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[经验分享] C/C++调用Golang 二

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发表于 2018-9-20 08:15:10 | 显示全部楼层 |阅读模式
C/C++调用Golang 二
  《C/C++调用Golang 一》简单介绍了C/C++调用Golang的方法步骤,只涉及一个简单的函数调用。本文总结具体项目中的使用场景,将介绍三种较复杂的调用方式:一,C++向golang传入复杂结构体;二,C++向golang传入回调函数,在golang中调用C++函数;三,C++调用golang函数,返回复杂的结构体。
  (本文后面涉及三个例子,省略了编译步骤,仅展示关键代码。具体操作步骤参考《C/C++调用Golang 一》)
一 C++向golang传入复杂结构体
  采用avro来序列化与反序列化结构体。C++版avro使用官方版本,golang版avro使用gopkg.in/alanctgardner/gogen-avro.v4 。(C++代码省略了avro结构体的序列化与反序列化,仅展示C++与Golang的交互部分)
1.1 Golang 代码
  package main
  import "C"
  import "fmt"
  //export WriteData
  func WriteData(data []byte) int {
  fmt.Println("WriteData ", data, len(data))
  return 0
  }
  func main() {
  }
  编译生成的头文件
  /* Created by "go tool cgo" - DO NOT EDIT. */
  /* package c_references_to_go/sample1 */
  /* Start of preamble from import "C" comments.  */
  /* End of preamble from import "C" comments.  */
  /* Start of boilerplate cgo prologue.  */
  #line 1 "cgo-gcc-export-header-prolog"
  #ifndef GO_CGO_PROLOGUE_H
  #define GO_CGO_PROLOGUE_H
  typedef signed char GoInt8;
  typedef unsigned char GoUint8;
  typedef short GoInt16;
  typedef unsigned short GoUint16;
  typedef int GoInt32;
  typedef unsigned int GoUint32;
  typedef long long GoInt64;
  typedef unsigned long long GoUint64;
  typedef GoInt32 GoInt;
  typedef GoUint32 GoUint;
  //typedef __SIZE_TYPE__ GoUintptr;
  typedef float GoFloat32;
  typedef double GoFloat64;
  //typedef float _Complex GoComplex64;
  //typedef double _Complex GoComplex128;
  /*
  static assertion to make sure the file is being used on architecture

