In the final push to add syntax highlighting to iVersion I have been working on optimising the parser.
In the inner parsing loop I have been using the standard NSMutableArray to keep track of various objects and tokens. Objective C message passing is of course an order of times slower than a C function call, even if purely for the fact that they can’t be inlined. A great article that explains more about the objective c runtime an be found on the cocoa samurai blog
So I decided to drop down to a dynamic array using plain C. However even though I’m sure dynamic arrays have been implement thousands of times I couldn’t seem to find any simple implementations.
//** Usage //Create an array with capacity 2 CArray * array = CArrayInit(2); //Add two buckets CArrayAdd(array, "test"); CArrayAdd(array, "another test"); //Add another and it will resize accordingly CArrayAdd(array, "yet another"); //Print All for (int ii = 0; ii < array->count; ++ii) { const char * buffer = CArrayObjectAtIndex(array, ii); printf("Index: %d - %s\n", ii, buffer); }
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Notes:
The following test function usually reports about 5x faster than NSMutableArray which I think is a credit to how efficient the Objective C library and messaging system really is considering all the things your missing out on (exceptions, null pointers etc)
void CArrayTestRoutine() { CArray * array = CArrayInit(0); NSTimeInterval start = [[NSDate date] timeIntervalSince1970]; NSString * test; for (int ii = 0; ii < 10000000; ++ii) { CArrayAdd(array, @"test"); test = CArrayObjectAtIndex(array, CArrayCount(array)-1); } CArrayRemoveObjectAtIndex(array, 0); NSTimeInterval end = [[NSDate date] timeIntervalSince1970]; printf("CArray 100,000,000 Elements took %fs\n", end-start); NSMutableArray * nsarray = [[NSMutableArray alloc] initWithCapacity:0]; start = [[NSDate date] timeIntervalSince1970]; NSString * string; for (int ii = 0; ii < 10000000; ++ii) { [nsarray addObject:@"test"]; string = [nsarray objectAtIndex:[nsarray count]-1]; } [nsarray removeObjectAtIndex:0]; end = [[NSDate date] timeIntervalSince1970]; [nsarray release]; printf("NSMutableArray 100,000,000 Elements took %fs\n", end-start); printf("%s\n", [string UTF8String]); printf("%s\n", [test UTF8String]); CArrayDestroy(array); }
