本文转载至 http://www.cnblogs.com/A-Long-Way-Chris/p/3539679.html

前段时间在公司的产品中支持了够快网盘，用于云盘存储。

在这个过程中，学习到了很多新的知识，也遇到了很多问题，在此记录一下。

首先就够快的API总结一下。

一、请求参数中的签名。第一点是生成字符串，例如”2\n3\n1”，在C#中是不需要加上@前置符号的，这是我一个同事犯过的错误。第二点是签名算法，按照原文提示：将生成的字符利用client_secret作为key进行hmac-sha1加密，然后再进行base64 encode，最后对结果进行rfc3986 URL编码，即：encodeURI(base64_encode(hmac-sha1([string], [client_secret])))。OC的代码如下：

- (NSString*)getRequestSign:(NSString*)string
{
const char *cString = [string cStringUsingEncoding:NSUTF8StringEncoding];
const char *cSecret = [kCHRISGoKuaiClientSecret cStringUsingEncoding:NSUTF8StringEncoding];

char cHMAC\[CC\_SHA1\_DIGEST\_LENGTH\];  
CCHmac(kCCHmacAlgSHA1, cSecret, strlen(cSecret), cString, strlen(cString), cHMAC);

NSData \*HMAC = \[\[NSData alloc\] initWithBytes:cHMAC length:CC\_SHA1\_DIGEST\_LENGTH\];  
NSString \*hash = \[HMAC base64Encoding\];  
\[HMAC release\];

NSString \*sign = (NSString\*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)hash, NULL, (CFStringRef)@"!\*'();:@&=+$,/?%#\[\]", kCFStringEncodingUTF8);  
return sign;  

}

在此，需要先添加头文件引用：

#import 和#import

二、删除和上传api中的路径参数。对象若为文件，则api中路径参数需要去掉首尾的”/”符号；对象若为文件夹，则api中需要在上述基础上，再在末尾加上一个”/”符号。

保存access_token。

在得到用户的access_token、expires_in、refresh_token以后，可以保存到设备端，避免繁琐的登陆授权操作。采用NSUserDefaults是不安全的，证书和密码之类的私密信息需要更为安全的keychain来保存。封装的keychain如下：

#import

@interface CHRISKeyChain : NSObject

@property (readwrite, nonatomic, retain) NSDictionary* keyChainDic;

• (id)keyChainForId:(NSString*)keyChainId;

• (NSDictionary *)credentials;

• (void)setCredentials:(NSDictionary *)credentials;

• (void)deleteCredentials;
  @end

#import "CHRISKeyChain.h"

static NSMutableDictionary* g_keyChainDic = nil;

@implementation CHRISKeyChain
@synthesize keyChainDic = _keyChainDic;

• (id)keyChainForId:(NSString*)keyChainId
  {
  if (!g_keyChainDic)
  {
  g_keyChainDic = [[NSMutableDictionary dictionary] retain];
  }
  CHRISKeyChain* keyChainObject = [g_keyChainDic objectForKey:keyChainId];
  if (!keyChainObject)
  {
  NSDictionary* keyChainDict = [NSDictionary dictionaryWithObjectsAndKeys:
  (id)kSecClassGenericPassword, (id)kSecClass,
  keyChainId, (id)kSecAttrService, nil];
  keyChainObject = [[[CHRISKeyChain alloc] init] autorelease];
  keyChainObject.keyChainDic = keyChainDict;
  [g_keyChainDic setObject:keyChainObject forKey:keyChainId];
  return keyChainObject;
  }
  return keyChainObject;
  }

• (void)dealloc
  {
  self.keyChainDic = nil;
  [super dealloc];
  }

• (NSDictionary *)credentials
  {
  NSMutableDictionary *searchDict = [NSMutableDictionary dictionaryWithDictionary:_keyChainDic];
  [searchDict setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
  [searchDict setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnAttributes];
  [searchDict setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];

  NSDictionary *attrDict = nil;
  OSStatus status = SecItemCopyMatching((CFDictionaryRef)searchDict, (CFTypeRef *)&attrDict);
  [attrDict autorelease];
  NSData *foundValue = [attrDict objectForKey:(id)kSecValueData];

  if (status == noErr && foundValue)
  {
  return [NSKeyedUnarchiver unarchiveObjectWithData:foundValue];
  }
  if (status != errSecItemNotFound)
  {
  NSLog(@"error reading stored credentials (%ld)", status);
  }
  return nil;
  }

