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git-svn-id: svn://svn.cc65.org/cc65/trunk@3 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/_hadd.c

@@ -0,0 +1,106 @@
+/*
+ * _hadd.c
+ *
+ * Ullrich von Bassewitz, 19.06.1998
+ */
+
+
+
+#include <stddef.h>
+#include "_heap.h"
+
+
+
+void _hadd (void* mem, size_t size)
+/* Add an arbitrary memory block to the heap. This function is used by
+ * free(), but it does also allow usage of otherwise unused memory
+ * blocks as heap space. The given block is entered in the free list
+ * without any checks, so beware!
+ */
+{
+    struct freeblock* f;
+    struct freeblock* left;
+    struct freeblock* right;
+
+    if (size >= sizeof (struct freeblock)) {
+
+    	/* Set the admin data */
+    	f = (struct freeblock*) mem;
+    	f->size = size;
+
+    	/* Check if the freelist is empty */
+    	if (_hfirst == 0) {
+
+    	    /* The freelist is empty until now, insert the block */
+    	    f->prev = 0;
+    	    f->next = 0;
+    	    _hfirst = f;
+    	    _hlast  = f;
+
+    	} else {
+
+    	    /* We have to search the free list. As we are doing so, we check
+    	     * if it is possible to combine this block with another already
+    	     * existing block. Beware: The block may be the "missing link"
+             * between *two* other blocks.
+    	     */
+    	    left = 0;
+    	    right = _hfirst;
+    	    while (right && f > right) {
+    		left = right;
+    		right = right->next;
+    	    }
+
+
+    	    /* Ok, the current block must be inserted between left and right (but
+    	     * beware: one of the two may be zero!). Also check for the condition
+    	     * that we have to merge two or three blocks.
+    	     */
+    	    if (right) {
+    		/* Check if we must merge the block with the right one */
+    		if (((int) f) + size == (int) right) {
+    		    /* Merge with the right block */
+    		    f->size += right->size;
+    		    if (f->next = right->next) {
+       			f->next->prev = f;
+    		    } else {
+    			/* This is now the last block */
+    			_hlast = f;
+    		    }
+    		} else {
+    		    /* No merge, just set the link */
+    		    f->next = right;
+    		    right->prev = f;
+    		}
+    	    } else {
+    		f->next = 0;
+    		/* Special case: This is the new freelist end */
+    		_hlast = f;
+    	    }
+    	    if (left) {
+    		/* Check if we must merge the block with the left one */
+    		if ((int) f == ((int) left) + left->size) {
+    		    /* Merge with the left block */
+    		    left->size += f->size;
+    		    if (left->next = f->next) {
+    			left->next->prev = left;
+    		    } else {
+    			/* This is now the last block */
+    			_hlast = left;
+    		    }
+    		} else {
+    		    /* No merge, just set the link */
+    		    left->next = f;
+    		    f->prev = left;
+    		}
+    	    } else {
+    		f->prev = 0;
+    		/* Special case: This is the new freelist start */
+    		_hfirst = f;
+    	    }
+	}
+    }
+}
+
+
+