文件的上传和下载

一、文件下载

获取资源文件大小有两张方式

1、

HTTP HEAD方法
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:kTimeout];
request.HTTPMethod = @"HEAD";
[NSURLConnection sendAsynchronousRequest:request queue:self.myQueue completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
    NSLog(@"%@", response);
    NSLog(@"---------------");
    NSLog(@"%@", data);
}];
运行测试代码可以发现，HEAD方法只是返回资源信息，而不会返回数据体
应用场景：
获取资源Mimetype
获取资源文件大小，用于端点续传或多线程下载

2

使用块代码获取网络资源大小的方法
- (void)fileSizeWithURL:(NSURL *)url completion:(void (^)(long long contentLength))completion
{
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:kTimeout];
    request.HTTPMethod = @"HEAD";
    NSURLResponse *response = nil;
    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:NULL];

    completion(response.expectedContentLength);
}

确定每次下载数据包的伪代码实现

- (void)downloadFileWithURL:(NSURL *)url
{
    [self fileSizeWithURL:url completion:^(long long contentLength) {
        NSLog(@"文件总大小：%lld", contentLength);
        // 根据大小下载文件
               while (contentLength > kDownloadBytes) {
            NSLog(@"每次下载长度：%lld", (long long)kDownloadBytes);
            contentLength -= kDownloadBytes;
        }
        NSLog(@"最后下载字节数：%lld", contentLength);
    }];
}

HTTP Range的示例
通过设置Range可以指定每次从网路下载数据包的大小
Range示例
bytes=0-499 从0到499的头500个字节
bytes=500-999 从500到999的第二个500字节
bytes=500- 从500字节以后的所有字节
bytes=-500 最后500个字节
bytes=500-599,800-899 同时指定几个范围
Range小结
- 用于分隔
前面的数字表示起始字节数
后面的数组表示截止字节数，没有表示到末尾
, 用于分组，可以一次指定多个Range，不过很少用

分段Range代码实现
long long fromBytes = 0;
long long toBytes = 0;
while (contentLength > kDownloadBytes) {
    toBytes = fromBytes + kDownloadBytes - 1;
    NSString *range = [NSString stringWithFormat:@"bytes=%lld-%lld", fromBytes, toBytes];
    NSLog(@"range %@", range);
    fromBytes += kDownloadBytes;
    contentLength -= kDownloadBytes;
}
fromBytes = fromBytes + contentLength - 1;
NSString *range = [NSString stringWithFormat:@"bytes=%lld-%lld", fromBytes, toBytes];
NSLog(@"range %@", range);

分段下载文件
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:kTimeout];
NSString *range = [NSString stringWithFormat:@"bytes=%lld-%lld", from, end];
[request setValue:range forHTTPHeaderField:@"Range"];

NSURLResponse *response = nil;
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:NULL];

NSLog(@"%@-%@-%ld", range, response, (unsigned long)data.length);
提示：
如果GET包含Range请求头，响应会以状态码206（PartialContent）返回而不是200（OK）

将数据写入文件
// 打开缓存文件
NSFileHandle *fp = [NSFileHandle fileHandleForWritingAtPath:self.cachePath];
// 如果文件不存在，直接写入数据
if (!fp) {
    [data writeToFile:self.cachePath atomically:YES];
} else {
    // 移动到文件末尾
    [fp seekToEndOfFile];
    // 将数据文件追加到文件末尾
    [fp writeData:data];
    // 关闭文件句柄
    [fp closeFile];
}

检查文件大小
// 判断文件是否存在
if ([[NSFileManager defaultManager] fileExistsAtPath:self.cachePath]) {
    NSDictionary *dict = [[NSFileManager defaultManager] attributesOfItemAtPath:self.cachePath error:NULL];
    return [dict[NSFileSize] longLongValue];
} else {
    return 0;
}

提示：由于数据是追加的，为了避免重复从网络下载文件，在下载之前
判断缓存路径中文件是否已经存在
如果存在检查文件大小
如果文件大小与网络资源大小一致，则不再下载

全部代码如下

//
//  MJViewController.m
//  01.文件下载
//
//  Created by apple on 14-4-29.
//  Copyright (c) 2014年 itcast. All rights reserved.
//

#import "MJViewController.h"
#import "FileDownload.h"

@interface MJViewController ()
@property (nonatomic, strong) FileDownload *download;
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@end

@implementation MJViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.download = [[FileDownload alloc] init];
    [self.download downloadFileWithURL:[NSURL URLWithString:@"http://localhost/itcast/images/head4.png"] completion:^(UIImage *image) {

        self.imageView.image = image;
    }];
}

@end

//
//  FileDownload.m
//  01.文件下载
//
//  Created by apple on 14-4-29.
//  Copyright (c) 2014年 itcast. All rights reserved.
//

