#include "fitz.h"

/*
Simple hashtable with open adressing linear probe.
Unlike text book examples, removing entries works
correctly in this implementation, so it wont start
exhibiting bad behaviour if entries are inserted
and removed frequently.
*/

enum { MAXKEYLEN = 48 };
typedef struct fz_hashentry_s fz_hashentry;

struct fz_hashentry_s
{
	unsigned char key[MAXKEYLEN];
	void *val;
};

struct fz_hashtable_s
{
	int keylen;
	int size;
	int load;
	fz_hashentry *ents;
};

static unsigned hash(unsigned char *s, int len)
{
	unsigned val = 0;
	int i;
	for (i = 0; i < len; i++)
	{
		val += s[i];
		val += (val << 10);
		val ^= (val >> 6);
	}
	val += (val << 3);
	val ^= (val >> 11);
	val += (val << 15);
	return val;
}

fz_hashtable *
fz_newhash(int initialsize, int keylen)
{
	fz_hashtable *table;

	assert(keylen <= MAXKEYLEN);

	table = fz_malloc(sizeof(fz_hashtable));
	table->keylen = keylen;
	table->size = initialsize;
	table->load = 0;
	table->ents = fz_malloc(sizeof(fz_hashentry) * table->size);
	memset(table->ents, 0, sizeof(fz_hashentry) * table->size);

	return table;
}

void
fz_emptyhash(fz_hashtable *table)
{
	table->load = 0;
	memset(table->ents, 0, sizeof(fz_hashentry) * table->size);
}

int
fz_hashlen(fz_hashtable *table)
{
	return table->size;
}

void *
fz_hashgetkey(fz_hashtable *table, int idx)
{
	return table->ents[idx].key;
}

void *
fz_hashgetval(fz_hashtable *table, int idx)
{
	return table->ents[idx].val;
}

void
fz_freehash(fz_hashtable *table)
{
	fz_free(table->ents);
	fz_free(table);
}

static void
fz_resizehash(fz_hashtable *table, int newsize)
{
	fz_hashentry *oldents = table->ents;
	int oldsize = table->size;
	int oldload = table->load;
	int i;

	if (newsize < oldload * 8 / 10)
	{
		fz_throw("assert: resize hash too small");
		return;
	}

	table->ents = fz_malloc(sizeof(fz_hashentry) * newsize);
	memset(table->ents, 0, sizeof(fz_hashentry) * newsize);
	table->size = newsize;
	table->load = 0;

	for (i = 0; i < oldsize; i++)
	{
		if (oldents[i].val)
		{
			fz_hashinsert(table, oldents[i].key, oldents[i].val);
		}
	}

	fz_free(oldents);
}

void *
fz_hashfind(fz_hashtable *table, void *key)
{
	fz_hashentry *ents = table->ents;
	unsigned size = table->size;
	unsigned pos = hash(key, table->keylen) % size;

	while (1)
	{
		if (!ents[pos].val)
			return nil;

		if (memcmp(key, ents[pos].key, table->keylen) == 0)
			return ents[pos].val;

		pos = (pos + 1) % size;
	}
}

void
fz_hashinsert(fz_hashtable *table, void *key, void *val)
{
	fz_hashentry *ents;
	unsigned size;
	unsigned pos;

	if (table->load > table->size * 8 / 10)
	{
		fz_resizehash(table, table->size * 2);
	}

	ents = table->ents;
	size = table->size;
	pos = hash(key, table->keylen) % size;

	while (1)
	{
		if (!ents[pos].val)
		{
			memcpy(ents[pos].key, key, table->keylen);
			ents[pos].val = val;
			table->load ++;
			return;
		}

		if (memcmp(key, ents[pos].key, table->keylen) == 0)
			fz_warn("assert: overwrite hash slot");

		pos = (pos + 1) % size;
	}
}

void
fz_hashremove(fz_hashtable *table, void *key)
{
	fz_hashentry *ents = table->ents;
	unsigned size = table->size;
	unsigned pos = hash(key, table->keylen) % size;
	unsigned hole, look, code;

	while (1)
	{
		if (!ents[pos].val)
		{
			fz_warn("assert: remove inexistant hash entry");
			return;
		}

		if (memcmp(key, ents[pos].key, table->keylen) == 0)
		{
			ents[pos].val = nil;

			hole = pos;
			look = (hole + 1) % size;

			while (ents[look].val)
			{
				code = hash(ents[look].key, table->keylen) % size;
				if ((code <= hole && hole < look) ||
					(look < code && code <= hole) ||
					(hole < look && look < code))
				{
					ents[hole] = ents[look];
					ents[look].val = nil;
					hole = look;
				}

				look = (look + 1) % size;
			}

			table->load --;

			return;
		}

		pos = (pos + 1) % size;
	}
}

void
fz_debughash(fz_hashtable *table)
{
	int i, k;

	printf("cache load %d / %d\n", table->load, table->size);

	for (i = 0; i < table->size; i++)
	{
		if (!table->ents[i].val)
			printf("table % 4d: empty\n", i);
		else
		{
			printf("table % 4d: key=", i);
			for (k = 0; k < MAXKEYLEN; k++)
				printf("%02x", ((char*)table->ents[i].key)[k]);
			printf(" val=$%p\n", table->ents[i].val);
		}
	}
}