RLP implementation

Former-commit-id: 1a6144cb6f46b16281b79cb999acd838a01cd110 [formerly 42f939e8c110dd9982dbb7db25ef77d64219f2c2]
Former-commit-id: a0ebe69fd061ef85e26f87c02f7e1d4029d79133

sharding/contracts/RLP.sol

@@ -0,0 +1,398 @@
+pragma solidity ^0.4.19;
+
+/**
+* @title RLPReader
+*
+* RLPReader is used to read and parse RLP encoded data in memory.
+*
+* @author Andreas Olofsson (androlo1980@gmail.com)
+*/
+library RLP {
+
+ uint constant DATA_SHORT_START = 0x80;
+ uint constant DATA_LONG_START = 0xB8;
+ uint constant LIST_SHORT_START = 0xC0;
+ uint constant LIST_LONG_START = 0xF8;
+
+ uint constant DATA_LONG_OFFSET = 0xB7;
+ uint constant LIST_LONG_OFFSET = 0xF7;
+
+
+ struct RLPItem {
+     uint _unsafe_memPtr;    // Pointer to the RLP-encoded bytes.
+     uint _unsafe_length;    // Number of bytes. This is the full length of the string.
+ }
+
+ struct Iterator {
+     RLPItem _unsafe_item;   // Item that's being iterated over.
+     uint _unsafe_nextPtr;   // Position of the next item in the list.
+ }
+
+ /* Iterator */
+
+ function next(Iterator memory self) internal pure returns (RLPItem memory subItem) {
+     if(hasNext(self)) {
+         var ptr = self._unsafe_nextPtr;
+         var itemLength = _itemLength(ptr);
+         subItem._unsafe_memPtr = ptr;
+         subItem._unsafe_length = itemLength;
+         self._unsafe_nextPtr = ptr + itemLength;
+     }
+     else
+         revert();
+ }
+
+ function next(Iterator memory self, bool strict) internal pure returns (RLPItem memory subItem) {
+     subItem = next(self);
+     require(!strict || _validate(subItem));
+     return;
+ }
+
+ function hasNext(Iterator memory self) internal pure returns (bool) {
+     var item = self._unsafe_item;
+     return self._unsafe_nextPtr < item._unsafe_memPtr + item._unsafe_length;
+ }
+
+ /* RLPItem */
+
+ /// @dev Creates an RLPItem from an array of RLP encoded bytes.
+ /// @param self The RLP encoded bytes.
+ /// @return An RLPItem
+ function toRLPItem(bytes memory self) internal pure returns (RLPItem memory) {
+     uint len = self.length;
+     if (len == 0) {
+         return RLPItem(0, 0);
+     }
+     uint memPtr;
+     assembly {
+         memPtr := add(self, 0x20)
+     }
+     return RLPItem(memPtr, len);
+ }
+
+ /// @dev Creates an RLPItem from an array of RLP encoded bytes.
+ /// @param self The RLP encoded bytes.
+ /// @param strict Will throw if the data is not RLP encoded.
+ /// @return An RLPItem
+ function toRLPItem(bytes memory self, bool strict) internal pure returns (RLPItem memory) {
+     var item = toRLPItem(self);
+     if(strict) {
+         uint len = self.length;
+         assert(_payloadOffset(item) <= len);
+         assert(_itemLength(item._unsafe_memPtr) == len);
+         assert(_validate(item));
+     }
+     return item;
+ }
+
+ /// @dev Check if the RLP item is null.
+ /// @param self The RLP item.
+ /// @return 'true' if the item is null.
+ function isNull(RLPItem memory self) internal pure returns (bool ret) {
+     return self._unsafe_length == 0;
+ }
+
+ /// @dev Check if the RLP item is a list.
+ /// @param self The RLP item.
+ /// @return 'true' if the item is a list.
+ function isList(RLPItem memory self) internal pure returns (bool ret) {
+     if (self._unsafe_length == 0)
+         return false;
+     uint memPtr = self._unsafe_memPtr;
+     assembly {
+         ret := iszero(lt(byte(0, mload(memPtr)), 0xC0))
+     }
+ }
+
+ /// @dev Check if the RLP item is data.
+ /// @param self The RLP item.
+ /// @return 'true' if the item is data.
+ function isData(RLPItem memory self) internal pure returns (bool ret) {
+     if (self._unsafe_length == 0)
+         return false;
+     uint memPtr = self._unsafe_memPtr;
+     assembly {
+         ret := lt(byte(0, mload(memPtr)), 0xC0)
+     }
+ }
+
+ /// @dev Check if the RLP item is empty (string or list).
