From cb16004443bb3a958e1ac9a1a316dab198a37aba Mon Sep 17 00:00:00 2001
From: b00ste <daniel@lukso.io>
Date: Thu, 12 Oct 2023 17:13:32 +0300
Subject: [PATCH] refactor: replace `BytesLib` with assembly block

---
 .../extensions/LSP8CompatibleERC721.sol       | 27 ++++++++++++-------
 .../LSP8CompatibleERC721InitAbstract.sol      | 27 ++++++++++++-------
 2 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721.sol b/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721.sol
index 6136f4cf1..dc82cb0e0 100644
--- a/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721.sol
+++ b/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721.sol
@@ -102,15 +102,24 @@ abstract contract LSP8CompatibleERC721 is
         uint256 /* tokenId */
     ) public view virtual returns (string memory) {
         bytes memory data = _getData(_LSP4_METADATA_KEY);
-
-        // offset = bytes4(hashSig) + bytes32(contentHash) -> 4 + 32 = 36
-        uint256 offset = 36;
-
-        bytes memory uriBytes = BytesLib.slice(
-            data,
-            offset,
-            data.length - offset
-        );
+        uint256 requiredLength = data.length - 36;
+
+        bytes memory uriBytes;
+        assembly {
+            uriBytes := mload(0x40)
+            mstore(uriBytes, requiredLength)
+            for {
+                let i := 0
+            } lt(i, requiredLength) {
+                i := add(i, 0x20)
+            } {
+                mstore(
+                    add(uriBytes, add(i, 0x20)),
+                    mload(add(data, add(i, 68)))
+                )
+            }
+            mstore(0x40, add(uriBytes, add(0x20, requiredLength)))
+        }
         return string(uriBytes);
     }
 
diff --git a/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721InitAbstract.sol b/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721InitAbstract.sol
index 851a0e361..60ef44e97 100644
--- a/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721InitAbstract.sol
+++ b/contracts/LSP8IdentifiableDigitalAsset/extensions/LSP8CompatibleERC721InitAbstract.sol
@@ -110,15 +110,24 @@ abstract contract LSP8CompatibleERC721InitAbstract is
         uint256 /* tokenId */
     ) public view virtual returns (string memory) {
         bytes memory data = _getData(_LSP4_METADATA_KEY);
-
-        // offset = bytes4(hashSig) + bytes32(contentHash) -> 4 + 32 = 36
-        uint256 offset = 36;
-
-        bytes memory uriBytes = BytesLib.slice(
-            data,
-            offset,
-            data.length - offset
-        );
+        uint256 requiredLength = data.length - 36;
+
+        bytes memory uriBytes;
+        assembly {
+            uriBytes := mload(0x40)
+            mstore(uriBytes, requiredLength)
+            for {
+                let i := 0
+            } lt(i, requiredLength) {
+                i := add(i, 0x20)
+            } {
+                mstore(
+                    add(uriBytes, add(i, 0x20)),
+                    mload(add(data, add(i, 68)))
+                )
+            }
+            mstore(0x40, add(uriBytes, add(0x20, requiredLength)))
+        }
         return string(uriBytes);
     }