  at least with matching>  */
  typedef char _check_for_32_bit_pointer_matching_GoInt[sizeof(void*)==32/8 ? 1:-1];
  typedef struct { const char *p; GoInt n; } GoString;
  typedef void *GoMap;
  typedef void *GoChan;
  typedef struct { void *t; void *v; } GoInterface;
  typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
  #endif
  /* End of boilerplate cgo prologue.  */
  #ifdef __cplusplus
  extern "C" {
  #endif
  extern GoInt WriteData(GoSlice p0);
  #ifdef __cplusplus
  }
  #endif
1.2 C++代码
  #include
  #include
  #include "sample1.h"
  //#include "LargeStruct.h"
  typedef GoInt (*funcPtrWriteData)(GoSlice p0);
  int main(){
  HMODULE h = LoadLibraryA("sample1.dll");
  if (NULL == h || INVALID_HANDLE_VALUE == h)
  {
  return -1;
  }
  funcPtrWriteData pfWriteData = (funcPtrWriteData)GetProcAddress(h,"WriteData");
  if (pfWriteData)
  {
  /* LargeStruct ls;
  ls.ID = "100001";
  ls.Name = "Peter";
  Pet pet;
  pet.Type = "Dog";
  pet.Name = "WangCai";
  pet.Age = 5;
  ls.Pets.push_back(pet);*/
  GoSlice p0;
  p0.data = 0;  //serial ls to binary
  p0.len = p0.cap = 0;  //binary len
  pfWriteData(p0);
  }
  FreeLibrary(h);
  return 0;
  }
二 C++向golang传入回调函数
2.1 Golang 代码
  设置回调需要中间的桥接函数 CReportData
  package main
  import (
  "fmt"
  )
  /*
  #include
  #include
  #include
  typedef int (*ptfFuncReportData)(const char* data,int len);
  extern int CReportData(ptfFuncReportData pf,const char* data,int len);
  */
  import "C"
  import (
  "bytes"
  "c_references_to_go/sample3/avro_struct"
  "unsafe"
  )
  var callBackFunc C.ptfFuncReportData
  //export SetCallBack
  func SetCallBack(f C.ptfFuncReportData) {
  callBackFunc = f
  }
  //export BeginWork
  func BeginWork() {
  go func() {
  for index := 0; index < 10; index++ {
  var ls avro_struct.LargeStruct
  ls.ID = fmt.Sprintf("ID%d", 1000+index)
  ls.Name = fmt.Sprintf("Peter%d", index)
  ls.Pets = []*avro_struct.Pet{&avro_struct.Pet{Type: "Dog", Name: "WangCai", Age: 5}}
  var buf bytes.Buffer
  ls.Serialize(&buf)
  dataSlice := buf.Bytes()
  GoReportData(dataSlice)
  }
  }()
  }
  func GoReportData(data []byte) {
  C.CReportData(callBackFunc, (*C.char)(unsafe.Pointer(&data[0])), C.int(len(data)))
  }
  func main() {
  }
  bridge.c
  #include "_cgo_export.h"
  int CReportData(ptfFuncReportData pf,const char* data,int len){
  return pf(data,len);
  }
  编译后产生的头文件
  /* Created by "go tool cgo" - DO NOT EDIT. */
  /* package c_references_to_go/sample2 */
  /* Start of preamble from import "C" comments. */
  #line 7 "Y:\\mygo\\src\\c_references_to_go\\sample2\\main.go"
  #include
  #include
  #include
  typedef int (*ptfFuncReportData)(const char* data,int len);
  extern int CReportData(ptfFuncReportData pf,const char* data,int len);
  #line 1 "cgo-generated-wrapper"
  /* End of preamble from import "C" comments. */
  /* Start of boilerplate cgo prologue. */
  #line 1 "cgo-gcc-export-header-prolog"
  #ifndef GO_CGO_PROLOGUE_H
  #define GO_CGO_PROLOGUE_H
  typedef signed char GoInt8;
  typedef unsigned char GoUint8;
  typedef short GoInt16;
  typedef unsigned short GoUint16;
  typedef int GoInt32;
  typedef unsigned int GoUint32;
  typedef long long GoInt64;
  typedef unsigned long long GoUint64;
  typedef GoInt32 GoInt;
  typedef GoUint32 GoUint;
  typedef __SIZE_TYPE__ GoUintptr;
  typedef float GoFloat32;
  typedef double GoFloat64;
  typedef float _Complex GoComplex64;
  typedef double _Complex GoComplex128;
  /*
  static assertion to make sure the file is being used on architecture

  at least with matching>  */
  typedef char _check_for_32_bit_pointer_matching_GoInt[sizeof(void*)==32/8 ? 1:-1];
  typedef struct { const char *p; GoInt n; } GoString;
  typedef void *GoMap;
  typedef void *GoChan;
  typedef struct { void *t; void *v; } GoInterface;
  typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
  #endif
  /* End of boilerplate cgo prologue. */
  #ifdef __cplusplus
  extern "C" {
  #endif
  extern void SetCallBack(ptfFuncReportData p0);
  extern void BeginWork();
  #ifdef __cplusplus
  }
  #endif
2.2 C++代码
  #include
  #include
  #include "sample2.h"
  typedef void (*funcPtrSetCallBack)(ptfFuncReportData p0);
  typedef void (*funcPtrBeginWork)();
  int OnReportData(const char* data,int len){
  printf("OnReportData %x %d\r\n",data,len);
  return 0;
  }
  int main(){
  HMODULE h = LoadLibraryA("sample2.dll");
  if (NULL == h || INVALID_HANDLE_VALUE == h)
  {
  return -1;
  }
  funcPtrSetCallBack pfSetCallBack = (funcPtrSetCallBack)GetProcAddress(h,"SetCallBack");
  funcPtrBeginWork pfBeginWork = (funcPtrBeginWork)GetProcAddress(h,"BeginWork");
  if (pfSetCallBack)
  {
  pfSetCallBack(OnReportData);
  }
  if (pfBeginWork)
  {
  pfBeginWork();
  }
  Sleep(1000*10);
  FreeLibrary(h);
  return 0;
  }
  运行之后的输出:
DSC0000.png

