LRU Implementation for disk cache with overridable limit for disk cache size

MKNetworkKit/Categories/NSArray+RequestEncoding.h

@@ -0,0 +1,17 @@
+//
+//  NSArray+RequestEncoding.h
+//  Bild.de-iPad
+//
+//  Created by Vittorio Monaco on 07/10/13.
+//  Copyright (c) 2013 Axel Springer Verlag. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+@interface NSArray (RequestEncoding)
+
+-(NSString*) urlEncodedKeyValueString;
+-(NSString*) jsonEncodedKeyValueString;
+-(NSString*) plistEncodedKeyValueString;
+
+@end

MKNetworkKit/Categories/NSArray+RequestEncoding.m

@@ -0,0 +1,45 @@
+//
+//  NSArray+RequestEncoding.m
+//  Bild.de-iPad
+//
+//  Created by Vittorio Monaco on 07/10/13.
+//  Copyright (c) 2013 Axel Springer Verlag. All rights reserved.
+//
+
+#import "NSArray+RequestEncoding.h"
+#import "MKNetworkKit.h"
+
+@implementation NSArray (RequestEncoding)
+
+-(NSString*) jsonEncodedKeyValueString
+{
+
+    NSError *error = nil;
+    NSData *data = [NSJSONSerialization dataWithJSONObject:self
+                                                   options:0 // non-pretty printing
+                                                     error:&error];
+    if(error)
+        DLog(@"JSON Parsing Error: %@", error);
+
+    return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
+}
+
+-(NSString*) urlEncodedKeyValueString {
+
+    //How to correctly URL-encode NSArray?
+    return nil;
+}
+
+-(NSString*) plistEncodedKeyValueString {
+
+    NSError *error = nil;
+    NSData *data = [NSPropertyListSerialization dataWithPropertyList:self
+                                                              format:NSPropertyListXMLFormat_v1_0
+                                                             options:0 error:&error];
+    if(error)
+        DLog(@"JSON Parsing Error: %@", error);
+
+    return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
+}
+
+@end

MKNetworkKit/MKNetworkEngine.h

@@ -422,4 +422,16 @@
  */
 @property (nonatomic, assign) BOOL shouldSendAcceptLanguageHeader;
 
+//Disk cache management additions
+/*!
+ *  @abstract Cache Directory In Disk Size
+ *
+ *  @discussion
+ *  This method can be over-ridden by subclasses to provide an alternative in disk cache size.
+ *  By default, MKNetworkKit caches MKNETWORKCACHE_DEFAULT_DISK_SIZE bytes in disk cache
+ *  The default size is MKNETWORKCACHE_DEFAULT_DISK_SIZE (50 MB)
+ *  Overriding this method is optional
+ */
+-(unsigned long long int) cacheDiskSize;
+
 @end

MKNetworkKit/MKNetworkEngine.m

@@ -724,6 +724,12 @@ -(void) useCache {
                                                name:UIApplicationWillTerminateNotification
                                              object:nil];
 
+  //check for emptyCache whenever coming to app
+  [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(emptyCache)
+                                                 name:UIApplicationDidBecomeActiveNotification
+                                               object:nil];
+
 #elif TARGET_OS_MAC
 
   [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(saveCache)
@@ -745,16 +751,63 @@ -(void) emptyCache {
 
   [self saveCache]; // ensures that invalidation params are written to disk properly
   NSError *error = nil;
-  NSArray *directoryContents = [[NSFileManager defaultManager]
-                                contentsOfDirectoryAtPath:[self cacheDirectoryName] error:&error];
+  NSArray *directoryContents = [[NSFileManager defaultManager] contentsOfDirectoryAtURL:[NSURL fileURLWithPath:[self cacheDirectoryName]]
+                                                               includingPropertiesForKeys:@[NSURLContentModificationDateKey]
+                                                                                  options:NSDirectoryEnumerationSkipsHiddenFiles
+                                                                                    error:&error];
+
   if(error) DLog(@"%@", error);
 
