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Application/iTunesRSSImporter.h

/*

     File: iTunesRSSImporter.h

 Abstract: Downloads, parses, and imports the iTunes top songs RSS feed into Core Data.

  Version: 1.4

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 not agree with these terms, please do not use, install, modify or

 redistribute this Apple software.

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 subject to these terms, Apple grants you a personal, non-exclusive

 license, under Apple's copyrights in this original Apple software (the

 "Apple Software"), to use, reproduce, modify and redistribute the Apple

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 Neither the name, trademarks, service marks or logos of Apple Inc. may

 be used to endorse or promote products derived from the Apple Software

 without specific prior written permission from Apple.  Except as

 expressly stated in this notice, no other rights or licenses, express or

 implied, are granted by Apple herein, including but not limited to any

 patent rights that may be infringed by your derivative works or by other

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 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE

 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS

 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND

 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL

 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

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 Copyright (C) 2013 Apple Inc. All Rights Reserved.

*/

#import <UIKit/UIKit.h>

#import <libxml/tree.h>

@class iTunesRSSImporter, Song, Category, CategoryCache;

// Protocol for the importer to communicate with its delegate.

@protocol iTunesRSSImporterDelegate <NSObject>

@optional

// Notification posted by NSManagedObjectContext when saved.

- (void)importerDidSave:(NSNotification *)saveNotification;

// Called by the importer when parsing is finished.

- (void)importerDidFinishParsingData:(iTunesRSSImporter *)importer;

// Called by the importer in the case of an error.

- (void)importer:(iTunesRSSImporter *)importer didFailWithError:(NSError *)error;

@end

@interface iTunesRSSImporter : NSOperation {

@private

    id <iTunesRSSImporterDelegate> __unsafe_unretained delegate;

    // Reference to the libxml parser context

    xmlParserCtxtPtr context;

    NSURLConnection *rssConnection;

    // Overall state of the importer, used to exit the run loop.

    BOOL done;

    // State variable used to determine whether or not to ignore a given XML element

    BOOL parsingASong;

    // The following state variables deal with getting character data from XML elements. This is a potentially expensive

    // operation. The character data in a given element may be delivered over the course of multiple callbacks, so that

    // data must be appended to a buffer. The optimal way of doing this is to use a C string buffer that grows exponentially.

    // When all the characters have been delivered, an NSString is constructed and the buffer is reset.

    BOOL storingCharacters;

    NSMutableData *characterBuffer;

    // A reference to the current song the importer is working with.

    Song *currentSong;

    // The number of parsed songs is tracked so that the autorelease pool for the parsing thread can be periodically

    // emptied to keep the memory footprint under control.

    NSUInteger countForCurrentBatch;

    NSUInteger rankOfCurrentSong;

    NSDateFormatter *dateFormatter;

    NSManagedObjectContext *insertionContext;

    NSPersistentStoreCoordinator *persistentStoreCoordinator;

    NSEntityDescription *songEntityDescription;

    CategoryCache *theCache;

    NSURL *iTunesURL;

@property (nonatomic, retain) NSURL *iTunesURL;

@property (nonatomic, assign) id <iTunesRSSImporterDelegate> delegate;

@property (nonatomic, retain) NSPersistentStoreCoordinator *persistentStoreCoordinator;

@property (nonatomic, retain, readonly) NSManagedObjectContext *insertionContext;

@property (nonatomic, retain, readonly) NSEntityDescription *songEntityDescription;

@property (nonatomic, retain, readonly) CategoryCache *theCache;

// Although NSURLConnection is inherently asynchronous, the parsing can be quite CPU intensive on the device, so

// the user interface can be kept responsive by moving that work off the main thread. This does create additional

// complexity, as any code which interacts with the UI must then do so in a thread-safe manner.

- (void)main;

@end

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