+ /// @param self The RLP item.
+ /// @return 'true' if the item is null.
+ function isEmpty(RLPItem memory self) internal pure returns (bool ret) {
+     if(isNull(self))
+         return false;
+     uint b0;
+     uint memPtr = self._unsafe_memPtr;
+     assembly {
+         b0 := byte(0, mload(memPtr))
+     }
+     return (b0 == DATA_SHORT_START || b0 == LIST_SHORT_START);
+ }
+
+ /// @dev Get the number of items in an RLP encoded list.
+ /// @param self The RLP item.
+ /// @return The number of items.
+ function items(RLPItem memory self) internal pure returns (uint) {
+     if (!isList(self))
+         return 0;
+     uint b0;
+     uint memPtr = self._unsafe_memPtr;
+     assembly {
+         b0 := byte(0, mload(memPtr))
+     }
+     uint pos = memPtr + _payloadOffset(self);
+     uint last = memPtr + self._unsafe_length - 1;
+     uint itms;
+     while(pos <= last) {
+         pos += _itemLength(pos);
+         itms++;
+     }
+     return itms;
+ }
+
+ /// @dev Create an iterator.
+ /// @param self The RLP item.
+ /// @return An 'Iterator' over the item.
+ function iterator(RLPItem memory self) internal pure returns (Iterator memory it) {
+   require(isList(self));
+     uint ptr = self._unsafe_memPtr + _payloadOffset(self);
+     it._unsafe_item = self;
+     it._unsafe_nextPtr = ptr;
+ }
+
+ /// @dev Return the RLP encoded bytes.
+ /// @param self The RLPItem.
+ /// @return The bytes.
+ function toBytes(RLPItem memory self) internal constant returns (bytes memory bts) {
+     var len = self._unsafe_length;
+     if (len == 0)
+         return;
+     bts = new bytes(len);
+     _copyToBytes(self._unsafe_memPtr, bts, len);
+ }
+
+ /// @dev Decode an RLPItem into bytes. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toData(RLPItem memory self) internal constant returns (bytes memory bts) {
+     require(isData(self));
+     var (rStartPos, len) = _decode(self);
+     bts = new bytes(len);
+     _copyToBytes(rStartPos, bts, len);
+ }
+
+ /// @dev Get the list of sub-items from an RLP encoded list.
+ /// Warning: This is inefficient, as it requires that the list is read twice.
+ /// @param self The RLP item.
+ /// @return Array of RLPItems.
+ function toList(RLPItem memory self) internal pure returns (RLPItem[] memory list) {
+     require(isList(self));
+     var numItems = items(self);
+     list = new RLPItem[](numItems);
+     var it = iterator(self);
+     uint idx;
+     while(hasNext(it)) {
+         list[idx] = next(it);
+         idx++;
+     }
+ }
+
+ /// @dev Decode an RLPItem into an ascii string. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toAscii(RLPItem memory self) internal constant returns (string memory str) {
+     require(isData(self));
+     var (rStartPos, len) = _decode(self);
+     bytes memory bts = new bytes(len);
+     _copyToBytes(rStartPos, bts, len);
+     str = string(bts);
+ }
+
+ /// @dev Decode an RLPItem into a uint. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toUint(RLPItem memory self) internal pure returns (uint data) {
+     require(isData(self));
+     var (rStartPos, len) = _decode(self);
+     assert(len <= 32 && len != 0);
+     assembly {
+         data := div(mload(rStartPos), exp(256, sub(32, len)))
+     }
+ }
+
+ /// @dev Decode an RLPItem into a boolean. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toBool(RLPItem memory self) internal pure returns (bool data) {
+     require(isData(self));
+     var (rStartPos, len) = _decode(self);
+     assert(len == 1);
+     uint temp;
+     assembly {
+         temp := byte(0, mload(rStartPos))
+     }
+     assert(temp <= 1);
+     return temp == 1 ? true : false;
+ }
+
+ /// @dev Decode an RLPItem into a byte. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toByte(RLPItem memory self) internal pure returns (byte data) {
+     require(isData(self));
+     var (rStartPos, len) = _decode(self);
+     assert(len == 1);
+     uint temp;
+     assembly {
+         temp := byte(0, mload(rStartPos))
+     }
+     return byte(temp);
+ }
+
+ /// @dev Decode an RLPItem into an int. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toInt(RLPItem memory self) internal pure returns (int data) {
+     return int(toUint(self));
+ }
+
+ /// @dev Decode an RLPItem into a bytes32. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toBytes32(RLPItem memory self) internal pure returns (bytes32 data) {
+     return bytes32(toUint(self));
+ }
+
+ /// @dev Decode an RLPItem into an address. This will not work if the
+ /// RLPItem is a list.
