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vt: improved key hash algorithm -> reduces number of key collisions

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Daniel Eklöf 2021-06-24 19:18:06 +02:00
parent 9a7c6bdcf2
commit 88ce0e4375
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GPG key ID: 5BBD4992C116573F
1 changed files with 10 additions and 3 deletions
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13
vt.c
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@ -611,7 +611,6 @@ action_utf8_print(struct terminal *term, wchar_t wc)
xassert(col >= 0 && col < term->cols); xassert(col >= 0 && col < term->cols);
wchar_t base = row->cells[col].wc; wchar_t base = row->cells[col].wc;
wchar_t UNUSED last = base; wchar_t UNUSED last = base;
uint32_t key = base ^ wc;
/* Is base cell already a cluster? */ /* Is base cell already a cluster? */
const struct composed *composed = const struct composed *composed =
@ -619,11 +618,18 @@ action_utf8_print(struct terminal *term, wchar_t wc)
? composed_lookup(term->composed, base - CELL_COMB_CHARS_LO) ? composed_lookup(term->composed, base - CELL_COMB_CHARS_LO)
: NULL; : NULL;
#define chain_key(old, new) (((old) << 8) ^ (new))
uint32_t key;
if (composed != NULL) { if (composed != NULL) {
base = composed->chars[0]; base = composed->chars[0];
last = composed->chars[composed->count - 1]; last = composed->chars[composed->count - 1];
key = composed->key ^ wc; key = chain_key(composed->key, wc);
} } else
key = chain_key(base, wc);
#undef chain_key
key &= CELL_COMB_CHARS_HI - CELL_COMB_CHARS_LO; key &= CELL_COMB_CHARS_HI - CELL_COMB_CHARS_LO;
@ -706,6 +712,7 @@ action_utf8_print(struct terminal *term, wchar_t wc)
* again. * again.
*/ */
xassert(key == cc->key);
if (cc->chars[0] != base || if (cc->chars[0] != base ||
cc->count != wanted_count || cc->count != wanted_count ||
cc->chars[wanted_count - 1] != wc) cc->chars[wanted_count - 1] != wc)