@fry/bits
Version:
Simplifies reading and writing bits in Buffers
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Markdown
A tool for twiddling bits in buffers
`npm install --save @fry/bits`
Create a 0-filled bit-buffer with a length of any given bit-length
```javascript
const { Bits } = require('bits');
const bits = new Bits(15 * 8); // 15 bytes capacity
```
Or reference an already exisiting `Buffer`
```javascript
const buffer = Buffer.from([0xff, 0x00, 0xff, 0x00]);
const bits = new Bits(buffer);
```
There are also convenience functions to create prefilled buffers (note that these use byte-length arguments)
```javascript
const bits = Bits.alloc(6, 0xaa); // 6 * 8 bits capacity, with 0b10101010... repeated for all bits
```
```javascript
const bits = Bits.from('Yml0YnVm', 'base64'); // 48 bits capacity prefilled with data
```
After instantiating the bit-buffer you can begin manipulating the bits
```javascript
const bits = new Bits(2 * 8);
// Write some bits, jump to the beginning of the buffer and read all bits
const value = bits
.write(7, 3)
.write(0x55, 7)
.write(0b10, 2)
.seek(0)
.read(12); // value = 0b111101010110
// Turn on bit 4 and 5
bits.insert(0b11, 2, 4);
// Read the same 2 bits, not moving the offset
bits.peek(2, 4); // 0b11
// Get bit 4
bits.getBit(4); // 0b1
// Set bit 5 to 1
bits.setBit(5);
// Test if bit 5 is 1
bits.testBit(5); // true
// Clear bit 5 and flip bit 6
bits
.clearBit(5)
.flipBit(6);
// Stringify the buffer (e.g. ascii, utf8, ucs2, base64, binary, hex)
bits.toString('hex'); // 'fb60'
```