exceljs/lib/csv/stream-converter.js

Excel Workbook Manager - Read and Write xlsx and csv Files.

// =======================================================================================================
// StreamConverter
//
// convert between encoding schemes in a stream
// Work in Progress - Will complete this at some point

//var jconv = require("jconv");
var _ = require("underscore");

var StreamConverter = module.exports = function (inner, options) {

    this.inner = inner;

    options = options || {};
    this.innerEncoding = (options.innerEncoding || "UTF8").toUpperCase();
    this.outerEncoding = (options.outerEncoding || "UTF8").toUpperCase();

    this.innerBOM = options.innerBOM || null;
    this.outerBOM = options.outerBOM || null;

    this.writeStarted = false;
}

StreamConverter.prototype.convertInwards = function(data) {
    var self = this;
    if (data) {
        if (typeof(data) == "string") {
            data = new Buffer(data, this.outerEncoding);
        }

        if (this.innerEncoding != this.outerEncoding) {
            data = jconv.convert(data, this.outerEncoding, this.innerEncoding);
        }
    }

    return data;
}
StreamConverter.prototype.convertOutwards = function(data) {
    var self = this;
    if (typeof(data) == "string") {
        data = new Buffer(data, this.innerEncoding);
    }

    if (this.innerEncoding != this.outerEncoding) {
        data = jconv.convert(data, this.innerEncoding, this.outerEncoding);
    }
    return data;
}

StreamConverter.prototype.addListener = function(event, handler) {
    this.inner.addListener(event, handler);
}

StreamConverter.prototype.removeListener = function(event, handler) {
    this.inner.removeListener(event, handler);
}

StreamConverter.prototype.write = function(data, encoding, callback) {
    if (encoding instanceof Function) {
        callback = encoding;
        encoding = undefined;
    }

    if (!this.writeStarted) {

        // if inner encoding has BOM, write it now
        if (this.innerBOM) {
            this.inner.write(this.innerBOM);
        }

        // if outer encoding has BOM, delete it now
        if (this.outerBOM) {
            if (data.length <= this.outerBOM.length) {
                if (callback) { callback(); }
                return;
            }
            var bomless = new Buffer(data.length - this.outerBOM.length);
            data.copy(bomless, 0, this.outerBOM.length, data.length);
            data = bomless;
        }

        this.writeStarted = true;
    }

    this.inner.write(
        this.convertInwards(data),
        encoding ? this.innerEncoding : undefined,
        callback);
}

StreamConverter.prototype.read = function() {
    // TBD
}

StreamConverter.prototype.pipe = function(destination, options) {
    var reverseConverter = new StreamConverter(destination, {
        innerEncoding: this.outerEncoding,
        outerEncoding: this.innerEncoding,
        innerBOM: this.outerBOM,
        outerBOM: this.innerBOM
    });

    this.inner.pipe(reverseConverter, options)
}

StreamConverter.prototype.close = function() {
    this.inner.close();
}

StreamConverter.prototype.on = function(type, callback) {
    var self = this;
    switch (type) {
        case "data":
            this.inner.on("data", function(chunk) {
                callback(self.convertOutwards(chunk));
            });
            return this;
        default:
            this.inner.on(type, callback);
            return this;
    }
}

StreamConverter.prototype.once = function(type, callback) {
    this.inner.once(type, callback);
}

StreamConverter.prototype.end = function(chunk, encoding, callback) {
    this.inner.end(
        this.convertInwards(chunk),
        this.innerEncoding,
        callback);
}

StreamConverter.prototype.emit = function(type, value) {
    this.inner.emit(type, value);
}