ioredis-mock-with-info/lib/commands/setbit.js

This library emulates ioredis by performing all operations in-memory.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.setbit = setbit;
var MAX_OFFSET = Math.pow(2, 32) - 1;
var STR_BIT_0 = String.fromCharCode(0);

var constantLengthOf = function constantLengthOf(len) {
  return function (str) {
    return str + Array(Math.max(0, len - str.length)).fill(STR_BIT_0).join('');
  };
};

/* eslint-disable no-bitwise */
var getBitAt = function getBitAt(position) {
  return function (byte) {
    return byte >> position & 1;
  };
};
var setBitAt = function setBitAt(position) {
  return function (byte) {
    return byte | 1 << position;
  };
};
var resetBitAt = function resetBitAt(position) {
  return function (byte) {
    return byte & ~(1 << position);
  };
};
/* eslint-enable no-bitwise */
var setOrResetBitAt = function setOrResetBitAt(bit) {
  return bit === 1 ? setBitAt : resetBitAt;
};

var getByteAt = function getByteAt(position) {
  return function (str) {
    return str.charCodeAt(position);
  };
};
var setByteAt = function setByteAt(byte) {
  return function (position) {
    return function (str) {
      return str.substr(0, position) + String.fromCharCode(byte) + str.substr(position + 1);
    };
  };
};

function setbit(key, offset, value) {
  if (offset > MAX_OFFSET) throw new Error('ERR bit offset is not an integer or out of range');
  var bit = parseInt(value, 10);
  if (bit !== 0 && bit !== 1) throw new Error('ERR bit is not an integer or out of range');

  var byteOffset = parseInt(offset / 8, 10);
  var bitOffset = 7 - offset % 8; // redis store bit in reverse order (left to right)

  var prev = this.data.has(key) ? this.data.get(key) : '';
  var prevByte = getByteAt(byteOffset)(prev);
  var padded = constantLengthOf(byteOffset + 1)(prev);
  var newByte = setOrResetBitAt(bit)(bitOffset)(prevByte);
  var newValue = setByteAt(newByte)(byteOffset)(padded);

  this.data.set(key, newValue);

  return getBitAt(bitOffset)(prevByte);
}