只演示c和python
首先,让我们编写Go代码。 假设我们已经编写了一个Go库,希望将其提供给其他语言使用。 在将代码编译到共享库中之前,要遵循四个要求:
- 该软件包必须是main包。 编译器会将软件包及其所有依赖项构建到单个共享库二进制文件中。
- 源必须import "C"。
- 使用//export注释来注释希望其他语言可以使用的功能。
- 必须声明一个空的main函数。
以下Go源代码导出了四个函数Add,Cosine,Sort和Log。
package main
import "C"
import (
"fmt"
"math"
"sort"
"sync"
)
var count int
var mtx sync.Mutex
//export Add
func Add(a, b int) int {
return a + b
}
//export Cosine
func Cosine(x float64) float64 {
return math.Cos(x)
}
//export Sort
func Sort(vals []int) {
sort.Ints(vals)
}
//export Log
func Log(msg string) int {
mtx.Lock()
defer mtx.Unlock()
fmt.Println(msg)
count++
return count
}
func main() {}
使用-buildmode=c-shared
build标志编译该软件包,以创建共享库二进制文件:
go build -o awesome.so -buildmode=c-shared awesome.go
最后生成awesome.h和awesome.so
c
有两种方法可以使用共享库从C调用Go函数。首先,我们可以在编译时静态绑定共享库,但可以在运行时动态链接它。或者,在运行时动态加载和绑定Go功能符号。
动态链接
在这种方法中,我们使用头文件来静态引用共享对象文件中导出的类型和函数。代码简单干净,如下所示:
#include <stdio.h>
#include "awesome.h"
int main() {
printf("Using awesome lib from C:\n");
//Call Add() - passing integer params, interger result
GoInt a = 12;
GoInt b = 99;
printf("awesome.Add(12,99) = %d\n", Add(a, b));
//Call Cosine() - passing float param, float returned
printf("awesome.Cosine(1) = %f\n", (float)(Cosine(1.0)));
//Call Sort() - passing an array pointer
GoInt data[6] = {77, 12, 5, 99, 28, 23};
GoSlice nums = {data, 6, 6};
Sort(nums);
printf("awesome.Sort(77,12,5,99,28,23): ");
for (int i = 0; i < 6; i++){
printf("%d,", ((GoInt *)nums.data)[i]);
}
printf("\n");
//Call Log() - passing string value
GoString msg = {"Hello from C!", 13};
Log(msg);
}
接下来我们编译C代码,指定共享对象库:
$> gcc -o client client1.c ./awesome.so
当生成的二进制文件被执行时,它会链接到awesome。调用从Go导出的函数,如下所示。
$> ./client
awesome.Add(12,99) = 111
awesome.Cosine(1) = 0.540302
awesome.Sort(77,12,5,99,28,23): 5,12,23,28,77,99,
Hello from C!
Dynamically Loaded
在这种方法中,C代码使用动态链接加载器库(libdll .so
)来动态加载和绑定导出的符号。它使用dhfcn.h
,例如dlopen
打开库文件,dlsym
查找符号,dlerror
检索错误,dlclose
关闭共享库文件。
#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>
// define types needed
typedef long long go_int;
typedef double go_float64;
typedef struct{void *arr; go_int len; go_int cap;} go_slice;
typedef struct{const char *p; go_int len;} go_str;
int main(int argc, char **argv) {
void *handle;
char *error;
// use dlopen to load shared object
handle = dlopen ("./awesome.so", RTLD_LAZY);
if (!handle) {
fputs (dlerror(), stderr);
exit(1);
}
// resolve Add symbol and assign to fn ptr
go_int (*add)(go_int, go_int) = dlsym(handle, "Add");
if ((error = dlerror()) != NULL) {
fputs(error, stderr);
exit(1);
}
// call Add()
go_int sum = (*add)(12, 99);
printf("awesome.Add(12, 99) = %d\n", sum);
// resolve Cosine symbol
go_float64 (*cosine)(go_float64) = dlsym(handle, "Cosine");
if ((error = dlerror()) != NULL) {
fputs(error, stderr);
exit(1);
}
// Call Cosine
go_float64 cos = (*cosine)(1.0);
printf("awesome.Cosine(1) = %f\n", cos);
// resolve Sort symbol
void (*sort)(go_slice) = dlsym(handle, "Sort");
if ((error = dlerror()) != NULL) {
fputs(error, stderr);
exit(1);
}
// call Sort
go_int data[5] = {44,23,7,66,2};
go_slice nums = {data, 5, 5};
sort(nums);
printf("awesome.Sort(44,23,7,66,2): ");
for (int i = 0; i < 5; i++){
printf("%d,", ((go_int *)data)[i]);
}
printf("\n");
// resolve Log symbol
go_int (*log)(go_str) = dlsym(handle, "Log");
if ((error = dlerror()) != NULL) {
fputs(error, stderr);
exit(1);
}
// call Log
go_str msg = {"Hello from C!", 13};
log(msg);
// close file handle when done
dlclose(handle);
}
在前面的代码中,我们定义了兼容Go的C类型go_int
、go_float
、go_slice
和go_str
的子集。我们使用dlsym
加载符号Add
、Cosine
、Sort
和Log
,并将它们分配给各自的函数指针。接下来,我们编译将其与dl
库(不是awesome.so)连接的代码,如下所示:
$> gcc -o client client2.c -ldl
$> ./client
awesome.Add(12, 99) = 111
awesome.Cosine(1) = 0.540302
awesome.Sort(44,23,7,66,2): 2,7,23,44,66,
Hello from C!
