elinks/src/dom/stack.h

#ifndef EL_DOM_STACK_H
#define EL_DOM_STACK_H

#include "dom/node.h"
#include "util/error.h"
#include "util/hash.h"

struct dom_stack;

typedef void (*dom_stack_callback_T)(struct dom_stack *, struct dom_node *, void *);

#define DOM_STACK_MAX_DEPTH	4096

struct dom_stack_state {
	struct dom_node *node;

	/* The depth of the state in the stack. This is amongst other things
	 * used to get the state object data. */
	unsigned int depth;

	/* Wether this stack state can be popped with pop_dom_*() family. */
	unsigned int immutable:1;
};

struct dom_stack_context_info {
	/* The @object_size member tells whether the stack should allocate
	 * objects for each state to be assigned to the state's @data member.
	 * Zero means no state data should be allocated. */
	size_t object_size;

	/* Callbacks to be called when pushing and popping nodes. */
	dom_stack_callback_T push[DOM_NODES];
	dom_stack_callback_T pop[DOM_NODES];
};

struct dom_stack_context {
	/* Data specific to the context. */
	void *data;

	/* This is one big array of context specific objects. */
	/* For the SGML parser this holds DTD-oriented info about the node
	 * (recorded in struct sgml_node_info). E.g.  whether an element node
	 * is optional. */
	unsigned char *state_objects;

	/* Info about node callbacks and such. */
	struct dom_stack_context_info *info;
};

enum dom_stack_flag {
	/* Keep nodes when popping them or call done_dom_node() on them. */
	DOM_STACK_KEEP_NODES = 1,
};

/* The DOM stack is a convenient way to traverse DOM trees. Also it
 * maintains needed state info and is therefore also a holder of the current
 * context since the stack is used to when the DOM tree is manipulated. */
struct dom_stack {
	/* The stack of nodes */
	struct dom_stack_state *states;
	size_t depth;

	enum dom_stack_flag flags;

	/* Contexts for the pushed and popped nodes. */
	struct dom_stack_context **contexts;
	size_t contexts_size;

	/* The current context. */
	/* XXX: Only meaningful within dom_stack_callback_T functions. */
	struct dom_stack_context *current;
};

#define dom_stack_is_empty(stack) \
	(!(stack)->states || (stack)->depth == 0)

static inline struct dom_stack_state *
get_dom_stack_state(struct dom_stack *stack, int top_offset)
{
	assertm(stack->depth - 1 - top_offset >= 0,
		"Attempting to access invalid state");
	return &stack->states[stack->depth - 1 - top_offset];
}

#define get_dom_stack_top(stack)	get_dom_stack_state(stack, 0)

static inline void *
get_dom_stack_state_data(struct dom_stack_context *context,
			 struct dom_stack_state *state)
{
	size_t object_size = context->info->object_size;

	if (!object_size) return NULL;

	assertm(context->state_objects);

	return (void *) &context->state_objects[state->depth * object_size];
}

/* Define to have debug info about the nodes added printed to the log.
 * Run as: ELINKS_LOG=/tmp/dom-dump.txt ./elinks -no-connect <url>
 * to have the debug dumped into a file. */
/*#define DOM_STACK_TRACE*/

#ifdef DOM_STACK_TRACE
extern struct dom_stack_context_info dom_stack_trace_context_info;
#define add_dom_stack_tracer(stack, name) \
	add_dom_stack_context(stack, name, &dom_stack_trace_context_info)
#else
#define add_dom_stack_tracer(stack, name) /* Nada */
#endif

/* The state iterators do not include the bottom state */

#define foreach_dom_stack_state(stack, state, pos)			\
	for ((pos) = 0; (pos) < (stack)->depth; (pos)++)		\
		if (((state) = &(stack)->states[(pos)]))

#define foreachback_dom_stack_state(stack, state, pos)			\
	for ((pos) = (stack)->depth - 1; (pos) >= 0; (pos)--)		\
		if (((state) = &(stack)->states[(pos)]))


/* Life cycle functions. */

void init_dom_stack(struct dom_stack *stack, enum dom_stack_flag flags);
void done_dom_stack(struct dom_stack *stack);

/* Add a context to the stack. This is needed if either you want to have the
 * stack allocated objects for created states and/or if you want to install
 * callbacks for pushing or popping. . */
struct dom_stack_context *
add_dom_stack_context(struct dom_stack *stack, void *data,
		      struct dom_stack_context_info *context_info);

/* Unregister a stack @context. This should be done especially for temporary
 * stack contexts (without any callbacks) so that they do not increasing the
 * memory usage. */
void done_dom_stack_context(struct dom_stack *stack, struct dom_stack_context *context);

/* Decends down to the given node making it the current parent */
/* If an error occurs the node is free()d and NULL is returned */
struct dom_node *push_dom_node(struct dom_stack *stack, struct dom_node *node);

/* Ascends the stack to the current parent */
void pop_dom_node(struct dom_stack *stack);

/* Ascends the stack looking for specific parent */
void pop_dom_nodes(struct dom_stack *stack, enum dom_node_type type,
		   struct dom_string *string);

/* Pop all stack states until a specific state is reached. */
void pop_dom_state(struct dom_stack *stack, struct dom_stack_state *target);

/* Dive through the stack states in search for the specified match. */
struct dom_stack_state *
search_dom_stack(struct dom_stack *stack, enum dom_node_type type,
		 struct dom_string *string);

/* Visit each node in the tree rooted at @root pre-order */
void walk_dom_nodes(struct dom_stack *stack, struct dom_node *root);

#endif