5 ms·

But String is heap allocated, right? Can you just declare a static array and return a pointer pointing to any part of it? Like in the C example? BUF is also v

by scoutt 5y ago

But String is heap allocated, right? Can you just declare a static array and return a pointer pointing to any part of it? Like in the C example? BUF is also visible to other parts of the program, correct? If so, it's not quite similar to the C example.

littlestymaar 5y ago
> Can you just declare a static array and return a pointer pointing to any part of it? Like in the C example? Indeed: lazy_static! { static ref BUF: [[u8;1024]; 16] = [ [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024]]; static ref BUF_INDEX: usize = 0; } (You'll need to re-implement a `push_str` method on arrays yourself though) > BUF is also visible to other parts of the program, correct? If so, it's not quite similar to the C example. No, because it's not marked as `pub`, nobody outside the current module can access it.
drran 5y ago
String is heap allocated by default, but String can be made from raw pointer to buffer and buffer length: https://doc.rust-lang.org/std/string/struct.String.html#method.from_raw_parts https://doc.rust-lang.org/std/string/struct.String.html#meth... . Yes, of course. BTW: You can use a c2rust converter to convert a C code to it exact equivalent in Rust. No, buf is not exported, so it's "static" in C terminology.
- scoutt 5y ago
  > No, buf is not exported, so it's "static" in C terminology. Yes, I know that is not exported. What I wanted to say is that in the C example, no one outside tmpstr(void) can access static char buf[16][1024]. In the Rust example I can access static ref BUF from fn main() function, for example.
  - littlestymaar 5y ago
    > In the Rust example I can access static ref BUF from fn main() function, for example. Only because in that simple example, BUF was defined directly in the main module. In a more realistic exemple, BUF and tmpstr would belong to their own module, with only tmpstr being exported (and then accessible). See: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=5ab2b41b09a19806de5fdb0922a279ca https://play.rust-lang.org/?version=stable&mode=debug&editio...

by scoutt 5y ago

littlestymaar 5y ago

> Can you just declare a static array and return a pointer pointing to any part of it? Like in the C example? Indeed: lazy_static! { static ref BUF: [[u8;1024]; 16] = [ [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024], [0;1024]]; static ref BUF_INDEX: usize = 0; } (You'll need to re-implement a `push_str` method on arrays yourself though) > BUF is also visible to other parts of the program, correct? If so, it's not quite similar to the C example. No, because it's not marked as `pub`, nobody outside the current module can access it.

drran 5y ago

String is heap allocated by default, but String can be made from raw pointer to buffer and buffer length: https://doc.rust-lang.org/std/string/struct.String.html#method.from_raw_parts https://doc.rust-lang.org/std/string/struct.String.html#meth... . Yes, of course. BTW: You can use a c2rust converter to convert a C code to it exact equivalent in Rust. No, buf is not exported, so it's "static" in C terminology.

scoutt 5y ago
> No, buf is not exported, so it's "static" in C terminology. Yes, I know that is not exported. What I wanted to say is that in the C example, no one outside tmpstr(void) can access static char buf[16][1024]. In the Rust example I can access static ref BUF from fn main() function, for example.
- littlestymaar 5y ago
  > In the Rust example I can access static ref BUF from fn main() function, for example. Only because in that simple example, BUF was defined directly in the main module. In a more realistic exemple, BUF and tmpstr would belong to their own module, with only tmpstr being exported (and then accessible). See: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=5ab2b41b09a19806de5fdb0922a279ca https://play.rust-lang.org/?version=stable&mode=debug&editio...