What I am hoping to do may or may not be possible but I'll give it a shot. I am attempting to load huge multiple gigabyte text files. I am currently using an memory mapped NSData and only loading portions at a time and just infinite scrolling through it and load the currently visible chunk and it all is happy and it barely breaks a sweat with memory (<30mb).
Next I wanted to add editing of the data. I casually assumed I could just edit that memory mapped data and have it reflect on disk. This does not seem to be the case. Is there a way I can say hey the data changed! update the file. I am a little vague on how the file and NSData are linked.
Here is how it is currently working.
// create the memory mapped data:
self.fileData = [NSMutableData dataWithContentsOfURL:url options:NSDataReadingMappedAlways error:outError];
//load a chunk
self.currentRange = NSMakeRange(0, 4096);
void* data = malloc(4096);
[self.fileData getBytes:data range:self.currentRange];
NSString* currentView = [[NSString alloc] initWithBytes:data length:4096 encoding:NSUTF8StringEncoding];
//replace a chunk:
NSData* currentData = [[self.textArea string] dataUsingEncoding:NSUTF8StringEncoding];
[self.fileData replaceBytesInRange:self.currentRange withBytes:[currentData bytes] length:[currentData length]];
//If I close and re-open it doesn't actually work
Is there a way of doing this or would it be possible to create an NSOutputStream to the URL and somehow stream portions of it back to disk? Is there another way to write/save memory mapped data? If I try to do a writeToURL: or comparable function it will load it all to actual memory which is really no good.