feat[contracts]: Replace Lib_RingBuffer with a much simpler Lib_Buffer (#821)

* feat[contracts]: replace Lib_RingBuffer with a simpler Lib_Buffer

* chore: changeset

* test: add tests for Lib_Buffer

* lint: fix

* test: add extra coverage for Lib_Buffer

* Update packages/contracts/contracts/optimistic-ethereum/libraries/utils/Lib_Buffer.sol
Co-authored-by: ben-chain <ben@pseudonym.party>

* add some extra comments
Co-authored-by: ben-chain <ben@pseudonym.party>

.changeset/fair-donuts-lick.md

+---
+'@eth-optimism/contracts': patch
+---
+
+Replaces RingBuffer with a simpler Buffer library

packages/contracts/contracts/optimistic-ethereum/OVM/chain/OVM_ChainStorageContainer.sol

@@ -2,7 +2,7 @@
 pragma solidity >0.5.0 <0.8.0;
 
 /* Library Imports */
-import { Lib_RingBuffer } from "../../libraries/utils/Lib_RingBuffer.sol";
+import { Lib_Buffer } from "../../libraries/utils/Lib_Buffer.sol";
 import { Lib_AddressResolver } from "../../libraries/resolver/Lib_AddressResolver.sol";
 
 /* Interface Imports */
@@ -28,7 +28,7 @@ contract OVM_ChainStorageContainer is iOVM_ChainStorageContainer, Lib_AddressRes
      * Libraries *
      *************/
 
-    using Lib_RingBuffer for Lib_RingBuffer.RingBuffer;
+    using Lib_Buffer for Lib_Buffer.Buffer;
 
 
     /*************
@@ -36,7 +36,7 @@ contract OVM_ChainStorageContainer is iOVM_ChainStorageContainer, Lib_AddressRes
      *************/
 
     string public owner;
-    Lib_RingBuffer.RingBuffer internal buffer;
+    Lib_Buffer.Buffer internal buffer;
 
 
     /***************
@@ -189,17 +189,4 @@ contract OVM_ChainStorageContainer is iOVM_ChainStorageContainer, Lib_AddressRes
             _globalMetadata
         );
     }
-
-    /**
-     * @inheritdoc iOVM_ChainStorageContainer
-     */
-    function setNextOverwritableIndex(
-        uint256 _index
-    )
-        override
-        public
-        onlyOwner
-    {
-        buffer.nextOverwritableIndex = _index;
-    }
 }

packages/contracts/contracts/optimistic-ethereum/iOVM/chain/iOVM_ChainStorageContainer.sol

@@ -99,13 +99,4 @@ interface iOVM_ChainStorageContainer {
         bytes27 _globalMetadata
     )
         external;
-
-    /**
-     * Marks an index as overwritable, meaing the underlying buffer can start to write values over
-     * any objects before and including the given index.
-     */
-    function setNextOverwritableIndex(
-        uint256 _index
-    )
-        external;
 }

packages/contracts/contracts/test-libraries/utils/TestLib_RingBuffer.sol → packages/contracts/contracts/test-libraries/utils/TestLib_Buffer.sol

@@ -3,15 +3,15 @@ pragma solidity >0.5.0 <0.8.0;
 pragma experimental ABIEncoderV2;
 
 /* Library Imports */
-import { Lib_RingBuffer } from "../../optimistic-ethereum/libraries/utils/Lib_RingBuffer.sol";
+import { Lib_Buffer } from "../../optimistic-ethereum/libraries/utils/Lib_Buffer.sol";
 
 /**
- * @title TestLib_RingBuffer
+ * @title TestLib_Buffer
  */
-contract TestLib_RingBuffer {
-    using Lib_RingBuffer for Lib_RingBuffer.RingBuffer;
+contract TestLib_Buffer {
+    using Lib_Buffer for Lib_Buffer.Buffer;
 
-    Lib_RingBuffer.RingBuffer internal buf;
+    Lib_Buffer.Buffer internal buf;
 
     function push(
         bytes32 _value,
@@ -37,11 +37,21 @@ contract TestLib_RingBuffer {
         return buf.get(_index);
     }
 
+    function deleteElementsAfterInclusive(
+        uint40 _index
+    )
+        public
+    {
+        return buf.deleteElementsAfterInclusive(
+            _index
+        );
+    }
+
     function deleteElementsAfterInclusive(
         uint40 _index,
         bytes27 _extraData
     )
-        internal
+        public
     {
         return buf.deleteElementsAfterInclusive(
             _index,
@@ -50,7 +60,7 @@ contract TestLib_RingBuffer {
     }
 
     function getLength()
-        internal
+        public
         view
         returns (
             uint40
@@ -59,8 +69,18 @@ contract TestLib_RingBuffer {
         return buf.getLength();
     }
 
+    function setExtraData(
+        bytes27 _extraData
+    )
+        public
+    {
+        return buf.setExtraData(
+            _extraData
+        );
+    }
+
     function getExtraData()
-        internal
+        public
         view
         returns (
             bytes27

