feat(core): mol.padding for padding codec

Author: Hanssen0

.changeset/fair-items-shout.md

@@ -0,0 +1,6 @@
+---
+"@ckb-ccc/core": minor
+---
+
+feat(core): `mol.padding` for padding codec
+  

packages/core/src/ckb/epoch.test.ts

@@ -99,13 +99,13 @@ describe("Epoch", () => {
     expect(c.denominator).toBe(e.denominator);
   });
 
-  it("genesis and oneNervosDaoCycle helpers", () => {
-    const g = Epoch.genesis();
+  it("Genesis and OneNervosDaoCycle helpers", () => {
+    const g = Epoch.Genesis;
     expect(g.integer).toBe(0n);
     expect(g.numerator).toBe(0n);
     expect(g.denominator).toBe(0n);
 
-    const o = Epoch.oneNervosDaoCycle();
+    const o = Epoch.OneNervosDaoCycle;
     expect(o.integer).toBe(180n);
     expect(o.numerator).toBe(0n);
     expect(o.denominator).toBe(1n);

packages/core/src/ckb/epoch.ts

@@ -56,14 +56,10 @@ export type EpochLike =
  */
 @mol.codec(
   mol.struct({
-    padding: mol.Codec.from({
-      byteLength: 1,
-      encode: (_) => new Uint8Array(1),
-      decode: (_) => "0x00",
-    }),
-    denominator: mol.uint(2, false),
-    numerator: mol.uint(2, false),
-    integer: mol.uint(3, false),
+    padding: mol.padding(1),
+    denominator: mol.uint(2),
+    numerator: mol.uint(2),
+    integer: mol.uint(3),
   }),
 )
 export class Epoch extends mol.Entity.Base<EpochLike, Epoch>() {
@@ -290,7 +286,7 @@ export class Epoch extends mol.Entity.Base<EpochLike, Epoch>() {
    *
    * @returns Epoch with integer = 0, numerator = 0, denominator = 0.
    */
-  static genesis(): Epoch {
+  static get Genesis(): Epoch {
     return new Epoch(Zero, Zero, Zero);
   }
 
@@ -299,7 +295,7 @@ export class Epoch extends mol.Entity.Base<EpochLike, Epoch>() {
    *
    * @returns Epoch equal to 180 with denominator set to 1 to represent an exact whole unit.
    */
-  static oneNervosDaoCycle(): Epoch {
+  static get OneNervosDaoCycle(): Epoch {
     return new Epoch(numFrom(180), Zero, numFrom(1));
   }
 

packages/core/src/molecule/codec.ts

@@ -718,3 +718,20 @@ export function uintNumber(
     outMap: (num) => Number(num),
   });
 }
+
+/**
+ * Create a codec for padding bytes.
+ * The padding bytes are zero-filled when encoding and ignored when decoding.
+ * @param byteLength The length of the padding in bytes.
+ */
+export function padding(
+  byteLength: number,
+): Codec<void | undefined | null, void> {
+  return Codec.from({
+    byteLength,
+    encode: () => {
+      return new Uint8Array(byteLength);
+    },
+    decode: () => {},
+  });
+}