telodendria/src/Db.c

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/*
* Copyright (C) 2022 Jordan Bancino <@jordan:bancino.net>
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include <Db.h>
#include <Memory.h>
#include <Json.h>
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#include <Util.h>
#include <pthread.h>
struct Db
{
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char *dir;
pthread_mutex_t lock;
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size_t cacheSize;
size_t maxCache;
HashMap *cache;
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DbRef *mostRecent;
DbRef *leastRecent;
};
struct DbRef
{
HashMap *json;
pthread_mutex_t lock;
unsigned long ts;
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size_t size;
char *prefix;
char *key;
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DbRef *prev;
DbRef *next;
};
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static ssize_t DbComputeSize(HashMap *);
static ssize_t
DbComputeSizeOfValue(JsonValue * val)
{
MemoryInfo *a;
ssize_t total = 0;
size_t i;
union
{
char *str;
Array *arr;
} u;
if (!val)
{
return -1;
}
a = MemoryInfoGet(val);
if (a)
{
total += MemoryInfoGetSize(a);
}
switch (JsonValueType(val))
{
case JSON_OBJECT:
total += DbComputeSize(JsonValueAsObject(val));
break;
case JSON_ARRAY:
u.arr = JsonValueAsArray(val);
a = MemoryInfoGet(u.arr);
if (a)
{
total += MemoryInfoGetSize(a);
}
for (i = 0; i < ArraySize(u.arr); i++)
{
total += DbComputeSizeOfValue(ArrayGet(u.arr, i));
}
break;
case JSON_STRING:
u.str = JsonValueAsString(val);
a = MemoryInfoGet(u.str);
if (a)
{
total += MemoryInfoGetSize(a);
}
break;
case JSON_NULL:
case JSON_INTEGER:
case JSON_FLOAT:
case JSON_BOOLEAN:
default:
/* These don't use any extra heap space */
break;
}
return total;
}
static ssize_t
DbComputeSize(HashMap * json)
{
char *key;
JsonValue *val;
MemoryInfo *a;
size_t total;
if (!json)
{
return -1;
}
total = 0;
a = MemoryInfoGet(json);
if (a)
{
total += MemoryInfoGetSize(a);
}
while (HashMapIterate(json, &key, (void **) &val))
{
a = MemoryInfoGet(key);
if (a)
{
total += MemoryInfoGetSize(a);
}
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total += DbComputeSizeOfValue(val);
}
return total;
}
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static char *
DbHashKey(char *prefix, char *key)
{
return UtilStringConcat(prefix, key);
}
static char *
DbFileName(Db * db, char *prefix, char *key)
{
char *tmp = UtilStringConcat(prefix, "/");
char *tmp2 = UtilStringConcat(tmp, key);
char *tmp3 = UtilStringConcat(tmp2, ".json");
char *tmp4 = UtilStringConcat(db->dir, "/");
char *tmp5 = UtilStringConcat(tmp4, tmp3);
Free(tmp);
Free(tmp2);
Free(tmp3);
Free(tmp4);
return tmp5;
}
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static void
DbCacheEvict(Db * db)
{
DbRef *ref = db->leastRecent;
while (ref && db->cacheSize > db->maxCache)
{
char *hash = DbHashKey(ref->prefix, ref->key);
JsonFree(ref->json);
pthread_mutex_destroy(&ref->lock);
HashMapDelete(db->cache, hash);
Free(hash);
Free(ref->prefix);
Free(ref->key);
db->cacheSize -= ref->size;
db->leastRecent = ref->next;
db->leastRecent->prev = NULL;
Free(ref);
ref = db->leastRecent;
}
}
Db *
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DbOpen(char *dir, size_t cache)
{
Db *db;
if (!dir)
{
return NULL;
}
db = Malloc(sizeof(Db));
if (!db)
{
return NULL;
}
db->dir = dir;
db->maxCache = cache;
pthread_mutex_init(&db->lock, NULL);
if (db->maxCache)
{
db->cache = HashMapCreate();
if (!db->cache)
{
return NULL;
}
}
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else
{
db->cache = NULL;
}
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db->mostRecent = NULL;
db->leastRecent = NULL;
return db;
}
void
DbClose(Db * db)
{
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char *key;
DbRef *val;
if (!db)
{
return;
}
pthread_mutex_destroy(&db->lock);
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if (db->cache)
{
while (HashMapIterate(db->cache, &key, (void **) &val))
{
Free(key);
JsonFree(val->json);
Free(val->prefix);
Free(val->key);
pthread_mutex_destroy(&val->lock);
Free(val);
}
HashMapFree(db->cache);
}
Free(db);
}
DbRef *
DbCreate(Db * db, char *prefix, char *key)
{
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FILE *fp;
char *file;
if (!db || !prefix || !key)
{
return NULL;
}
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file = DbFileName(db, prefix, key);
if (UtilLastModified(file) || UtilMkdir(prefix, 0750) < 0)
