C: Implement more efficient buffer resizing #539
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marcoroth
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Sep 30, 2025
asilano
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Oct 21, 2025
## Problem If the buffer is nearly full even one extra character can trigger an expansion of the buffer. Since the buffer only grows by twice the number of required characters per resize, in this case 2 characters, the buffer has to be constantly resized. ### Visualization  ## How the problem is addressed Rather than just checking the required length, we test whether doubling the current capacity will be enough. If it is, we expand to the doubled capacity. If not, we double the required length itself and resize the buffer to that size. ## Performance impact Lexing a [real world html page](https://shop.herthabsc.com) Before: ~88.255ms After: ~79.208ms Parsing showed no significant performance impact though
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Problem
If the buffer is nearly full even one extra character can trigger an expansion of the buffer. Since the buffer only grows by twice the number of required characters per resize, in this case 2 characters, the buffer has to be constantly resized.
Visualization
How the problem is addressed
Rather than just checking the required length, we test whether doubling the current capacity will be enough. If it is, we expand to the doubled capacity. If not, we double the required length itself and resize the buffer to that size.
Performance impact
Lexing a real world html page
Before: ~88.255ms
After: ~79.208ms
Parsing showed no significant performance impact though