uci/uci.h

/*
 * libuci - Library for the Unified Configuration Interface
 * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
 *
 * this program is free software; you can redistribute it and/or modify
 * it under the terms of the gnu lesser general public license version 2.1
 * as published by the free software foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#ifndef __LIBUCI_H
#define __LIBUCI_H

/*
 * you can use these defines to enable debugging behavior for
 * apps compiled against libuci:
 *
 * #define UCI_DEBUG_TYPECAST:
 *   enable uci_element typecast checking at run time
 *
 */

#ifdef DEBUG_ALL
#define UCI_DEBUG
#define UCI_DEBUG_TYPECAST
#endif

#include <setjmp.h>
#include <stdio.h>

#define UCI_CONFDIR "/etc/config"

enum
{
	UCI_OK = 0,
	UCI_ERR_MEM,
	UCI_ERR_INVAL,
	UCI_ERR_NOTFOUND,
	UCI_ERR_IO,
	UCI_ERR_PARSE,
	UCI_ERR_UNKNOWN,
	UCI_ERR_LAST
};

struct uci_list;
struct uci_list
{
	struct uci_list *next;
	struct uci_list *prev;
};

struct uci_element;
struct uci_package;
struct uci_section;
struct uci_option;
struct uci_history;
struct uci_parse_context;


/**
 * uci_alloc_context: Allocate a new uci context
 */
extern struct uci_context *uci_alloc_context(void);

/**
 * uci_free_context: Free the uci context including all of its data
 */
extern void uci_free_context(struct uci_context *ctx);

/**
 * uci_perror: Print the last uci error that occured
 * @ctx: uci context
 * @str: string to print before the error message
 */
extern void uci_perror(struct uci_context *ctx, const char *str);

/**
 * uci_import: Import uci config data from a stream
 * @ctx: uci context
 * @stream: file stream to import from
 * @name: (optional) assume the config has the given name
 * @package: (optional) store the last parsed config package in this variable
 *
 * the name parameter is for config files that don't explicitly use the 'package <...>' keyword
 */
extern int uci_import(struct uci_context *ctx, FILE *stream, const char *name, struct uci_package **package);

/**
 * uci_export: Export one or all uci config packages
 * @ctx: uci context
 * @stream: output stream
 * @package: (optional) uci config package to export
 */
extern int uci_export(struct uci_context *ctx, FILE *stream, struct uci_package *package);

/**
 * uci_load: Parse an uci config file and store it in the uci context
 *
 * @ctx: uci context
 * @name: name of the config file (relative to the config directory)
 * @package: store the loaded config package in this variable
 */
extern int uci_load(struct uci_context *ctx, const char *name, struct uci_package **package);

/**
 * uci_unload: Unload a config file from the uci context
 *
 * @ctx: uci context
 * @name: name of the config file
 */
extern int uci_unload(struct uci_context *ctx, const char *name);

/**
 * uci_cleanup: Clean up after an error
 *
 * @ctx: uci context
 */
extern int uci_cleanup(struct uci_context *ctx);

/**
 * uci_lookup: Look up an uci element
 *
 * @ctx: uci context
 * @res: where to store the result
 * @package: config package
 * @section: config section (optional)
 * @option: option to search for (optional)
 *
 * If section is omitted, then a pointer to the config package is returned
 * If option is omitted, then a pointer to the config section is returned
 */
extern int uci_lookup(struct uci_context *ctx, struct uci_element **res, char *package, char *section, char *option);

/**
 * uci_list_configs: List available uci config files
 *
 * @ctx: uci context
 */
extern char **uci_list_configs(struct uci_context *ctx);

/* UCI data structures */
enum uci_type {
	UCI_TYPE_PACKAGE = 0,
	UCI_TYPE_SECTION = 1,
	UCI_TYPE_OPTION = 2
};

struct uci_element
{
	struct uci_list list;
	enum uci_type type;
	char *name;
};

struct uci_context
{
	/* list of config packages */
	struct uci_list root;

	/* parser context, use for error handling only */
	struct uci_parse_context *pctx;

	/* private: */
	int errno;
	jmp_buf trap;
	char *buf;
	int bufsz;
};

struct uci_parse_context
{
	/* error context */
	const char *reason;
	int line;
	int byte;

