HUGE NSString decoding, out of memory

Question

I’m looking for ideas on how to improve the decoding process of a 40 MB base64 encoded NSString and save it to a file, with the ability to fine-tune the process on the iPad's 1 256 MB RAM.

I get NSString from NSXMLParser:

id pointerToString;

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
if ([currentElement isEqualToString:@"myElement"]) 
    {
    pointerToString = [string retain];
}
}

Then I use the ToString pointer in the callback:

[handler performSelector: action withObject: pointerToString];

In the callback (id value is a ToString pointer). I initialize the NSData with a ToString pointer, decoding it with base64 encoding.

^(id value)
{
    if ( [[value class] isSubclassOfClass:[NSString class]] ) 
    {
    NSData *data = [NSData dataFromBase64String:value];
    [data writeToFile:file.path atomically:YES];
}
}

iPad 1 runs out of memory and is killed by iOS when the memory allocation reaches about 130 MB after or during an NSData call.

I decided that to handle 40 MB of NSString in this way I would need about 180 MB of RAM (this is that the maximum memory allocation on the iPad 2 and 3, where the process works because of more RAM)

Any ideas / tips?

thank

Answer 1

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Answer 2

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