Golang丰富的I/O 二----cgo版Hello World

Posted 2020-10-16 majianguo

Golang丰富的I/O 二----cgo版Hello World

在《Golang丰富的I/O----用N种Hello World展示》中用多种Hello World的写法展示了golang丰富强大的I/O功能，在此补充一种cgo版的Hello World。以下代码源自go源码：

main.go

package main


import"stdio"


func main() {

    stdio.Stdout.WriteString(stdio.Greeting + "\\n")

}

　　

file.go

// skip


// Copyright 2009 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.


/*

A trivial example of wrapping a C library in Go.

For a more complex example and explanation,

see ../gmp/gmp.go.

*/



package stdio


/*

#include <stdio.h>

#include <stdlib.h>

#include <sys/stat.h>

#include <errno.h>


char* greeting = "hello, world";

*/

import"C"

import"unsafe"


typeFile C.FILE


// Test reference to library symbol.

// Stdout and stderr are too special to be a reliable test.

//var = C.environ


func (f *File) WriteString(s string) {

    p := C.CString(s)

    C.fputs(p, (*C.FILE)(f))

    C.free(unsafe.Pointer(p))

    f.Flush()

}


func (f *File) Flush() {

    C.fflush((*C.FILE)(f))

}


var Greeting = C.GoString(C.greeting)

var Gbytes = C.GoBytes(unsafe.Pointer(C.greeting), C.int(len(Greeting)))

　　

stdio.go

// skip


// Copyright 2009 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.


package stdio


/*

#include <stdio.h>


// on mingw, stderr and stdout are defined as &_iob[FILENO]

// on netbsd, they are defined as &__sF[FILENO]

// and cgo doesn\'t recognize them, so write a function to get them,

// instead of depending on internals of libc implementation.

FILE *getStdout(void) { return stdout; }

FILE *getStderr(void) { return stderr; }

*/

import"C"


var Stdout = (*File)(C.getStdout())

var Stderr = (*File)(C.getStderr())

　　

Go程序可以通过cgo工具非常方便地调用c函数。关于go调用C/C++或者C/C++调用go程序可以参考之前的系列随笔《C/C++调用golang》和《calling c++ from golang with swig---windows dll》