Module 0x1::function_info

The function_info module defines the FunctionInfo type which simulates a function pointer.

• Struct FunctionInfo
• Constants
• Function new_function_info
• Function new_function_info_from_address
• Function check_dispatch_type_compatibility
• Function load_module_from_function
• Function check_dispatch_type_compatibility_impl
• Function is_identifier
• Function load_function_impl
• Specification
  • Function new_function_info
  • Function new_function_info_from_address
  • Function check_dispatch_type_compatibility
  • Function load_module_from_function
  • Function check_dispatch_type_compatibility_impl
  • Function is_identifier
  • Function load_function_impl

use 0x1::signer;
use 0x1::string;

Struct FunctionInfo

A String holds a sequence of bytes which is guaranteed to be in utf8 format.

struct FunctionInfo has copy, drop, store

Constants

Function specified in the FunctionInfo doesn’t exist on chain.

const EINVALID_FUNCTION: u64 = 2;

String is not a valid Move identifier

const EINVALID_IDENTIFIER: u64 = 1;

Function new_function_info

Creates a new function info from names.

public fun new_function_info(module_signer: &signer, module_name: string::String, function_name: string::String): function_info::FunctionInfo

public fun new_function_info(
    module_signer: &signer,
    module_name: String,
    function_name: String,
): FunctionInfo {
    new_function_info_from_address(
        signer::address_of(module_signer),
        module_name,
        function_name,
    )
}

Function new_function_info_from_address

public fun new_function_info_from_address(module_address: address, module_name: string::String, function_name: string::String): function_info::FunctionInfo

public fun new_function_info_from_address(
    module_address: address,
    module_name: String,
    function_name: String,
): FunctionInfo {
    assert!(
        is_identifier(module_name.bytes()),
        EINVALID_IDENTIFIER
    );
    assert!(
        is_identifier(function_name.bytes()),
        EINVALID_IDENTIFIER
    );
    FunctionInfo {
        module_address,
        module_name,
        function_name,
    }
}

Function check_dispatch_type_compatibility

Check if the dispatch target function meets the type requirements of the disptach entry point.

framework_function is the dispatch native function defined in the aptos_framework. dispatch_target is the function passed in by the user.

dispatch_target should have the same signature (same argument type, same generics constraint) except that the framework_function will have a &FunctionInfo in the last argument that will instruct the VM which function to jump to.

dispatch_target also needs to be public so the type signature will remain unchanged.

public(friend) fun check_dispatch_type_compatibility(framework_function: &function_info::FunctionInfo, dispatch_target: &function_info::FunctionInfo): bool

public(friend) fun check_dispatch_type_compatibility(
    framework_function: &FunctionInfo,
    dispatch_target: &FunctionInfo,
): bool {
    load_function_impl(dispatch_target);
    check_dispatch_type_compatibility_impl(framework_function, dispatch_target)
}

Function load_module_from_function

Load up a function into VM’s loader and charge for its dependencies

It is critical to make sure that this function is invoked before check_dispatch_type_compatibility or performing any other dispatching logic to ensure:

1. We properly charge gas for the function to dispatch.
2. The function is loaded in the cache so that we can perform further type checking/dispatching logic.

Calling check_dispatch_type_compatibility_impl or dispatch without loading up the module would yield an error if such module isn’t accessed previously in the transaction.

public(friend) fun load_module_from_function(f: &function_info::FunctionInfo)

public(friend) fun load_module_from_function(f: &FunctionInfo) {
    load_function_impl(f)
}

Function check_dispatch_type_compatibility_impl

fun check_dispatch_type_compatibility_impl(lhs: &function_info::FunctionInfo, r: &function_info::FunctionInfo): bool

native fun check_dispatch_type_compatibility_impl(lhs: &FunctionInfo, r: &FunctionInfo): bool;

Function is_identifier

fun is_identifier(s: &vector<u8>): bool

native fun is_identifier(s: &vector<u8>): bool;

Function load_function_impl

fun load_function_impl(f: &function_info::FunctionInfo)

native fun load_function_impl(f: &FunctionInfo);

Specification

fun spec_is_identifier(s: vector<u8>): bool;

Function new_function_info

public fun new_function_info(module_signer: &signer, module_name: string::String, function_name: string::String): function_info::FunctionInfo

aborts_if !spec_is_identifier(string::bytes(module_name));
aborts_if !spec_is_identifier(string::bytes(function_name));
ensures result == FunctionInfo {
    module_address: signer::address_of(module_signer),
    module_name,
    function_name,
};

Function new_function_info_from_address

public fun new_function_info_from_address(module_address: address, module_name: string::String, function_name: string::String): function_info::FunctionInfo

aborts_if !spec_is_identifier(string::bytes(module_name));
aborts_if !spec_is_identifier(string::bytes(function_name));
ensures result == FunctionInfo {
    module_address,
    module_name,
    function_name,
};

Function check_dispatch_type_compatibility

public(friend) fun check_dispatch_type_compatibility(framework_function: &function_info::FunctionInfo, dispatch_target: &function_info::FunctionInfo): bool

pragma verify = false;
pragma opaque;

Function load_module_from_function

public(friend) fun load_module_from_function(f: &function_info::FunctionInfo)

pragma verify = false;
pragma opaque;

Function check_dispatch_type_compatibility_impl

fun check_dispatch_type_compatibility_impl(lhs: &function_info::FunctionInfo, r: &function_info::FunctionInfo): bool

pragma opaque;

Function is_identifier

fun is_identifier(s: &vector<u8>): bool

pragma opaque;
aborts_if [abstract] false;
ensures [abstract] result == spec_is_identifier(s);

Function load_function_impl

fun load_function_impl(f: &function_info::FunctionInfo)

pragma opaque;