 * The type will be in a format valid for JSZip.utils.transformTo : string, array, uint8array, arraybuffer.
 * @param {Object} input the input to identify.
 * @return {String} the (lowercase) type of the input.
 */
exports.getTypeOf = function(input) {
    if (typeof input === "string") {
        return "string";
    }
    if (Object.prototype.toString.call(input) === "[object Array]") {
        return "array";
    }
    if (support.nodebuffer && nodejsUtils.isBuffer(input)) {
        return "nodebuffer";
    }
    if (support.uint8array && input instanceof Uint8Array) {
        return "uint8array";
    }
    if (support.arraybuffer && input instanceof ArrayBuffer) {
        return "arraybuffer";
    }
};

/**
 * Throw an exception if the type is not supported.
 * @param {String} type the type to check.
 * @throws {Error} an Error if the browser doesn't support the requested type.
 */
exports.checkSupport = function(type) {
    var supported = support[type.toLowerCase()];
    if (!supported) {
        throw new Error(type + " is not supported by this platform");
    }
};

exports.MAX_VALUE_16BITS = 65535;
exports.MAX_VALUE_32BITS = -1; // well, "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF" is parsed as -1

/**
 * Prettify a string read as binary.
 * @param {string} str the string to prettify.
 * @return {string} a pretty string.
 */
exports.pretty = function(str) {
    var res = '',
        code, i;
    for (i = 0; i < (str || "").length; i++) {
        code = str.charCodeAt(i);
        res += '\\x' + (code < 16 ? "0" : "") + code.toString(16).toUpperCase();
    }
    return res;
};

/**
 * Defer the call of a function.
 * @param {Function} callback the function to call asynchronously.
 * @param {Array} args the arguments to give to the callback.
 */
exports.delay = function(callback, args, self) {
    setImmediate(function () {
        callback.apply(self || null, args || []);
    });
};

/**
 * Extends a prototype with an other, without calling a constructor with
 * side effects. Inspired by nodejs' `utils.inherits`
 * @param {Function} ctor the constructor to augment
 * @param {Function} superCtor the parent constructor to use
 */
exports.inherits = function (ctor, superCtor) {
    var Obj = function() {};
    Obj.prototype = superCtor.prototype;
    ctor.prototype = new Obj();
};

/**
 * Merge the objects passed as parameters into a new one.
 * @private
 * @param {...Object} var_args All objects to merge.
 * @return {Object} a new object with the data of the others.
 */
exports.extend = function() {
    var result = {}, i, attr;
    for (i = 0; i < arguments.length; i++) { // arguments is not enumerable in some browsers
        for (attr in arguments[i]) {
            if (arguments[i].hasOwnProperty(attr) && typeof result[attr] === "undefined") {
                result[attr] = arguments[i][attr];
            }
        }
    }
    return result;
};

/**
 * Transform arbitrary content into a Promise.
 * @param {String} name a name for the content being processed.
 * @param {Object} inputData the content to process.
 * @param {Boolean} isBinary true if the content is not an unicode string
 * @param {Boolean} isOptimizedBinaryString true if the string content only has one byte per character.
 * @param {Boolean} isBase64 true if the string content is encoded with base64.
 * @return {Promise} a promise in a format usable by JSZip.
 */
exports.prepareContent = function(name, inputData, isBinary, isOptimizedBinaryString, isBase64) {

    // if inputData is already a promise, this flatten it.
    var promise = external.Promise.resolve(inputData).then(function(data) {
        
        
        var isBlob = support.blob && (data instanceof Blob || ['[object File]', '[object Blob]'].indexOf(Object.prototype.toString.call(data)) !== -1);

        if (isBlob && typeof FileReader !== "undefined") {
            return new external.Promise(function (resolve, reject) {
                var reader = new FileReader();

                reader.onload = function(e) {
                    resolve(e.target.result);
                };
                reader.onerror = function(e) {
                    reject(e.target.error);
                };
                reader.readAsArrayBuffer(data);
            });
        } else {
            return data;
        }
    });

    return promise.then(function(data) {
        var dataType = exports.getTypeOf(data);

        if (!dataType) {
            return external.Promise.reject(
                new Error("Can't read the data of '" + name + "'. Is it " +
                          "in a supported JavaScript type (String, Blob, ArrayBuffer, etc) ?")
            );
        }
        // special case : it's way easier to work with Uint8Array than with ArrayBuffer
        if (dataType === "arraybuffer") {
            data = exports.transformTo("uint8array", data);
        } else if (dataType === "string") {
            if (isBase64) {
                data = base64.decode(data);
            }
            else if (isBinary) {
                // optimizedBinaryString === true means that the file has already been filtered with a 0xFF mask
                if (isOptimizedBinaryString !== true) {
                    // this is a string, not in a base64 format.
                    // Be sure that this is a correct "binary string"
                    data = string2binary(data);
                }
            }
        }
        return data;
    });
};