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author | chriseth <c@ethdev.com> | 2015-12-21 23:54:32 +0800 |
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committer | chriseth <c@ethdev.com> | 2015-12-21 23:54:32 +0800 |
commit | 8fe89455b378acae43898185f6c9c0f67dba967e (patch) | |
tree | a9b6d405c18ac45dbbacd0015a662e8cd58820e4 | |
parent | 6c6295b74e6e93d838672e70109880e27bb5f614 (diff) | |
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Fixes in the misc section.
-rw-r--r-- | docs/contracts.rst | 4 | ||||
-rw-r--r-- | docs/miscellaneous.rst | 80 |
2 files changed, 44 insertions, 40 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index 16809586..1d292c25 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -124,6 +124,8 @@ This means that cyclic creation dependencies are impossible. .. index:: ! visibility, external, public, private, internal +.. _visibility-and-accessors: + ************************ Visibility and Accessors ************************ @@ -232,6 +234,8 @@ is no good way to provide the key for the mapping. .. index:: ! function;modifier +.. _modifiers: + ****************** Function Modifiers ****************** diff --git a/docs/miscellaneous.rst b/docs/miscellaneous.rst index a9b23c53..dcd12c60 100644 --- a/docs/miscellaneous.rst +++ b/docs/miscellaneous.rst @@ -115,13 +115,13 @@ If `solc` is called with the option `--link`, all input files are interpreted to Tips and Tricks *************** - * Use `delete` on arrays to delete all its elements. - * Use shorter types for struct elements and sort them such that short types are grouped together. This can lower the gas costs as multiple SSTORE operations might be combined into a single (SSTORE costs 5000 or 20000 gas, so this is what you want to optimise). Use the gas price estimator (with optimiser enabled) to check! - * Make your state variables public - the compiler will create [getters](#accessor-functions) for you for free. - * If you end up checking conditions on input or state a lot at the beginning of your functions, try using [modifiers](#function-modifiers) - * If your contract has a function called `send` but you want to use the built-in send-function, use `address(contractVariable).send(amount)`. - * If you want your contracts to receive ether when called via `send`, you have to implement the [fallback function](#fallback-functions). - * Initialise storage structs with a single assignment: `x = MyStruct({a: 1, b: 2});` +* Use `delete` on arrays to delete all its elements. +* Use shorter types for struct elements and sort them such that short types are grouped together. This can lower the gas costs as multiple SSTORE operations might be combined into a single (SSTORE costs 5000 or 20000 gas, so this is what you want to optimise). Use the gas price estimator (with optimiser enabled) to check! +* Make your state variables public - the compiler will create :ref:`getters <visibility-and-accessors>` for you for free. +* If you end up checking conditions on input or state a lot at the beginning of your functions, try using :ref:`modifiers`. +* If your contract has a function called `send` but you want to use the built-in send-function, use `address(contractVariable).send(amount)`. +* If you do **not** want your contracts to receive ether when called via `send`, you can add a throwing fallback function `function() { throw; }`. +* Initialise storage structs with a single assignment: `x = MyStruct({a: 1, b: 2});` ******** Pitfalls @@ -129,7 +129,7 @@ Pitfalls Unfortunately, there are some subtleties the compiler does not yet warn you about. - - In `for (var i = 0; i < arrayName.length; i++) { ... }`, the type of `i` will be `uint8`, because this is the smallest type that is required to hold the value `0`. If the array has more than 255 elements, the loop will not terminate. +- In `for (var i = 0; i < arrayName.length; i++) { ... }`, the type of `i` will be `uint8`, because this is the smallest type that is required to hold the value `0`. If the array has more than 255 elements, the loop will not terminate. ********** Cheatsheet @@ -140,30 +140,30 @@ Cheatsheet Global Variables ================ - - `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 works 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.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) - - `sha3(...) returns (bytes32)`: compute the Ethereum-SHA3 hash of the (tightly packed) arguments - - `sha256(...) returns (bytes32)`: compute the SHA256 hash of the (tightly packed) arguments - - `ripemd160(...) returns (bytes20)`: compute RIPEMD of 256 the (tightly packed) arguments - - `ecrecover(bytes32, uint8, bytes32, bytes32) returns (address)`: recover public key from elliptic curve signature - - `addmod(uint x, uint y, uint k) returns (uint)`: compute `(x + y) % k` where the addition is performed with arbitrary precision and does not wrap around at `2**256`. - - `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`. - - `this` (current contract's type): the current contract, explicitly convertible to `address` - - `super`: the contract one level higher in the inheritance hierarchy - - `selfdestruct(address)`: destroy the current contract, sending its funds to the given address - - `<address>.balance`: balance of the address in Wei - - `<address>.send(uint256) returns (bool)`: send given amount of Wei to address, returns `false` on failure. +- `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 works 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.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) +- `sha3(...) returns (bytes32)`: compute the Ethereum-SHA3 hash of the (tightly packed) arguments +- `sha256(...) returns (bytes32)`: compute the SHA256 hash of the (tightly packed) arguments +- `ripemd160(...) returns (bytes20)`: compute RIPEMD of 256 the (tightly packed) arguments +- `ecrecover(bytes32, uint8, bytes32, bytes32) returns (address)`: recover public key from elliptic curve signature +- `addmod(uint x, uint y, uint k) returns (uint)`: compute `(x + y) % k` where the addition is performed with arbitrary precision and does not wrap around at `2**256`. +- `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`. +- `this` (current contract's type): the current contract, explicitly convertible to `address` +- `super`: the contract one level higher in the inheritance hierarchy +- `selfdestruct(address)`: destroy the current contract, sending its funds to the given address +- `<address>.balance`: balance of the address in Wei +- `<address>.send(uint256) returns (bool)`: send given amount of Wei to address, returns `false` on failure. .. index:: visibility, public, private, external, internal @@ -176,10 +176,10 @@ Function Visibility Specifiers return true; } - - `public`: visible externally and internally (creates accessor function for storage/state variables) - - `private`: only visible in the current contract - - `external`: only visible externally (only for functions) - i.e. can only be message-called (via `this.fun`) - - `internal`: only visible internally +- `public`: visible externally and internally (creates accessor function for storage/state variables) +- `private`: only visible in the current contract +- `external`: only visible externally (only for functions) - i.e. can only be message-called (via `this.fun`) +- `internal`: only visible internally .. index:: modifiers, constant, anonymous, indexed @@ -187,8 +187,8 @@ Function Visibility Specifiers Modifiers ========= - - `constant` for state variables: Disallows assignment (except initialisation), does not occupy storage slot. - - `constant` for functions: Disallows modification of state - this is not enforced yet. - - `anonymous` for events: Does not store event signature as topic. - - `indexed` for event parameters: Stores the parameter as topic. +- `constant` for state variables: Disallows assignment (except initialisation), does not occupy storage slot. +- `constant` for functions: Disallows modification of state - this is not enforced yet. +- `anonymous` for events: Does not store event signature as topic. +- `indexed` for event parameters: Stores the parameter as topic. |