三 C++调用golang函数返回复杂结构体
  不能向C++程序返回Go slice、Go struct。(详情见master分支 src/cmd/cgo/doc.go ,参考5)
3.1 Golang代码
  package main
  import (
  "bytes"
  "unsafe"
  )
  /*
  #include
  #include
  #include
  typedef struct {
  char* Data;
  int DataLen;
  } GetLargeStruct_return;
  extern GetLargeStruct_return* CopyLargeSturct(char* data,int dataLen);
  extern void FreeLargeSturct(GetLargeStruct_return* ptr);
  */
  import "C"
  import (
  "c_references_to_go/sample3/avro_struct"
  )
  //export GetLargeStruct
  func GetLargeStruct(paraIn int) *C.GetLargeStruct_return {
  var ls avro_struct.LargeStruct
  ls.ID = "1000001"
  ls.Name = "Peter"
  ls.Pets = []*avro_struct.Pet{&avro_struct.Pet{Type: "Dog", Name: "WangCai", Age: 5}}
  var buf bytes.Buffer
  ls.Serialize(&buf)
  dataSlice := buf.Bytes()
  return C.CopyLargeSturct((*C.char)(unsafe.Pointer(&dataSlice[0])), C.int(len(dataSlice)))
  }
  //export FreeLargeStruct
  func FreeLargeStruct(ptr *C.GetLargeStruct_return) {
  C.FreeLargeSturct(ptr)
  }
  //export GetLargeStruct2
  func GetLargeStruct2(paraIn int) (*C.char, int) {
  var ls avro_struct.LargeStruct
  ls.ID = "1000001"
  ls.Name = "Peter"
  ls.Pets = []*avro_struct.Pet{&avro_struct.Pet{Type: "Dog", Name: "WangCai", Age: 5}}
  var buf bytes.Buffer
  ls.Serialize(&buf)
  dataSlice := buf.Bytes()
  return (*C.char)(unsafe.Pointer(C.CBytes(dataSlice))), len(dataSlice)
  }
  //export FreeCBytes
  func FreeCBytes(ptr *C.char) {
  C.free(unsafe.Pointer(ptr))
  }
  func main() {
  }
  C函数源码文件 (释放C分配的内存)
  #include "_cgo_export.h"
  GetLargeStruct_return* CopyLargeSturct(char* data,int dataLen){
  GetLargeStruct_return* result = (GetLargeStruct_return*)malloc(sizeof(GetLargeStruct_return));
  result->DataLen = dataLen;
  result->Data = 0;
  if(dataLen>0){
  result->Data = malloc(dataLen);
  memcpy(result->Data,data,dataLen);
  }
  return result;
  }
  void FreeLargeSturct(GetLargeStruct_return* ptr){
  if(ptr != 0){
  if(ptr->Data != 0 ){
  free(ptr->Data);
  }
  free(ptr);
  }
  }
  编译后产生的头文件
  /* Created by "go tool cgo" - DO NOT EDIT. */
  /* package c_references_to_go/sample3 */
  /* Start of preamble from import "C" comments. */
  #line 8 "Y:\\mygo\\src\\c_references_to_go\\sample3\\main.go"
  #include
  #include
  #include
  typedef struct {
  char* Data;
  int DataLen;
  } GetLargeStruct_return;
  extern GetLargeStruct_return* CopyLargeSturct(char* data,int dataLen);
  extern void FreeLargeSturct(GetLargeStruct_return* ptr);
  #line 1 "cgo-generated-wrapper"
  /* End of preamble from import "C" comments. */
  /* Start of boilerplate cgo prologue. */
  #line 1 "cgo-gcc-export-header-prolog"
  #ifndef GO_CGO_PROLOGUE_H
  #define GO_CGO_PROLOGUE_H
  typedef signed char GoInt8;
  typedef unsigned char GoUint8;
  typedef short GoInt16;
  typedef unsigned short GoUint16;
  typedef int GoInt32;
  typedef unsigned int GoUint32;
  typedef long long GoInt64;
  typedef unsigned long long GoUint64;
  typedef GoInt32 GoInt;
  typedef GoUint32 GoUint;
  typedef __SIZE_TYPE__ GoUintptr;
  typedef float GoFloat32;
  typedef double GoFloat64;
  typedef float _Complex GoComplex64;
  typedef double _Complex GoComplex128;
  /*
  static assertion to make sure the file is being used on architecture

