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authorchriseth <chris@ethereum.org>2018-06-13 23:49:41 +0800
committerAlex Beregszaszi <alex@rtfs.hu>2018-06-25 23:17:18 +0800
commit17493e64ed986c33bb5562eabafca2d52b212f19 (patch)
tree25ac5961633e2813bd4a6bc53b883f690f61f506 /docs/units-and-global-variables.rst
parent237788c0bc204eb08ba7000cd51c0c62ecb777c6 (diff)
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Documentation.
Diffstat (limited to 'docs/units-and-global-variables.rst')
-rw-r--r--docs/units-and-global-variables.rst52
1 files changed, 18 insertions, 34 deletions
diff --git a/docs/units-and-global-variables.rst b/docs/units-and-global-variables.rst
index 3b0be438..455231cd 100644
--- a/docs/units-and-global-variables.rst
+++ b/docs/units-and-global-variables.rst
@@ -100,16 +100,16 @@ ABI Encoding Functions
----------------------
- ``abi.encode(...) returns (bytes)``: ABI-encodes the given arguments
-- ``abi.encodePacked(...) returns (bytes)``: Performes packed encoding of the given arguments
+- ``abi.encodePacked(...) returns (bytes)``: Performes :ref:`packed encoding <abi_packed_mode>` of the given arguments
- ``abi.encodeWithSelector(bytes4 selector, ...) returns (bytes)``: ABI-encodes the given arguments
starting from the second and prepends the given four-byte selector
-- ``abi.encodeWithSignature(string signature, ...) returns (bytes)``: Equivalent to ``abi.encodeWithSelector(bytes4(keccak256(signature), ...)```
+- ``abi.encodeWithSignature(string signature, ...) returns (bytes)``: Equivalent to ``abi.encodeWithSelector(bytes4(keccak256(bytes(signature)), ...)```
.. note::
These encoding functions can be used to craft data for function calls without actually
- calling a function. Furthermore, ``keccak256(abi.encodePacked(a, b))`` is a more
- explicit way to compute ``keccak256(a, b)``, which will be deprecated in future
- versions.
+ calling a function. Furthermore, ``keccak256(abi.encodePacked(a, b))`` is a way
+ to compute the hash of structured data (although be aware that it is possible to
+ craft a "hash collision" using different inputs types).
See the documentation about the :ref:`ABI <ABI>` and the
:ref:`tightly packed encoding <abi_packed_mode>` for details about the encoding.
@@ -139,34 +139,18 @@ Mathematical and Cryptographic Functions
compute ``(x + y) % k`` where the addition is performed with arbitrary precision and does not wrap around at ``2**256``. Assert that ``k != 0`` starting from version 0.5.0.
``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``. Assert that ``k != 0`` starting from version 0.5.0.
-``keccak256(...) returns (bytes32)``:
- compute the Ethereum-SHA-3 (Keccak-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>`
-``sha3(...) returns (bytes32)``:
+``keccak256(bytes memory) returns (bytes32)``:
+ compute the Ethereum-SHA-3 (Keccak-256) hash of the input
+``sha256(bytes memory) returns (bytes32)``:
+ compute the SHA-256 hash of the input
+``sha3(bytes memory) returns (bytes32)``:
alias to ``keccak256``
-``ripemd160(...) returns (bytes20)``:
- compute RIPEMD-160 hash of the :ref:`(tightly packed) arguments <abi_packed_mode>`
+``ripemd160(bytes memory) returns (bytes20)``:
+ compute RIPEMD-160 hash of the input
``ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address)``:
recover the address associated with the public key from elliptic curve signature or return zero on error
(`example usage <https://ethereum.stackexchange.com/q/1777/222>`_)
-In the above, "tightly packed" means that the arguments are concatenated without padding.
-This means that the following are all identical::
-
- keccak256("ab", "c")
- keccak256("abc")
- keccak256(0x616263)
- keccak256(6382179)
- keccak256(97, 98, 99)
-
-If padding is needed, explicit type conversions can be used: ``keccak256("\x00\x12")`` is the
-same as ``keccak256(uint16(0x12))``.
-
-Note that constants will be packed using the minimum number of bytes required to store them.
-This means that, for example, ``keccak256(0) == keccak256(uint8(0))`` and
-``keccak256(0x12345678) == keccak256(uint32(0x12345678))``.
-
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.
.. index:: balance, send, transfer, call, callcode, delegatecall
@@ -181,12 +165,12 @@ Address Related
send given amount of Wei to :ref:`address`, throws on failure, forwards 2300 gas stipend, not adjustable
``<address>.send(uint256 amount) returns (bool)``:
send given amount of Wei to :ref:`address`, returns ``false`` on failure, forwards 2300 gas stipend, not adjustable
-``<address>.call(...) returns (bool)``:
- issue low-level ``CALL``, returns ``false`` on failure, forwards all available gas, adjustable
-``<address>.callcode(...) returns (bool)``:
- issue low-level ``CALLCODE``, returns ``false`` on failure, forwards all available gas, adjustable
-``<address>.delegatecall(...) returns (bool)``:
- issue low-level ``DELEGATECALL``, returns ``false`` on failure, forwards all available gas, adjustable
+``<address>.call(bytes memory) returns (bool)``:
+ issue low-level ``CALL`` with the given payload, returns ``false`` on failure, forwards all available gas, adjustable
+``<address>.callcode(bytes memory) returns (bool)``:
+ issue low-level ``CALLCODE`` with the given payload, returns ``false`` on failure, forwards all available gas, adjustable
+``<address>.delegatecall(bytes memory) returns (bool)``:
+ issue low-level ``DELEGATECALL`` with the given payload, returns ``false`` on failure, forwards all available gas, adjustable
For more information, see the section on :ref:`address`.