Commit 9f76dcd6 authored by Committed by Damien GeorgeBrowse files
py: Prevent many extra vstr allocations.
I checked the entire codebase, and every place that vstr_init_len was called, there was a call to mp_obj_new_str_from_vstr after it. mp_obj_new_str_from_vstr always tries to reallocate a new buffer 1 byte larger than the original to store the terminating null character. In many cases, if we allocated the initial buffer to be 1 byte longer, we can prevent this extra allocation, and just reuse the originally allocated buffer. Asking to read 256 bytes and only getting 100 will still cause the extra allocation, but if you ask to read 256 and get 256 then the extra allocation will be optimized away. Yes - the reallocation is optimized in the heap to try and reuse the buffer if it can, but it takes quite a few cycles to figure this out. Note by Damien: vstr_init_len should now be considered as a string-init convenience function and used only when creating null-terminated objects.