• (void)setCredentials:(NSDictionary *)credentials
  {
  NSData *credentialData = [NSKeyedArchiver archivedDataWithRootObject:credentials];

  NSMutableDictionary *attrDict = [NSMutableDictionary dictionaryWithDictionary:_keyChainDic];
  [attrDict setObject:credentialData forKey:(id)kSecValueData];

  NSArray *version = [[[UIDevice currentDevice] systemVersion] componentsSeparatedByString:@"."];
  if ([[version objectAtIndex:0] intValue] >= 4) {
  [attrDict setObject:(id)kSecAttrAccessibleWhenUnlocked forKey:(id)kSecAttrAccessible];
  }

  OSStatus status = noErr;

  if ([self credentials])
  {
  [attrDict removeObjectForKey:(id)kSecClass];
  status = SecItemUpdate((CFDictionaryRef)_keyChainDic, (CFDictionaryRef)attrDict);
  }
  else
  {
  status = SecItemAdd((CFDictionaryRef)attrDict, NULL);
  }

  if (status != noErr)
  {
  NSLog(@"error saving credentials (%ld)", status);
  }
  }

• (void)deleteCredentials
  {
  OSStatus status = SecItemDelete((CFDictionaryRef)_keyChainDic);

  if (status != noErr)
  {
  NSLog(@"error deleting credentials (%ld)", status);
  }
  }

@end

够快网盘之ASIHTTPRequest框架。

既然是网盘，必然涉及文件上传和下载等网络请求，这里采用了ASIHTTPRequest框架来实现网络请求和文件的上传、下载。

一、够快网盘的下载api采用get方式：

ASIHTTPRequest* request = [ASIHTTPRequest requestWithURL: url];
[request setCompletionBlock:^{
NSDictionary* params = [request.responseString objectFromJSONString];
….
}];
[request setFailedBlock:^{…}];
[request setStartedBlock:^{…}];
[request setBytesReceivedBlock:^(unsigned long long size, unsigned long long total){
Meta.synProgress =( (double)request.totalBytesRead + request.partialDownloadSize) / total;
}];
[request setDownloadDestinationPath: filePath];
[request setAllowCompressedResponse: NO];
[request setAllowResumeForFileDownloads: YES];
[request setShouldPresentCredentialsBeforeChallenge: YES];
[request setShowAccurateProress: YES];
[request startAsynchronous];

说明：url为NSURL对象；filePath为本地存储路径；BytesReceivedBlock可以用来显示当前下载进度的百分比。objectFromJSONString方法需要先添加JSONKit并引用头文件。

二、够快网盘的上传api步骤2采用了post multipart/form-data方式：

ASIFormDataRequest* request = [ASIHTTPRequest requestWithURL: url];
[request setPostValue: … forKey: …];
…..
[request setPostValue: @”file” forKey: @”filefield”];
request.requestMethod = @”POST”;
[request addRequestHeader:@”Content-Type” value:@”Multipart/form-data”]
[request setCompletionBlock:^{
NSDictionary* params = [request.responseString objectFromJSONString];
…..
}];
[request setFailedBlock:^{….}];
[request setStartedBlock:^{…..}];
[request setBytesReceivedBlock:^(unsigned long long size, unsigned long long total){
Meta.synProgress =( (double)request.totalBytesSent )/ total;
}];
[request setDownloadDestinationPath: filePath];
[request setAllowCompressedResponse: NO];
[request setAllowResumeForFileDownloads: YES];
[request setShouldPresentCredentialsBeforeChallenge: YES];
[request setShowAccurateProress: YES];
[request setShouldStreamPostFromDisk: YES]；
[request setFile: localPath withFileName: [meta.path lastPathComponent] andContentType: meta.contentType forKey: @”file”];
[request startAsynchronous];

说明：[request setPostValue: @”file” forKey: @”filefield”];中的value必须和后面的forKey一致，这也符合api最后一个参数的说明。

当然还有其他方面，比如之前删除和上传没有成功，但是状态码返回200，经过与够快的开发人员一番沟通，发现了这两个api的缺陷，现在已经完善了，不会再遇到。

通过对够快网盘的支持，我也进一步学习了iOS的网络编程，收获还是很多的。