Open Radar

 
Summary:
When memory mapping a file of 305mb on iOS 7 using NSData or directly with mmap the operation will fail. 

Steps to Reproduce:

Via NSData:
NSString* dataFileName = @"path to 305mb file on the device";
NSError *error = nil;
NSData *data = [NSData dataWithContentsOfFile:dataFileName options:NSDataReadingMappedAlways error:&error];

Expected Results:
A pointer to an NSData object with the mapped data.

Actual Results:

A nil pointer and the following error:
Error Domain=NSCocoaErrorDomain Code=256 "The operation couldn’t be completed. (Cocoa error 256.)" UserInfo=0x1640f910 {NSFilePath=/var/mobile/Applications/BED90A40-2303-4C4B-A4A3-E60D627A96B4/theapp.app/dataFile.blob, NSUnderlyingError=0x1640f5b0 "The operation couldn’t be completed. Cannot allocate memory"}

Regression:
This has been reproduced on an iPhone 4, but not on an iPhone 5. Both running iOS 7 beta 3. All devices are able to map the file on iOS 6.

Notes:
The following code will also fail on the iPhone 4:

- (NSData*)manuallyMapFile:(NSString*)file
{
	int fd = open([file fileSystemRepresentation], O_RDONLY);
	if(fd < 0)
	{
		return nil;
	}
	
	NSDictionary* attributes = [[NSFileManager defaultManager] attributesOfItemAtPath:file error:nil];
	if(attributes == nil)
	{
		close(fd);
		return nil;
	}
	
	self.size = [attributes objectForKey:NSFileSize];
	
	_mappedPointer = mmap(0, [_size intValue], PROT_READ, MAP_FILE|MAP_PRIVATE, fd, 0);
	close(fd);
	
	if(_mappedPointer == MAP_FAILED)
	{
		DDLogError(@"Map failed, errno=%d, %s", errno, strerror(errno));
		_mappedPointer = NULL;
		return nil;
	}
	
	NSData* retVal = [NSData dataWithBytesNoCopy:_mappedPointer length:[_size intValue] freeWhenDone:NO];
	return retVal;
}