复制文件: 节约内存 每次读取5k

　　　　

　　　　     NSString *homePath = NSHomeDirectory();//获得根目录
            NSString *filePath = [homePath stringByAppendingPathComponent: @"/Movies/wp.MP4"];//获得源文件路径
            NSString *targetPath = [homePath stringByAppendingPathComponent: @"/Documents/wpvdisk.MP4"];//获得目标文件路径

            //获得文件的大小;
            NSFileManager *fileManage = [NSFileManager defaultManager];
            if ([fileManage fileExistsAtPath: filePath] == NO) {
                NSLog(@"file not exist");
                return 1;
            }

            BOOL succeed = [fileManage createFileAtPath: targetPath contents: nil attributes: nil];
            if (succeed) {
                NSLog(@"创建成功...");
            }

            NSFileHandle *srcHandle = [NSFileHandle fileHandleForReadingAtPath: filePath];//将通道插入源文件

            NSFileHandle *targetHandle = [NSFileHandle fileHandleForUpdatingAtPath: targetPath];//讲通道插入目标文件

            NSInteger readLength = 0;//初始化读取的字节数
            NSDictionary *fileAttributes = [fileManage attributesOfItemAtPath:filePath error:nil];//获得文件属性
            NSInteger fileSize = [[fileAttributes objectForKey: NSFileSize] longValue];//获得文件的大小


            BOOL isEnd = YES;
            NSData *data = nil;
            NSAutoreleasePool *pool = nil;

            int i = 0;
            while (isEnd) {
                if (i == 10) {//5mb清楚一次内存
                    [pool release];
                    pool = [[NSAutoreleasePool alloc] init];
                }
                NSInteger subLength = fileSize - readLength;            
                if (subLength < 5000) {//长度小于5000的就把剩下的读完吧.
                    isEnd = NO;
                    data = [srcHandle readDataToEndOfFile];
                }else{
                    data = [srcHandle readDataOfLength: 5000];
                    readLength += 5000;
                    [srcHandle seekToFileOffset: readLength];
                }
                [targetHandle writeData: data];
                i++;
            }
                
                [srcHandle closeFile];
                [targetHandle closeFile];
                NSLog(@"Copy is over!");

            

如果没有关闭ARC的会自动报错,建议关闭ARC.