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Use boyer-moore-horspool with all types of T

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This commit is contained in:
dec05eba 2020-09-05 11:46:41 +02:00
parent e297b4815c
commit d012507a8f
1 changed files with 19 additions and 11 deletions
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30
lib/std/mem.zig
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@ -888,18 +888,22 @@ fn boyerMooreHorspoolPreprocess(pattern: []const u8, table: []usize) void {
/// To start looking at a different index, slice the haystack first.
// Reverse boyer-moore-horspool algorithm
pub fn lastIndexOf(comptime T: type, haystack: []const T, needle: []const T) ?usize {
if (T != u8 or haystack.len < 32 or needle.len <= 2)
if (haystack.len < 32 or needle.len <= 2)
return lastIndexOfNaive(T, haystack, needle);
if (needle.len > haystack.len or needle.len == 0) return null;
const haystackU8 = @bitCast([]const u8, haystack);
const needleU8 = @bitCast([]const u8, needle);
var table: [256]usize = undefined;
boyerMooreHorspoolPreprocess(needle, table[0..]);
boyerMooreHorspoolPreprocess(needleU8, table[0..]);
var i: usize = 0;
while (i <= haystack.len - needle.len) {
const reverseIndex = haystack.len - i - needle.len - 1;
if (mem.eql(T, haystack[reverseIndex .. reverseIndex + needle.len], needle)) return i;
i += table[haystack[reverseIndex + needle.len - 1]];
while (i <= haystackU8.len - needleU8.len) {
const reverseIndex = haystackU8.len - i - needleU8.len - 1;
if (mem.eql(u8, haystackU8[reverseIndex .. reverseIndex + needleU8.len], needleU8)) return i;
i += table[haystackU8[reverseIndex + needleU8.len - 1]];
}
return null;
@ -907,17 +911,21 @@ pub fn lastIndexOf(comptime T: type, haystack: []const T, needle: []const T) ?us
// Boyer-moore-horspool algorithm
pub fn indexOfPos(comptime T: type, haystack: []const T, start_index: usize, needle: []const T) ?usize {
if (T != u8 or haystack.len < 32 or needle.len <= 2)
if (haystack.len < 32 or needle.len <= 2)
return indexOfPosNaive(T, haystack, start_index, needle);
if (needle.len > haystack.len or needle.len == 0) return null;
const haystackU8 = @bitCast([]const u8, haystack);
const needleU8 = @bitCast([]const u8, needle);
var table: [256]usize = undefined;
boyerMooreHorspoolPreprocess(needle, table[0..]);
boyerMooreHorspoolPreprocess(needleU8, table[0..]);
var i: usize = start_index;
while (i <= haystack.len - needle.len) {
if (mem.eql(T, haystack[i .. i + needle.len], needle)) return i;
i += table[haystack[i + needle.len - 1]];
while (i <= haystackU8.len - needleU8.len) {
if (mem.eql(u8, haystackU8[i .. i + needleU8.len], needleU8)) return i;
i += table[haystackU8[i + needleU8.len - 1]];
}
return null;