common/misc/stack.c

24  * pointer stack routines
27 static const char id_stack[] = "\n@(#)$Id: stack (AT&T Bell Laboratories) 1984-05-01 $\0\n";
30 #include <stack.h>
33  * create a new stack
39 	register STACK			stack;
43 	if (!(stack = newof(0, struct stacktable, 1, 0))) return(0);
46 		free(stack);
49 	if (!(b->stack = newof(0, void*, size, 0)))
52 		free(stack);
55 	stack->blocks = b;
56 	stack->size = size;
57 	stack->error = error;
58 	stack->position.block = b;
59 	stack->position.index = -1;
62 	return(stack);
66  * remove a stack
70 stackfree(register STACK stack)
75 	b = stack->blocks;
79 		free(p->stack);
82 	free(stack);
86  * clear stack
90 stackclear(register STACK stack)
92 	stack->position.block = stack->blocks;
93 	stack->position.index = -1;
97  * get value on top of stack
101 stackget(register STACK stack)
103 	if (stack->position.index < 0) return(stack->error);
104 	else return(stack->position.block->stack[stack->position.index]);
108  * push value on to stack
112 stackpush(register STACK stack, void* value)
116 	if (++stack->position.index >= stack->size)
118 		b = stack->position.block;
125 			if (!(b->stack = newof(0, void*, stack->size, 0)))
127 			b->prev = stack->position.block;
130 		stack->position.block = b;
131 		stack->position.index = 0;
133 	stack->position.block->stack[stack->position.index] = value;
138  * pop value off stack
142 stackpop(register STACK stack)
147 	 *	-1	if stack empty before pop
148 	 *	 0	if stack empty after pop
149 	 *	 1	if stack not empty before & after pop
152 	if (stack->position.index < 0) return(-1);
153 	else if (--stack->position.index < 0)
155 		if (!stack->position.block->prev) return(0);
156 		stack->position.block = stack->position.block->prev;
157 		stack->position.index = stack->size - 1;
164  * set|get stack position
168 stacktell(register STACK stack, int set, STACKPOS* position)
170 	if (set) stack->position = *position;
171 	else *position = stack->position;