cmap_api.md

STC cmap: Unordered Map

A cmap is an associative container that contains key-value pairs with unique keys. Search, insertion, and removal of elements have average constant-time complexity. Internally, the elements are not sorted in any particular order, but organized into buckets. Which bucket an element is placed into depends entirely on the hash of its key. This allows fast access to individual elements, since once the hash is computed, it refers to the exact bucket the element is placed into. It is implemented as closed hashing (aka open addressing) with linear probing, and without leaving tombstones on erase.

Iterator invalidation: References and iterators are invalidated after erase. No iterators are invalidated after insert, unless the hash-table need to be extended. The hash table size can be reserved prior to inserts if the total max size is known. The order of elements is preserved after erase and insert. This makes it possible to erase individual elements while iterating through the container by using the returned iterator from erase_at(), which references the next element.

See the c++ class std::unordered_map for a functional description.

Header file and declaration

#include <stc/cmap.h>

using_cmap(X, Key, Mapped);
using_cmap(X, Key, Mapped, keyEquals, keyHash);
using_cmap(X, Key, Mapped, keyEquals, keyHash, mappedDel, mappedClone = c_no_clone);
using_cmap(X, Key, Mapped, keyEquals, keyHash, mappedDel, mappedFromRaw, mappedToRaw, RawMapped);
using_cmap(X, Key, Mapped, keyEqualsRaw, keyHashRaw, mappedDel, mappedFromRaw, mappedToRaw, RawMapped,
                                                     keyDel, keyFromRaw, keyToRaw, RawKey);
using_cmap_keydef(X, Key, Mapped, keyEquals, keyHash, keyDel, keyClone);
using_cmap_keydef(X, Key, Mapped, keyEqualsRaw, keyHashRaw, keyDel, keyFromRaw, keyToRaw, RawKey);

using_cmap_strkey(X, Mapped);                   // using_cmap(X, cstr, Mapped, ...)
using_cmap_strkey(X, Mapped, mappedDel, mappedClone = c_no_clone);
using_cmap_strkey(X, Mapped, mappedDel, mappedFromRaw, mappedToRaw, RawMapped);

using_cmap_strval(X, Key);                      // using_cmap(X, Key, cstr, ...)
using_cmap_strval(X, Key, keyEquals, keyHash);
using_cmap_strval(X, Key, keyEquals, keyHash, keyDel, keyClone = c_no_clone);
using_cmap_strval(X, Key, keyEqualsRaw, keyHashRaw, keyDel, keyFromRaw, keyToRaw, RawKey);

using_cmap_str()                                // using_cmap(str, cstr, cstr, ...)

The using_cmap() macro family must be instantiated in the global scope. X is a type tag name and will affect the names of all cmap types and methods. E.g. declaring using_cmap(ii, int, int);, X should be replaced by ii in all of the following documentation.

Methods

cmap_X              cmap_X_init(void);
cmap_X              cmap_X_with_capacity(size_t cap);
cmap_X              cmap_X_clone(cmap_x map);

void                cmap_X_clear(cmap_X* self);
void                cmap_X_max_load_factor(cmap_X* self, float max_load);                    // default: 0.85
void                cmap_X_reserve(cmap_X* self, size_t size);
void                cmap_X_shrink_to_fit(cmap_X* self);
void                cmap_X_swap(cmap_X* a, cmap_X* b);
void                cmap_X_del(cmap_X* self);                                                // destructor

bool                cmap_X_empty(cmap_X map);
size_t              cmap_X_size(cmap_X map);
size_t              cmap_X_capacity(cmap_X map);                                             // buckets * max_load_factor
size_t              cmap_X_bucket_count(cmap_X map);                                         // num. of allocated buckets

cmap_X_iter_t       cmap_X_find(const cmap_X* self, RawKey rkey);
bool                cmap_X_contains(const cmap_X* self, RawKey rkey);
cmap_X_mapped_t*    cmap_X_at(const cmap_X* self, RawKey rkey);                              // rkey must be in map.

