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NOTES:

Solidity code -> compiles to bytecode -> EVM can understand only bytecode and process the instructions in Assembly.

  1. get the amount of ether stored in this contract
uint amount = address(this).balance;
  1. send ether to other address
address payable public owner;

uint amount = address(this).balance; // get total balance of ether in current SC
(bool success,) = owner.call{value: amount}("");
require(sucess,"Failed to  send ether to owner")

Caller methods

msg.data (bytes): complete calldata
msg.gas (uint): remaining gas.
msg.sender (address): send of the message (current call) : address of the caller or sender to sended eth to our SC address.
msg.sig (bytes4): first four bytes of  the calldata
msg.value (uint): number of wei send with the message : number of wei sent by the caller.

msg.value is automatically set to the amount of ether sent with that payable function.

gasleft() : (uint) : number of remaining gas


address(0) -> is same as 0x0 an uniniatialized address ex: 0x0000000000000000
balances[address(0)] then means how many tokens the address 0 (0x00000000...00) owns.

address(this) -> address of the current Smart contract deployed.
address(this).balance -> total balance amount of the current smart contract

Transactions properities :

block.number (uint) : current block number
block.timestamp (uint) : current block timestamp as seconds since uinx epoch
block.gaslimit  (uint) : current block gaslimit
block.difficuly (uint) : current block difficulty
block.coinbase  (address) : current block miner's address

block.blockhash(uint blockNumber) returns (bytes32) : takes blocknumber as input, returns hash of the given block.

now(uint) : current block timestampt, same to (block.timestamp)

tx.gasprice (uint) : gas price of the transaction
tx.origin (address) : sender of the transaction address


msg.sender.transfer(1000); // transfer the 1000 wei from SC to the caller address who called the function
msg.sender.transfer(address(this).balance) // transfer all the SC balance amount to  the function caller address.
  • ABI works similar like api, to call functions,variables to get information about those

call function has a api called "abi.encodeWithSignature"

first arg: is function structure along with arguments.
second arg: arguments values 

1. _addr.call{value:msg.value,gas:5000}(
	abi.encodeWithSignature("somepublicfunction(string,uint256)","this is a string",1337) 
)

Hashing:

Keccak-256

  • Like any hash, it has an infinite input space. This enables one to "make a hash" of a super large file. The hash should entirely change if a single bit of data in the source is different - unlike say a CRC32, or a checksum. It means your password could be a million chars long maybe. It's stored on disk as a hash, much smaller in size. fixed length

https://emn178.github.io/online-tools/keccak_256.html

https://www.w3schools.com/java/java_data_types.asp -> boolean takes 1 bit

Bitfields are to used memory in more efficient way:

In solidity bool is stored in 1byte(8 bits), However single bit can actually used.
hex value of true is 0x01 and false is 0x00 converted to binary these are 00000001 and 00000000 where 7 of the total 8 bits are not used.