NSFileHandle(文件对接器) 

 1 #import "ViewController.h"
 2 
 3 @interface ViewController ()
 4 
 5 @end
 6 
 7 @implementation ViewController
 8 
 9 - (void)viewDidLoad {
10     [super viewDidLoad];
11    //由于文件对接器不能创建文件,所以必须借助文件管理器创建文件,
12     NSString *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
13     
14     NSString *filePath = [documents stringByAppendingPathComponent:@"text.txt"];
15     NSString *str = @"123456789abcdedfghij";
16     [str writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
17     NSLog(@"%@",filePath);
18     
19     //文件对接器,对文件内容进行操作
20     
21     //读取
22     NSFileHandle *readFileHandle = [NSFileHandle fileHandleForReadingAtPath:filePath];
23     //从文件中得到可用数据
24     //NSData *availableData = [readFileHandle availableData];
25     //NSLog(@"%@",[[NSString alloc] initWithData:availableData encoding:NSUTF8StringEncoding]);
26     
27     //从当前节点,读取指定长度的数据,须把前边的availbleData注掉,不然取不到
28     NSData *lengthData = [readFileHandle readDataOfLength:10];
29     NSLog(@"%@",[[NSString alloc] initWithData:lengthData encoding:NSUTF8StringEncoding]);
30     
31     //设置节点偏移量
32     [readFileHandle seekToFileOffset:0];
33     NSData *lengthData2 = [readFileHandle readDataOfLength:5];
34     NSLog(@"%@",[[NSString alloc] initWithData:lengthData2 encoding:NSUTF8StringEncoding]);
35     
36     NSData *lengthData3 = [readFileHandle readDataOfLength:5];
37     NSLog(@"%@",[[NSString alloc] initWithData:lengthData3 encoding:NSUTF8StringEncoding]);
38     //从当前节点读取到文件末尾
39     NSData *endData = [readFileHandle readDataToEndOfFile];
40     NSLog(@"%@",[[NSString alloc] initWithData:endData encoding:NSUTF8StringEncoding]);
41     
42     //关闭文件
43     [readFileHandle closeFile];
44     //写入数据
45     NSFileHandle *writeHandle = [NSFileHandle fileHandleForWritingAtPath:filePath];
46     
47     //设置节点位置
48     [writeHandle  seekToFileOffset:10];
49     //写入
50     [writeHandle writeData:lengthData];
51     //获取节点偏移量
52     NSInteger offset = [writeHandle offsetInFile];
53     NSLog(@"%ld",offset);
54     
55     //将文件长度设置为偏移量
56     [writeHandle truncateFileAtOffset:40];
57     //关闭文件
58     [writeHandle closeFile];
59     
60     
61 }

 

posted @ 2016-03-10 22:06  恒远也  阅读(214)  评论(0)    收藏  举报