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author | chriseth <chris@ethereum.org> | 2018-08-09 21:36:00 +0800 |
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committer | chriseth <chris@ethereum.org> | 2018-08-14 21:50:46 +0800 |
commit | 6cf299bec6b89b22d97e39d7db54f9dc4f652cfb (patch) | |
tree | c68420316cbbfb30522a13a5aeae7c716ea49d1a /docs/assembly.rst | |
parent | f873389c6227d41dbba9ba4c23ed055f286ecb71 (diff) | |
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Update documentation examples.
Diffstat (limited to 'docs/assembly.rst')
-rw-r--r-- | docs/assembly.rst | 18 |
1 files changed, 4 insertions, 14 deletions
diff --git a/docs/assembly.rst b/docs/assembly.rst index 91ba076a..2cbad06f 100644 --- a/docs/assembly.rst +++ b/docs/assembly.rst @@ -82,7 +82,7 @@ you really know what you are doing. library VectorSum { // This function is less efficient because the optimizer currently fails to // remove the bounds checks in array access. - function sumSolidity(uint[] memory _data) public view returns (uint o_sum) { + function sumSolidity(uint[] memory _data) public pure returns (uint o_sum) { for (uint i = 0; i < _data.length; ++i) o_sum += _data[i]; } @@ -90,7 +90,7 @@ you really know what you are doing. // We know that we only access the array in bounds, so we can avoid the check. // 0x20 needs to be added to an array because the first slot contains the // array length. - function sumAsm(uint[] memory _data) public view returns (uint o_sum) { + function sumAsm(uint[] memory _data) public pure returns (uint o_sum) { for (uint i = 0; i < _data.length; ++i) { assembly { o_sum := add(o_sum, mload(add(add(_data, 0x20), mul(i, 0x20)))) @@ -99,7 +99,7 @@ you really know what you are doing. } // Same as above, but accomplish the entire code within inline assembly. - function sumPureAsm(uint[] memory _data) public view returns (uint o_sum) { + function sumPureAsm(uint[] memory _data) public pure returns (uint o_sum) { assembly { // Load the length (first 32 bytes) let len := mload(_data) @@ -378,23 +378,13 @@ used ``x_slot`` and to retrieve the byte-offset you used ``x_offset``. In assignments (see below), we can even use local Solidity variables to assign to. -Functions external to inline assembly can also be accessed: The assembly will -push their entry label (with virtual function resolution applied). The calling semantics -in solidity are: - - - the caller pushes ``return label``, ``arg1``, ``arg2``, ..., ``argn`` - - the call returns with ``ret1``, ``ret2``, ..., ``retm`` - -This feature is still a bit cumbersome to use, because the stack offset essentially -changes during the call, and thus references to local variables will be wrong. - .. code:: pragma solidity ^0.4.11; contract C { uint b; - function f(uint x) public returns (uint r) { + function f(uint x) public view returns (uint r) { assembly { r := mul(x, sload(b_slot)) // ignore the offset, we know it is zero } |