Postgres95 1.01 Distribution - Virgin Sources

src/backend/lib/fstack.c

@@ -0,0 +1,153 @@
+/*-------------------------------------------------------------------------
+ *
+ * fstack.c--
+ *    Fixed format stack definitions.
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *    $Header: /cvsroot/pgsql/src/backend/lib/Attic/fstack.c,v 1.1.1.1 1996/07/09 06:21:28 scrappy Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "c.h"
+#include "lib/fstack.h"
+
+/*
+ * Internal function definitions
+ */
+
+/*
+ * FixedItemIsValid --
+ *	True iff item is valid.
+ */
+#define FixedItemIsValid(item)	PointerIsValid(item)
+
+/*
+ * FixedStackGetItemBase --
+ *	Returns base of enclosing structure.
+ */
+#define FixedStackGetItemBase(stack, item) \
+	((Pointer)((char *)(item) - (stack)->offset))
+
+/*
+ * FixedStackGetItem --
+ *	Returns item of given pointer to enclosing structure.
+ */
+#define FixedStackGetItem(stack, pointer) \
+	((FixedItem)((char *)(pointer) + (stack)->offset))
+
+/*
+ * External functions
+ */
+
+/*
+ * FixedStackIsValid --
+ *	True iff stack is valid.
+ */
+static bool
+FixedStackIsValid(FixedStack stack)
+{
+    return ((bool)PointerIsValid(stack));
+}
+
+
+void
+FixedStackInit(FixedStack stack, Offset offset)
+{
+    AssertArg(PointerIsValid(stack));
+    
+    stack->top = NULL;
+    stack->offset = offset;
+}
+
+Pointer
+FixedStackPop(FixedStack stack)
+{
+    Pointer	pointer;
+    
+    AssertArg(FixedStackIsValid(stack));
+    
+    if (!PointerIsValid(stack->top)) {
+	return (NULL);
+    }
+    
+    pointer = FixedStackGetItemBase(stack, stack->top);
+    stack->top = stack->top->next;
+    
+    return (pointer);
+}
+
+void
+FixedStackPush(FixedStack stack, Pointer pointer)
+{
+    FixedItem	item = FixedStackGetItem(stack, pointer);
+    
+    AssertArg(FixedStackIsValid(stack));
+    AssertArg(PointerIsValid(pointer));
+    
+    item->next = stack->top;
+    stack->top = item;
+}
+
+
+/*
+ * FixedStackContains --
+ *	True iff ordered stack contains given element.
+ *
+ * Note:
+ *	This is inefficient.  It is intended for debugging use only.
+ *
+ * Exceptions:
+ *	BadArg if stack is invalid.
+ *	BadArg if pointer is invalid.
+ */
+static bool
+FixedStackContains(FixedStack stack, Pointer pointer)
+{
+    FixedItem	next;
+    FixedItem	item;
+    
+    AssertArg(FixedStackIsValid(stack));
+    AssertArg(PointerIsValid(pointer));
+    
+    item = FixedStackGetItem(stack, pointer);
+    
+    for (next = stack->top; FixedItemIsValid(next); next = next->next) {
+	if (next == item) {
+	    return (true);
+	}
+    }
+    return (false);
+}
+
+Pointer
+FixedStackGetTop(FixedStack stack)
+{
+    AssertArg(FixedStackIsValid(stack));
+    
+    if (!PointerIsValid(stack->top)) {
+	return (NULL);
+    }
+    
+    return (FixedStackGetItemBase(stack, stack->top));
+}
+
+Pointer
+FixedStackGetNext(FixedStack stack, Pointer pointer)
+{
+    FixedItem	item;
+    
+    /* AssertArg(FixedStackIsValid(stack)); */
+    /* AssertArg(PointerIsValid(pointer)); */
+    AssertArg(FixedStackContains(stack, pointer));
+    
+    item = FixedStackGetItem(stack, pointer)->next;
+    
+    if (!PointerIsValid(item)) {
+	return (NULL);
+    }
+    
+    return(FixedStackGetItemBase(stack, item));
+}