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Diffstat (limited to 'contracts/utils/contracts/src/LibAddressArray.sol')
-rw-r--r-- | contracts/utils/contracts/src/LibAddressArray.sol | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/contracts/utils/contracts/src/LibAddressArray.sol b/contracts/utils/contracts/src/LibAddressArray.sol new file mode 100644 index 000000000..892c486f1 --- /dev/null +++ b/contracts/utils/contracts/src/LibAddressArray.sol @@ -0,0 +1,84 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; + +import "./LibBytes.sol"; + + +library LibAddressArray { + + /// @dev Append a new address to an array of addresses. + /// The `addressArray` may need to be reallocated to make space + /// for the new address. Because of this we return the resulting + /// memory location of `addressArray`. + /// @param addressToAppend Address to append. + /// @return Array of addresses: [... addressArray, addressToAppend] + function append(address[] memory addressArray, address addressToAppend) + internal pure + returns (address[]) + { + // Get stats on address array and free memory + uint256 freeMemPtr = 0; + uint256 addressArrayBeginPtr = 0; + uint256 addressArrayEndPtr = 0; + uint256 addressArrayLength = addressArray.length; + uint256 addressArrayMemSizeInBytes = 32 + (32 * addressArrayLength); + assembly { + freeMemPtr := mload(0x40) + addressArrayBeginPtr := addressArray + addressArrayEndPtr := add(addressArray, addressArrayMemSizeInBytes) + } + + // Cases for `freeMemPtr`: + // `freeMemPtr` == `addressArrayEndPtr`: Nothing occupies memory after `addressArray` + // `freeMemPtr` > `addressArrayEndPtr`: Some value occupies memory after `addressArray` + // `freeMemPtr` < `addressArrayEndPtr`: Memory has not been managed properly. + require( + freeMemPtr >= addressArrayEndPtr, + "INVALID_FREE_MEMORY_PTR" + ); + + // If free memory begins at the end of `addressArray` + // then we can append `addressToAppend` directly. + // Otherwise, we must copy the array to free memory + // before appending new values to it. + if (freeMemPtr > addressArrayEndPtr) { + LibBytes.memCopy(freeMemPtr, addressArrayBeginPtr, addressArrayMemSizeInBytes); + assembly { + addressArray := freeMemPtr + addressArrayBeginPtr := addressArray + } + } + + // Append `addressToAppend` + addressArrayLength += 1; + addressArrayMemSizeInBytes += 32; + addressArrayEndPtr = addressArrayBeginPtr + addressArrayMemSizeInBytes; + freeMemPtr = addressArrayEndPtr; + assembly { + // Store new array length + mstore(addressArray, addressArrayLength) + + // Update `freeMemPtr` + mstore(0x40, freeMemPtr) + } + addressArray[addressArrayLength - 1] = addressToAppend; + return addressArray; + } +} |