[−][src]Crate arraystring
Generic-array based string
String based on generic array
Since rust doesn't have constant generics yet typenum
is used to allow for generic arrays (U1
to U255
)
If you need bigger than U255
open an issue explaining your use-case and we may implement
Can't outgrow initial capacity (defined at compile time), always occupies capacity
+ 1
bytes of memory
Doesn't allocate memory on the heap and never panics in release (all panic branches are stripped at compile time - except Index
/IndexMut
traits, since they are supposed to)
Why
Data is generally bounded, you don't want a phone number with 30 characters, nor a username with 100. You probably don't even support it in your database.
Why pay the cost of heap allocations of strings with unlimited capacity if you have limited boundaries?
Stack based strings are generally faster to create, clone and append to than heap based strings (custom allocators and thread-locals may help with heap based ones).
But that becomes less true as you increase the array size, 255 bytes is the maximum we accept (bigger will just wrap) and it's probably already slower than heap based strings of that size (like in std::string::String
)
There are other stack based strings out there, they generally can have "unlimited" capacity (heap allocate), but the stack based size is defined by the library implementor, we go through a different route by implementing a string based in a generic array.
Array based strings always occupies the full space in memory, so they may use more memory (in the stack) than dynamic strings.
Features
default: std
-
std
enabled by default, enablesstd
compatibility -impl Error
trait for errors (remove it to be#[no_std]
compatible) -
serde-traits
enables serde traits integration (Serialize
/Deserialize
)Opperates like
String
, but truncates it if it's bigger than capacity -
diesel-traits
enables diesel traits integration (Insertable
/Queryable
)Opperates like
String
, but truncates it if it's bigger than capacity -
logs
enables internal loggingYou will probably only need this if you are debugging this library
Examples
use arraystring::{Error, ArrayString, typenum::U5, typenum::U20}; type Username = ArrayString<U20>; type Role = ArrayString<U5>; #[derive(Debug)] pub struct User { pub username: Username, pub role: Role, } fn main() -> Result<(), Error> { let user = User { username: Username::try_from_str("user")?, role: Role::try_from_str("admin")? }; println!("{:?}", user); Ok(()) }
Benchmarks
This benchmarks ran while I streamed video and used my computer (with non-disclosed specs) as usual, so don't take the actual times too serious, just focus on the comparison
string clone 25.850 ns
string from 25.815 ns
---------------------------------------------------------
small-string (21 bytes) clone 4.556 ns
small-string (21 bytes) try_from_str 15.749 ns
small-string (21 bytes) from_str_truncate 10.991 ns
small-string (21 bytes) from_str_unchecked 11.195 ns
---------------------------------------------------------
cache-string (63 bytes) clone 10.345 ns
cache-string (63 bytes) try_from_str 24.959 ns
cache-string (63 bytes) from_str_truncate 17.485 ns
cache-string (63 bytes) from_str_unchecked 16.684 ns
---------------------------------------------------------
max-string (255 bytes) clone 145.750 ns
max-string (255 bytes) try_from_str 157.890 ns
max-string (255 bytes) from_str_truncate 193.870 ns
max-string (255 bytes) from_str_unchecked 163.740 ns
Licenses
MIT
and Apache-2.0
Re-exports
pub use typenum; |
pub use crate::error::Error; |
Modules
drain | Draining iterator for |
error | Contains all of this crate errors |
prelude | Most used traits and data-strucutres |
Structs
ArrayString | String based on a generic array (size defined at compile time through |
CacheString | Newtype string that occupies 64 bytes in memory and is 64 bytes aligned (full cache line) |
Type Definitions
MaxString | Biggest array based string (255 bytes of string) |
SmallString | String with the same |