streambuf.js

/**
 * Created with JetBrains WebStorm.
 * User: kiyangqi
 * Date: 13-6-9
 * Time: 下午11:36
 * To change this template use File | Settings | File Templates.
 */

function StreamBuf() {
    this.chunks = [];
    this.length = 0;
}

// chunk must be Buffer
StreamBuf.prototype.write = function(chunk) {
    if(typeof chunk == 'string') {
        chunk = Buffer(chunk);
    }
    if(chunk.constructor != Buffer) {
        throw new Error("chunk must be Buffer or String");
    }
    this.chunks.push(chunk);
    this.length += chunk.length;
}

StreamBuf.prototype.read = function(need) {
    if(need <= this.length) {
        var bytes = 0, i = 0;
        var out = [];
        while(bytes < need) {
            if(bytes + this.chunks[0] <= need) {
                var item = this.chunks.shift();
                out.push(item);
                bytes += item.length;
            } else {
                var item = this.chunks.shift();
                out.push(item.slice(0, need - bytes));
                this.chunks.unshift(item.slice(need-bytes));
                bytes = need;
            }
        }
        this.length -= need;
        return Buffer.concat(out, need);
    }

    throw new Error("not enough bytes");
}

StreamBuf.prototype.readSome = function(needMax) {
    return this.read(Math.min(needMax, this.length));
}

module.exports = StreamBuf;