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more map progress

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This commit is contained in:
Ivar Fatland
2026-04-12 22:59:50 +02:00
parent 9a07b00a2c
commit 84f982329e
2 changed files with 120 additions and 63 deletions
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map.c
+103 -49
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@@ -2,7 +2,7 @@
#include <assert.h>
#define FLAG_FREE (-1)
#define FLAG_GRAVESTONE (-2)
#define FLAG_TOMBSTONE (-2)
static inline unsigned int mapping_cap(unsigned int capacity) {
return capacity * 2;
@@ -52,18 +52,113 @@ void *map_create_func(
header->mapping_arr = (int*) &header->bytes[sizes.real_cap_of_items_arr];
header->mapping_capacity = mapping_cap(args.initial_capacity);
for ( int i = 0; i < header->mapping_capacity; i++ ) {
for ( unsigned int i = 0; i < header->mapping_capacity; i++ ) {
header->mapping_arr[i] = FLAG_FREE;
}
return header->bytes;
}
typedef struct index_pair {
unsigned int new_index;
unsigned int old_index;
bool has_old_index;
} index_pair_t;
static const void *internal_cig_key_ptr_from_pair_ptr(const void *this, const void *pair) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
return (const void *) &((const char *)pair)[header->key_offset];
}
// TODO: just make these internal probably
bool map_key_equals(void *this, const void *key1, const void *key2) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
if (header->equals != NULL) {
return header->equals(key1, key2);
}
const char *key1_bytes = key1;
const char *key2_bytes = key2;
for ( unsigned int i = 0; i < header->key_size; i++ ) {
if (key1_bytes[i] != key2_bytes[i]) {
return false;
}
}
return true;
}
/*
* Hashes modulo the header->mapping_capacity. Will linearly probe until a free
* slot is found. If the key already exists in the mapping array, that will be
* indicated in the return value, and the user is expected to overwrite the old
* index with a tombstone if they are going to write a new value for that key.
*/
index_pair_t map_pair_hash(void *this, void *pair) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
const void *key = internal_cig_key_ptr_from_pair_ptr(this, pair);
// find the initial index based on hash
uint32_t mapping_index;
if (header->hash != NULL) {
mapping_index = header->hash(key) % header->mapping_capacity;
} else {
mapping_index = fnv_1a(key, header->key_size) % header->mapping_capacity;
}
uint32_t tombstone_index;
bool found_tombstone = false;
// begin probing
int existing_value_index = header->mapping_arr[mapping_index];
while (
existing_value_index != FLAG_FREE &&
!map_key_equals(
this,
internal_cig_key_ptr_from_pair_ptr(
this,
&header->bytes[existing_value_index * header->item_size]
),
key
)
) {
const bool is_tombstone = existing_value_index == FLAG_TOMBSTONE;
if ((!found_tombstone) && is_tombstone) {
tombstone_index = mapping_index;
found_tombstone = true;
}
mapping_index = (mapping_index + 1) % header->mapping_capacity;
existing_value_index = header->mapping_arr[mapping_index];
}
// Whatever is at index is either free, or the key is already in the map.
//
// If the key is already in the map, we instead want to use the earliest
// tombstone index we found, if we found one.
//
// But this also means that we have to know to set the existing mapping
// slot to a tombstone value at the time where we insert the key-value
// pair.
if (found_tombstone) {
return (index_pair_t) {
.has_old_index=true,
.new_index=tombstone_index,
.old_index=mapping_index,
};
} else {
return (index_pair_t) {
.has_old_index=false,
.new_index=mapping_index,
};
}
}
// Checks that the map can handle one more item. The maps capacity grows if not,
// usually by doubling the capacity.
void map_assure_growable_by_1(void **this, const char *file, int line) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, *this);
int new_n_items = header->n_items + 1;
unsigned int new_n_items = header->n_items + 1;
if (new_n_items <= header->mapping_capacity) {
return;
}
@@ -95,6 +190,9 @@ void map_assure_growable_by_1(void **this, const char *file, int line) {
// TODO: make the map_pair_hash more private? would be nice to just
// pass in the header, and I don't really think it is needed
// directly by the user of the library.
// TODO: this now just completely is wrong, though there will be no
// old_indexes in this case, assuming no bugs in the rest of the
// program.
unsigned int mapping_index = map_pair_hash(this, pair);
header->mapping_arr[mapping_index] = i;
}
@@ -105,7 +203,7 @@ uint32_t fnv_1a(const uint8_t *bytes, const unsigned int size) {
const uint32_t PRIME = 0x01000193;
const uint32_t OFFSET = 0x811c9dc5;
uint32_t hash = OFFSET;
for (int i = 0; i < size; i++) {
for (unsigned int i = 0; i < size; i++) {
uint32_t byte = (uint32_t)bytes[i];
hash = hash ^ byte;
hash = hash * PRIME;
@@ -113,50 +211,6 @@ uint32_t fnv_1a(const uint8_t *bytes, const unsigned int size) {
return hash;
}
static void *internal_cig_key_ptr_from_pair_ptr(void *this, void *pair) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
return &pair[header->key_offset];
}
// TODO: just make these internal probably
bool map_key_equals(void *this, const void *key1, const void *key2) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
if (header->equals != NULL) {
return header->equals(key1, key2);
}
const char *key1_bytes = key1;
const char *key2_bytes = key2;
for ( int i = 0; i < header->key_size; i++ ) {
if (key1_bytes[i] != key2_bytes[i]) {
return false;
}
}
return true;
}
unsigned int map_pair_hash(void *this, void *pair) {
map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
void *key = internal_cig_key_ptr_from_pair_ptr(this, pair);
// find the initial index based on hash
uint32_t index;
if (header->hash != NULL) {
index = header->hash(key) % header->mapping_capacity;
} else {
index = fnv_1a(key, header->key_size) % header->mapping_capacity;
}
int existing_index = header->mapping_arr[index];
while (!(existing_index == FLAG_FREE || existing_index == FLAG_GRAVESTONE)) {
index = fnv_1a(
(const uint8_t *) &index,
sizeof(index)
) % header->mapping_capacity;
int existing_index = header->mapping_arr[index];
}
return (unsigned int) index;
}
int map_len(void *this) {
if (this == NULL) {
return 0;
@@ -174,5 +228,5 @@ int map_cap(void *this) {
}
#undef FLAG_FREE
#undef FLAG_GRAVESTONE
#undef FLAG_TOMBSTONE