bip322-js
Version:
A Javascript library that provides utility functions related to the BIP-322 signature scheme
77 lines • 2.73 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
/**
* Class that implement variable length integer (VarInt) in Javascript.
* Reference: https://en.bitcoin.it/wiki/Protocol_documentation#Variable_length_integer
*/
class VarInt {
/**
* Encode an integer i as a variable length integer.
* Reference: https://github.com/buidl-bitcoin/buidl-python/blob/d79e9808e8ca60975d315be41293cb40d968626d/buidl/helper.py#L180
* @param i Integer to be encoded
* @returns Encoded varint
*/
static encode(i) {
if (i < 0xFD) {
const buffer = Buffer.alloc(1);
buffer.writeUInt8(i);
return buffer;
}
else if (i < 0x10000) {
const buffer = Buffer.alloc(3);
buffer.writeUInt8(0xfd);
buffer.writeUInt16LE(i, 1);
return buffer;
}
else if (i < 0x100000000) {
const buffer = Buffer.alloc(5);
buffer.writeUInt8(0xfe);
buffer.writeUInt32LE(i, 1);
return buffer;
}
else if (i < 0x1000000000000) {
const buffer = Buffer.alloc(9);
buffer.writeUInt8(0xff);
buffer.writeUIntLE(i, 1, 6); // Cannot write UInt64LE in Node JS
buffer.writeUInt8(0x00, 7); // Pad two extra 0x00 at the end to emulate UInt64LE
buffer.writeUInt8(0x00, 8);
return buffer;
}
else {
throw new Error(`Integer too large: ${i}`);
}
}
/**
* Decode a variable length integer from a Buffer into a number.
* Reference: https://github.com/buidl-bitcoin/buidl-python/blob/d79e9808e8ca60975d315be41293cb40d968626d/buidl/helper.py#L160
* @param b Buffer which contain the varint
* @returns Decoded number
*/
static decode(b) {
// Check for empty buffer
if (b.byteLength === 0) {
throw new Error('Empty buffer provided');
}
// Read first byte from the buffer
const i = b.readUInt8();
// Check if i is indicating its length
if (i === 0xfd) {
// 0xfd means the next two bytes are the number
return b.readUInt16LE(1);
}
else if (i === 0xfe) {
// 0xfe means the next four bytes are the number
return b.readUInt32LE(1);
}
else if (i === 0xff) {
// 0xff means the next eight bytes are the number, but Node JS can only read up to 6 bytes
return b.readUIntLE(1, 6);
}
else {
// Anything else is just the integer
return i;
}
}
}
exports.default = VarInt;
//# sourceMappingURL=VarInt.js.map