#import "FileDownload.h"
#import "NSString+Password.h"

#define kTimeOut        2.0f
// 每次下载的字节数
#define kBytesPerTimes  20250

@interface FileDownload()
@property (nonatomic, strong) NSString *cacheFile;
@property (nonatomic, strong) UIImage *cacheImage;
@end

@implementation FileDownload
/**
 为了保证开发的简单,所有方法都不使用多线程,所有的注意力都保持在文件下载上

 在开发中如果碰到比较绕的计算问题时,建议:
 1> 测试数据不要太大
 2> 测试数据的数值变化,能够用笔算计算出准确的数值
 3> 编写代码对照测试

 */
//- (NSString *)cacheFile
//{
//    if (!_cacheFile) {
//        NSString *cacheDir = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
//        _cacheFile = [cacheDir stringByAppendingPathComponent:@"123.png"];
//    }
//    return _cacheFile;
//}
- (UIImage *)cacheImage
{
    if (!_cacheImage) {
        _cacheImage = [UIImage imageWithContentsOfFile:self.cacheFile];
    }
    return _cacheImage;
}

- (void)setCacheFile:(NSString *)urlStr
{
    NSString *cacheDir = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
    urlStr = [urlStr MD5];

    _cacheFile = [cacheDir stringByAppendingPathComponent:urlStr];
}

- (void)downloadFileWithURL:(NSURL *)url completion:(void (^)(UIImage *image))completion
{
    // GCD中的串行队列异步方法
    dispatch_queue_t q = dispatch_queue_create("cn.itcast.download", DISPATCH_QUEUE_SERIAL);

    dispatch_async(q, ^{
        NSLog(@"%@", [NSThread currentThread]);

        // 把对URL进行MD5加密之后的结果当成文件名
        self.cacheFile = [url absoluteString];

        // 1. 从网络下载文件,需要知道这个文件的大小
        long long fileSize = [self fileSizeWithURL:url];
        // 计算本地缓存文件大小
        long long cacheFileSize = [self localFileSize];

        if (cacheFileSize == fileSize) {
            dispatch_async(dispatch_get_main_queue(), ^{
                completion(self.cacheImage);
            });
            NSLog(@"文件已经存在");
            return;
        }

        // 2. 确定每个数据包的大小
        long long fromB = 0;
        long long toB = 0;
        // 计算起始和结束的字节数
        while (fileSize > kBytesPerTimes) {
            // 20480 + 20480
            //
            toB = fromB + kBytesPerTimes - 1;

            // 3. 分段下载文件
            [self downloadDataWithURL:url fromB:fromB toB:toB];

            fileSize -= kBytesPerTimes;
            fromB += kBytesPerTimes;
        }
        [self downloadDataWithURL:url fromB:fromB toB:fromB + fileSize - 1];

        dispatch_async(dispatch_get_main_queue(), ^{
            completion(self.cacheImage);
        });
    });
}

#pragma mark 下载指定字节范围的数据包
/**
 NSURLRequestUseProtocolCachePolicy = 0,        // 默认的缓存策略,内存缓存

 NSURLRequestReloadIgnoringLocalCacheData = 1,  // 忽略本地的内存缓存
 NSURLRequestReloadIgnoringCacheData
 */
- (void)downloadDataWithURL:(NSURL *)url fromB:(long long)fromB toB:(long long)toB
{
    NSLog(@"数据包:%@", [NSThread currentThread]);

    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:kTimeOut];

    // 指定请求中所要GET的字节范围
    NSString *range = [NSString stringWithFormat:@"Bytes=%lld-%lld", fromB, toB];
    [request setValue:range forHTTPHeaderField:@"Range"];
    NSLog(@"%@", range);

    NSURLResponse *response = nil;
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:NULL];

    // 写入文件,覆盖文件不会追加
//    [data writeToFile:@"/Users/aplle/Desktop/1.png" atomically:YES];
    [self appendData:data];

    NSLog(@"%@", response);
}

#pragma mark - 读取本地缓存文件大小
- (long long)localFileSize
{
    // 读取本地文件信息
    NSDictionary *dict = [[NSFileManager defaultManager] attributesOfItemAtPath:self.cacheFile error:NULL];
    NSLog(@"%lld", [dict[NSFileSize] longLongValue]);

    return [dict[NSFileSize] longLongValue];
}

#pragma mark - 追加数据到文件
- (void)appendData:(NSData *)data
{
    // 判断文件是否存在
    NSFileHandle *fp = [NSFileHandle fileHandleForWritingAtPath:self.cacheFile];
    // 如果文件不存在创建文件
    if (!fp) {
        [data writeToFile:self.cacheFile atomically:YES];
    } else {
        // 如果文件已经存在追加文件
        // 1> 移动到文件末尾
        [fp seekToEndOfFile];
        // 2> 追加数据
        [fp writeData:data];
        // 3> 写入文件
        [fp closeFile];
    }
}

