////  main.m//  复制大型文件（一次读5K）////  Created by on 14-10-19.//  Copyright (c) 2014年. All rights reserved.//#import 
    
     int main(int argc, const char * argv[]) {    @autoreleasepool {        NSString *srcPath = @"/Users/wujiafeng/Downloads/A.tud";        NSString *targetPath = @"/Users/wujiafeng/Desktop/B.tud";        NSFileManager *fileManager = [NSFileManager defaultManager];        BOOL success = [fileManager createFileAtPath:targetPath contents:nil attributes:nil];        if (!success) {            NSLog(@"创建文件失败");        }        NSFileHandle *infile = [NSFileHandle fileHandleForReadingAtPath:srcPath];        NSFileHandle *outfile = [NSFileHandle fileHandleForWritingAtPath:targetPath];//        用attributesOfItemAtPath方法获取文件的属性//        获取文件的长度//        这里不要使用//        [infile availableData];//        因为这个方法是“从设备或通道返回可用的数据”//        所以如果文件很大的话，那么程序占用资源会很多        NSDictionary *fileAttri = [fileManager attributesOfItemAtPath:srcPath error:nil];        NSNumber *fileSizeNum = [fileAttri objectForKey:NSFileSize];        BOOL isEnd = YES;        NSInteger readSize = 0;        NSInteger fileSize = [fileSizeNum longValue];        /* ====== 关闭ARC模式下的写法 =====*/        /*        NSAutoreleasePool *pool = nil;        int n = 0;        while (isEnd) {            if (n % 10 == 0) {//                循环10次，release一下自动释放池//                保证程序占用少量的内存                [pool release];                pool = [[NSAutoreleasePool alloc] init];            }            NSData *data = nil;//            文件剩余的大小            NSInteger subSize = fileSize - readSize;            if (subSize <= 5000) {                isEnd = NO;//                如果源文件剩余读取大小少于5000字节，则直接读取到文件末尾即可                data = [infile readDataToEndOfFile];            } else {                data = [infile readDataOfLength:5000];                readSize += 5000;//                将偏移量移动至刚才读取到的位置，以便下一次从偏移量开始读取                [infile seekToFileOffset:readSize];            }            [outfile writeData:data];            n++;        }        */                /*===== 启动ARC模式下的写法 =====*/        int n = 0;        while (isEnd) {//            这里的@autoreleasepool{}是写在循环内的，不要将其写在循环外            @autoreleasepool {                NSData *data = nil;                NSInteger subSize = fileSize - readSize;                if (subSize <= 5000) {                    isEnd = NO;                    data = [infile readDataToEndOfFile];                } else {                    data = [infile readDataOfLength:5000];                    readSize += 5000;                    [infile seekToFileOffset:readSize];                }                [outfile writeData:data];                n++;            }        }        [infile closeFile];        [outfile closeFile];        NSLog(@"文件复制完毕");    }    return 0;}