v2 payload data length retreival

Changelog.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## 2.0.0
+### Added
+- `payloadLen` returns the length of the data payload
+
+### Changed/Breaking
+- `size` to `rlpLen` returns the size of the rlp payload
+
 ## 1.2.3
 ### Added
 - `toUintStrict` strict uint conversion. Encoded data must be 32 bytes in length

README.md

@@ -23,7 +23,8 @@ Transformations(All take an RLPItem as an arg):
 5. `toUintStrict(RLPItem) uint` : returns the encoded uint. Encoded data must be padded to 32 bytes.
 6. `toBoolean(RLPItem) bool`: returns the encoded boolean
 7. `toRlpBytes(RLPItem) bytes `: returns the raw rlp encoded byte form
-8. `size(RLPItem) uint` : returns the byte length of the rlp item
+8. `rlpLen(RLPItem) uint` : returns the byte length of the rlp item
+9. `payloadLen(RLPItem) uint` : returns the byte length of the data payload
 
 **Note**: The reader contract only provides only these conversion functions. All other solidity data types can be derived from
 this base. For example, a `bytes32` encoded data type is equivalent to `bytes32(toUint(RLPItem))`. Start with a uint and convert from there.

contracts/Helper.sol

@@ -24,9 +24,14 @@ contract Helper {
         return _itemLength(memPtr);
     }
 
-    function size(bytes memory item) public pure returns (uint) {
+    function rlpLen(bytes memory item) public pure returns (uint) {
         RLPReader.RLPItem memory rlpItem = item.toRlpItem();
-        return rlpItem.size();
+        return rlpItem.rlpLen();
+    }
+
+    function payloadLen(bytes memory item) public pure returns (uint) {
+        RLPReader.RLPItem memory rlpItem = item.toRlpItem();
+        return rlpItem.payloadLen();
     }
 
     function numItems(bytes memory item) public pure returns (uint) {

contracts/RLPReader.sol

@@ -32,10 +32,17 @@ library RLPReader {
     /*
     * @param item RLP encoded bytes
     */
-    function size(RLPItem memory item) internal pure returns (uint) {
+    function rlpLen(RLPItem memory item) internal pure returns (uint) {
         return item.len;
     }
 
+    /*
+    * @param item RLP encoded bytes
+    */
+    function payloadLen(RLPItem memory item) internal pure returns (uint) {
+        return item.len - _payloadOffset(item.memPtr);
+    }
+
     /*
     * @param item RLP encoded list in bytes
     */

package.json

@@ -1,7 +1,7 @@
 {
   "name": "solidity-rlp",
   "author": "Hamdi Allam",
-  "version": "1.2.3",
+  "version": "2.0.0",
   "description": "solidity rlp encoder/decoder",
   "keywords": [
     "solidity",

test/basic-tests.js

@@ -78,6 +78,19 @@ contract("RLPReader", async (accounts) => {
         assert(result.toNumber() == 1, "Incorrect calculate rlp item byte length for empty list");
     });
 
+    it("detects the payload length of encoded data", async () => {
+        let result;
+
+        result = await helper.payloadLen.call(toHex(rlp.encode(1)));
+        assert(result.toNumber() == 1, "incorrect payload length of a single byte encoding");
+
+        result = await helper.payloadLen.call(toHex(rlp.encode(toHex(Array(36).fill(0).join('')))));
+        assert(result.toNumber() == 18, "incorrect payload length of a 18 bytes");
+
+        result = await helper.payloadLen.call(toHex(rlp.encode(toHex(Array(200).fill(0).join('')))));
+        assert(result.toNumber() == 100, "incorrect payload length of a 100 bytes");
+    });
+
     it("detects the correct amount of items in a list", async () => {
         let assertString = "Number of items in an rlp encoded list wrongly detected: ";
         let str = [1, 2, 3];