mdb-reader
Version:
JavaScript library to read data from Access databases
54 lines (53 loc) • 1.43 kB
JavaScript
/**
* Reads a specific bit of a bitmap. Returns true for 1 and false for 0.
*
* @param pos 0-based
*/
export function getBitmapValue(bitmap, pos) {
const byteNumber = Math.floor(pos / 8);
const bitNumber = pos % 8;
return !!(bitmap[byteNumber] & (1 << bitNumber));
}
/**
* Returns the number of bytes required to store a specific number of bits.
*/
export function roundToFullByte(bits) {
return Math.floor((bits + 7) / 8);
}
/**
* @see https://github.com/crypto-browserify/buffer-xor
*/
export function xor(a, b) {
const length = Math.max(a.length, b.length);
const buffer = Buffer.allocUnsafe(length);
for (let i = 0; i < length; i++) {
buffer[i] = a[i] ^ b[i];
}
return buffer;
}
/**
* Returns true if buffer only contains zeros.
*/
export function isEmptyBuffer(buffer) {
return buffer.every((v) => v === 0);
}
export function intToBuffer(n) {
const buffer = Buffer.allocUnsafe(4);
buffer.writeInt32LE(n);
return buffer;
}
export function fixBufferLength(buffer, length, padByte = 0) {
if (buffer.length > length) {
return buffer.slice(0, length);
}
if (buffer.length < length) {
return Buffer.from(buffer).fill(padByte, buffer.length, length);
}
return buffer;
}
export function isInRange(from, to, value) {
return from <= value && value <= to;
}
export function maskTableId(id) {
return id & 0x00ffffff;
}