4 ms·

In order for this to matter, you'd need to expect the possibility of strings with huge numbers of leading spaces. Why then would you use this naive algorithm f

In order for this to matter, you'd need to expect the possibility of strings with huge numbers of leading spaces. Why then would you use this naive algorithm for comparison? An obvious and more straight forward improvement would be to compare 4 bytes at a time with 0x20202020. (or maybe 8) There would be a maximum of 3 spaces to identify individually.

rkunde 4y ago
I was confused too but the author uses “trim” to mean “remove anywhere in the string”, rather than just from the beginning and end.
- layer8 4y ago
  What are the use cases for that, though?
  - pkaye 4y ago
    Maybe for processing the code for an obfuscated C contest?
  - xxpor 4y ago
    There's a ton if you think of it as a byte array, rather than just a string. For example, network proxies that may remove various protocol TLV options from a packet.
    - layer8 4y ago
      Is that an example of “remove all occurrences of a specific byte value from an array”? Wouldn’t packet processing require some sort of structural parsing?
      - xxpor 4y ago
        Packets are usually parsed by casting a uint8_t * to a struct. Frequently, the part that needs to be removed is always at the same offset in the non-error case.
  - eklitzke 4y ago
    This particular routine doesn't seem that useful, but sometimes these weird vector algorithms that don't seem useful on their own are composed together in interesting ways to solve a larger, more interesting problem. For example, there was a cppcon talk a few years ago where the presenter came up with a novel way of using AVX instructions to efficiently find the median of seven (yes, exactly seven) integers, by coming up with a novel representation of the problem that AVX instructions were well-suited for.^[1] That said, I don't know if this particular routine is something the author came up with while working on some other problem, or if it's just a neat idea that he came up with and wrote a short blog post about. [1] https://www.youtube.com/watch?v=qejTqnxQRcw https://www.youtube.com/watch?v=qejTqnxQRcw
- tuananh 4y ago
  better word is compact?

rkunde 4y ago

I was confused too but the author uses “trim” to mean “remove anywhere in the string”, rather than just from the beginning and end.

layer8 4y ago
What are the use cases for that, though?
- pkaye 4y ago
  Maybe for processing the code for an obfuscated C contest?
- xxpor 4y ago
  There's a ton if you think of it as a byte array, rather than just a string. For example, network proxies that may remove various protocol TLV options from a packet.
  - layer8 4y ago
    Is that an example of “remove all occurrences of a specific byte value from an array”? Wouldn’t packet processing require some sort of structural parsing?
    - xxpor 4y ago
      Packets are usually parsed by casting a uint8_t * to a struct. Frequently, the part that needs to be removed is always at the same offset in the non-error case.
- eklitzke 4y ago
  This particular routine doesn't seem that useful, but sometimes these weird vector algorithms that don't seem useful on their own are composed together in interesting ways to solve a larger, more interesting problem. For example, there was a cppcon talk a few years ago where the presenter came up with a novel way of using AVX instructions to efficiently find the median of seven (yes, exactly seven) integers, by coming up with a novel representation of the problem that AVX instructions were well-suited for.^[1] That said, I don't know if this particular routine is something the author came up with while working on some other problem, or if it's just a neat idea that he came up with and wrote a short blog post about. [1] https://www.youtube.com/watch?v=qejTqnxQRcw https://www.youtube.com/watch?v=qejTqnxQRcw
tuananh 4y ago
better word is compact?