packages/contracts/test/contracts/libraries/utils/Lib_Buffer.spec.ts

+import { expect } from '../../../setup'
+
+import hre from 'hardhat'
+import { Contract, ethers } from 'ethers'
+
+describe('Lib_Buffer', () => {
+  let Lib_Buffer: Contract
+  beforeEach(async () => {
+    const Factory__Lib_Buffer = await hre.ethers.getContractFactory(
+      'TestLib_Buffer'
+    )
+    Lib_Buffer = await Factory__Lib_Buffer.deploy()
+  })
+
+  describe('push', () => {
+    for (const len of [1, 2, 4, 8, 32]) {
+      it(`it should be able to add ${len} element(s) to the array`, async () => {
+        for (let i = 0; i < len; i++) {
+          await expect(
+            Lib_Buffer.push(
+              ethers.utils.keccak256(`0x${i.toString(16).padStart(16, '0')}`),
+              `0x${'00'.repeat(27)}`
+            )
+          ).to.not.be.reverted
+        }
+      })
+    }
+  })
+
+  describe('get', () => {
+    for (const len of [1, 2, 4, 8, 32]) {
+      describe(`when the array has ${len} element(s)`, () => {
+        const values = []
+        beforeEach(async () => {
+          for (let i = 0; i < len; i++) {
+            const value = ethers.utils.keccak256(
+              `0x${i.toString(16).padStart(16, '0')}`
+            )
+            values.push(value)
+            await Lib_Buffer.push(value, `0x${'00'.repeat(27)}`)
+          }
+        })
+
+        for (let i = 0; i < len; i += Math.max(1, len / 4)) {
+          it(`should be able to get the ${i}th/st/rd/whatever value`, async () => {
+            expect(await Lib_Buffer.get(i)).to.equal(values[i])
+          })
+        }
+
+        it('should throw if attempting to access an element that does not exist', async () => {
+          await expect(Lib_Buffer.get(len + 1)).to.be.reverted
+        })
+      })
+    }
+  })
+
+  describe('getLength', () => {
+    it('should return zero by default', async () => {
+      expect(await Lib_Buffer.getLength()).to.equal(0)
+    })
+
+    for (const len of [1, 2, 4, 8, 32]) {
+      describe(`when the array has ${len} element(s)`, () => {
+        const values = []
+        beforeEach(async () => {
+          for (let i = 0; i < len; i++) {
+            const value = ethers.utils.keccak256(
+              `0x${i.toString(16).padStart(16, '0')}`
+            )
+            values.push(value)
+            await Lib_Buffer.push(value, `0x${'00'.repeat(27)}`)
+          }
+        })
+
+        it(`should return a value of ${len}`, async () => {
+          expect(await Lib_Buffer.getLength()).to.equal(len)
+        })
+      })
+    }
+  })
+
+  describe('getExtraData', () => {
+    it('should be bytes27(0) by default', async () => {
+      expect(await Lib_Buffer.getExtraData()).to.equal(`0x${'00'.repeat(27)}`)
+    })
+
+    it('should change if set by a call to push()', async () => {
+      const extraData = `0x${'11'.repeat(27)}`
+      await Lib_Buffer.push(ethers.utils.keccak256('0x00'), extraData)
+
+      expect(await Lib_Buffer.getExtraData()).to.equal(extraData)
+    })
+
+    it('should change if set multiple times', async () => {
+      await Lib_Buffer.push(
+        ethers.utils.keccak256('0x00'),
+        `0x${'11'.repeat(27)}`
+      )
+
+      const extraData = `0x${'22'.repeat(27)}`
+
+      await Lib_Buffer.push(ethers.utils.keccak256('0x00'), extraData)
+
+      expect(await Lib_Buffer.getExtraData()).to.equal(extraData)
+    })
+  })
+
+  describe('setExtraData', () => {
+    it('should modify the extra data', async () => {
+      const extraData = `0x${'11'.repeat(27)}`
+      await Lib_Buffer.setExtraData(extraData)
+
+      expect(await Lib_Buffer.getExtraData()).to.equal(extraData)
+    })
+
+    it('should be able to modify the extra data multiple times', async () => {
+      const extraData1 = `0x${'22'.repeat(27)}`
+      await Lib_Buffer.setExtraData(extraData1)
+      expect(await Lib_Buffer.getExtraData()).to.equal(extraData1)
+
+      const extraData2 = `0x${'11'.repeat(27)}`
+      await Lib_Buffer.setExtraData(extraData2)
+
+      expect(await Lib_Buffer.getExtraData()).to.equal(extraData2)
+    })
+  })
+
+  describe('deleteElementsAfterInclusive', () => {
+    it('should revert when the array is empty', async () => {
+      await expect(Lib_Buffer['deleteElementsAfterInclusive(uint40)'](0)).to.be
+        .reverted
+    })
+
+    for (const len of [1, 2, 4, 8, 32]) {
+      describe(`when the array has ${len} element(s)`, () => {
+        const values = []
+        beforeEach(async () => {
+          for (let i = 0; i < len; i++) {
+            const value = ethers.utils.keccak256(
+              `0x${i.toString(16).padStart(16, '0')}`
+            )
+            values.push(value)
+            await Lib_Buffer.push(value, `0x${'00'.repeat(27)}`)
+          }
+        })
+
+        for (let i = len - 1; i > 0; i -= Math.max(1, len / 4)) {
+          it(`should be able to delete everything after and including the ${i}th/st/rd/whatever element`, async () => {
+            await expect(Lib_Buffer['deleteElementsAfterInclusive(uint40)'](i))
+              .to.not.be.reverted
+
+            expect(await Lib_Buffer.getLength()).to.equal(i)
+            await expect(Lib_Buffer.get(i)).to.be.reverted
+          })
+        }
+
+        for (let i = len - 1; i > 0; i -= Math.max(1, len / 4)) {
+          it(`should be able to delete after and incl. ${i}th/st/rd/whatever element while changing extra data`, async () => {
+            const extraData = `0x${i.toString(16).padStart(54, '0')}`
+            await expect(
+              Lib_Buffer['deleteElementsAfterInclusive(uint40,bytes27)'](
+                i,
+                extraData
+              )
+            ).to.not.be.reverted
+
+            expect(await Lib_Buffer.getLength()).to.equal(i)
+            await expect(Lib_Buffer.get(i)).to.be.reverted
+            expect(await Lib_Buffer.getExtraData()).to.equal(extraData)
+          })
+        }
+      })
+    }
+  })
+})