Dead4W / jsAesCrypt

/** global: FileReader */

/**

 * read file as string, bytes (uint8Array), int (1 byte)

 *

 *

 * @return The fileBytesReader object.

 *

 * @static

 *

 * @example

 *     var fileElement = document.getElementById('file').files[0];

 *     var file = fileBytesReader(fileElement);

 *

 * @param file a fileElement object

 */

    let _i = 0;

    let _fileSize = file.size;

    let _reader = new FileReader();

    let _file = file;

    function readChunk(length) {

        return new Promise((resolve, reject) => {

            let blob = _file.slice(_i, _i += length);

            _reader.onload = () => {

                // return Uint8Array

                resolve(new Uint8Array(_reader.result));

            };

            _reader.onerror = reject;

            _reader.readAsArrayBuffer(blob);

        });

    }

    async function readBytes(length) {

        return await readChunk(length);

    }

    async function readByte() {

        let bytes = await readBytes(1);

        return bytes[0];

    }

    function getCurrentPosition() {

        return _i;

    }

    return {

        readByte: readByte,

        readBytes: readBytes,

        getCurrentPosition: getCurrentPosition,

        getLength: getLength,

    };

};