cmap_X_result_t     cmap_X_insert(cmap_X* self, Key key, Mapped mapped);                     // no change if key in map
cmap_X_result_t     cmap_X_insert_or_assign(cmap_X* self, Key key, Mapped mapped);           // always update mapped
cmap_X_result_t     cmap_X_put(cmap_X* self, Key key, Mapped mapped);                        // alias for insert_or_assign

cmap_X_result_t     cmap_X_emplace(cmap_X* self, RawKey rkey, RawMapped rmapped);            // no change if rkey in map
cmap_X_result_t     cmap_X_emplace_or_assign(cmap_X* self, RawKey rkey, RawMapped rmapped);  // always update rmapped
void                cmap_X_emplace_n(cmap_X* self, const cmap_X_rawvalue_t arr[], size_t n);

size_t              cmap_X_erase(cmap_X* self, RawKey rkey);                                 // return 0 or 1
cmap_X_iter_t       cmap_X_erase_at(cmap_X* self, cmap_X_iter_t it);                         // return iter after it
void                cmap_X_erase_entry(cmap_X* self, cmap_X_value_t* entry);

cmap_X_iter_t       cmap_X_begin(const cmap_X* self);
cmap_X_iter_t       cmap_X_end(const cmap_X* self);
void                cmap_X_next(cmap_X_iter_t* it);

cmap_X_value_t      cmap_X_value_clone(cmap_X_value_t val);

uint64_t            c_default_hash(const void *data, size_t len);         // key any trivial type
uint64_t            c_default_hash32(const void* data, size_t);           // key one 32bit int
uint64_t            c_default_hash64(const void* data, size_t);           // key one 64bit int
int                 c_default_equals(const RawKey* a, const RawKey* b);   // the == operator
int                 c_trivial_equals(const RawKey* a, const RawKey* b);   // memcmp
Type                c_no_clone(Type val);
Type                c_trivial_fromraw(Type val);                          // plain copy
Type                c_trivial_toraw(Type* val);
void                c_trivial_del(Type* val);                             // does nothing

Types

Type name	Type definition	Used to represent...
cmap_X	struct { ... }	The cmap type
cmap_X_rawkey_t	RawKey	The raw key type
cmap_X_rawmapped_t	RawMapped	The raw mapped type
cmap_X_rawvalue_t	struct { RawKey first; RawMapped second; }	RawKey + RawMapped type
cmap_X_key_t	Key	The key type
cmap_X_mapped_t	Mapped	The mapped type
cmap_X_value_t	struct { Key first; Mapped second; }	The value type
cmap_X_result_t	struct { cmap_X_value_t *ref; bool inserted; }	Result of insert/put/emplace
cmap_X_iter_t	struct { cmap_X_value_t *ref; ... }	Iterator type

Examples

#include <stc/cmap.h>
#include <stc/cstr.h>

using_cmap_str();

int main()
{
    // Create an unordered_map of three strings (that map to strings)
    c_init (cmap_str, u, {
        {"RED", "#FF0000"},
        {"GREEN", "#00FF00"},
        {"BLUE", "#0000FF"}
    });

    // Iterate and print keys and values of unordered map
    c_foreach (n, cmap_str, u) {
        printf("Key:[%s] Value:[%s]\n", n.ref->first.str, n.ref->second.str);
    }

    // Add two new entries to the unordered map
    cmap_str_emplace(&u, "BLACK", "#000000");
    cmap_str_emplace(&u, "WHITE", "#FFFFFF");

    // Output values by key
    printf("The HEX of color RED is:[%s]\n", cmap_str_at(&u, "RED")->str);
    printf("The HEX of color BLACK is:[%s]\n", cmap_str_at(&u, "BLACK")->str);

    cmap_str_del(&u);
    return 0;
}

Output:

Key:[RED] Value:[#FF0000]
Key:[GREEN] Value:[#00FF00]
Key:[BLUE] Value:[#0000FF]
The HEX of color RED is:[#FF0000]
The HEX of color BLACK is:[#000000]

Example 2

This example uses a cmap with cstr as mapped value, by the using_cmap_strval(id, int) macro.

#include <stc/cmap.h>
#include <stc/cstr.h>

/* cmap<int, cstr>: */
using_cmap_strval(id, int);

int main()
{
    uint32_t col = 0xcc7744ff;
    c_init (cmap_id, idnames, {
        {100, "Red"},
        {110, "Blue"},
    });
    /* put replaces existing mapped value: */
    cmap_id_emplace_or_assign(&idnames, 110, "White");
    /* put a constructed mapped value into map: */
    cmap_id_insert_or_assign(&idnames, 120, cstr_from_fmt("#%08x", col));
    /* emplace inserts only when key does not exist: */
    cmap_id_emplace(&idnames, 100, "Green");

    c_foreach (i, cmap_id, idnames)
        printf("%d: %s\n", i.ref->first, i.ref->second.str);

    cmap_id_del(&idnames);
}

Output:

100: Red
110: White
120: #cc7744ff

Example 3

Demonstrate cmap with plain-old-data key type Vec3i and int as mapped type: cmap<Vec3i, int>.

