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The following tutorial column from golang will introduce to you how golang calls C programs through cgo. I hope it will be helpful to friends in need!
golang calls C program through cgo
Implementation function: call the dynamic library .so generated by C in golang to realize some functions, such as: call opencv called by C in golang The results obtained by the library
Required things:
1: C dynamic library compiled using Makefile
2: C file
3: Calling code in golang
1: Makefile writing:
HASH_LIBS += -L./lib -L./ -lopencv_core -lopencv_highgui -lopencv_imgproc -lopencv_imgcodecs -lopencv_img_hash TEST_LIBS += $(HASH_LIBS) -lCImageUtil -lboost_filesystem -lopencv_videoio INCS += -I./include -I ./ CXXFLAGS += $(INCS) -fPIC -Wall -O2 -std=c++11 TARGET = -shared -o lib/libCImageUtil.so COMM_SRCS+= opencv_hash.cc scale_image.cc algo.cc md5.cc #COMM_OBJS=$(COMM_SRCS:.cc=.o) main_test : main-test.cc $(CXX) $(CXXFLAGS) $< -o $@ $(TEST_LIBS) CImageUtil: $(CXX) $(CXXFLAGS) $(COMM_SRCS) -o $@ $(HASH_LIBS) $(TARGET) all: CImageUtil main_test
2: The called header file
#pragma once #ifdef __cplusplus extern "C" { #endif void calc_phash(const char *str, int len, char* test, int* flag); int scale_image(const char* src, int srclen, char** dist, int* distlen, char* error); #ifdef __cplusplus } #endif
3:The called cpp file
#include "CImageUtil.h" int scale_image(const char* src, int srclen, char** dist, int* distlen, char* err) { return 0; } void calc_phash(const char *img, int len, char* phash_result, int* flag) { }
4: Calling in golang
package common /* #cgo CFLAGS: -I ../../../ccgo/include/ #cgo LDFLAGS: -L ../../../ccgo/lib/ -lrt -lCImageUtil -lopencv_core -lopencv_highgui -lboost_system -lopencv_imgproc -lopencv_imgcodecs -lboost_filesystem -lopencv_img_hash -lopencv_videoio -lstdc++ #include "CImageUtil.h" #include <stdlib.h> */ import "C" //注意这里要空一行。 import ( "encoding/json" "errors" "fmt" "shumei/mainif/log" "shumei/mainif/config" "strconv" "strings" "time" "unsafe" ) func (this *ParamsChecker) PhashProcess(ip *ImgParams, imgBytes []byte) error { st := time.Now().UnixNano() var phash [32]byte var flag int = 10 C.calc_phash((*C.char)(unsafe.Pointer(&imgBytes[0])), C.int(len(imgBytes)), (*C.char)(unsafe.Pointer(&phash[0])), (*C.int)(unsafe.Pointer(&flag))) if flag != 10 { return errors.New(fmt.Sprintf("ERROR cgo image info wrong: %v", flag)) } ip.Data["phash_vector"] = phash return nil } func (this *ParamsChecker) ScaleImage(ip *ImgParams, imgBytes []byte) error { st := time.Now().UnixNano() var distimg *C.char var distlen C.int var errscale []byte = make([]byte, 256) defer func() { if distimg != nil { defer C.free(unsafe.Pointer(distimg)) distimg = nil } }() code := C.scale_image((*C.char)(unsafe.Pointer(&imgBytes[0])), C.int(len(imgBytes)), &distimg, &distlen, (*C.char)(unsafe.Pointer(&errscale[0]))) distmsgstr := C.GoStringN(distimg, distlen) if code == 0 && distimg != nil { imgBytes = []byte(distmsgstr) ip.Data["img"] = utils.Base64Encode(imgBytes) } else { return errors.New("image scale error") } return nil }
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