From 3a4838bed13b767132cbdf06364b2658da6cc356 Mon Sep 17 00:00:00 2001
From: chatty
Date: Tue, 15 Dec 1992 10:55:33 +0000
Subject: Initial revision

---
 utils/Allocator.cc | 147 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 utils/Allocator.cc

(limited to 'utils/Allocator.cc')

diff --git a/utils/Allocator.cc b/utils/Allocator.cc
new file mode 100644
index 0000000..d89ebf6
--- /dev/null
+++ b/utils/Allocator.cc
@@ -0,0 +1,147 @@
+/*
+ *	CENA C++ Utilities
+ *
+ *	by Stephane Chatty
+ *
+ *	Copyright 1992
+ *	Centre d'Etudes de la Navigation Aerienne (CENA)
+ *
+ *	Memory allocation (original C version by Michel Beaudouin-Lafon)
+ *
+ *	$Id$
+ *	$CurLog$
+ */
+
+#include "Allocator.h"
+#include <stdlib.h>
+#include <unistd.h>
+#include "Signal.h"
+
+/*?class CcuAllocator
+The memory manager is implemented through a C++ class called \typ{CcuAllocator}.
+Each instance of this class is a memory allocator, which delivers memory blocks of
+a given size.
+
+Allocators work as follow: each allocator obtains pages of memory through \fun{malloc}.
+It then splits that memory in blocks in order to deliver them. When a block is freed, it
+is stored in a list of free blocks so as to be reused. In the current implementation,
+memory pages are never released.
+?*/
+
+
+#define CHUNKSIZE	1024
+
+/* 
+ *	Supposing that memory blocks must always be aligned on
+ *	word boundaries, we allocate chunks as arrays of words,
+ *	and express all sizes in words.
+ *	
+ */
+#ifndef WORD_TYPE
+#define WORD_TYPE int
+#endif
+
+typedef WORD_TYPE Word;
+
+inline unsigned int
+SizeInWords (unsigned int size)
+{
+	return (size + sizeof (Word) -1) / sizeof (Word);
+}
+
+/*?
+This function is called when there is no more memory. It issues an error message to
+the standard error output, then calls \fun{exit}.
+?*/
+void
+CcuAllocator :: MemoryOverflow ()
+{
+	static char msg [] = "Memory overflow. Bye ...\n";
+
+	write (2, msg, sizeof (msg));
+	exit (99);
+}
+
+/*?
+Constructor for \typ{CcuAllocator}s. It initializes an allocator for structures of size \var{size}.
+For implementation reasons, allocated blocks will be at least the size of a pointer.
+?*/
+CcuAllocator :: CcuAllocator (unsigned int size)
+: BlockSize (SizeInWords (size)),
+  ChunkSize (SizeInWords (CHUNKSIZE)),
+  FreeList (0),
+  AllocEnd (0),
+  AllocNext (0)
+{
+	/* if blocks are too small to hold a pointer, enlarge them */
+	unsigned int ptr_size = SizeInWords (sizeof (Word*));
+	if (BlockSize < ptr_size)
+		BlockSize = ptr_size;
+
+	/* if chunks are too small to hold two blocks, enlarge them */
+	if (ChunkSize < 2*BlockSize)
+		ChunkSize = 2*BlockSize;
+}
+
+/*?nodoc?*/
+CcuAllocator :: ~CcuAllocator ()
+{
+}
+
+/*?
+Allocate a block of memory with an \typ{CcuAllocator}.
+This function  returns the address of the allocated block, or 0 if the allocation failed
+for some reason.
+The allocated block is aligned on a word boundary, and it is {\em not} filled with zeroes.
+?*/
+void*
+CcuAllocator :: Alloc ()
+{
+#ifdef MEMORY_DEBUG
+	CcuSignalBlocker b (AllSigs);
+	void* w = new Word [BlockSize];
+	return w;
+#else
+	register Word* block;
+
+	/* give memory from the free-list */
+	if (FreeList) {
+		block = (Word*) FreeList;
+		FreeList = ((Word**) FreeList)[0];
+	/* or from fresh memory */
+	} else {
+		block = (Word*) AllocNext;
+		AllocNext = ((Word*) AllocNext) + BlockSize;
+		if (AllocNext > AllocEnd) {
+			/* here we have to get new chunk */
+			CcuSignalBlocker b (AllSigs);
+			block = new Word [ChunkSize];
+			if (block == 0)
+				MemoryOverflow ();
+			/* we suppose we can put at least 2 objects in a chunk */
+			AllocNext = block + BlockSize;
+			AllocEnd  = block + ChunkSize;
+		} 
+	}
+	return block;
+#endif
+}
+
+
+/*?
+Free the memory allocated at \var{p} by this \typ{CcuAllocator}. 
+No check is performed, and you should take care that \var{p}
+was allocated by this allocator.
+?*/
+void
+CcuAllocator :: Free (void* p)
+{
+#ifdef MEMORY_DEBUG
+	CcuSignalBlocker b (AllSigs);
+	delete [] ((Word*) p);
+#else
+	/* Prepend the block to the list of free blocks */
+	((Word**) p)[0] = (Word*) FreeList;
+	FreeList = p;
+#endif
+}
-- 
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