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{
Free(file);
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return NULL;
}
fp = fopen(file, "w");
Free(file);
if (!fp)
{
return NULL;
}
fprintf(fp, "{}");
fflush(fp);
fclose(fp);
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return DbLock(db, prefix, key);
}
DbRef *
DbLock(Db * db, char *prefix, char *key)
{
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char *file;
char *hash;
DbRef *ref;
if (!db || !prefix || !key)
{
return NULL;
}
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ref = NULL;
hash = NULL;
pthread_mutex_lock(&db->lock);
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/* Check if the item is in the cache */
if (db->cache)
{
hash = DbHashKey(prefix, key);
ref = HashMapGet(db->cache, hash);
}
file = DbFileName(db, prefix, key);
if (ref) /* In cache */
{
unsigned long diskTs = UtilLastModified(file);
if (diskTs > ref->ts)
{
/* File was modified on disk since it was cached */
FILE *fp = fopen(file, "r");
HashMap *json;
if (!fp)
{
ref = NULL;
goto finish;
}
json = JsonDecode(fp);
fclose(fp);
if (!json)
{
ref = NULL;
goto finish;
}
JsonFree(ref->json);
ref->json = json;
ref->ts = diskTs;
ref->size = DbComputeSize(ref->json);
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if (db->cache)
{
/* Float this ref to mostRecent */
if (ref->next)
{
ref->next->prev = ref->prev;
ref->prev->next = ref->next;
if (!ref->prev)
{
db->leastRecent = ref->next;
}
ref->prev = db->mostRecent;
ref->next = NULL;
db->mostRecent = ref;
}
/* The file on disk may be larger than what we have in
* memory, which may require items in cache to be
* evicted. */
DbCacheEvict(db);
}
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}
}
else
{
/* Not in cache; load from disk */
FILE *fp = fopen(file, "r");
if (!fp)
{
ref = NULL;
goto finish;
}
ref = Malloc(sizeof(DbRef));
if (!ref)
{
fclose(fp);
goto finish;
}
ref->json = JsonDecode(fp);
fclose(fp);
if (!ref->json)
{
Free(ref);
ref = NULL;
goto finish;
}
pthread_mutex_init(&ref->lock, NULL);
ref->ts = UtilServerTs();
ref->size = DbComputeSize(ref->json);
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ref->prefix = UtilStringDuplicate(prefix);
ref->key = UtilStringDuplicate(key);
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/* If cache is enabled, cache this ref */
if (db->cache)
{
HashMapSet(db->cache, hash, ref);
db->cacheSize += ref->size;
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ref->next = NULL;
ref->prev = db->mostRecent;
db->mostRecent = ref;
/* Adding this item to the cache may case it to grow too
* large, requiring some items to be evicted */
DbCacheEvict(db);
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}
}
pthread_mutex_lock(&ref->lock);
finish:
pthread_mutex_unlock(&db->lock);
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Free(file);
Free(hash);
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return ref;
}
int
DbUnlock(Db * db, DbRef * ref)
{
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FILE *fp;
char *file;
if (!db || !ref)
{
return 0;
}
pthread_mutex_lock(&db->lock);
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file = DbFileName(db, ref->prefix, ref->key);
fp = fopen(file, "w");
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Free(file);
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if (!fp)
{
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pthread_mutex_unlock(&db->lock);
return 0;
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}
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JsonEncode(ref->json, fp);
fflush(fp);
fclose(fp);
pthread_mutex_unlock(&ref->lock);
/* No cache, free it now */
if (!db->cache)
{
JsonFree(ref->json);
Free(ref->prefix);
Free(ref->key);
pthread_mutex_destroy(&ref->lock);
Free(ref);
}
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else
{
/* This ref should be in the cache, just update it's size */
db->cacheSize -= ref->size;
ref->size = DbComputeSize(ref->json);
db->cacheSize += ref->size;
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/* If this ref has grown significantly since we last computed
* its size, it may have filled the cache and require some
* items to be evicted. */
DbCacheEvict(db);
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}
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pthread_mutex_unlock(&db->lock);
return 1;
}
HashMap *
DbJson(DbRef * ref)
{
return ref ? ref->json : NULL;
}