NSMutableDictionaryRESTParser.m

// © 2010 Mirek Rusin
// Released under the Apache License, Version 2.0
// http://www.apache.org/licenses/LICENSE-2.0
//
// Based on Apple XMLPerformance example:
// http://developer.apple.com/iphone/library/samplecode/XMLPerformance/Listings/ReadMe_txt.html#//apple_ref/doc/uid/DTS40008094-ReadMe_txt-DontLinkElementID_23

#import "NSMutableDictionaryRESTParser.h"

// Declaration for SAX callbacks and structure
static void NSMutableDictionaryRESTParserElementStart(void *ctx, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI, int nb_namespaces, const xmlChar **namespaces, int nb_attributes, int nb_defaulted, const xmlChar **attributes);
static void NSMutableDictionaryRESTParserElementEnd(void *ctx, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI);
static void NSMutableDictionaryRESTParserCharactersFound(void * ctx, const xmlChar * ch, int len);
static void NSMutableDictionaryRESTParserErrorEncountered(void * ctx, const char * msg, ...);
static xmlSAXHandler NSMutableDictionaryRESTParserHandlerStruct;

@implementation NSMutableDictionaryRESTParser

@synthesize tree;
@synthesize stack;
@synthesize typeStack;
@synthesize nameStack;
@synthesize data;

@synthesize delegate;
@synthesize urlConnection;
@synthesize processing;
@synthesize pool;

- (void) parseWithURL: (NSURL *) url {
  self.pool = [[NSAutoreleasePool alloc] init];

  self.processing = YES;

  self.tree = [NSMutableDictionary dictionary];
  self.stack = [NSMutableArray arrayWithObject: self.tree];
  self.typeStack = [NSMutableArray arrayWithObject: [NSNumber numberWithInt: NSMutableDictionaryRESTParserElementTypeStringOrDictionary]];
  self.nameStack = [NSMutableArray arrayWithObject: @""];

  [[NSURLCache sharedURLCache] removeAllCachedResponses];
  NSURLRequest *urlRequest = [NSURLRequest requestWithURL: url];
  urlConnection = [[NSURLConnection alloc] initWithRequest: urlRequest delegate: self];
  context = xmlCreatePushParserCtxt(&NSMutableDictionaryRESTParserHandlerStruct, self, NULL, 0, NULL);

  // [self performSelectorOnMainThread: @selector(downloadStarted) withObject: nil waitUntilDone: NO];

  if (urlConnection != nil) {
    do {
      [[NSRunLoop currentRunLoop] runMode: NSDefaultRunLoopMode
                               beforeDate: [NSDate distantFuture]];
    } while (processing);
  }

  // Release resources used only in this thread
  xmlFreeParserCtxt(context);

  self.urlConnection = nil;

  [pool drain];
  self.pool = nil;
}

#pragma mark NSURLConnection delegate methods

// Disable caching
- (NSCachedURLResponse *) connection: (NSURLConnection *) connection willCacheResponse: (NSCachedURLResponse *) cachedResponse {
  return nil;
}

// Forward errors to the delegate
- (void) connection: (NSURLConnection *) connection didFailWithError: (NSError *) error {
  self.processing = NO;
  [self performSelectorOnMainThread: @selector(parseError:) withObject: error waitUntilDone: NO];
}

- (void) connection: (NSURLConnection *) connection didReceiveData: (NSData *) receivedData {
  xmlParseChunk(context, (const char *)[receivedData bytes], [receivedData length], NO);
}

- (void) connectionDidFinishLoading: (NSURLConnection *) connection {
  xmlParseChunk(context, NULL, 0, YES);
  self.processing = NO; 
//  if ([delegate respondsToSelector: @selector(parseEnded)])
//    [delegate performSelectorOnMainThread: @selector(parseEnded) withObject: self waitUntilDone: NO];
}

@end

#pragma mark SAX Stuff

static void NSMutableDictionaryRESTParserElementStart(void *ctx,
                                                      const xmlChar *localname,
                                                      const xmlChar *prefix,
                                                      const xmlChar *URI, 
                                                      int nb_namespaces,
                                                      const xmlChar **namespaces, 
                                                      int nb_attributes,
                                                      int nb_defaulted,
                                                      const xmlChar **attributes)
{
  NSMutableDictionaryRESTParser *parser = (NSMutableDictionaryRESTParser *)ctx;
  
  id new = [NSMutableDictionary dictionary];
  NSMutableDictionaryRESTParserElementType newType = NSMutableDictionaryRESTParserElementTypeStringOrDictionary;
  parser.data = [NSMutableData data];
  
  if (nb_attributes > 0) {
    int i, j;
    for (j = 0, i = 0; i < nb_attributes; i++, j += 5) {
      