	/* private: */
	struct uci_package *package;
	struct uci_section *section;
	FILE *file;
	const char *name;
	char *buf;
	int bufsz;
};

struct uci_package
{
	struct uci_element e;
	struct uci_list sections;
	struct uci_context *ctx;
	/* private: */
	int n_section;
};

struct uci_section
{
	struct uci_element e;
	struct uci_list options;
	struct uci_package *package;
	char *type;
};

struct uci_option
{
	struct uci_element e;
	struct uci_section *section;
	char *value;
};

enum uci_command {
	UCI_CMD_ADD,
	UCI_CMD_REMOVE,
	UCI_CMD_CHANGE
};

struct uci_history
{
	struct uci_list list;
	enum uci_command cmd;
	union {
		struct uci_element element;
		struct uci_package package;
		struct uci_section section;
		struct uci_option option;
	} data;
};

/* linked list handling */
#ifndef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif

/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:    the pointer to the member.
 * @type:   the type of the container struct this is embedded in.
 * @member: the name of the member within the struct.
 */
#define container_of(ptr, type, member) \
	((type *) ((char *)ptr - offsetof(type,member)))


/**
 * uci_list_entry: casts an uci_list pointer to the containing struct.
 * @_type: config, section or option
 * @_ptr: pointer to the uci_list struct
 */
#define element_to(type, ptr) \
	container_of(ptr, struct uci_ ## type, e)

#define list_to_element(ptr) \
	container_of(ptr, struct uci_element, list)

/**
 * uci_foreach_entry: loop through a list of uci elements
 * @_list: pointer to the uci_list struct
 * @_ptr: iteration variable, struct uci_element
 *
 * use like a for loop, e.g:
 *   uci_foreach(&list, p) {
 *   	...
 *   }
 */
#define uci_foreach_element(_list, _ptr)		\
	for(_ptr = list_to_element((_list)->next);	\
		&_ptr->list != (_list);			\
		_ptr = list_to_element(_ptr->list.next))

/**
 * uci_foreach_entry_safe: like uci_foreach_safe, but safe for deletion
 * @_list: pointer to the uci_list struct
 * @_tmp: temporary variable, struct uci_element *
 * @_ptr: iteration variable, struct uci_element *
 *
 * use like a for loop, e.g:
 *   uci_foreach(&list, p) {
 *   	...
 *   }
 */
#define uci_foreach_element_safe(_list, _tmp, _ptr)		\
	for(_ptr = list_to_element((_list)->next),		\
		_tmp = list_to_element(_ptr->list.next);	\
		&_ptr->list != (_list);			\
		_ptr = _tmp, _tmp = list_to_element(_ptr->list.next))

/* returns true if a list is empty */
#define uci_list_empty(list) ((list)->next == (list))

/* wrappers for dynamic type handling */
#define uci_type_package UCI_TYPE_PACKAGE
#define uci_type_section UCI_TYPE_SECTION
#define uci_type_option UCI_TYPE_OPTION

/* element typecasting */
#ifdef UCI_DEBUG_TYPECAST
static const char *uci_typestr[] = {
	[uci_type_package] = "package",
	[uci_type_section] = "section",
	[uci_type_option] = "option"
};

static void uci_typecast_error(int from, int to)
{
	fprintf(stderr, "Invalid typecast from '%s' to '%s'\n", uci_typestr[from], uci_typestr[to]);
}

#define BUILD_CAST(_type) \
	static inline struct uci_ ## _type *uci_to_ ## _type (struct uci_element *e) \
	{ \
		if (e->type != uci_type_ ## _type) { \
			uci_typecast_error(e->type, uci_type_ ## _type); \
		} \
		return (struct uci_ ## _type *) e; \
	}

BUILD_CAST(package)
BUILD_CAST(section)
BUILD_CAST(option)

#else
#define uci_to_package(ptr) container_of(ptr, struct uci_package, e)
#define uci_to_section(ptr) container_of(ptr, struct uci_section, e)
#define uci_to_option(ptr)  container_of(ptr, struct uci_option, e)
#endif

/**
 * uci_alloc_element: allocate a generic uci_element, reserve a buffer and typecast
 * @ctx: uci context
 * @type: {package,section,option}
 * @name: string containing the name of the element
 * @datasize: additional buffer size to reserve at the end of the struct
 */
#define uci_alloc_element(ctx, type, name, datasize) \
	uci_to_ ## type (uci_alloc_generic(ctx, uci_type_ ## type, name, sizeof(struct uci_ ## type) + datasize))

#define uci_dataptr(ptr) \
	(((char *) ptr) + sizeof(*ptr))

#endif