Add reverseBits operations to Bytes.sol (#5724)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

test/utils/Bytes.test.js

@@ -1,6 +1,14 @@
 const { ethers } = require('hardhat');
 const { expect } = require('chai');
 const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+const { MAX_UINT128, MAX_UINT64, MAX_UINT32, MAX_UINT16 } = require('../helpers/constants');
+
+// Helper functions for fixed bytes types
+const bytes32 = value => ethers.toBeHex(value, 32);
+const bytes16 = value => ethers.toBeHex(value, 16);
+const bytes8 = value => ethers.toBeHex(value, 8);
+const bytes4 = value => ethers.toBeHex(value, 4);
+const bytes2 = value => ethers.toBeHex(value, 2);
 
 async function fixture() {
   const mock = await ethers.deployContract('$Bytes');
@@ -85,4 +93,120 @@ describe('Bytes', function () {
       }
     });
   });
+
+  describe('reverseBits', function () {
+    describe('reverseBytes32', function () {
+      it('reverses bytes correctly', async function () {
+        await expect(this.mock.$reverseBytes32(bytes32(0))).to.eventually.equal(bytes32(0));
+        await expect(this.mock.$reverseBytes32(bytes32(ethers.MaxUint256))).to.eventually.equal(
+          bytes32(ethers.MaxUint256),
+        );
+
+        // Test complex pattern that clearly shows byte reversal
+        await expect(
+          this.mock.$reverseBytes32('0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef'),
+        ).to.eventually.equal('0xefcdab8967452301efcdab8967452301efcdab8967452301efcdab8967452301');
+      });
+
+      it('double reverse returns original', async function () {
+        const values = [0n, 1n, 0x12345678n, ethers.MaxUint256];
+        for (const value of values) {
+          const reversed = await this.mock.$reverseBytes32(bytes32(value));
+          await expect(this.mock.$reverseBytes32(reversed)).to.eventually.equal(bytes32(value));
+        }
+      });
+    });
+
+    describe('reverseBytes16', function () {
+      it('reverses bytes correctly', async function () {
+        await expect(this.mock.$reverseBytes16(bytes16(0))).to.eventually.equal(bytes16(0));
+        await expect(this.mock.$reverseBytes16(bytes16(MAX_UINT128))).to.eventually.equal(bytes16(MAX_UINT128));
+
+        // Test complex pattern that clearly shows byte reversal
+        await expect(this.mock.$reverseBytes16('0x0123456789abcdef0123456789abcdef')).to.eventually.equal(
+          '0xefcdab8967452301efcdab8967452301',
+        );
+      });
+
+      it('double reverse returns original', async function () {
+        const values = [0n, 1n, 0x12345678n, MAX_UINT128];
+        for (const value of values) {
+          const reversed = await this.mock.$reverseBytes16(bytes16(value));
+          // Cast back to uint128 for comparison since function returns uint256
+          await expect(this.mock.$reverseBytes16(reversed)).to.eventually.equal(bytes16(value & MAX_UINT128));
+        }
+      });
+    });
+
+    describe('reverseBytes8', function () {
+      it('reverses bytes correctly', async function () {
+        await expect(this.mock.$reverseBytes8(bytes8(0))).to.eventually.equal(bytes8(0));
+        await expect(this.mock.$reverseBytes8(bytes8(MAX_UINT64))).to.eventually.equal(bytes8(MAX_UINT64));
+
+        // Test known pattern: 0x123456789ABCDEF0 -> 0xF0DEBC9A78563412
+        await expect(this.mock.$reverseBytes8('0x123456789abcdef0')).to.eventually.equal('0xf0debc9a78563412');
+      });
+
+      it('double reverse returns original', async function () {
+        const values = [0n, 1n, 0x12345678n, MAX_UINT64];
+        for (const value of values) {
+          const reversed = await this.mock.$reverseBytes8(bytes8(value));
+          // Cast back to uint64 for comparison since function returns uint256
+          await expect(this.mock.$reverseBytes8(reversed)).to.eventually.equal(bytes8(value & MAX_UINT64));
+        }
+      });
+    });
+
+    describe('reverseBytes4', function () {
+      it('reverses bytes correctly', async function () {
+        await expect(this.mock.$reverseBytes4(bytes4(0))).to.eventually.equal(bytes4(0));
+        await expect(this.mock.$reverseBytes4(bytes4(MAX_UINT32))).to.eventually.equal(bytes4(MAX_UINT32));
+
+        // Test known pattern: 0x12345678 -> 0x78563412
+        await expect(this.mock.$reverseBytes4(bytes4(0x12345678))).to.eventually.equal(bytes4(0x78563412));
+      });
+
+      it('double reverse returns original', async function () {
+        const values = [0n, 1n, 0x12345678n, MAX_UINT32];
+        for (const value of values) {
+          const reversed = await this.mock.$reverseBytes4(bytes4(value));
+          // Cast back to uint32 for comparison since function returns uint256
+          await expect(this.mock.$reverseBytes4(reversed)).to.eventually.equal(bytes4(value & MAX_UINT32));
+        }
+      });
+    });
+
+    describe('reverseBytes2', function () {
+      it('reverses bytes correctly', async function () {
+        await expect(this.mock.$reverseBytes2(bytes2(0))).to.eventually.equal(bytes2(0));
+        await expect(this.mock.$reverseBytes2(bytes2(MAX_UINT16))).to.eventually.equal(bytes2(MAX_UINT16));
+
+        // Test known pattern: 0x1234 -> 0x3412
+        await expect(this.mock.$reverseBytes2(bytes2(0x1234))).to.eventually.equal(bytes2(0x3412));
+      });
+
+      it('double reverse returns original', async function () {
+        const values = [0n, 1n, 0x1234n, MAX_UINT16];
+        for (const value of values) {
+          const reversed = await this.mock.$reverseBytes2(bytes2(value));
+          // Cast back to uint16 for comparison since function returns uint256
+          await expect(this.mock.$reverseBytes2(reversed)).to.eventually.equal(bytes2(value & MAX_UINT16));
+        }
+      });
+    });
+
+    describe('edge cases', function () {
+      it('handles single byte values', async function () {
+        await expect(this.mock.$reverseBytes2(bytes2(0x00ff))).to.eventually.equal(bytes2(0xff00));
+        await expect(this.mock.$reverseBytes4(bytes4(0x000000ff))).to.eventually.equal(bytes4(0xff000000));
+      });
+
+      it('handles alternating patterns', async function () {
+        await expect(this.mock.$reverseBytes2(bytes2(0xaaaa))).to.eventually.equal(bytes2(0xaaaa));
+        await expect(this.mock.$reverseBytes2(bytes2(0x5555))).to.eventually.equal(bytes2(0x5555));
+        await expect(this.mock.$reverseBytes4(bytes4(0xaaaaaaaa))).to.eventually.equal(bytes4(0xaaaaaaaa));
+        await expect(this.mock.$reverseBytes4(bytes4(0x55555555))).to.eventually.equal(bytes4(0x55555555));
+      });
+    });
+  });
 });