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Diffstat (limited to 'docs/units-and-global-variables.rst')
| -rw-r--r-- | docs/units-and-global-variables.rst | 56 |
1 files changed, 37 insertions, 19 deletions
diff --git a/docs/units-and-global-variables.rst b/docs/units-and-global-variables.rst index 8f910c80..167c694d 100644 --- a/docs/units-and-global-variables.rst +++ b/docs/units-and-global-variables.rst @@ -48,22 +48,22 @@ namespace and are mainly used to provide information about the blockchain. Block and Transaction Properties ------------------------------------- - - - ``block.coinbase`` (``address``): current block miner's address - - ``block.difficulty`` (``uint``): current block difficulty - - ``block.gaslimit`` (``uint``): current block gaslimit - - ``block.number`` (``uint``): current block number - - ``block.blockhash`` (``function(uint) returns (bytes32)``): hash of the given block - only for 256 most recent blocks - - ``block.timestamp`` (``uint``): current block timestamp - - ``msg.data`` (``bytes``): complete calldata - - ``msg.gas`` (``uint``): remaining gas - - ``msg.sender`` (``address``): sender of the message (current call) - - ``msg.sig`` (``bytes4``): first four bytes of the calldata (i.e. function identifier) - - ``msg.value`` (``uint``): number of wei sent with the message - - ``now`` (``uint``): current block timestamp (alias for ``block.timestamp``) - - ``tx.gasprice`` (``uint``): gas price of the transaction - - ``tx.origin`` (``address``): sender of the transaction (full call chain) +-------------------------------- + +- ``block.blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent blocks +- ``block.coinbase`` (``address``): current block miner's address +- ``block.difficulty`` (``uint``): current block difficulty +- ``block.gaslimit`` (``uint``): current block gaslimit +- ``block.number`` (``uint``): current block number +- ``block.timestamp`` (``uint``): current block timestamp +- ``msg.data`` (``bytes``): complete calldata +- ``msg.gas`` (``uint``): remaining gas +- ``msg.sender`` (``address``): sender of the message (current call) +- ``msg.sig`` (``bytes4``): first four bytes of the calldata (i.e. function identifier) +- ``msg.value`` (``uint``): number of wei sent with the message +- ``now`` (``uint``): current block timestamp (alias for ``block.timestamp``) +- ``tx.gasprice`` (``uint``): gas price of the transaction +- ``tx.origin`` (``address``): sender of the transaction (full call chain) .. note:: The values of all members of ``msg``, including ``msg.sender`` and @@ -89,12 +89,12 @@ Mathematical and Cryptographic Functions ``mulmod(uint x, uint y, uint k) returns (uint)``: compute ``(x * y) % k`` where the multiplication is performed with arbitrary precision and does not wrap around at ``2**256``. ``sha3(...) returns (bytes32)``: - compute the Ethereum-SHA-3 hash of the (tightly packed) arguments + compute the Ethereum-SHA-3 (KECCAK-256) hash of the (tightly packed) arguments ``sha256(...) returns (bytes32)``: compute the SHA-256 hash of the (tightly packed) arguments ``ripemd160(...) returns (bytes20)``: compute RIPEMD-160 hash of the (tightly packed) arguments -``ecrecover(bytes32 data, uint8 v, bytes32 r, bytes32 s) returns (address)``: +``ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address)``: recover the address associated with the public key from elliptic curve signature In the above, "tightly packed" means that the arguments are concatenated without padding. @@ -111,6 +111,24 @@ same as ``sha3(uint16(0x12))``. It might be that you run into Out-of-Gas for ``sha256``, ``ripemd160`` or ``ecrecover`` on a *private blockchain*. The reason for this is that those are implemented as so-called precompiled contracts and these contracts only really exist after they received the first message (although their contract code is hardcoded). Messages to non-existing contracts are more expensive and thus the execution runs into an Out-of-Gas error. A workaround for this problem is to first send e.g. 1 Wei to each of the contracts before you use them in your actual contracts. This is not an issue on the official or test net. +.. _address_related: + +Address Related +--------------- + +``<address>.balance`` (``uint256``): + balance of the :ref:`address` in Wei +``<address>.send(uint256 amount) returns (bool)``: + send given amount of Wei to :ref:`address`, returns ``false`` on failure + +For more information, see the section on :ref:`address`. + +.. warning:: + There are some dangers in using ``send``: The transfer fails if the call stack depth is at 1024 + (this can always be forced by the caller) and it also fails if the recipient runs out of gas. So in order + to make safe Ether transfers, always check the return value of ``send`` or even better: + Use a pattern where the recipient withdraws the money. + .. index:: this, selfdestruct Contract Related @@ -119,7 +137,7 @@ Contract Related ``this`` (current contract's type): the current contract, explicitly convertible to :ref:`address` -``selfdestruct(address)``: +``selfdestruct(address recipient)``: destroy the current contract, sending its funds to the given :ref:`address` Furthermore, all functions of the current contract are callable directly including the current function. |