Static Map

A static round-robin hashmap implementation, using the same hasher found in rustc. This is currently written using a bang variant of procedural macros that is only avialable in nightly at the moment. Procedural macros are currently in active development, so I woulnd't expect any kind of stability here for the moment. This was just an exercise to gain experience for how procedural macro development may become.

Example

#[macro_use]externcrate static_map;#[macro_use]externcrate static_map_macros;use static_map::Map;#[derive(Clone,Copy)]structRGB(u8,u8,u8);staticCSS_COLORS:Map<&'staticstr,RGB> = static_map!{Default:RGB(0x00,0x00,0x00),"black" => RGB(0x00,0x00,0x00),"silver" => RGB(0xc0,0xc0,0xc0),"gray" => RGB(0x80,0x80,0x80),"white" => RGB(0xff,0xff,0xff),"maroon" => RGB(0x80,0x00,0x00),"red" => RGB(0xff,0x00,0x00),"purple" => RGB(0x80,0x00,0x80),"fuchsia" => RGB(0xff,0x00,0xff),"green" => RGB(0x00,0x80,0x00),};pubfnrgb_from_str(color:&str) -> Option<RGB>{CSS_COLORS.get(color).cloned()}

Notice that Default: RGB(0, 0, 0),. This is required since we are initializing an array which will contain empty slots. We need a default value for those slots and you declare it as such. PHF maps do not require this since they are, well, perfect. Also note that #[macro_use] is required for bothstatic_map and static_map_macros. This is because proc_macros are not allowed to export items, so the static_map! macro lives in the static_map crate. (Note: This is not entirely true, and may be fixed soon).

Benchmarks

The idea is that a static round-robin hashmap maybe more efficient than PHF for certain datasets. The trade-off is that a PHF hashmap implementation is nearly optimal with respect to memory efficiency; static_map! may use upto 2x as much memory in the worst case scenario. Keep that in mind, here are some benchmarks (found in static_map_macro/benches).

CSS Colors

This contains about 150 &str -> RGB(u8, u8, u8) entries (like in the example above).

test bench_phf ... bench: 2,027 ns/iter (+/- 224)
test bench_static_map ... bench: 935 ns/iter (+/- 90)

Codepoints

This benchmark contains about 4500 u32 -> GlyphMetrics entries.

test bench_phf ... bench: 44,502 ns/iter (+/- 3,971)
test bench_static_map ... bench: 13,097 ns/iter (+/- 2,768)

TeX Symbols

This benchmark contains about 1500 &str -> Symbol entries, mapping tex symbols to codepoints.

test bench_phf ... bench: 20,382 ns/iter (+/- 133)
test bench_static_map ... bench: 24,589 ns/iter (+/- 188)