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/* lib9p/map.h - A really dumb map/dict data structur
*
* Copyright (C) 2024 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-Licence-Identifier: AGPL-3.0-or-later
*/
#include "internal.h"
/**
* `#define` `NAME`, `KEY_T`, `VAL_T`, and `CAP`; then `#include
* "map.h".
*/
#ifndef NAME
# error NAME must be defined
#endif
#ifndef KEY_T
# error KEY_T must be defined
#endif
#ifndef VAL_T
# error VAL_T must be defined
#endif
#ifndef CAP
# error CAP must be defined
#endif
#ifndef MAP_KEY
#define MAP_KV(TNAME) CAT3(_,TNAME,_kv)
#define MAP_METHOD(TNAME, MNAME) CAT3(TNAME,_,MNAME)
#endif
/* This implementation is just an array that we brute-force search
* over for a slot. I don't want to use the heap, which means
* statically-sized maps, and I'm probably going to choose a low
* static size, so this is fine. */
struct MAP_KV(NAME) {
bool set;
KEY_T key;
VAL_T val;
};
struct NAME {
size_t len;
struct MAP_KV(NAME) items[CAP];
};
/**
* Load an item from the map; return a pointer to the in-map value, or
* NULL if the item is not in the map.
*/
static VAL_T *MAP_METHOD(NAME,load)(struct NAME *m, KEY_T k) {
if (!m->len)
return NULL;
for (size_t i = 0; i < ARRAY_LEN(m->items); i++)
if (m->items[i].set && m->items[i].key == k)
return &(m->items[i].val);
return NULL;
}
/**
* Store an item into the map, perhaps replacing an existing value.
* Return a pointer to the in-map value, or NULL if the map is full.
*/
static VAL_T *MAP_METHOD(NAME,store)(struct NAME *m, KEY_T k, VAL_T v) {
VAL_T *old = MAP_METHOD(NAME,load)(m, k);
if (old) {
*old = v;
return old;
}
if (m->len == ARRAY_LEN(m->items))
return NULL;
for (size_t i = 0; i < ARRAY_LEN(m->items); i++)
if (!m->items[i].set) {
m->items[i].set = true;
m->items[i].key = k;
m->items[i].val = v;
return &(m->items[i].val);
}
assert(false);
}
/**
* Delete an item from the map. Returns true if an item was deleted,
* false if no such item was in the map.
*/
static bool MAP_METHOD(NAME,del)(struct NAME *m, KEY_T k) {
if (!m->len)
return NULL;
for (size_t i = 0; i < ARRAY_LEN(m->items); i++)
if (m->items[i].set && m->items[i].key == k) {
m->items[i].set = false;
m->len--;
return true;
}
return false;
}
#undef NAME
#undef KEY_T
#undef VAL_T
#undef CAP
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