Add `strings.Intern`

core/strings/intern.odin

@@ -0,0 +1,54 @@
+package strings
+
+import "core:mem"
+
+Intern_Entry :: struct {
+	len:  int,
+	str:  [1]byte, // string is allocated inline with the entry to keep allocations simple
+}
+
+Intern :: struct {
+	allocator: mem.Allocator,
+	entries: map[string]^Intern_Entry,
+}
+
+intern_init :: proc(m: ^Intern, allocator := context.allocator, map_allocator := context.allocator) {
+	m.allocator = allocator;
+	m.entries = make(map[string]^Intern_Entry, 16, map_allocator);
+}
+
+intern_destroy :: proc(m: ^Intern) {
+	for _, value in m.entries {
+		free(value, m.allocator);
+	}
+	delete(m.entries);
+}
+
+intern_get :: proc(m: ^Intern, text: string) -> string {
+	entry := _intern_get_entry(m, text);
+	return #no_bounds_check string(entry.str[:entry.len]);
+}
+intern_get_cstring :: proc(m: ^Intern, text: string) -> cstring {
+	entry := _intern_get_entry(m, text);
+	return cstring(&entry.str[0]);
+}
+
+_intern_get_entry :: proc(m: ^Intern, text: string) -> ^Intern_Entry #no_bounds_check {
+	if prev, ok := m.entries[text]; ok {
+		return prev;
+	}
+	if m.allocator.procedure == nil {
+		m.allocator = context.allocator;
+	}
+
+	entry_size := int(offset_of(Intern_Entry, str)) + len(text) + 1;
+	new_entry := (^Intern_Entry)(mem.alloc(entry_size, align_of(Intern_Entry), m.allocator));
+
+	new_entry.len = len(text);
+	copy(new_entry.str[:new_entry.len], text);
+	new_entry.str[new_entry.len] = 0;
+
+	key := string(new_entry.str[:new_entry.len]);
+	m.entries[key] = new_entry;
+	return new_entry;
+}