Initial import.

RSXML/RSFeedParser.m

@@ -0,0 +1,216 @@
+//
+//  FeedParser.m
+//  RSXML
+//
+//  Created by Brent Simmons on 1/4/15.
+//  Copyright (c) 2015 Ranchero Software LLC. All rights reserved.
+//
+
+#import "RSFeedParser.h"
+#import "FeedParser.h"
+#import "RSXMLData.h"
+#import "RSRSSParser.h"
+#import "RSAtomParser.h"
+
+static NSArray *parserClasses(void) {
+	
+	static NSArray *gParserClasses = nil;
+	
+	static dispatch_once_t onceToken;
+	dispatch_once(&onceToken, ^{
+		
+		gParserClasses = @[[RSRSSParser class], [RSAtomParser class]];
+	});
+	
+	return gParserClasses;
+}
+
+static BOOL feedMayBeParseable(RSXMLData *xmlData) {
+	
+	/*Sanity checks.*/
+	
+	if (!xmlData.data) {
+		return NO;
+	}
+
+	/*TODO: check size, type, etc.*/
+	
+	return YES;
+}
+
+static BOOL optimisticCanParseRSSData(const char *bytes, NSUInteger numberOfBytes);
+static BOOL optimisticCanParseAtomData(const char *bytes, NSUInteger numberOfBytes);
+static BOOL optimisticCanParseRDF(const char *bytes, NSUInteger numberOfBytes);
+static BOOL dataIsProbablyHTML(const char *bytes, NSUInteger numberOfBytes);
+static BOOL dataIsSomeWeirdException(const char *bytes, NSUInteger numberOfBytes);
+static BOOL dataHasLeftCaret(const char *bytes, NSUInteger numberOfBytes);
+
+static const NSUInteger maxNumberOfBytesToSearch = 4096;
+static const NSUInteger minNumberOfBytesToSearch = 20;
+
+static Class parserClassForXMLData(RSXMLData *xmlData) {
+	
+	if (!feedMayBeParseable(xmlData)) {
+		return nil;
+	}
+	
+	// TODO: check for things like images and movies and return nil.
+	
+	const char *bytes = xmlData.data.bytes;
+	NSUInteger numberOfBytes = xmlData.data.length;
+	
+	if (numberOfBytes > minNumberOfBytesToSearch) {
+		
+		if (numberOfBytes > maxNumberOfBytesToSearch) {
+			numberOfBytes = maxNumberOfBytesToSearch;
+		}
+
+		if (!dataHasLeftCaret(bytes, numberOfBytes)) {
+			return nil;
+		}
+
+		if (optimisticCanParseRSSData(bytes, numberOfBytes)) {
+			return [RSRSSParser class];
+		}
+		if (optimisticCanParseAtomData(bytes, numberOfBytes)) {
+			return [RSAtomParser class];
+		}
+		
+		if (optimisticCanParseRDF(bytes, numberOfBytes)) {
+			return nil; //TODO: parse RDF feeds
+		}
+		
+		if (dataIsProbablyHTML(bytes, numberOfBytes)) {
+			return nil;
+		}
+		if (dataIsSomeWeirdException(bytes, numberOfBytes)) {
+			return nil;
+		}
+	}
+	
+	for (Class parserClass in parserClasses()) {
+		if ([parserClass canParseFeed:xmlData]) {
+			return [[parserClass alloc] initWithXMLData:xmlData];
+		}
+	}
+	
+	return nil;
+}
+
+static id<FeedParser> parserForXMLData(RSXMLData *xmlData) {
+	
+	Class parserClass = parserClassForXMLData(xmlData);
+	if (!parserClass) {
+		return nil;
+	}
+	return [[parserClass alloc] initWithXMLData:xmlData];
+}
+
+static BOOL canParseXMLData(RSXMLData *xmlData) {
+	
+	return parserClassForXMLData(xmlData) != nil;
+}
+
+static BOOL didFindString(const char *string, const char *bytes, NSUInteger numberOfBytes) {
+	
+	char *foundString = strnstr(bytes, string, numberOfBytes);
+	return foundString != NULL;
+}
+
+static BOOL dataHasLeftCaret(const char *bytes, NSUInteger numberOfBytes) {
+
+	return didFindString("<", bytes, numberOfBytes);
+}
+
+static BOOL dataIsProbablyHTML(const char *bytes, NSUInteger numberOfBytes) {
+	
+	// Won’t catch every single case, which is fine.
+	
+	if (didFindString("<html", bytes, numberOfBytes)) {
+		return YES;
+	}
+	if (didFindString("<body", bytes, numberOfBytes)) {
+		return YES;
+	}
+	if (didFindString("doctype html", bytes, numberOfBytes)) {
+		return YES;
+	}
+	if (didFindString("DOCTYPE html", bytes, numberOfBytes)) {
+		return YES;
+	}
+	if (didFindString("DOCTYPE HTML", bytes, numberOfBytes)) {
+		return YES;
+	}
+	if (didFindString("<meta", bytes, numberOfBytes)) {
+		return YES;
+	}
+	if (didFindString("<HTML", bytes, numberOfBytes)) {
+		return YES;
+	}
+	
+	return NO;
+}
+
+static BOOL dataIsSomeWeirdException(const char *bytes, NSUInteger numberOfBytes) {
+
+	if (didFindString("<errors xmlns='http://schemas.google", bytes, numberOfBytes)) {
+		return YES;
+	}
+
+	return NO;
+}
+
+static BOOL optimisticCanParseRDF(const char *bytes, NSUInteger numberOfBytes) {
+	
+	return didFindString("<rdf:RDF", bytes, numberOfBytes);
+}
+
+static BOOL optimisticCanParseRSSData(const char *bytes, NSUInteger numberOfBytes) {
+	
+	if (!didFindString("<rss", bytes, numberOfBytes)) {
+		return NO;
+	}
+	return didFindString("<channel", bytes, numberOfBytes);
+}
+
+static BOOL optimisticCanParseAtomData(const char *bytes, NSUInteger numberOfBytes) {
+	
+	return didFindString("<feed", bytes, numberOfBytes);
+}
+
+static void callCallback(RSParsedFeedBlock callback, RSParsedFeed *parsedFeed, NSError *error) {
+	
+	dispatch_async(dispatch_get_main_queue(), ^{
+		
+		@autoreleasepool {
+			if (callback) {
+				callback(parsedFeed, error);
+			}
+		}
+	});
+}
+
+
+#pragma mark - API
+
+BOOL RSCanParseFeed(RSXMLData *xmlData) {
+
+	return canParseXMLData(xmlData);
+}
+
+void RSParseFeed(RSXMLData *xmlData, RSParsedFeedBlock callback) {
+
+	dispatch_async(dispatch_get_global_queue(QOS_CLASS_UTILITY, 0), ^{
+
+		NSError *error = nil;
+		RSParsedFeed *parsedFeed = RSParseFeedSync(xmlData, &error);
+		callCallback(callback, parsedFeed, error);
+	});
+}
+
+RSParsedFeed *RSParseFeedSync(RSXMLData *xmlData, NSError **error) {
+
+	id<FeedParser> parser = parserForXMLData(xmlData);
+	return [parser parseFeed:error];
+}
+