NetNewsWire/Parser/Sources/ObjC/NSData+RSParser.m

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//
// NSData+RSParser.m
// RSParser
//
// Created by Brent Simmons on 6/24/17.
// Copyright © 2017 Ranchero Software, LLC. All rights reserved.
//
#import "NSData+RSParser.h"
/* TODO: find real-world cases where the isProbably* cases fail when they should succeed, and add them to tests.*/
static BOOL bytesAreProbablyHTML(const char *bytes, NSUInteger numberOfBytes);
static BOOL bytesAreProbablyXML(const char *bytes, NSUInteger numberOfBytes);
static BOOL bytesStartWithStringIgnoringWhitespace(const char *string, const char *bytes, NSUInteger numberOfBytes);
static BOOL didFindString(const char *string, const char *bytes, NSUInteger numberOfBytes);
static BOOL bytesStartWithRSS(const char *bytes, NSUInteger numberOfBytes);
static BOOL bytesStartWithRDF(const char *bytes, NSUInteger numberOfBytes);
static BOOL bytesStartWithAtom(const char *bytes, NSUInteger numberOfBytes);
@implementation NSData (RSParser)
- (BOOL)isProbablyHTML {
return bytesAreProbablyHTML(self.bytes, self.length);
}
- (BOOL)isProbablyXML {
return bytesAreProbablyXML(self.bytes, self.length);
}
- (BOOL)isProbablyJSON {
return bytesStartWithStringIgnoringWhitespace("{", self.bytes, self.length);
}
- (BOOL)isProbablyJSONFeed {
if (![self isProbablyJSON]) {
return NO;
}
return didFindString("://jsonfeed.org/version/", self.bytes, self.length) || didFindString(":\\/\\/jsonfeed.org\\/version\\/", self.bytes, self.length);
}
- (BOOL)isProbablyRSSInJSON {
if (![self isProbablyJSON]) {
return NO;
}
const char *bytes = self.bytes;
NSUInteger length = self.length;
return didFindString("rss", bytes, length) && didFindString("channel", bytes, length) && didFindString("item", bytes, length);
}
- (BOOL)isProbablyRSS {
if (didFindString("<rss", self.bytes, self.length) || didFindString("<rdf:RDF", self.bytes, self.length)) {
return YES;
}
// At this writing (7 Dec. 2017), https://www.natashatherobot.com/feed/ is missing an opening <rss> tag, but it should be parsed anyway. It does have some other distinct RSS markers we can find.
return (didFindString("<channel>", self.bytes, self.length) && didFindString("<pubDate>", self.bytes, self.length));
}
- (BOOL)isProbablyAtom {
return didFindString("<feed", self.bytes, self.length);
}
@end
static BOOL didFindString(const char *string, const char *bytes, NSUInteger numberOfBytes) {
char *foundString = strnstr(bytes, string, numberOfBytes);
return foundString != NULL;
}
static BOOL bytesStartWithStringIgnoringWhitespace(const char *string, const char *bytes, NSUInteger numberOfBytes) {
NSUInteger i = 0;
for (i = 0; i < numberOfBytes; i++) {
const char ch = bytes[i];
if (ch == ' ' || ch == '\r' || ch == '\n' || ch == '\t') {
continue;
}
if (ch == string[0]) {
return strnstr(bytes, string, numberOfBytes) == bytes + i;
}
// Allow for a BOM of up to four bytes. ASSUMPTION: BOM will only be at the start of the data.
if (i < 4) continue;
break;
}
return NO;
}
static BOOL bytesAreProbablyHTML(const char *bytes, NSUInteger numberOfBytes) {
if (didFindString("<html", bytes, numberOfBytes)) {
return YES;
}
if (didFindString("<HTML", bytes, numberOfBytes)) {
return YES;
}
if (didFindString("<body", bytes, numberOfBytes)) {
return YES;
}
if (didFindString("<meta", bytes, numberOfBytes)) {
return YES;
}
if (didFindString("<", bytes, numberOfBytes)) {
if (didFindString("doctype html", bytes, numberOfBytes)) {
return YES;
}
if (didFindString("DOCTYPE html", bytes, numberOfBytes)) {
return YES;
}
if (didFindString("DOCTYPE HTML", bytes, numberOfBytes)) {
return YES;
}
}
return NO;
}
static BOOL bytesAreProbablyXML(const char *bytes, NSUInteger numberOfBytes) {
return bytesStartWithStringIgnoringWhitespace("<?xml", bytes, numberOfBytes);
}