1 files changed, 274 insertions, 0 deletions
diff --git a/base/base_hash.c b/base/base_hash.c
new file mode 100644
index 00000000..65bc7130
--- /dev/null
+++ b/base/base_hash.c
@@ -0,0 +1,274 @@
+/* Linear probe hash table.
+ * 2004 (C) Tor Andersson.
+ * BSD license.
+ *
+ * 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.
+ */ 
+
+#include <fitz.h>
+
+enum { MAXKEYLEN = 16 };
+
+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 hash = 0;
+	int i;
+	for (i = 0; i < len; i++)
+	{
+		hash += s[i];
+		hash += (hash << 10);
+		hash ^= (hash >> 6);
+	}
+	hash += (hash << 3);
+	hash ^= (hash >> 11);
+	hash += (hash << 15);
+	return hash;
+}
+
+fz_error *
+fz_newhash(fz_hashtable **tablep, int initialsize, int keylen)
+{
+	fz_hashtable *table;
+
+	assert(keylen <= MAXKEYLEN);
+
+	table = *tablep = fz_malloc(sizeof(fz_hashtable));
+	if (!table)
+		return fz_outofmem;
+
+	table->keylen = keylen;
+	table->size = initialsize;
+	table->load = 0;
+
+	table->ents = fz_malloc(sizeof(fz_hashentry) * table->size);
+	if (!table->ents)
+	{
+		fz_free(table);
+		*tablep = nil;
+		return fz_outofmem;
+	}
+
+	memset(table->ents, 0, sizeof(fz_hashentry) * table->size);
+
+	return nil;
+}
+
+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_drophash(fz_hashtable *table)
+{
+	fz_free(table->ents);
+	fz_free(table);
+}
+
+fz_error *
+fz_resizehash(fz_hashtable *table, int newsize)
+{
+	fz_error *error;
+	fz_hashentry *newents;
+	fz_hashentry *oldents;
+	int oldload;
+	int oldsize;
+	int i;
+
+	oldsize = table->size;
+	oldload = table->load;
+	oldents = table->ents;
+
+	if (newsize < oldload * 8 / 10)
+		return fz_throw("rangecheck: resize hash too small");
+
+	newents = fz_malloc(sizeof(fz_hashentry) * newsize);
+	if (!newents)
+		return fz_outofmem;
+
+	table->size = newsize;
+	table->load = 0;
+	table->ents = newents;
+	memset(table->ents, 0, sizeof(fz_hashentry) * table->size);
+
+	for (i = 0; i < oldsize; i++)
+	{
+		if (oldents[i].val)
+		{
+			error = fz_hashinsert(table, oldents[i].key, oldents[i].val);
+			if (error)
+			{
+				table->size = oldsize;
+				table->load = oldload;
+				table->ents = oldents;
+				fz_free(newents);
+				return error;
+			}
+		}
+	}
+
+	fz_free(oldents);
+	return nil;
+}
+
+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;
+	}
+}
+
+fz_error *
+fz_hashinsert(fz_hashtable *table, void *key, void *val)
+{
+	fz_error *error;
+	fz_hashentry *ents;
+	unsigned size;
+	unsigned pos;
+
+	if (table->load > table->size * 8 / 10)
+	{
+		error = fz_resizehash(table, table->size * 2);
+		if (error)
+			return error;
+	}
+
+	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 nil;
+		}
+
+		if (memcmp(key, &ents[pos].key, table->keylen) == 0)
+			return fz_throw("rangecheck: overwrite hash slot");
+
+		pos = (pos + 1) % size;
+	}
+
+	return nil;
+}
+
+fz_error *
+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)
+			return fz_throw("rangecheck: remove inexistant hash entry");
+
+		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 nil;
+		}
+
+		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);
+		}
+	}
+}
+