Python
Python 我们使用 ctypes
foreign function library 来调用 awesome.so
from __future__ import print_function
from ctypes import *
lib = cdll.LoadLibrary("./awesome.so")
# describe and invoke Add()
lib.Add.argtypes = [c_longlong, c_longlong]
lib.Add.restype = c_longlong
print("awesome.Add(12,99) = %d" % lib.Add(12,99))
# describe and invoke Cosine()
lib.Cosine.argtypes = [c_double]
lib.Cosine.restype = c_double
print("awesome.Cosine(1) = %f" % lib.Cosine(1))
# define class GoSlice to map to:
# C type struct { void *data; GoInt len; GoInt cap; }
class GoSlice(Structure):
_fields_ = [("data", POINTER(c_void_p)), ("len", c_longlong), ("cap", c_longlong)]
nums = GoSlice((c_void_p * 5)(74, 4, 122, 9, 12), 5, 5)
# call Sort
lib.Sort.argtypes = [GoSlice]
lib.Sort.restype = None
lib.Sort(nums)
print("awesome.Sort(74,4,122,9,12) = %s" % [nums.data[i] for i in range(nums.len)])
# define class GoString to map:
# C type struct { const char *p; GoInt n; }
class GoString(Structure):
_fields_ = [("p", c_char_p), ("n", c_longlong)]
# describe and call Log()
lib.Log.argtypes = [GoString]
lib.Log.restype = c_longlong
msg = GoString(b"Hello Python!", 13)
print("log id %d"% lib.Log(msg))
$> python client.py
awesome.Add(12,99) = 111
awesome.Cosine(1) = 0.540302
awesome.Sort(74,4,122,9,12) = [4, 9, 12, 74, 122]
Hello Python!
log id 1
Python CFFI (contributed)
The following example was contributed by @sbinet (thank you!)
Python还有一个可移植的CFFI库,可以在Python2/Python3/pypy下正常工作。的
下面的示例使用c包装器定义导出的Go类型。这使得python示例更容易理解。
from __future__ import print_function
import sys
from cffi import FFI
is_64b = sys.maxsize > 2**32
ffi = FFI()
if is_64b: ffi.cdef("typedef long GoInt;\n")
else: ffi.cdef("typedef int GoInt;\n")
ffi.cdef("""
typedef struct {
void* data;
GoInt len;
GoInt cap;
} GoSlice;
typedef struct {
const char *data;
GoInt len;
} GoString;
GoInt Add(GoInt a, GoInt b);
double Cosine(double v);
void Sort(GoSlice values);
GoInt Log(GoString str);
""")
lib = ffi.dlopen("./awesome.so")
print("awesome.Add(12,99) = %d" % lib.Add(12,99))
print("awesome.Cosine(1) = %f" % lib.Cosine(1))
data = ffi.new("GoInt[]", [74,4,122,9,12])
nums = ffi.new("GoSlice*", {'data':data, 'len':5, 'cap':5})
lib.Sort(nums[0])
print("awesome.Sort(74,4,122,9,12) = %s" % [
ffi.cast("GoInt*", nums.data)[i]
for i in range(nums.len)])
data = ffi.new("char[]", b"Hello Python!")
msg = ffi.new("GoString*", {'data':data, 'len':13})
print("log id %d" % lib.Log(msg[0]))
更多的语言demo请点击https://github.com/vladimirvivien/go-cshared-examples