From 0203426f6ba8198759f07fe2ff66858c464b1890 Mon Sep 17 00:00:00 2001
From: Unknown <0.tamas.marton@gmail.com>
Date: Thu, 2 May 2019 07:51:37 +0100
Subject: [PATCH] added simple map implementation for descriptor sets

---
 driver/map.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 driver/map.h | 34 +++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 driver/map.c
 create mode 100644 driver/map.h

diff --git a/driver/map.c b/driver/map.c
new file mode 100644
index 0000000..e7bc5d5
--- /dev/null
+++ b/driver/map.c
@@ -0,0 +1,65 @@
+#include "map.h"
+
+uint32_t getIndex(uint32_t key, uint32_t maxData)
+{
+	//multiplicative hash
+	//with power of 2 W
+	uint32_t a = 0x678DDE6F;
+	return ((a * key) >> (32 - maxData)) % maxData;
+}
+
+void* getMapElement(map m, uint32_t key)
+{
+	assert(m.maxData > 0);
+	assert(m.elements);
+	uint32_t index = getIndex(key, m.maxData);
+	//linear open addressing
+	while(m.elements[index].key != key && m.elements[index].data != 0){index = (index + 1) % m.maxData;}
+	return m.elements[index].data;
+}
+
+void setMapElement(map* m, uint32_t key, void* data)
+{
+	assert(m);
+	assert(m->elements);
+	assert(m->maxData > 0);
+	uint32_t index = getIndex(key, m->maxData);
+	while(m->elements[index].key != key && m->elements[index].data != 0){index = (index + 1) % m->maxData;}
+	m->elements[index].data = data;
+	m->elements[index].key = key;
+}
+
+void deleteMapElement(map* m, uint32_t key)
+{
+	assert(m);
+	assert(m->elements);
+	assert(m->maxData > 0);
+	uint32_t index = getIndex(key, m->maxData);
+	while(m->elements[index].key != key){++index;}
+	m->elements[index].data = 0;
+}
+
+map createMap(void* buf, uint32_t maxData)
+{
+	map m =
+	{
+		.elements = buf,
+		.maxData = maxData
+	};
+
+	//lazy hashing
+	//0 means bucket is empty
+	for(uint32_t c = 0; c < m.maxData; ++c)
+	{
+		m.elements[c].data = 0;
+	}
+
+	return m;
+}
+
+void destroyMap(map* m)
+{
+	//actual memory freeing is done by caller
+	m->elements = 0;
+	m->maxData = 0;
+}
\ No newline at end of file
diff --git a/driver/map.h b/driver/map.h
new file mode 100644
index 0000000..bdda595
--- /dev/null
+++ b/driver/map.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include "CustomAssert.h"
+
+typedef struct
+{
+	void* data;
+	uint32_t key;
+} mapElem;
+
+typedef struct
+{
+	mapElem* elements;
+	uint32_t maxData;
+} map;
+
+void* getMapElement(map m, uint32_t key);
+void setMapElement(map* m, uint32_t key, void* data);
+void deleteMapElement(map* m, uint32_t key);
+map createMap(void* buf, uint32_t maxData);
+void destroyMap(map* m);
+
+
+#if defined (__cplusplus)
+}
+#endif
+
+
+