BufferExt: rename to bufferutils

src/bufferutils.js

@@ -0,0 +1,94 @@
+var assert = require('assert')
+
+function readUInt64LE(buffer, offset) {
+  var a = buffer.readUInt32LE(offset)
+  var b = buffer.readUInt32LE(offset + 4)
+  b *= 0x100000000
+
+  // Javascript Safe Integer limitation
+  // assert(Number.isSafeInteger(value), 'value must be < 2^53')
+  assert(b + a < 0x0020000000000000, 'value must be < 2^53')
+
+  return b + a
+}
+
+function readVarInt(buffer, offset) {
+  var t = buffer.readUInt8(offset)
+  var number, size
+
+  // 8-bit
+  if (t < 253) {
+    number = t
+    size = 1
+
+  // 16-bit
+  } else if (t < 254) {
+    number = buffer.readUInt16LE(offset + 1)
+    size = 3
+
+  // 32-bit
+  } else if (t < 255) {
+    number = buffer.readUInt32LE(offset + 1)
+    size = 5
+
+  // 64 bit
+  } else {
+    number = readUInt64LE(buffer, offset + 1)
+    size = 9
+  }
+
+  return {
+    number: number,
+    size: size
+  }
+}
+
+function writeUInt64LE(buffer, value, offset) {
+  // Javascript Safe Integer limitation
+  // assert(Number.isSafeInteger(value), 'value must be < 2^53')
+  assert(value < 0x0020000000000000, 'value must be < 2^53')
+
+  buffer.writeInt32LE(value & -1, offset)
+  buffer.writeUInt32LE(Math.floor(value / 0x100000000), offset + 4)
+}
+
+function varIntSize(i) {
+  return i < 253      ? 1
+    : i < 0x10000     ? 3
+    : i < 0x100000000 ? 5
+    :                   9
+}
+
+function writeVarInt(buffer, number, offset) {
+  var size = varIntSize(number)
+
+  // 8 bit
+  if (size === 1) {
+    buffer.writeUInt8(number, offset)
+
+  // 16 bit
+  } else if (size === 3) {
+    buffer.writeUInt8(253, offset)
+    buffer.writeUInt16LE(number, offset + 1)
+
+  // 32 bit
+  } else if (size === 5) {
+    buffer.writeUInt8(254, offset)
+    buffer.writeUInt32LE(number, offset + 1)
+
+  // 64 bit
+  } else {
+    buffer.writeUInt8(255, offset)
+    writeUInt64LE(buffer, number, offset + 1)
+  }
+
+  return size
+}
+
+module.exports = {
+  readUInt64LE: readUInt64LE,
+  readVarInt: readVarInt,
+  varIntSize: varIntSize,
+  writeUInt64LE: writeUInt64LE,
+  writeVarInt: writeVarInt
+}