Crate intern_str
source · [−]Expand description
Simple, fast and allocation-free string interning.
intern-str is a library for interning strings in Rust. It allows
you to build a graph that can convert strings (and byte strings)
into arbitrary values. In addition, these graphs are no_std and
can be embedded into projects at compile time.
The goal is to allow for low-cost, efficient string interning that does not require an allocator or the standard library. The intended use case is MIME Types, but it is likely to be useful in many other cases as well.
intern-str is no_std, no extern crate alloc,
forbid(unsafe_code), and has no dependencies aside from the Rust
core library.
To generate intern-str graphs as code, see the [builder] module
and the intern-str-codegen crate.
Implementation
intern-str generates a DFA consisting of all possible options for
a given set of strings. This DFA is then used to convert a string
into a value. The DFA is generated at compile time, and is embedded
into the binary. This allows for efficient string interning without
the need for an allocator or the standard library.
In many cases, this approach is significantly faster than converting
the string to lowercase and matching on it. When matching on
/usr/share/dict/words, intern-str usually completes queries in
50 ns.
The main advantage of this approach is that it can be used to create
case-insensitive matching, which is significantly more difficult to
do with other libraries like phf. When compared against phf
when phf has to convert strings to lower case before running,
intern-str is usually as fast as phf if not faster.