+ /// @param self The RLPItem.
+ /// @return The decoded string.
+ function toAddress(RLPItem memory self) internal pure returns (address data) {
+     require(isData(self));
+     var (rStartPos, len) = _decode(self);
+     assert(len == 20);
+     assembly {
+         data := div(mload(rStartPos), exp(256, 12))
+     }
+ }
+
+ // Get the payload offset.
+ function _payloadOffset(RLPItem memory self) private pure returns (uint) {
+     if(self._unsafe_length == 0)
+         return 0;
+     uint b0;
+     uint memPtr = self._unsafe_memPtr;
+     assembly {
+         b0 := byte(0, mload(memPtr))
+     }
+     if(b0 < DATA_SHORT_START)
+         return 0;
+     if(b0 < DATA_LONG_START || (b0 >= LIST_SHORT_START && b0 < LIST_LONG_START))
+         return 1;
+     if(b0 < LIST_SHORT_START)
+         return b0 - DATA_LONG_OFFSET + 1;
+     return b0 - LIST_LONG_OFFSET + 1;
+ }
+
+ // Get the full length of an RLP item.
+ function _itemLength(uint memPtr) private pure returns (uint len) {
+     uint b0;
+     assembly {
+         b0 := byte(0, mload(memPtr))
+     }
+     if (b0 < DATA_SHORT_START)
+         len = 1;
+     else if (b0 < DATA_LONG_START)
+         len = b0 - DATA_SHORT_START + 1;
+     else if (b0 < LIST_SHORT_START) {
+         assembly {
+             let bLen := sub(b0, 0xB7) // bytes length (DATA_LONG_OFFSET)
+             let dLen := div(mload(add(memPtr, 1)), exp(256, sub(32, bLen))) // data length
+             len := add(1, add(bLen, dLen)) // total length
+         }
+     }
+     else if (b0 < LIST_LONG_START)
+         len = b0 - LIST_SHORT_START + 1;
+     else {
+         assembly {
+             let bLen := sub(b0, 0xF7) // bytes length (LIST_LONG_OFFSET)
+             let dLen := div(mload(add(memPtr, 1)), exp(256, sub(32, bLen))) // data length
+             len := add(1, add(bLen, dLen)) // total length
+         }
+     }
+ }
+
+ // Get start position and length of the data.
+ function _decode(RLPItem memory self) private pure returns (uint memPtr, uint len) {
+     require(isData(self));
+     uint b0;
+     uint start = self._unsafe_memPtr;
+     assembly {
+         b0 := byte(0, mload(start))
+     }
+     if (b0 < DATA_SHORT_START) {
+         memPtr = start;
+         len = 1;
+         return;
+     }
+     if (b0 < DATA_LONG_START) {
+         len = self._unsafe_length - 1;
+         memPtr = start + 1;
+     } else {
+         uint bLen;
+         assembly {
+             bLen := sub(b0, 0xB7) // DATA_LONG_OFFSET
+         }
+         len = self._unsafe_length - 1 - bLen;
+         memPtr = start + bLen + 1;
+     }
+     return;
+ }
+
+ // Assumes that enough memory has been allocated to store in target.
+ function _copyToBytes(uint btsPtr, bytes memory tgt, uint btsLen) private constant {
+     // Exploiting the fact that 'tgt' was the last thing to be allocated,
+     // we can write entire words, and just overwrite any excess.
+     assembly {
+         {
+                 let i := 0 // Start at arr + 0x20
+                 let words := div(add(btsLen, 31), 32)
+                 let rOffset := btsPtr
+                 let wOffset := add(tgt, 0x20)
+             tag_loop:
+                 jumpi(end, eq(i, words))
+                 {
+                     let offset := mul(i, 0x20)
+                     mstore(add(wOffset, offset), mload(add(rOffset, offset)))
+                     i := add(i, 1)
+                 }
+                 jump(tag_loop)
+             end:
+                 mstore(add(tgt, add(0x20, mload(tgt))), 0)
+         }
+     }
+ }
+
+ // Check that an RLP item is valid.
+     function _validate(RLPItem memory self) private pure returns (bool ret) {
+         // Check that RLP is well-formed.
+         uint b0;
+         uint b1;
+         uint memPtr = self._unsafe_memPtr;
+         assembly {
+             b0 := byte(0, mload(memPtr))
+             b1 := byte(1, mload(memPtr))
+         }
+         if(b0 == DATA_SHORT_START + 1 && b1 < DATA_SHORT_START)
+             return false;
+         return true;
+     }
+}