append.js

// writing 3 buffers starting from offset 0
// 3 bytes | 5 bytes | 10 bytes
// second  | first   | third
// last byte of the last buffer should be at offset 18
// file should be 18 bytes long
// this is WRONG on linux, file grows up for 18 bytes after each run
// and every single written buffer can't be read properly
//
// holy fuck, the whole day lost.

var fs = require("fs"),
    f  = fs.openSync("ae", "a+");

b1  = new Buffer(5);
b1t = new Buffer(b1.length);
b2  = new Buffer(3);
b2t = new Buffer(b2.length);
b3  = new Buffer(10);
b3t = new Buffer(b3.length);

fs.write(f, b1, 0, b1.length, b2.length, function(error) {
    if (error) {
        return console.log(error);
    }

    fs.write(f, b2, 0, b2.length, 0, function(error) {
        if (error) {
            return console.log(error);
        }

        fs.write(f, b3, 0, b3.length, b1.length + b2.length, function(error) {
            if (error) {
                return console.log(error);
            }

            fs.read(f, b1t, 0, b1t.length, b2.length, function(error) {
                if (error) {
                    return console.log(error);
                }

                if (b1t.toString("base64") != b1.toString("base64")) {
                    console.log("wrong first buffer!", b1, b1t);
                }

                fs.read(f, b2t, 0, b2t.length, 0, function(error) {
                    if (error) {
                        return console.log(error);
                    }

                    if (b2t.toString("base64") != b2.toString("base64")) {
                        console.log("wrong second buffer!");
                    }

                    fs.read(f, b3t, 0, b3t.length, b1.length + b2.length, function(error) {
                        if (error) {
                            return console.log(error);
                        }

                        if (b3t.toString("base64") != b3.toString("base64")) {
                            console.log("wrong third buffer!");
                        }
                    });
                });
            });
        });
    });
});