Function yyensure_buffer_stack

src/Scanner.cpp:1684–1725

Allocates the stack if it does not exist. * Guarantees space for at least one push. */

 *  Guarantees space for at least one push.
 */
static void yyensure_buffer_stack (void)
{
	yy_size_t num_to_alloc;
    
	if (!(yy_buffer_stack)) {

		/* First allocation is just for 2 elements, since we don't know if this
		 * scanner will even need a stack. We use 2 instead of 1 to avoid an
		 * immediate realloc on the next call.
         */
      num_to_alloc = 1; /* After all that talk, this was set to 1 anyways... */
		(yy_buffer_stack) = (struct yy_buffer_state**)yyalloc
								(num_to_alloc * sizeof(struct yy_buffer_state*)
								);
		if ( ! (yy_buffer_stack) )
			YY_FATAL_ERROR( "out of dynamic memory in yyensure_buffer_stack()" );

		memset((yy_buffer_stack), 0, num_to_alloc * sizeof(struct yy_buffer_state*));

		(yy_buffer_stack_max) = num_to_alloc;
		(yy_buffer_stack_top) = 0;
		return;
	}

	if ((yy_buffer_stack_top) >= ((yy_buffer_stack_max)) - 1){

		/* Increase the buffer to prepare for a possible push. */
		yy_size_t grow_size = 8 /* arbitrary grow size */;

		num_to_alloc = (yy_buffer_stack_max) + grow_size;
		(yy_buffer_stack) = (struct yy_buffer_state**)yyrealloc
								((yy_buffer_stack),
								num_to_alloc * sizeof(struct yy_buffer_state*)
								);
		if ( ! (yy_buffer_stack) )
			YY_FATAL_ERROR( "out of dynamic memory in yyensure_buffer_stack()" );

		/* zero only the new slots.*/
		memset((yy_buffer_stack) + (yy_buffer_stack_max), 0, grow_size * sizeof(struct yy_buffer_state*));
		(yy_buffer_stack_max) = num_to_alloc;
	}
}

/** Setup the input buffer state to scan directly from a user-specified character buffer.
 * @param base the character buffer