rename getUint32 to getInt32 and collect readInt*() in util.js

src/shared/util.js

@@ -423,6 +423,28 @@ function string32(value) {
                              (value >> 8) & 0xff, value & 0xff);
 }
 
+function log2(x) {
+  var n = 1, i = 0;
+  while (x > n) {
+    n <<= 1;
+    i++;
+  }
+  return i;
+}
+
+function readInt8(data, start) {
+  return (data[start] << 24) >> 24;
+}
+
+function readUint16(data, offset) {
+  return (data[offset] << 8) | data[offset + 1];
+}
+
+function readUint32(data, offset) {
+  return ((data[offset] << 24) | (data[offset + 1] << 16) |
+         (data[offset + 2] << 8) | data[offset + 3]) >>> 0;
+}
+
 // Lazy test the endianness of the platform
 // NOTE: This will be 'true' for simulated TypedArrays
 function isLittleEndian() {