Golang使用CGO與Plugin技術執行載入C動態庫

// opencc.h
#include <stdlib.h>

void* Opencc_New(const char *configFile);
void* Opencc_Delete(void *id);
const char *Opencc_Convert(void *id, const char *input);
void Opencc_Free_String(char *p);

// opencc.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "opencc/src/opencc.h"

const char *Convert(const char *input, const char *config) {
        if(strlen(config) > 16) {
                return 0;
        }

        char configFile[256] = "/usr/share/opencc/";
        strcat(configFile, config);
        strcat(configFile, ".json");

        opencc_t p = opencc_open(configFile);
        char *out = opencc_convert_utf8(p, input, strlen(input));
        out[strlen(input)] = '';

        opencc_close(p);

        return out;
}

void Convert_free_string(char *p) {
        opencc_convert_utf8_free(p);
}

void* Opencc_New(const char *configFile) {
        return opencc_open(configFile);
}

void Opencc_Delete(void *id) {
        opencc_close(id);
}

const char *Opencc_Convert(void *id, const char *input) {
        char *output = opencc_convert_utf8(id, input, strlen(input));
        output[strlen(input)] = '';
        return output;
}

void Opencc_Free_String(char *p) {
        opencc_convert_utf8_free(p);
}

// opencc.go
package opencc

import "unsafe"
// #cgo LDFLAGS: -L${SRCDIR}/output/lib -lopencc
// #include "opencc.h"
import "C"
func NewConverter(config string) unsafe.Pointer {
        return C.Opencc_New(C.CString(config))
}
func Convert(p unsafe.Pointer, input string) string {
        inputChars := C.CString(input)
        outputChars := C.Opencc_Convert(p, inputChars)

        defer C.Opencc_Free_String(inputChars)
        defer C.Opencc_Free_String(outputChars)

        result := C.GoString(outputChars)
        return result
}
func Close(p unsafe.Pointer) {
        C.Opencc_Delete(p)
}
func ConvertOneTime(input string, config string) string {
        p := NewConverter(config)
        defer Close(p)
        return Convert(p, input)
}
func ConvertAsync(input string, config string, callback func(output string)) {
        go func() {
                callback(ConvertOneTime(input, config))
        }()
}

// test.go 呼叫OpenCC動態庫的函數。
package main

import "fmt"
import "your/repository/go-opencc"
const (
        input = "中國滑鼠軟體印表機"
        config_s2t = "/usr/share/opencc/s2t.json"
        config_t2s = "/usr/share/opencc/t2s.json"
)
func main() {
        fmt.Println("Test Converter class:")
        c := opencc.NewConverter(config_s2t)
        defer c.Close()
        output := c.Convert(input)
        fmt.Println(output)

        fmt.Println("Test Convert function:")
        s := opencc.Convert(input, config_s2t)
        fmt.Println(s)
        fmt.Println(opencc.Convert(s, config_t2s))

        fmt.Println("Test ConvertAsync function:")
        retChan := make(chan string)
        opencc.ConvertAsync(input, config_s2t, func(output string) {
                retChan <- output
        })

        fmt.Println(<- retChan)
}

// opencc_lib.go
package main
import (
        "unsafe"

        opencc "your/repository/go-opencc"
)

type openccConverter string

// NewConverter 建立Converter
func (s openccConverter) NewConverter(config string) unsafe.Pointer {
        return opencc.NewConverter(config)
}

// Convert 轉換函數
func (s openccConverter) Convert(p unsafe.Pointer, input string) string {
        return opencc.Convert(p, input)
}

// Close 釋放Converter佔用的記憶體資源(不再使用Converter了)
func (s openccConverter) Close(p unsafe.Pointer) {
        opencc.Close(p)
}
// ConvertOneTime 轉換函數(轉換一次，該函數每次呼叫都會載入組態檔，有效能影響)
func (s openccConverter) ConvertOneTime(input string, config string) string {
        return opencc.ConvertOneTime(input, config)
}
// OpenccConverter export symble
var OpenccConverter openccConverter

#!/bin/bash

mkdir -p output

cd opencc
./build.sh
cd ..
cp -rf opencc/output/* ./output
go build -buildmode=plugin -o ./output/lib/libgo_opencc.so ./lib/opencc_lib.go

package main
import (
        "os"
        "plugin"
        "testing"
        "unsafe"
        "fmt"
)
// 實現 opencc_lib.go 的介面
type OpenccConverter interface {
        NewConverter(config string) unsafe.Pointer
        Convert(p unsafe.Pointer, input string) string
        Close(p unsafe.Pointer)
        ConvertOneTime(input string, config string) string
}

func TestOpenccSo(t *testing.T) {
        openccPlugin, pluginErr := plugin.Open("/your/path/to/go-opencc/output/lib/libgo_opencc.so")
        if pluginErr != nil {
                panic(pluginErr)
        }

        symbol, cerr := openccPlugin.Lookup("OpenccConverter")
        if cerr != nil {
                fmt.Errorf("%+v", cerr)
                os.Exit(1)
        }

        plug, ok := symbol.(OpenccConverter)
        if !ok {
                fmt.Errorf("unexpected type from module symbol")
                os.Exit(1)
        }

        config := "/usr/share/opencc/hk2s.json"
        pointer := plug.NewConverter(config)
        defer plug.Close(pointer)

        input := "傳統漢字"

        output := plug.Convert(pointer, input)

        fmt.Printf("output: %s", output)
}
// 執行測試 TestOpenccSo，輸出 「傳統漢字」。