  at least with matching>  */
  typedef char _check_for_32_bit_pointer_matching_GoInt[sizeof(void*)==32/8 ? 1:-1];
  typedef struct { const char *p; GoInt n; } GoString;
  typedef void *GoMap;
  typedef void *GoChan;
  typedef struct { void *t; void *v; } GoInterface;
  typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
  #endif
  /* End of boilerplate cgo prologue. */
  #ifdef __cplusplus
  extern "C" {
  #endif
  extern GetLargeStruct_return* GetLargeStruct(GoInt p0);
  extern void FreeLargeStruct(GetLargeStruct_return* p0);
  /* Return type for GetLargeStruct2 */
  struct GetLargeStruct2_return {
  char* r0;
  GoInt r1;
  };
  extern struct GetLargeStruct2_return GetLargeStruct2(GoInt p0);
  extern void FreeCBytes(char* p0);
  #ifdef __cplusplus
  }
  #endif
3.2 C++ 代码
  #include
  #include
  #include "sample3.h"
  typedef GetLargeStruct_return* (*funcPtrGetLargeStruct)(GoInt p0);
  typedef void (*funcPtrFreeLargeStruct)(GetLargeStruct_return* p0);
  typedef struct GetLargeStruct2_return (*funcPtrGetLargeStruct2)(GoInt p0);
  typedef void (*funcPtrFreeCBytes)(char* p0);
  int main(){
  HMODULE h = LoadLibraryA("sample3.dll");
  if (NULL == h || INVALID_HANDLE_VALUE == h)
  {
  return -1;
  }
  funcPtrGetLargeStruct pfGetLargeStruct = (funcPtrGetLargeStruct)GetProcAddress(h,"GetLargeStruct");
  funcPtrFreeLargeStruct pfFreeLargeStruct = (funcPtrFreeLargeStruct)GetProcAddress(h,"FreeLargeStruct");
  if (pfGetLargeStruct)
  {
  GetLargeStruct_return* result = pfGetLargeStruct(5);
  if (result)
  {
  printf("GetLargeStruct(5) return  %x %d\r\n",result->Data,result->DataLen);
  if (pfFreeLargeStruct)
  {
  pfFreeLargeStruct(result);
  }
  }
  }
  funcPtrGetLargeStruct2 pfGetLargeStruct2 = (funcPtrGetLargeStruct2)GetProcAddress(h,"GetLargeStruct2");
  funcPtrFreeCBytes pfFreeCBytes = (funcPtrFreeCBytes)GetProcAddress(h,"FreeCBytes");
  if (pfGetLargeStruct)
  {
  GetLargeStruct2_return result = pfGetLargeStruct2(5);
  printf("GetLargeStruct2(5) return  %x %d\r\n",result.r0,result.r1);
  if (pfFreeCBytes)
  {
  pfFreeCBytes(result.r0);
  }
  }
  FreeLibrary(h);
  return 0;
  }
  运行之后的输出:
DSC0001.png


  本文只讲述C/C++怎么调用golang程序,细节、注意事项及其他在后续随笔中介绍。
参考文献:

  • C? Go? Cgo!      https://blog.golang.org/c-go-cgo
  • Command cgo     https://golang.org/cmd/cgo/
  • Cgo             https://github.com/golang/go/wiki/cgo
  • cmd/cgo: Go type not supported in export: struct #18412
  https://github.com/golang/go/issues/18412

  • https://go.googlesource.com/go/+/master/src/cmd/cgo/doc.go


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