/*****************************************************************************/
/*                                                                           */
/*				   istack.c				     */
/*                                                                           */
/*			  Input stack for the scanner			     */
/*                                                                           */
/*                                                                           */
/*                                                                           */
/* (C) 2000     Ullrich von Bassewitz                                        */
/*              Wacholderweg 14                                              */
/*              D-70597 Stuttgart                                            */
/* EMail:       uz@musoftware.de                                             */
/*                                                                           */
/*                                                                           */
/* This software is provided 'as-is', without any expressed or implied       */
/* warranty.  In no event will the authors be held liable for any damages    */
/* arising from the use of this software.                                    */
/*                                                                           */
/* Permission is granted to anyone to use this software for any purpose,     */
/* including commercial applications, and to alter it and redistribute it    */
/* freely, subject to the following restrictions:                            */
/*                                                                           */
/* 1. The origin of this software must not be misrepresented; you must not   */
/*    claim that you wrote the original software. If you use this software   */
/*    in a product, an acknowledgment in the product documentation would be  */
/*    appreciated but is not required.                                       */
/* 2. Altered source versions must be plainly marked as such, and must not   */
/*    be misrepresented as being the original software.                      */
/* 3. This notice may not be removed or altered from any source              */
/*    distribution.                                                          */
/*                                                                           */
/*****************************************************************************/



#include "error.h"
#include "mem.h"
#include "istack.h"



/*****************************************************************************/
/*     	       	    		     Data			   	     */
/*****************************************************************************/



/* Size of the stack (== maximum nested macro or repeat count) */
#define ISTACK_MAX  	256

/* Structure holding a stack element */
typedef struct IElement IElement;
struct IElement {
    IElement*  	Next;		/* Next stack element */
    int	       	(*Func)(void*);	/* Function called for input */
    void*      	Data;	  	/* User data given as argument */
    const char* Desc;		/* Description */
};

/* The stack */
static IElement* IStack = 0;	/* Input stack pointer */
static unsigned  ICount	= 0;	/* Number of items on the stack */



/*****************************************************************************/
/*     	       	    		     Code	 		   	     */
/*****************************************************************************/



void PushInput (int (*Func) (void*), void* Data, const char* Desc)
/* Push an input function onto the input stack */
{
    IElement* E;

    /* Check for a stack overflow */
    if (ICount > ISTACK_MAX) {
    	Fatal (FAT_NESTING);
    }

    /* Create a new stack element */
    E = Xmalloc (sizeof (*E));

    /* Initialize it */
    E->Func = Func;
    E->Data = Data;
    E->Desc = Desc;

    /* Push it */
    E->Next = IStack;
    IStack  = E;
}



void PopInput (void)
/* Pop the current input function from the input stack */
{
    IElement* E;

    /* We cannot pop from an empty stack */
    PRECONDITION (IStack != 0);

    /* Remember the last element */
    E = IStack;

    /* Pop it */
    IStack = IStack->Next;

    /* And delete it */
    Xfree (E);
}



int InputFromStack (void)
/* Try to get input from the input stack. Return true if we had such input,
 * return false otherwise.
 */
{
    /* Repeatedly call the TOS routine until we have a token or if run out of
     * routines.
     */
    while (IStack) {
	if (IStack->Func (IStack->Data) != 0) {
	    /* We have a token */
	    return 1;
	}
    }

    /* Nothing is on the stack */
    return 0;
}



void CheckInputStack (void)
/* Called from the scanner before closing an input file. Will check for any
 * stuff on the input stack.
 */
{
    if (IStack) {
	Error (ERR_OPEN_STMT, IStack->Desc);
    }
}