#pragma mark - 获取网络文件大小
- (long long)fileSizeWithURL:(NSURL *)url
{
    // 默认是GET
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:kTimeOut];

    // HEAD 头,只是返回文件资源的信息,不返回具体是数据
    // 如果要获取资源的MIMEType,也必须用HEAD,否则,数据会被重复下载两次
    request.HTTPMethod = @"HEAD";

    // 使用同步方法获取文件大小
    NSURLResponse *response = nil;

    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:NULL];

    // expectedContentLength文件在网络上的大小
    NSLog(@"%lld", response.expectedContentLength);

    return response.expectedContentLength;
}

@end

二、文件上传

代码如下

//
//  MJViewController.m
//  02.Post上传
//
//  Created by apple on 14-4-29.
//  Copyright (c) 2014年 itcast. All rights reserved.
//

#import "MJViewController.h"
#import "UploadFile.h"

@interface MJViewController ()

@end

@implementation MJViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UploadFile *upload = [[UploadFile alloc] init];

    NSString *urlString = @"http://localhost/upload.php";

    NSString *path = [[NSBundle mainBundle] pathForResource:@"头像1.png" ofType:nil];
    NSData *data = [NSData dataWithContentsOfFile:path];

    [upload uploadFileWithURL:[NSURL URLWithString:urlString] data:data];
}

@end

//
//  UploadFile.m
//  02.Post上传
//
//  Created by apple on 14-4-29.
//  Copyright (c) 2014年 itcast. All rights reserved.
//

#import "UploadFile.h"

@implementation UploadFile
// 拼接字符串
static NSString *boundaryStr = @"--";   // 分隔字符串
static NSString *randomIDStr;           // 本次上传标示字符串
static NSString *uploadID;              // 上传(php)脚本中，接收文件字段

- (instancetype)init
{
    self = [super init];
    if (self) {
        randomIDStr = @"itcast";
        uploadID = @"uploadFile";
    }
    return self;
}

#pragma mark - 私有方法
- (NSString *)topStringWithMimeType:(NSString *)mimeType uploadFile:(NSString *)uploadFile
{
    NSMutableString *strM = [NSMutableString string];

    [strM appendFormat:@"%@%@
", boundaryStr, randomIDStr];
    [strM appendFormat:@"Content-Disposition: form-data; name="%@"; filename="%@"
", uploadID, uploadFile];
    [strM appendFormat:@"Content-Type: %@

", mimeType];

    NSLog(@"%@", strM);
    return [strM copy];
}

- (NSString *)bottomString
{
    NSMutableString *strM = [NSMutableString string];

    [strM appendFormat:@"%@%@
", boundaryStr, randomIDStr];
    [strM appendString:@"Content-Disposition: form-data; name="submit"

"];
    [strM appendString:@"Submit
"];
    [strM appendFormat:@"%@%@--
", boundaryStr, randomIDStr];

    NSLog(@"%@", strM);
    return [strM copy];
}

#pragma mark - 上传文件
- (void)uploadFileWithURL:(NSURL *)url data:(NSData *)data
{
    // 1> 数据体
    NSString *topStr = [self topStringWithMimeType:@"image/png" uploadFile:@"头像1.png"];
    NSString *bottomStr = [self bottomString];

    NSMutableData *dataM = [NSMutableData data];
    [dataM appendData:[topStr dataUsingEncoding:NSUTF8StringEncoding]];
    [dataM appendData:data];
    [dataM appendData:[bottomStr dataUsingEncoding:NSUTF8StringEncoding]];

    // 1. Request
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:2.0f];

    // dataM出了作用域就会被释放,因此不用copy
    request.HTTPBody = dataM;

    // 2> 设置Request的头属性
    request.HTTPMethod = @"POST";

    // 3> 设置Content-Length
    NSString *strLength = [NSString stringWithFormat:@"%ld", (long)dataM.length];
    [request setValue:strLength forHTTPHeaderField:@"Content-Length"];

    // 4> 设置Content-Type
    NSString *strContentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", randomIDStr];
    [request setValue:strContentType forHTTPHeaderField:@"Content-Type"];

    // 3> 连接服务器发送请求
    [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@", result);
    }];
}



@end