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Handle initial state being final in merge_fsas()

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This commit is contained in:
Camden Dixie O'Brien 2024-10-27 13:22:23 +00:00
parent 755f3f6805
commit 280168bb6f
1 changed files with 38 additions and 25 deletions
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61
lib/construct.c
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@ -99,35 +99,33 @@ static void retarget_merged_rules(
if (0 == rules[i].next)
continue;
// IDs less than initial have to be offset by one less than
// base_count because the final state (ID zero) is not copied.
// If they are greater it's two less as the initial state is
// also not copied. Finally, if the target is the initial
// state then it should be changed to the base's initial
// state.
// If the state came before the initial state it should be
// offset by one less than base_count, because the final state
// (index zero) came before it and was not copied into the
// base.
const int before_offset = base_count - 1;
// If it came after the initial state it must be offset by two
// less than base_count because both the final state and the
// initial state came before it and were not copied -- unless
// the initial state is the same state as the final state, in
// which case the offset is still only one less than
// base_count.
const int after_offset = base_count - (0 != initial ? 2 : 1);
if (rules[i].next < initial)
rules[i].next += base_count - 1;
rules[i].next += before_offset;
else if (rules[i].next > initial)
rules[i].next += base_count - 2;
else
rules[i].next += after_offset;
else if (rules[i].next == initial)
rules[i].next = base_initial;
}
}
static void merge_fsas(fsa_t *base, const fsa_t *other)
{
const int new_count = base->count + other->count - 2;
if (base->capacity < new_count) {
do
base->capacity *= 2;
while (base->capacity < new_count);
base->states
= realloc(base->states, base->capacity * sizeof(fsa_state_t));
assert(base->states);
}
// Copy rules from the other's initial state into the base's, then
// retarget them.
// Copy rules from the other's initial state into the base's
// initial state.
fsa_state_t *initial = &base->states[base->initial];
const fsa_state_t *other_initial = &other->states[other->initial];
const int new_rule_count = initial->count + other_initial->count;
@ -142,13 +140,23 @@ static void merge_fsas(fsa_t *base, const fsa_t *other)
memcpy(
&initial->rules[initial->count], other_initial->rules,
other_initial->count * sizeof(fsa_rule_t));
// Retarget the copied rules.
retarget_merged_rules(
&initial->rules[initial->count], other_initial->count,
other->initial, base->initial, base->count);
initial->count = new_rule_count;
// Copy other states, skipping the initial state, then retarget
// their rules.
// Copy other states, skipping the initial state.
const int skipped_states = other->initial != 0 ? 2 : 1;
const int new_count = base->count + other->count - skipped_states;
if (base->capacity < new_count) {
do
base->capacity *= 2;
while (base->capacity < new_count);
base->states
= realloc(base->states, base->capacity * sizeof(fsa_state_t));
assert(base->states);
}
int offset = base->count;
if (1 < other->initial) {
const int copy_count = other->initial - 1;
@ -163,14 +171,19 @@ static void merge_fsas(fsa_t *base, const fsa_t *other)
&base->states[offset], &other->states[other->initial],
copy_size);
}
// Retarget the copied states' rules.
for (int i = base->count; i < new_count; ++i) {
retarget_merged_rules(
base->states[i].rules, base->states[i].count, other->initial,
base->initial, base->count);
}
initial->count = new_rule_count;
base->count = new_count;
free(other->states[0].rules);
if (other->initial != 0)
free(other->states[other->initial].rules);
free(other->states);