#include <stc/cmap.h>
#include <stdio.h>

typedef struct { int x, y, z; } Vec3i;

using_cmap(v3, Vec3i, int, c_trivial_equals, // bitwise equals
                           c_default_hash);  // bytewise hash

int main()
{
    cmap_v3 vecs = cmap_v3_init();

    cmap_v3_emplace(&vecs, (Vec3i){100,   0,   0}, 1);
    cmap_v3_emplace(&vecs, (Vec3i){  0, 100,   0}, 2);
    cmap_v3_emplace(&vecs, (Vec3i){  0,   0, 100}, 3);
    cmap_v3_emplace(&vecs, (Vec3i){100, 100, 100}, 4);

    c_foreach (i, cmap_v3, vecs)
        printf("{ %3d, %3d, %3d }: %d\n", i.ref->first.x,  i.ref->first.y,  i.ref->first.z,  i.ref->second);

    cmap_v3_del(&vecs);
}

Output:

{ 100,   0,   0 }: 1
{   0,   0, 100 }: 3
{ 100, 100, 100 }: 4
{   0, 100,   0 }: 2

Example 4

Inverse: demonstrate cmap with mapped POD type Vec3i: cmap<int, Vec3i>:

#include <stc/cmap.h>
#include <stdio.h>

typedef struct { int x, y, z; } Vec3i;
using_cmap(iv, int, Vec3i);

int main()
{
    cmap_iv vecs = cmap_iv_init();
    cmap_iv_emplace(&vecs, 1, (Vec3i){100,   0,   0});
    cmap_iv_emplace(&vecs, 2, (Vec3i){  0, 100,   0});
    cmap_iv_emplace(&vecs, 3, (Vec3i){  0,   0, 100});
    cmap_iv_emplace(&vecs, 4, (Vec3i){100, 100, 100});

    c_foreach (i, cmap_iv, vecs)
        printf("%d: { %3d, %3d, %3d }\n", i.ref->first, i.ref->second.x,  i.ref->second.y,  i.ref->second.z);

    cmap_iv_del(&vecs);
}

Output:

4: { 100, 100, 100 }
3: {   0,   0, 100 }
2: {   0, 100,   0 }
1: { 100,   0,   0 }

Example 5

Advanced, rare usage: Complex key type.

#include <stc/cmap.h>
#include <stc/cstr.h>

typedef struct Viking {
    cstr name;
    cstr country;
} Viking;

void viking_del(Viking* vk) {
    cstr_del(&vk->name);
    cstr_del(&vk->country);
}

// Define Viking raw struct with hash, equals, and convertion functions between Viking and VikingRaw structs:

typedef struct VikingRaw {
    const char* name;
    const char* country;
} VikingRaw;

uint32_t vikingraw_hash(const VikingRaw* raw, size_t ignore) {
    uint32_t hash = c_strhash(raw->name) ^ (c_strhash(raw->country) << 3);
    return hash;
}
static inline int vikingraw_equals(const VikingRaw* rx, const VikingRaw* ry) {
    return strcmp(rx->name, ry->name) == 0 && strcmp(rx->country, ry->country) == 0;
}

static inline Viking viking_fromRaw(VikingRaw raw) { // note: parameter is by value
    Viking vk = {cstr_from(raw.name), cstr_from(raw.country)}; return vk;
}
static inline VikingRaw viking_toRaw(Viking* vk) {
    VikingRaw raw = {vk->name.str, vk->country.str}; return raw;
}

// With this in place, we use the using_cmap_keydef() macro to define {Viking -> int} hash map type:
using_cmap_keydef(vk, Viking, int, vikingraw_equals, vikingraw_hash,
                      viking_del, viking_fromRaw, viking_toRaw, VikingRaw);

int main()
{
    c_init (cmap_vk, vikings, {
        { {"Einar", "Norway"}, 20 },
        { {"Olaf", "Denmark"}, 24 },
        { {"Harald", "Iceland"}, 12 },
    });
    cmap_vk_emplace_or_assign(&vikings, (VikingRaw){"Bjorn", "Sweden"}, 10);

    VikingRaw lookup = {"Einar", "Norway"};

    cmap_vk_value_t *e = cmap_vk_find(&vikings, lookup).ref;
    e->second += 3; // add 3 hp points to Einar
    cmap_vk_emplace(&vikings, lookup, 0).ref->second += 5; // add 5 more to Einar

    c_foreach (k, cmap_vk, vikings) {
        printf("%s of %s has %d hp\n", k.ref->first.name.str, k.ref->first.country.str, k.ref->second);
    }
    cmap_vk_del(&vikings);
}

Output:

Olaf of Denmark has 24 hp
Bjorn of Sweden has 10 hp
Einar of Norway has 28 hp
Harald of Iceland has 12 hp