sharemem.cpp

来自「包含客户和服务器的升级程序,在linux下可以运行的.」· C++ 代码 · 共 179 行

/*
 * Copyright (C) 2006, Binary Ma
 * Licence: GNU GPL 1991 - version 2
 * Bug report: [e-mail]
*/

#include "sharemem.h"
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/vfs.h>
#include <sys/mount.h>

static const char* VERSION = "0.6.2";

memmap::memmap( const char* file, off_t length )
{
	map = (char*)MAP_FAILED;
	if( NULL == file )
		return;
	
	bool create = true;
	map_size = length;
	if( map_size < 0 )
	{
		struct stat st;
		if( -1 == stat( file, &st ) )
			return;
		
		create = false;
		map_size = st.st_size;
	}
	
	int fd = open( file, O_RDWR | O_CREAT, 0644 );
	if( -1 == fd )
		return;
	
	if( create )
		ftruncate( fd, map_size );
	
	const int MMAP_PROT = PROT_READ | PROT_WRITE;
	map = (char*)mmap( 0, map_size, MMAP_PROT, MAP_SHARED, fd, 0 );
	close( fd );
}

memmap::~memmap()
{
	if( MAP_FAILED != map )
	{
		munmap( map, map_size );
		map = (char*)MAP_FAILED;
	}
}

int memmap::size()
{
	return map_size;
}

share::share( int _size, const char* _name ): size( _size )
{
	eno = 0;
	buf = (char*)MAP_FAILED;
	id = -1;
	create = false;
	mnt = "/_tmpfs";
	name = mnt;
	if( NULL == _name )
		_name = "/shm_default";
	else
	if( *_name != '/' )
		name += '/';
	
	name += _name;
	int flag = O_RDWR | O_SYNC;
	
	// for shm_open even then not set flag O_CREAT,
	// the mode must be explicit set 0
	int mode = 0;
	for( int i = 0; -1 == id && i < 2; i++ )
	{
		if( i != 0 )
		{
			flag |= O_CREAT;
			mode = 0770;
			create = true;
			init_tmpfs();
		}
		
		id = open( name.c_str(), flag, mode );
	}

	if( -1 == id )
	{
		eno = -__LINE__;
		return;
	}

	if( create )
		ftruncate( id, size );
}

share::share( int _size ): size( _size )
{
	eno = 0;
	buf = (char*)MAP_FAILED;
	id = -1;
	create = false;
}

share::~share()
{
	share_close();
}

void share::init_tmpfs()
{
	if( 0 != access( mnt, F_OK ) )
		mkdir( mnt, 0777 );
	
	struct statfs vfs;
	if( 0 == statfs( mnt, &vfs ) )
	{
	    // don't include linux/ext2_fs.h, some OS may compile failed, example: debian.
	    // TMPFS_MAGIC == 0x01021994.
        if( 0x01021994 != vfs.f_type )
            mount( NULL, mnt, "tmpfs", 0, NULL );
	}
}

char* share::share_open()
{
	if( 0 != eno )
		return NULL;
	
	int flag = MAP_SHARED;
	if( -1 == id )
	    flag |= MAP_ANONYMOUS;
	
	buf = (char*)mmap( 0, size, PROT_READ | PROT_WRITE, flag, id, 0 );
	return buf;
}

int share::share_close( bool force )
{
	if( 0 != eno )
		return -__LINE__;
	
	if( -1 != id )
	{
		close( id );
		id = -1;
	}
	
	if( MAP_FAILED != buf )
	{
		munmap( buf, size );
		buf = (char*)MAP_FAILED;
	}
	
	int retval = 0;
	if( create || force )
	{
		retval = remove( name.c_str() );
		
		// if have other process use sharemem, will failed,
		// so, dont judge return value
		umount( mnt );
		rmdir( mnt );
	}
	
	return retval;
}

int share::error()
{
	return eno;
}