diff --git a/core/strings/strings.odin b/core/strings/strings.odin index 8e774b367..a3d9fa93e 100644 --- a/core/strings/strings.odin +++ b/core/strings/strings.odin @@ -15,7 +15,7 @@ clone :: proc(s: string, allocator := context.allocator, loc := #caller_location } // returns a clone of the string `s` allocated using the `allocator` as a cstring -// a nul byte is appended to the clone, to make the cstring safe +// a nul byte is appended to the clone, to make the cstring safe clone_to_cstring :: proc(s: string, allocator := context.allocator, loc := #caller_location) -> cstring { c := make([]byte, len(s)+1, allocator, loc) copy(c, s) @@ -37,7 +37,7 @@ string_from_nul_terminated_ptr :: proc(ptr: ^byte, len: int) -> string { return s } -// returns the raw ^byte start of the string `str` +// returns the raw ^byte start of the string `str` ptr_from_string :: proc(str: string) -> ^byte { d := transmute(mem.Raw_String)str return d.data @@ -969,7 +969,7 @@ count :: proc(s, substr: string) -> int { repeats the string `s` multiple `count` times and returns the allocated string panics when `count` is below 0 - strings.repeat("abc", 2) -> "abcabc" + strings.repeat("abc", 2) -> "abcabc" */ repeat :: proc(s: string, count: int, allocator := context.allocator) -> string { if count < 0 { @@ -1378,7 +1378,7 @@ split_multi :: proc(s: string, substrs: []string, allocator := context.allocator // skip when no results if substrings_found < 1 { - return + return } buf = make([]string, substrings_found + 1, allocator) @@ -1809,3 +1809,65 @@ fields_iterator :: proc(s: ^string) -> (field: string, ok: bool) { s^ = s[len(s):] return } + +// `levenshtein_distance` returns the Levenshtein edit distance between 2 strings. +// This is a single-row-version of the Wagner–Fischer algorithm, based on C code by Martin Ettl. +// Note: allocator isn't used if the length of string b in runes is smaller than 64. +levenshtein_distance :: proc(a, b: string, allocator := context.allocator) -> int { + LEVENSHTEIN_DEFAULT_COSTS: []int : { + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, + 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, + 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, + 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, + 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, + 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, + 60, 61, 62, 63, + } + + m, n := utf8.rune_count_in_string(a), utf8.rune_count_in_string(b) + + if m == 0 { + return n + } + if n == 0 { + return m + } + + costs: []int + + if n + 1 > len(LEVENSHTEIN_DEFAULT_COSTS) { + costs = make([]int, n + 1, allocator) + for k in 0..=n { + costs[k] = k + } + } else { + costs = LEVENSHTEIN_DEFAULT_COSTS + } + + defer if n + 1 > len(LEVENSHTEIN_DEFAULT_COSTS) { + delete(costs, allocator) + } + + i: int + for c1 in a { + costs[0] = i + 1 + corner := i + j: int + for c2 in b { + upper := costs[j + 1] + if c1 == c2 { + costs[j + 1] = corner + } else { + t := upper if upper < corner else corner + costs[j + 1] = (costs[j] if costs[j] < t else t) + 1 + } + + corner = upper + j += 1 + } + + i += 1 + } + + return costs[n] +}