4 ms·

For strings, you need more than the allocated length: you need the current length too. Otherwise you end up with: - O(n) algorithms that are constantly scanni

by prirun 5y ago

For strings, you need more than the allocated length: you need the current length too. Otherwise you end up with: - O(n) algorithms that are constantly scanning strings looking for a zero byte - strings can't contain zero bytes - strings have to contain one zero byte - putting a zero byte in the middle of a string chops it off - probably other nonsense I haven't thought of Please don't adopt another half-assed solution just because it fits more easily into C's existing set of crap. That's how we got fake strings in the first place.

WalterBright 5y ago
This solution has been in D for 20 years. It works very well. It is fully assed. It is very, very rare to see a buffer overflow in D because the use of these arrays is so easy, convenient, and robust. Not only does it virtually eliminate buffer overflows (when used), it is more efficient than 0 terminated strings. It does not need to scan the strings, nor does it need to load the string into memory to determine its length. I understand your concerns about mixing it up with 0 terminated strings. They are real, but have not been a particular problem in practice. What happens is one simply moves away from using 0 terminated strings. A zero terminated string can be converted to a length one with: a = s[0 .. strlen(s)]; Going the other way requires a memory allocation similar to what strdup() does.
- prirun 5y ago
  I read your article before posting, and it says: ----- void foo(char a[..]) meaning an array is passed as a so-called “fat pointer”, i.e. a pair consisting of a pointer to the start of the array, and a size_t of the array dimension. ----- I didn't see a "current length" mentioned. Is it there? Can I have a string with an allocated length of 20 bytes and a current length of 10 bytes, without using a looking for a zero byte?
  - WalterBright 5y ago
    The capacity value is not part of it. This proposal is not about memory management any more than 0 termination is about memory management. It is just about finding the end of the array.

by prirun 5y ago

WalterBright 5y ago

This solution has been in D for 20 years. It works very well. It is fully assed. It is very, very rare to see a buffer overflow in D because the use of these arrays is so easy, convenient, and robust. Not only does it virtually eliminate buffer overflows (when used), it is more efficient than 0 terminated strings. It does not need to scan the strings, nor does it need to load the string into memory to determine its length. I understand your concerns about mixing it up with 0 terminated strings. They are real, but have not been a particular problem in practice. What happens is one simply moves away from using 0 terminated strings. A zero terminated string can be converted to a length one with: a = s[0 .. strlen(s)]; Going the other way requires a memory allocation similar to what strdup() does.

prirun 5y ago
I read your article before posting, and it says: ----- void foo(char a[..]) meaning an array is passed as a so-called “fat pointer”, i.e. a pair consisting of a pointer to the start of the array, and a size_t of the array dimension. ----- I didn't see a "current length" mentioned. Is it there? Can I have a string with an allocated length of 20 bytes and a current length of 10 bytes, without using a looking for a zero byte?
- WalterBright 5y ago
  The capacity value is not part of it. This proposal is not about memory management any more than 0 termination is about memory management. It is just about finding the end of the array.