medfall

commit 3c52cb7f64b84ac0e2467c9282e40b8c6d20a46e
parent 326f30b0c0d486e3a11fe647279fb7d58fd7d981
Author: Michael Savage <mikejsavage@gmail.com>
Date:   Sun Dec 11 14:18:45 +0200

Add memory pool class

Diffstat:
pool.h
 | 
113
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 113 insertions(+), 0 deletions(-)
diff --git a/pool.h b/pool.h
@@ -0,0 +1,113 @@
+#pragma once
+
+#include "intrinsics.h"
+#include "array.h"
+
+template< typename T, u32 N >
+class Pool;
+
+template< typename T, u32 N >
+class PoolIterator {
+public:
+	PoolIterator( Pool< T, N > * p, u32 start ) {
+		pool = p;
+		idx = start;
+		next = idx == Pool< T, N >::INVALID_IDX ? idx : pool->nexts[ idx ];
+	}
+
+	T * operator*() {
+		return &pool->elems[ idx ];
+	}
+
+	bool operator!=( PoolIterator< T, N > other ) {
+		return idx != other.idx || next != other.next || pool != other.pool;
+	}
+
+	void operator++() {
+		idx = next;
+		next = idx == Pool< T, N >::INVALID_IDX ? idx : pool->nexts[ idx ];
+	}
+
+private:
+	Pool< T, N > * pool;
+	u32 idx;
+	u32 next;
+};
+
+template< typename T, u32 N >
+class Pool {
+public:
+	Pool() {
+		for( u32 i = 0; i < N; i++ ) {
+			nexts[ i ] = i + 1;
+		}
+		nexts[ N - 1 ] = INVALID_IDX;
+
+		first_free = 0;
+		first_used = INVALID_IDX;
+		num_used = 0;
+	}
+
+	T * acquire() {
+		if( first_free == INVALID_IDX ) return NULL;
+
+		u32 idx = first_free;
+
+		// remove idx from head of the free list
+		first_free = nexts[ idx ];
+
+		// add idx to the head of the used list
+		nexts[ idx ] = first_used;
+		prev_useds[ idx ] = INVALID_IDX;
+		if( first_used != INVALID_IDX ) {
+			prev_useds[ first_used ] = idx;
+		}
+		first_used = idx;
+
+		num_used++;
+
+		return &elems[ idx ];
+	}
+
+	void release( T * elem ) {
+		u32 idx = checked_cast< u32 >( elem - elems.ptr() );
+		ASSERT( idx < N );
+
+		// remove idx from the middle of the used list
+		if( nexts[ idx ] != INVALID_IDX ) {
+			prev_useds[ nexts[ idx ] ] = prev_useds[ idx ];
+		}
+		if( prev_useds[ idx ] != INVALID_IDX ) {
+			nexts[ prev_useds[ idx ] ] = nexts[ idx ];
+		}
+		if( first_used == idx ) {
+			first_used = nexts[ idx ];
+		}
+
+		// add idx to the head of the free list
+		nexts[ idx ] = first_free;
+		first_free = idx;
+
+		num_used--;
+	}
+
+	PoolIterator< T, N > begin() {
+		return PoolIterator< T, N >( this, first_used );
+	}
+
+	PoolIterator< T, N > end() {
+		return PoolIterator< T, N >( this, INVALID_IDX );
+	}
+
+private:
+	enum { INVALID_IDX = U32_MAX };
+
+	StaticArray< T, N > elems;
+	StaticArray< u32, N > nexts;
+	StaticArray< u32, N > prev_useds;
+	u32 first_free;
+	u32 first_used;
+	u32 num_used;
+
+	friend class PoolIterator< T, N >;
+};