   error = nil;
-  for(NSString *fileName in directoryContents) {
 
+  unsigned long long int folderSize = [self folderSize:[self cacheDirectoryName]];
+  long long int sizeToRemove = folderSize - [self cacheDiskSize];
+
+  if (sizeToRemove <= 0) {
+    //return if we have not exceeded the limit
+    return;
+  }
+
+  NSArray *sortedContent = [directoryContents sortedArrayUsingComparator:
+                              ^(NSURL *file1, NSURL *file2)
+                              {
+                                  // compare
+                                  NSDate *file1Date;
+                                  [file1 getResourceValue:&file1Date forKey:NSURLContentModificationDateKey error:nil];
+
+                                  NSDate *file2Date;
+                                  [file2 getResourceValue:&file2Date forKey:NSURLContentModificationDateKey error:nil];
+
+                                  // Ascending:
+                                  return [file1Date compare: file2Date];
+                                  // Descending:
+                                  //return [file2Date compare: file1Date];
+                              }];
+
+
+  unsigned long long int fileSize = 0;
+
+  for(NSString *fileName in sortedContent) {
+
     NSString *path = [[self cacheDirectoryName] stringByAppendingPathComponent:fileName];
+
+    //calcualte size and add to count
+    NSDictionary *fileDictionary = [[NSFileManager defaultManager]
+                                        attributesOfItemAtPath:path
+                                        error:&error];
+
+    fileSize += [fileDictionary fileSize];
+
+    //remove file
     [[NSFileManager defaultManager] removeItemAtPath:path error:&error];
-    if(error) DLog(@"%@", error);
+
+    if(error)
+      DLog(@"%@", error);
+
+    //break if we are back in limit
+    if (fileSize > sizeToRemove) {
+      break;
+    }
   }
 
   error = nil;
@@ -763,4 +816,38 @@ -(void) emptyCache {
   if(error) DLog(@"%@", error);
 }
 
-@end
+- (NSOperationQueue *)networkQueue
+{
+    return _sharedNetworkQueue;
+}
+
+#pragma mark - Disk cache size management additions
+
+-(unsigned long long int) cacheDiskSize{
+
+  return MKNETWORKCACHE_DEFAULT_DISK_SIZE;
+}
+
+- (unsigned long long int)folderSize:(NSString *)folderPath {
+
+  NSArray *filesArray = [[NSFileManager defaultManager] subpathsOfDirectoryAtPath:folderPath error:nil];
+  NSEnumerator *filesEnumerator = [filesArray objectEnumerator];
+  NSString *fileName;
+  unsigned long long int fileSize = 0;
+
+  while (fileName = [filesEnumerator nextObject]) {
+
+    NSString *path = [[self cacheDirectoryName] stringByAppendingPathComponent:fileName];
+    NSError *error = nil;
+
+    NSDictionary *fileDictionary = [[NSFileManager defaultManager]
+                                        attributesOfItemAtPath:path
+                                        error:&error];
+
+    fileSize += [fileDictionary fileSize];
+  }
+
+  return fileSize;
+}
+
+@end

MKNetworkKit/MKNetworkKit.h

@@ -66,6 +66,7 @@
 
 #import "Categories/NSString+MKNetworkKitAdditions.h"
 #import "Categories/NSDictionary+RequestEncoding.h"
+#import "Categories/NSArray+RequestEncoding.h"
 #import "Categories/NSDate+RFC1123.h"
 #import "Categories/NSData+MKBase64.h"
 #import "Categories/UIImageView+MKNetworkKitAdditions.h"
@@ -87,6 +88,8 @@
 #define kMKNetworkKitDefaultImageHeadRequestDuration 3600*24*1 // 1 day (HEAD requests with eTag are sent only after expiry of this. Not that these are not RFC compliant, but needed for performance tuning)
 #define kMKNetworkKitDefaultImageCacheDuration 3600*24*7 // 1 day
 
+#define MKNETWORKCACHE_DEFAULT_DISK_SIZE 50*1024*1024 //50 MB
+
 // if your server takes longer than 30 seconds to provide real data,
 // you should hire a better server developer.
 // on iOS (or any mobile device), 30 seconds is already considered high.