use buffer functions

...instead of adhoc uint functions

lib/bip32.js

@@ -68,10 +68,10 @@ BIP32.prototype.initFromBytes = function(bytes) {
   if (bytes.length != 78)
     throw new Error('not enough data');
 
-  this.version = u32(bytes.slice(0, 4));
-  this.depth = u8(bytes.slice(4, 5));
+  this.version = bytes.slice(0, 4).readUInt32BE(0);
+  this.depth = bytes.slice(4, 5).readUInt8(0);
   this.parentFingerprint = bytes.slice(5, 9);
-  this.childIndex = u32(bytes.slice(9, 13));
+  this.childIndex = bytes.slice(9, 13).readUInt32BE(0);
   this.chainCode = bytes.slice(13, 45);
 
   var keyBytes = bytes.slice(45, 78);
@@ -303,31 +303,4 @@ BIP32.prototype.toString = function() {
     return this.extendedPublicKeyString();
 };
 
-function uint(f, size) {
-  if (f.length < size)
-    throw new Error('not enough data');
-  var n = 0;
-  for (var i = 0; i < size; i++) {
-    n *= 256;
-    n += f[i];
-  }
-  return n;
-}
-
-function u8(f) {
-  return uint(f, 1);
-}
-
-function u16(f) {
-  return uint(f, 2);
-}
-
-function u32(f) {
-  return uint(f, 4);
-}
-
-function u64(f) {
-  return uint(f, 8);
-}
-
 module.exports = BIP32;

test/bip32.js

@@ -324,7 +324,6 @@ describe('BIP32', function() {
       tip32b.toString().slice(0, 4).should.equal('tpub');
     });
 
-
   });
 
 });