Add base32 codec

Author: jcoglan

lib/base32.js

@@ -0,0 +1,35 @@
+'use strict'
+
+const { transcode } = require('./transcode')
+const utf8 = require('./utf8')
+
+const Base32 = {
+  encode (buf) {
+    let str = transcode(8, 5, buf, bitsToChar)
+    return utf8.encode(str)
+  },
+
+  decode (str) {
+    let buf = utf8.decode(str)
+    return transcode(5, 8, buf, charToBits)
+  }
+}
+
+//      input       | char      | code
+//      ------------+-----------+-----------
+//      00 - 19     | A - Z     | 41 - 5a
+//                  | a - z     | 61 - 7a
+//      1a - 1f     | 2 - 7     | 32 - 37
+
+function bitsToChar (b) {
+  return ~((b - 0x00) | (0x19 - b)) >> 8 & (b + 0x41) // 0x41 - 0x00
+       | ~((b - 0x1a) | (0x1f - b)) >> 8 & (b + 0x18) // 0x32 - 0x1a
+}
+
+function charToBits (c) {
+  return ~((c - 0x41) | (0x5a - c)) >> 8 & (c - 0x41) // 0x00 - 0x41
+       | ~((c - 0x61) | (0x7a - c)) >> 8 & (c - 0x61) // 0x00 - 0x61
+       | ~((c - 0x32) | (0x37 - c)) >> 8 & (c - 0x18) // 0x1a - 0x32
+}
+
+module.exports = Base32

test/base32_test.js

@@ -0,0 +1,41 @@
+'use strict'
+
+const base32 = require('../lib/base32')
+const { randomBytes, assertBuffer, HELLO_WORLD } = require('./utils')
+const { assert } = require('chai')
+
+describe('base32', () => {
+  it('encodes to base32', () => {
+    assert.equal(base32.encode(HELLO_WORLD), 'NBSWY3DPEB3W64TMMQ======')
+  })
+
+  it('decodes a string from base32', () => {
+    let buf = base32.decode('NBSWY3DPEB3W64TMMQ======')
+    assertBuffer(buf, HELLO_WORLD)
+  })
+
+  it('decodes from lowercase base32', () => {
+    let buf = base32.decode('nbswy3dpeb3w64tmmq======')
+    assertBuffer(buf, HELLO_WORLD)
+  })
+
+  it('decodes arbitrary bytes from base32', () => {
+    let buf = base32.decode('AAS5T6NYGDF72NPX')
+    let bytes = [0x00, 0x25, 0xd9, 0xf9, 0xb8, 0x30, 0xcb, 0xfd, 0x35, 0xf7]
+    assertBuffer(buf, bytes)
+    assert.equal(base32.encode(buf), 'AAS5T6NYGDF72NPX')
+  })
+
+  it('converts to and from base32', () => {
+    for (let i = 0; i < 100; i++) {
+      let buf = randomBytes(200)
+
+      let str = base32.encode(buf)
+      assert.equal(str.length, 8 * Math.ceil(buf.length / 5))
+      assert.match(str, /^[A-Z2-7]*={0,7}$/)
+
+      let parsed = base32.decode(str)
+      assertBuffer(parsed, buf)
+    }
+  })
+})