Import Functions

To use functions from another plugin in your Go plugin, you need to generate language-specific header files. These headers provide the necessary wrappers to call functions exported by other plugins. This guide explains how to generate these headers and how to use them in your Go plugin.

Generating Header Files

Plugify provides a Python script (generator.py) to automatically generate header files for importing functions from other plugins. These headers include wrapper functions that handle the function calls and parameter passing.

Steps to Generate Header Files

python generator.py ./plugins/MyPlugin/MyPlugin.pplugin ./output/

Using Generated Wrapper Functions

The generated header file contains wrapper functions that allow you to call functions from the other plugin. These wrappers handle the function address lookup and parameter passing.

Example Generated Header

Here’s an example of a generated header file for a plugin named plugin_from_another_language:

package plugin_from_another_language

// Generated from plugin_from_another_language.pplugin by https://github.com/untrustedmodders/plugify-module-golang/blob/main/generator/generator.py

// #include "plugin_from_another_language.h"
import "C"
import "unsafe"

func ParamCallback(a int32, b float32, c float64, d Vector4, e []int64, f int8, g string, h uint16, k int16) {
    C_a := C.int32_t(a)
    C_b := C.float(b)
    C_c := C.double(c)
    C_d := *(*C.Vector4)(unsafe.Pointer(&d))
    var A_e unsafe.Pointer
    S_e := len(e)
    if S_e > 0 {
        A_e = unsafe.Pointer(&e[0])
    } else {
        A_e = nil
    }
    C_e := C.Plugify_ConstructVector(A_e, C.ptrdiff_t(S_e), C.INT64)
    C_f := C.char(f)
    C_g := C.Plugify_ConstructString(g)
    C_h := C.uint16_t(h)
    C_k := C.int16_t(k)

    C.ParamCallback(C_a, C_b, C_c, &C_d, &C_e, C_f, &C_g, C_h, C_k)

    C.Plugify_DestroyVector(&C_e, C.INT64)
    C.Plugify_DestroyString(&C_g)
}

typedef void (*ParamCallbackFn)(int32_t, float, double, Vector4*, Vector*, char, String*, uint16_t, int16_t);
static void ParamCallback(int32_t a, float b, double c, Vector4* d, Vector* e, char f, String* g, uint16_t h, int16_t k) {
    static ParamCallbackFn __func = NULL;
    if (__func == NULL) Plugify_GetMethodPtr2("cross_call_master.ParamCallback", (void**)&__func);
    __func(a, b, c, d, e, f, g, h, k);
}

How It Works

• The wrapper function (ParamCallback) handles parameter marshaling and cleanup.
• The C.ParamCallback function is set by the language module during plugin load.
• The wrapper function ensures that Go types are correctly converted to C types and vice versa.

Example: Using the Generated Header

Here’s how you can use the generated header in your Go plugin:

package main

import (
    "plugin_from_another_language"
    "fmt"
)

func main() {
    // Call the exported function from the other plugin
    plugin_from_another_language.ParamCallback(
        42,                // int32 a
        3.14,              // float32 b
        2.718,             // float64 c
        plugin_from_another_language.Vector4{1, 2, 3, 4}, // Vector4 d
        []int64{100, 200}, // []int64 e
        'x',               // int8 f
        "Hello, Plugify!", // string g
        123,               // uint16 h
        10,                // int16 k
    )
}

When is Header Generation Necessary?

Header generation is essential when importing functions from plugins written in statically-typed languages like C++ or Go. Without these headers, the compiler cannot reference the exported functions. For dynamically-typed languages like Python, header generation is not necessary because method binding happens at runtime.

Best Practices

1. Use the Generator Script: Always use the generator.py script to generate headers for imported functions.
2. Include Generated Headers: Include the generated headers in your plugin source files to access the exported functions.
3. Test Thoroughly: Test the imported functions to ensure they work as expected.
4. Document Dependencies: Clearly document the plugins and functions your plugin depends on.

Conclusion

Importing functions from another plugin in Go is straightforward when you use the generator.py script to generate the necessary headers. These headers provide wrapper functions that handle function address lookup and parameter passing, making it easy to integrate functionality from other plugins. By following the steps and best practices outlined in this guide, you can create robust and interoperable plugins in the Plugify ecosystem.