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Examine 8 bytes at once for terminator char

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Kovid Goyal
2023-11-10 08:05:01 +05:30
parent f4819175b0
commit 200e5bf6e3
3 changed files with 37 additions and 10 deletions
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41
kitty/simd-string.c
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@@ -44,21 +44,48 @@ byte_loader_next(ByteLoader *self) {
if (!self->digits_left) byte_loader_init(self, self->next_load_at, self->sz_of_next_load);
return ans;
}
#undef SHIFT_OP
static void
byte_loader_skip(ByteLoader *self) {
if (self->num_left >= sizeof(BYTE_LOADER_T)) {
self->m = *(BYTE_LOADER_T*)self->next_load_at;
self->num_left -= sizeof(BYTE_LOADER_T);
self->digits_left = sizeof(BYTE_LOADER_T);
self->next_load_at += sizeof(BYTE_LOADER_T);
} else {
self->num_left = 0;
}
}
#define haszero(v) (((v) - 0x0101010101010101ULL) & ~(v) & 0x8080808080808080ULL)
#define prepare_for_hasvalue(n) (~0ULL/255 * (n))
#define hasvalue(x,n) (haszero((x) ^ (n)))
static uint8_t*
find_either_of_two_chars_simple(uint8_t *haystack, const size_t sz, const uint8_t x, const uint8_t y) {
ByteLoader b; byte_loader_init(&b, haystack, sz);
uint8_t ch;
while (b.num_left) {
ch = byte_loader_next(&b);
if (ch == x || ch == y) {
return haystack + sz - b.num_left - 1;
ByteLoader it; byte_loader_init(&it, haystack, sz);
// first align by testing the first few bytes one at a time
while (it.num_left && it.digits_left < sizeof(BYTE_LOADER_T)) {
const uint8_t ch = byte_loader_next(&it);
if (ch == x || ch == y) return haystack + sz - it.num_left - 1;
}
const BYTE_LOADER_T a = prepare_for_hasvalue(x), b = prepare_for_hasvalue(y);
while (it.num_left) {
if (hasvalue(it.m, a) || hasvalue(it.m, b)) {
uint8_t *ans = haystack + sz - it.num_left, q = hasvalue(it.m, a) ? x : y;
while (it.num_left) {
if (byte_loader_next(&it) == q) return ans;
ans++;
}
return NULL; // happens for final word and it.num_left < sizeof(BYTE_LOADER_T)
}
byte_loader_skip(&it);
}
return NULL;
}
#undef SHIFT_OP
uint8_t*
find_either_of_two_chars(uint8_t *haystack, const size_t sz, const uint8_t a, const uint8_t b) {