first commit

utils.js

@@ -0,0 +1,71 @@
+"use strict";
+var crypto = require('crypto');
+
+function swapHex(value) {
+  let s = value.toString(16);
+  s = s.replace(/^(.(..)*)$/, "0$1");
+  var a = s.match(/../g);
+  a.reverse();
+  var s2 = a.join("");
+  return s2;
+}
+
+function numToBytes(num, bytes) {
+  if (bytes === undefined) bytes = 8;
+  if (bytes == 0) return [];
+  else return [num % 256].concat(numToBytes(Math.floor(num / 256), bytes - 1));
+}
+
+function numToVarInt(num) {
+  if (num < 253) return [num];
+  else if (num < 65536) return [253].concat(numToBytes(num, 2));
+  else if (num < 4294967296) return [254].concat(numToBytes(num, 4));
+  else return [253].concat(numToBytes(num, 8));
+}
+
+function hexToBytes(hex) {
+  for (var bytes = [], c = 0; c < hex.length; c += 2)
+    bytes.push(parseInt(hex.substr(c, 2), 16));
+  return bytes;
+}
+
+function bytesToHex(bytes) {
+  for (var hex = [], i = 0; i < bytes.length; i++) {
+    hex.push((bytes[i] >>> 4).toString(16));
+    hex.push((bytes[i] & 0xf).toString(16));
+  }
+  return hex.join("");
+}
+function bytesLen(num) {
+  return Math.ceil(num.toString(2).length / 8);
+}
+
+
+function sha256(buffer) {
+    var hash1 = crypto.createHash('sha256');
+    hash1.update(buffer);
+    return hash1.digest();
+};
+
+function sha256d(buffer) {
+    return sha256(sha256(buffer));
+};
+
+function reverseBuffer(buff) {
+    var reversed = Buffer.alloc(buff.length);
+    for (var i = buff.length - 1; i >= 0; i--)
+        reversed[buff.length - i - 1] = buff[i];
+    return reversed;
+};
+
+module.exports = {
+  swapHex,
+  numToBytes,
+  numToVarInt,
+  hexToBytes,
+  bytesToHex,  
+  bytesLen,
+  sha256,
+  sha256d,
+  reverseBuffer
+};