Add actual real-test data, detect bitLength (#282)

* Add actual real-test data, detect bitLength

* Cleanup misplaced log

* Cleanup test, no length passed

packages/util/src/compact/addLength.ts

@@ -2,10 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { BitLength } from './types';
-
 import { u8aConcat } from '../u8a';
-import { DEFAULT_BITLENGTH } from './defaults';
 import compactToU8a from './toU8a';
 
 /**
@@ -20,9 +17,9 @@ import compactToU8a from './toU8a';
  * console.log(compactAddLength(new Uint8Array([0xde, 0xad, 0xbe, 0xef]))); // Uint8Array([4 << 2, 0xde, 0xad, 0xbe, 0xef])
  * ```
  */
-export default function compactAddLength (input: Uint8Array, bitLength: BitLength = DEFAULT_BITLENGTH): Uint8Array {
+export default function compactAddLength (input: Uint8Array): Uint8Array {
   return u8aConcat(
-    compactToU8a(input.length, bitLength),
+    compactToU8a(input.length),
     input
   );
 }

packages/util/src/compact/fromU8a.spec.ts

@@ -4,6 +4,7 @@
 
 import BN from 'bn.js';
 
+import hexToU8a from '../hex/toU8a';
 import compactFromU8a from './fromU8a';
 
 describe('compactFromU8a', () => {
@@ -36,4 +37,12 @@ describe('compactFromU8a', () => {
       compactFromU8a(new Uint8Array([3 + ((4 - 4) << 2), 249, 255, 255, 255]), 64)
     ).toEqual([5, new BN(0xfffffff9)]);
   });
+
+  it('decodes an actual value', () => {
+    expect(
+      compactFromU8a(
+        hexToU8a('0x0b00407a10f35a')
+      )
+    ).toEqual([7, new BN('5af3107a4000', 16)]);
+  });
 });

packages/util/src/compact/toU8a.spec.ts

@@ -9,7 +9,7 @@ import compactToU8a from './toU8a';
 describe('encode', () => {
   it('encodes short u8', () => {
     expect(
-      compactToU8a(18, 8)
+      compactToU8a(18)
     ).toEqual(
       new Uint8Array([18 << 2])
     );
@@ -17,7 +17,7 @@ describe('encode', () => {
 
   it('encodes max u8 values', () => {
     expect(
-      compactToU8a(new BN(63), 16)
+      compactToU8a(new BN(63))
     ).toEqual(
       new Uint8Array([0b11111100])
     );
@@ -25,7 +25,7 @@ describe('encode', () => {
 
   it('encodes basic u16 value', () => {
     expect(
-      compactToU8a(511, 32)
+      compactToU8a(511)
     ).toEqual(
       new Uint8Array([0b11111101, 0b00000111])
     );
@@ -33,7 +33,7 @@ describe('encode', () => {
 
   it('encodes basic u16 (not at edge)', () => {
     expect(
-      compactToU8a(111, 32)
+      compactToU8a(111)
     ).toEqual(
       new Uint8Array([0xbd, 0x01])
     );
@@ -41,7 +41,7 @@ describe('encode', () => {
 
   it('encodes basic u32 values (short)', () => {
     expect(
-      compactToU8a(0xffff, 32)
+      compactToU8a(0xffff)
     ).toEqual(
       new Uint8Array([254, 255, 3, 0])
     );
@@ -54,4 +54,14 @@ describe('encode', () => {
       new Uint8Array([3 + ((4 - 4) << 2), 249, 255, 255, 255])
     );
   });
+
+  it('encodes a large value', () => {
+    expect(
+      compactToU8a(
+        new BN('5af3107a4000', 16)
+      )
+    ).toEqual(
+      new Uint8Array([3 + ((6 - 4) << 2), 0x00, 0x40, 0x7a, 0x10, 0xf3, 0x5a])
+    );
+  });
 });

packages/util/src/compact/toU8a.ts

@@ -2,13 +2,10 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { BitLength } from './types';
-
 import BN from 'bn.js';
 
 import { bnToBn, bnToU8a } from '../bn';
 import { u8aConcat } from '../u8a';
-import { DEFAULT_BITLENGTH } from './defaults';
 
 const MAX_U8 = new BN(2).pow(new BN(8 - 2)).subn(1);
 const MAX_U16 = new BN(2).pow(new BN(16 - 2)).subn(1);
@@ -26,7 +23,7 @@ const MAX_U32 = new BN(2).pow(new BN(32 - 2)).subn(1);
  * console.log(compactToU8a(511, 32)); // Uint8Array([0b11111101, 0b00000111])
  * ```
  */
-export default function compactToU8a (_value: BN | number, bitLength: BitLength = DEFAULT_BITLENGTH): Uint8Array {
+export default function compactToU8a (_value: BN | number): Uint8Array {
   const value = bnToBn(_value);
 
   if (value.lte(MAX_U8)) {
@@ -37,11 +34,12 @@ export default function compactToU8a (_value: BN | number, bitLength: BitLength
     return bnToU8a(value.shln(2).addn(0b10), 32, true);
   }
 
+  const bitLength = value.bitLength();
+
   return u8aConcat(
     new Uint8Array([
-      // FIXME For optimal encoding, detemine actual used bit (do not just use max)
-      new BN(bitLength / 8)
-        .subn(4) // at least 4
+      new BN(Math.ceil(bitLength / 8))
+        .subn(4) // 4 bytes as a base
         .shln(2) // clear low
         .addn(0b11) // add flag
         .toNumber()