calldata

• CALLDATASIZE tells the size of the transaction data.

• CALLDATALOAD loads 32 bytes of the transaction data onto the stack.

• CALLDATACOPY copies a number of bytes of the transaction data to memory.

• https://betterprogramming.pub/solidity-tutorial-all-about-calldata-aebbe998a5fc

• offset is the position in the calldata where the actual data of the array starts, i.e. where the first array element is located. Let's take an example:

• https://medium.com/swlh/getting-deep-into-evm-how-ethereum-works-backstage-ab6ad9c0d0bf

• https://betterprogramming.pub/solidity-tutorial-all-about-calldata-aebbe998a5fc

• https://medium.com/@kalexotsu/understanding-solidity-assembly-hashing-a-string-from-calldata-fbd2ece82263

calldataload

• calldataload is the EVM opcode for getting 32 bytes from calldata.

• The parameter to calldataload is an offset: typically the first 4 bytes of calldata is a function selector, so calldataload(4) is used to get the 32 bytes starting from the fifth byte

• https://ethereum.stackexchange.com/questions/77475/what-data-is-in-calldataload