      // We're interested in type attribute only
      if (!xmlStrcmp((const xmlChar *)"type", attributes[j])) {
        if (!xmlStrncmp((const xmlChar *)"array", attributes[j+3], strlen("array"))) {
          newType = NSMutableDictionaryRESTParserElementTypeArray;
          new = [NSMutableArray array];
          break;
        } else if (!xmlStrncmp((const xmlChar *)"float", attributes[j+3], strlen("float"))) {
          newType = NSMutableDictionaryRESTParserElementTypeFloat;
          break;
        } else if (!xmlStrncmp((const xmlChar *)"integer", attributes[j+3], strlen("integer"))) {
          newType = NSMutableDictionaryRESTParserElementTypeInteger;
          break;
        }
      }
    }
  }
  
  // Push new element to the stack
  [parser.stack addObject: new];
  [parser.typeStack addObject: [NSNumber numberWithInt: newType]];
  [parser.nameStack addObject: [NSString stringWithUTF8String: (const char *)localname]];
}

static void	NSMutableDictionaryRESTParserElementEnd(void *ctx, const xmlChar *localname, const xmlChar *prefix, const xmlChar *URI) {    
  NSMutableDictionaryRESTParser *parser = (NSMutableDictionaryRESTParser *)ctx;
  
  // Let's get the current element
  id last = [parser.stack lastObject];
  NSMutableDictionaryRESTParserElementType lastType = (NSMutableDictionaryRESTParserElementType)[[parser.typeStack lastObject] intValue];
  NSString *lastName = [parser.nameStack lastObject];
  
  // Current string value
  NSString *string = [[NSString alloc] initWithData: parser.data encoding: NSUTF8StringEncoding];

  // Depending on the type we can mutate to the proper class
  id new;
  switch (lastType) {
    case NSMutableDictionaryRESTParserElementTypeArray:
      new = last;
      break;

    case NSMutableDictionaryRESTParserElementTypeFloat:
      new = [NSNumber numberWithFloat: [string floatValue]];
      break;
      
    case NSMutableDictionaryRESTParserElementTypeInteger:
      new = [NSNumber numberWithInteger: [string intValue]];
      break;
      
    case NSMutableDictionaryRESTParserElementTypeStringOrDictionary:
      if ([last count] > 0)
        // Current element is a dictionary
        new = last;
      else
        // Current element is just plain value (doesn't have any children elements)
        new = string;
      break;
  }

  // Let's notify delgate about the new object before removing it's name from the stack
  if ([parser.delegate respondsToSelector: @selector(didFinishElement:withPath:)])
    [parser.delegate performSelector: @selector(didFinishElement:withPath:) withObject: new withObject: [parser.nameStack componentsJoinedByString: @"/"]];
  
  // Now we can remove element from the stack
  [parser.stack removeLastObject];
  [parser.typeStack removeLastObject];
  [parser.nameStack removeLastObject];
    
  // We'll need current element's parent to assign new (mutated or not) element
  id parent = [parser.stack lastObject];
  NSMutableDictionaryRESTParserElementType parentType = (NSMutableDictionaryRESTParserElementType)[[parser.typeStack lastObject] intValue];
  
  // Parent had to be one of container types
  switch (parentType) {
    case NSMutableDictionaryRESTParserElementTypeArray: [parent addObject: new]; break;
    case NSMutableDictionaryRESTParserElementTypeStringOrDictionary: [parent setObject: new forKey: lastName]; break;
  }
  
  //[new release];
}

static void	NSMutableDictionaryRESTParserCharactersFound(void *ctx, const xmlChar *ch, int len) {
  NSMutableDictionaryRESTParser *parser = (NSMutableDictionaryRESTParser *)ctx;
  [parser.data appendBytes: ch length: len];
}

static void NSMutableDictionaryRESTParserErrorEncountered(void *ctx, const char *msg, ...) {
  NSCAssert(NO, @"Unhandled error encountered during SAX parse.");
}

static xmlSAXHandler NSMutableDictionaryRESTParserHandlerStruct = {
  NULL,                                          // internalSubset
  NULL,                                          // isStandalone
  NULL,                                          // hasInternalSubset
  NULL,                                          // hasExternalSubset
  NULL,                                          // resolveEntity
  NULL,                                          // getEntity
  NULL,                                          // entityDecl
  NULL,                                          // notationDecl
  NULL,                                          // attributeDecl
  NULL,                                          // elementDecl
  NULL,                                          // unparsedEntityDecl
  NULL,                                          // setDocumentLocator
  NULL,                                          // startDocument
  NULL,                                          // endDocument
  NULL,                                          // startElement*/
  NULL,                                          // endElement
  NULL,                                          // reference
  NSMutableDictionaryRESTParserCharactersFound,  // characters
  NULL,                                          // ignorableWhitespace
  NULL,                                          // processingInstruction
  NULL,                                          // comment
  NULL,                                          // warning
  NSMutableDictionaryRESTParserErrorEncountered, // error
  NULL,                                          // fatalError //: unused error() get all the errors
  NULL,                                          // getParameterEntity
  NULL,                                          // cdataBlock
  NULL,                                          // externalSubset
  XML_SAX2_MAGIC,                                //
  NULL,                                          //
  NSMutableDictionaryRESTParserElementStart,     // startElementNs
  NSMutableDictionaryRESTParserElementEnd,       // endElementNs
  NULL,                                          // serror
};