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Diffstat (limited to 'docs/miscellaneous.rst')
| -rw-r--r-- | docs/miscellaneous.rst | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/docs/miscellaneous.rst b/docs/miscellaneous.rst index 7d4cedb6..d00ffbe3 100644 --- a/docs/miscellaneous.rst +++ b/docs/miscellaneous.rst @@ -34,17 +34,17 @@ Statically-sized variables (everything except mapping and dynamically-sized arra The elements of structs and arrays are stored after each other, just as if they were given explicitly. -Due to their unpredictable size, mapping and dynamically-sized array types use a ``sha3`` +Due to their unpredictable size, mapping and dynamically-sized array types use a Keccak-256 hash computation to find the starting position of the value or the array data. These starting positions are always full stack slots. The mapping or the dynamic array itself occupies an (unfilled) slot in storage at some position ``p`` according to the above rule (or by recursively applying this rule for mappings to mappings or arrays of arrays). For a dynamic array, this slot stores the number of elements in the array (byte arrays and strings are an exception here, see below). For a mapping, the slot is unused (but it is needed so that two equal mappings after each other will use a different hash distribution). -Array data is located at ``sha3(p)`` and the value corresponding to a mapping key -``k`` is located at ``sha3(k . p)`` where ``.`` is concatenation. If the value is again a -non-elementary type, the positions are found by adding an offset of ``sha3(k . p)``. +Array data is located at ``keccak256(p)`` and the value corresponding to a mapping key +``k`` is located at ``keccak256(k . p)`` where ``.`` is concatenation. If the value is again a +non-elementary type, the positions are found by adding an offset of ``keccak256(k . p)``. -``bytes`` and ``string`` store their data in the same slot where also the length is stored if they are short. In particular: If the data is at most ``31`` bytes long, it is stored in the higher-order bytes (left aligned) and the lowest-order byte stores ``length * 2``. If it is longer, the main slot stores ``length * 2 + 1`` and the data is stored as usual in ``sha3(slot)``. +``bytes`` and ``string`` store their data in the same slot where also the length is stored if they are short. In particular: If the data is at most ``31`` bytes long, it is stored in the higher-order bytes (left aligned) and the lowest-order byte stores ``length * 2``. If it is longer, the main slot stores ``length * 2 + 1`` and the data is stored as usual in ``keccak256(slot)``. So for the following contract snippet:: @@ -54,7 +54,7 @@ So for the following contract snippet:: mapping(uint => mapping(uint => s)) data; } -The position of ``data[4][9].b`` is at ``sha3(uint256(9) . sha3(uint256(4) . uint256(1))) + 1``. +The position of ``data[4][9].b`` is at ``keccak256(uint256(9) . keccak256(uint256(4) . uint256(1))) + 1``. ***************** Esoteric Features @@ -281,7 +281,7 @@ The following is the order of precedence for operators, listed in order of evalu | *16* | Comma operator | ``,`` | +------------+-------------------------------------+--------------------------------------------+ -.. index:: block, coinbase, difficulty, number, block;number, timestamp, block;timestamp, msg, data, gas, sender, value, now, gas price, origin, sha3, ripemd160, sha256, ecrecover, addmod, mulmod, cryptography, this, super, selfdestruct, balance, send +.. index:: block, coinbase, difficulty, number, block;number, timestamp, block;timestamp, msg, data, gas, sender, value, now, gas price, origin, keccak256, ripemd160, sha256, ecrecover, addmod, mulmod, cryptography, this, super, selfdestruct, balance, send Global Variables ================ @@ -299,7 +299,8 @@ Global Variables - ``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) -- ``sha3(...) returns (bytes32)``: compute the Ethereum-SHA-3 (KECCAK-256) hash of the (tightly packed) arguments +- ``keccak256(...) returns (bytes32)``: compute the Ethereum-SHA-3 (Keccak-256) hash of the (tightly packed) arguments +- ``sha3(...) returns (bytes32)``: an alias to `keccak256()` - ``sha256(...) returns (bytes32)``: compute the SHA-256 hash of the (tightly packed) arguments - ``ripemd160(...) returns (bytes20)``: compute the RIPEMD-160 hash of the (tightly packed) arguments - ``ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address)``: recover address associated with the public key from elliptic curve signature, return zero on error |