Ethereum: getting address field from assembly

Ethereum address field decoding from the configuration

Solidity -based intelligent agreement is an understanding of how to interact with Ethereum’s virtual machine (EVM) is very important to develop and test decentralized applications. One of the most important aspects of this interaction is access to field values ​​in the function of the function. Especially by calling the address, we can use the configuration to disassemble the field.

This article looks at how the value of the parameter’s k parameter is obtained through the configuration of the” call “.

Problem: Function and Parameters decoding

When we call a feature such as a caller, it returns a income object that contains different fields. However, in this return object, field values ​​are encoded as a syllable group. The most common used coding is the Ethereum’s special Byte32 format, which means healthy value.

`Solidity

Function Caller (Uint K, Uint v) Public {

// Call the Callee feature and keep the result in a changing “score”.

(Bool success,) = address (this) .call (both.codewithsignature (“Callee (), both.encode (k, v));

// Check the call successful and return the result

If (! Success) {

return;

}

// parameter k is the value of the Uint32 coded by syllable32.

// We can use the configuration to dismantle it.

can kdecoded = both.encodeat (“k”, byti32 (k));

// Use the decoded K value

Print (KDecoded); // It prints the parameter Uint32 decimal number.

}

Field values ​​decoding with a configuration

To dismantle the value of the field, we need to know its type and length. In this case, the field is coded with 4 byte “syllable32” size.

`Solidity

// Specify the feature of the feature player with parameter K Coded bytos32.

Function Caller (Uint K, Uint v) Public {

// Call the Callee feature and keep the result in a changing “score”.

(Bool success,) = address (this) .call (both.codewithsignature (“Callee (), both.encode (k, v));

// Check the call successful and return the result

If (! Success) {

return;

}

// Parametri K parameter is the value of the UINT32, which is encoded by syllable32.

// We can use the configuration to dismantle it.

can kdecoded = both.encodeat (“k”, byti32 (k));

// Check that the value of the decoded K corresponds to our expected type and length.

Request (syllable32 (coded) .ing (0) == k, "predictable swim32 match");

}

conclusion

Understanding how field values ​​can be discharged through the configuration based on firmness, we can write more efficient and reliable features interacting with the virtual machine of Ethereum. This information allows developers to create stable and safe applications that use EVM power.

Note: In this example it assumes that you have basic stability and you have known the “call” syntax and parameters. In addition, it is not an exhaustive study of the decoding field; For more information, see the Stability Documentation and the relevant Ethereum project resources.