oc中NSFileHandle的初学-文件读取

1、NSFileHandle是oc中用来操作文件的类，通过此类可以读写文件，可以断点续传。2、NSFileHandle类中常用的方法//文件中的全部内容（有效数据，包括空格和汉字，其中空格在一个字节，汉字占三个字节）@property (readonly, copy) NSData *availableData;//读取文件中的全部内容- (NSData *)readDataToEndOfFile;//读取文件中指定长度(字节)的内容- (NSData *)readDataOfLength:(NSUInteger)length;//写数据到文件中- (void)writeData:(NSData *)data;//文件末尾的偏移量- (unsigned long long)seekToEndOfFile;//跳到文件中指定位置的偏移量- (void)seekToFileOffset:(unsigned long long)offset;//将文件的长度设定为指定长度的字节- (void)truncateFileAtOffset:(unsigned long long)offset;//关闭文件- (void)closeFile;//打开一个文件准备读取+ (instancetype)fileHandleForReadingAtPath:(NSString *)path;//打开一个文件准备写入+ (instancetype)fileHandleForWritingAtPath:(NSString *)path;//打开一个文件准备更新(写入、更新)+ (instancetype)fileHandleForUpdatingAtPath:(NSString *)path;3、例子////  main.m//  NSFileHandleStudy////  Created by 肖国健 on 15-3-4.//  Copyright (c) 2015年 Shone. All rights reserved.//#import <Foundation/Foundation.h>//读取文件中的内容void readFileContent(){    //获取根路径   /Users/xiaoguojian    NSString *homePath = NSHomeDirectory();    NSLog(@"homePath=%@",homePath);    NSString *path = [homePath stringByAppendingPathComponent:@"文本.txt"];    //打开一个文件准备读取    //NSFileHandle *fileHandle = [NSFileHandle fileHandleForReadingAtPath:path];    //打开一个文件准备更新    NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:path];    NSData *data1 = [fileHandle readDataToEndOfFile];//读取数据    //将NSDataz转换成NSString类型    NSString *sdata1 = [[NSString alloc] initWithData:data1 encoding:NSUTF8StringEncoding];    NSLog(@"content1=%@",sdata1);    //关闭    [fileHandle closeFile];}//在文件最后添加内容void appendFileContent(){    //获取根路径   /Users/xiaoguojian    NSString *homePath = NSHomeDirectory();    NSLog(@"homePath=%@",homePath);    NSString *path = [homePath stringByAppendingPathComponent:@"文本.txt"];    //打开一个文件准备更新    NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:path];    NSString *append = @"这是追加的内容";    //将NSString类型的字符串转换成NSData类型的    NSData *appData = [append dataUsingEncoding:NSUTF8StringEncoding];    //写数据到文件中    [fileHandle writeData:appData];    //关闭    [fileHandle closeFile];}//在指定的位置添加内容void appendFileContentInControl(){    //获取根路径   /Users/xiaoguojian    NSString *homePath = NSHomeDirectory();    NSLog(@"homePath=%@",homePath);    NSString *path = [homePath stringByAppendingPathComponent:@"文本.txt"];    //打开一个文件准备更新,只有更新的情况下才能对文件进行更新操作    NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:path];    //获取文件中的字节数，空格占一个，汉字占三个    NSUInteger length = [fileHandle availableData].length;    NSLog(@"length=%ld",length);    //在文件指定的位置添加内容，会替换掉节点后面的内容    [fileHandle seekToFileOffset:length/2];    NSString *append = @"这是追加的内容";    //将NSString类型的字符串转换成NSData类型的    NSData *appData = [append dataUsingEncoding:NSUTF8StringEncoding];    //写数据到文件中    [fileHandle writeData:appData];    [fileHandle closeFile];}//赋值一个文件中的内容到另外一个文件中void copyFileContentToAnotherFile(){    //获取根目录    NSString *homePath = NSHomeDirectory();    NSString *resourcePath = [homePath stringByAppendingPathComponent:@"resource.txt"];    NSString *destPath = [homePath stringByAppendingPathComponent:@"dest.txt"];    //用NSFileManager创建文件    NSFileManager *fileManager = [NSFileManager defaultManager];    BOOL success = [fileManager createFileAtPath:destPath contents:nil attributes:nil];    if (success) {        NSLog(@"create success!");    } else {        NSLog(@"create failure!");    }    NSFileHandle *resHandle = [NSFileHandle fileHandleForReadingAtPath:resourcePath];    NSFileHandle *destHandle = [NSFileHandle fileHandleForWritingAtPath:destPath];    //读取文件中的全部数据    NSData *content = [resHandle readDataToEndOfFile];    //NSData *content1 = [resHandle availableData];//这个也是读取文件中的全部数据    [destHandle writeData:content];    //关闭    [resHandle closeFile];    [destHandle closeFile];}int main(int argc, const char * argv[]) {    @autoreleasepool {        //获取根目录        NSString *homePath = NSHomeDirectory();        NSString *resourcePath = [homePath stringByAppendingPathComponent:@"resource.txt"];        NSString *destPath = [homePath stringByAppendingPathComponent:@"dest.txt"];        //用NSFileManager创建文件        NSFileManager *fileManager = [NSFileManager defaultManager];        BOOL success = [fileManager createFileAtPath:destPath contents:nil attributes:nil];        if (success) {            NSLog(@"create success!");        } else {            NSLog(@"create failure!");        }        NSFileHandle *resHandle = [NSFileHandle fileHandleForReadingAtPath:resourcePath];        NSFileHandle *destHandle = [NSFileHandle fileHandleForWritingAtPath:destPath];        NSUInteger l = 6;        //读取文件中的全部数据        NSData *content = [resHandle readDataOfLength:l];        //NSData *content1 = [resHandle availableData];//这个也是读取文件中的全部数据        [destHandle writeData:content];        //关闭        [resHandle closeFile];        [destHandle closeFile];    }    return 0;}