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Updates docs for blockhash changes.

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bitshift 2018-03-05 19:24:51 +01:00 committed by Alex Beregszaszi
parent be35a65eb3
commit bddfa47e77
2 changed files with 21 additions and 3 deletions
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20
docs/miscellaneous.rst
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@ -314,7 +314,7 @@ The following is the order of precedence for operators, listed in order of evalu
Global Variables Global Variables
================ ================
- ``block.blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent blocks - ``block.blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent, excluding current, blocks - deprecated in version 0.4.22 and replaced by ``blockhash(uint blockNumber)``.
- ``block.coinbase`` (``address``): current block miner's address - ``block.coinbase`` (``address``): current block miner's address
- ``block.difficulty`` (``uint``): current block difficulty - ``block.difficulty`` (``uint``): current block difficulty
- ``block.gaslimit`` (``uint``): current block gaslimit - ``block.gaslimit`` (``uint``): current block gaslimit
@ -331,6 +331,7 @@ Global Variables
- ``assert(bool condition)``: abort execution and revert state changes if condition is ``false`` (use for internal error) - ``assert(bool condition)``: abort execution and revert state changes if condition is ``false`` (use for internal error)
- ``require(bool condition)``: abort execution and revert state changes if condition is ``false`` (use for malformed input or error in external component) - ``require(bool condition)``: abort execution and revert state changes if condition is ``false`` (use for malformed input or error in external component)
- ``revert()``: abort execution and revert state changes - ``revert()``: abort execution and revert state changes
- ``blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent blocks
- ``keccak256(...) returns (bytes32)``: compute the Ethereum-SHA-3 (Keccak-256) hash of the :ref:`(tightly packed) arguments <abi_packed_mode>` - ``keccak256(...) returns (bytes32)``: compute the Ethereum-SHA-3 (Keccak-256) hash of the :ref:`(tightly packed) arguments <abi_packed_mode>`
- ``sha3(...) returns (bytes32)``: an alias to ``keccak256`` - ``sha3(...) returns (bytes32)``: an alias to ``keccak256``
- ``sha256(...) returns (bytes32)``: compute the SHA-256 hash of the :ref:`(tightly packed) arguments <abi_packed_mode>` - ``sha256(...) returns (bytes32)``: compute the SHA-256 hash of the :ref:`(tightly packed) arguments <abi_packed_mode>`
@ -346,6 +347,23 @@ Global Variables
- ``<address>.send(uint256 amount) returns (bool)``: send given amount of Wei to :ref:`address`, returns ``false`` on failure - ``<address>.send(uint256 amount) returns (bool)``: send given amount of Wei to :ref:`address`, returns ``false`` on failure
- ``<address>.transfer(uint256 amount)``: send given amount of Wei to :ref:`address`, throws on failure - ``<address>.transfer(uint256 amount)``: send given amount of Wei to :ref:`address`, throws on failure
.. note::
Do not rely on ``block.timestamp``, ``now`` and ``blockhash`` as a source of randomness,
unless you know what you are doing.
Both the timestamp and the block hash can be influenced by miners to some degree.
Bad actors in the mining community can for example run a casino payout function on a chosen hash
and just retry a different hash if they did not receive any money.
The current block timestamp must be strictly larger than the timestamp of the last block,
but the only guarantee is that it will be somewhere between the timestamps of two
consecutive blocks in the canonical chain.
.. note::
The block hashes are not available for all blocks for scalability reasons.
You can only access the hashes of the most recent 256 blocks, all other
values will be zero.
.. index:: visibility, public, private, external, internal .. index:: visibility, public, private, external, internal
Function Visibility Specifiers Function Visibility Specifiers

4
docs/units-and-global-variables.rst
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@ -52,7 +52,7 @@ namespace and are mainly used to provide information about the blockchain.
Block and Transaction Properties Block and Transaction Properties
-------------------------------- --------------------------------
- ``block.blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent blocks excluding current - ``block.blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent, excluding current, blocks - deprecated in version 0.4.22 and replaced by ``blockhash(uint blockNumber)``.
- ``block.coinbase`` (``address``): current block miner's address - ``block.coinbase`` (``address``): current block miner's address
- ``block.difficulty`` (``uint``): current block difficulty - ``block.difficulty`` (``uint``): current block difficulty
- ``block.gaslimit`` (``uint``): current block gaslimit - ``block.gaslimit`` (``uint``): current block gaslimit
@ -74,7 +74,7 @@ Block and Transaction Properties
This includes calls to library functions. This includes calls to library functions.
.. note:: .. note::
Do not rely on ``block.timestamp``, ``now`` and ``block.blockhash`` as a source of randomness, Do not rely on ``block.timestamp``, ``now`` and ``blockhash`` as a source of randomness,
unless you know what you are doing. unless you know what you are doing.
Both the timestamp and the block hash can be influenced by miners to some degree. Both the timestamp and the block hash can be influenced by miners to some degree.