iOS webview cache

WebViewImageCache

//
//  WebViewImageCache.m
//  DoubanShuo
//
//  Created by Jianjun Wu on 7/1/11.
//  Copyright 2011 Douban Inc. All rights reserved.
//

#import "WebViewImageCache.h"
#import "UserAppPreference.h"

@implementation WebViewImageCache

- (BOOL)isImageResource:(NSString *)resourceURL {
  
  static NSArray *nonImgSuffies = nil;
  static NSArray *imgSuffies = nil;
  if (!nonImgSuffies) {
    nonImgSuffies = [[NSArray arrayWithObjects:@".html", @".htm", @".js", @".css", nil] retain];
  }
  if (!imgSuffies) {
    imgSuffies = [[NSArray arrayWithObjects:@".bmp", @".gif", @".jpe", @".jpeg", @".jpg", 
                  @".ico", @".png", @".tif", @".tiff", nil] retain];
  }

  NSString *nonImgSuffix = nil;
  for (nonImgSuffix in nonImgSuffies) {
    if ([resourceURL hasSuffix:nonImgSuffix]) {
      return NO;
    }
  }
  
  NSString *imgSuffix = nil;
  for (imgSuffix in imgSuffies) {
    if ([resourceURL hasSuffix:imgSuffix]) {
      return YES;
    }
  }
  
  return NO;
}


- (NSCachedURLResponse *)cachedResponseForRequest:(NSURLRequest *)request {
  
  NSString *ua = [[request allHTTPHeaderFields] objectForKey:@"User-Agent"];

  if ([UserAppPreference sharedInstance].browserNoPictureMode
      && ua && [ua rangeOfString:@"AppleWebKit"].length > 0) {
    
    NSString *relativePath = [[request URL] relativePath];

    UIImage *defaultImg = [UIImage imageNamed:@"place_webimageholder.png"];
    NSData *imageData = UIImagePNGRepresentation(defaultImg);
    if ([self isImageResource:relativePath]) {
      //NSLog(@"return cached picture with data length: %d", [imageData length]);
      NSURLResponse *response = [[[NSURLResponse alloc] initWithURL:[request URL] 
                                                           MIMEType:@"image/png"
                                              expectedContentLength:[imageData length]
                                                   textEncodingName:nil] 
                                 autorelease];
     
      return [[[NSCachedURLResponse alloc] initWithResponse:response data:imageData] autorelease];
    }
    
  }  
  
  
  return [super cachedResponseForRequest:request];
}

@end