commit b0e4f055ad2182b44450e5750071cb4d26f9759a
parent 78a99de582d50d867624550033c33f4c134730da
Author: Pierre Curto <pierre.curto@gmail.com>
Date: Sun, 14 Aug 2022 17:38:02 +0200
bytes: implement special cases for 2, 3 and 4 needle sizes in index
Signed-off-by: Pierre Curto <pierre.curto@gmail.com>
Diffstat:
| M | bytes/index.ha | | | 67 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------- |
1 file changed, 59 insertions(+), 8 deletions(-)
diff --git a/bytes/index.ha b/bytes/index.ha
@@ -22,14 +22,65 @@ fn index_byte(haystack: []u8, needle: u8) (size | void) = {
};
};
-fn index_slice(haystack: []u8, b: []u8) (size | void) = switch (len(b)) {
-// TODO special-case 2, 3, 4
-case 0 =>
- yield 0;
-case 1 =>
- yield index_byte(haystack, b[0]);
-case =>
- yield index_tw(haystack, b);
+fn index_2bytes(haystack: []u8, needle: u16) (size | void) = {
+ if (len(haystack) > 1) {
+ let x = haystack[0]: u16;
+ for (let i = 1z; i < len(haystack); i += 1) {
+ x = x << 8 | haystack[i];
+ if (x == needle) {
+ return i - 1;
+ };
+ };
+ };
+};
+
+fn index_3bytes(haystack: []u8, needle: u32) (size | void) = {
+ if (len(haystack) > 2) {
+ let x = haystack[0]: u32 << 8 | haystack[1];
+ for (let i = 2z; i < len(haystack); i += 1) {
+ x = x << 16 >> 8 | haystack[i];
+ if (x == needle) {
+ return i - 2;
+ };
+ };
+ };
+};
+
+fn index_4bytes(haystack: []u8, needle: u32) (size | void) = {
+ if (len(haystack) > 3) {
+ let x = haystack[0]: u32 << 16 |
+ haystack[1]: u32 << 8 |
+ haystack[2];
+ for (let i = 3z; i < len(haystack); i += 1) {
+ x = x << 8 | haystack[i];
+ if (x == needle) {
+ return i - 3;
+ };
+ };
+ };
+};
+
+fn index_slice(haystack: []u8, b: []u8) (size | void) = {
+ switch (len(b)) {
+ case 0 =>
+ return 0;
+ case 1 =>
+ return index_byte(haystack, b[0]);
+ case 2 =>
+ return index_2bytes(haystack, b[0]: u16 << 8 | b[1]);
+ case 3 =>
+ return index_3bytes(
+ haystack,
+ b[0]: u32 << 16 | b[1]: u32 << 8 | b[2],
+ );
+ case 4 =>
+ return index_4bytes(
+ haystack,
+ b[0]: u32 << 24 | b[1]: u32 << 16 | b[2]: u32 << 8 | b[3],
+ );
+ case =>
+ return index_tw(haystack, b);
+ };
};
// Returns the offset of the last instance of "needle" in a "haystack" of
