/*

  silcconfig.h

  Author: Giovanni Giacobbi <giovanni@giacobbi.net>

  Copyright (C) 2002 - 2003 Giovanni Giacobbi

  The contents of this file are subject to one of the Licenses specified 
  in the COPYING file;  You may not use this file except in compliance 
  with the License.

  The software distributed under the License is distributed on an "AS IS"
  basis, in the hope that it will be useful, but WITHOUT WARRANTY OF ANY
  KIND, either expressed or implied.  See the COPYING file for more
  information.

*/

/****h* silcutil/SILC Config Interface
 *
 * DESCRIPTION
 *
 * The SILC Config util library is based on two main objects, SilcConfigFile
 * (or File object) and SilcConfigEntity (or Entity).  The File objects are
 * structs directly corresponding to the real files in the filesystem, while
 * Entities are a little more abstract.
 *
 * An Entity is composed by delimited area on a File object (it can take the
 * whole File object or just part of it), plus a group of known options.
 * In order to parse this file, first you need to create a File object with
 * the silc_config_open() function, and then you need to create the Entity
 * with the silc_config_init() function.
 *
 * Now you can use the newly created Entity to register a group of expected
 * known options and sub-blocks, and then you can call the main parsing loop
 * with the silc_config_main() function. When silc_config_main() will 
 * return, if some error encoured the object file will point to the file 
 * that caused this error (this can be different from the originally 
 * opened file if it contained `Include' directives).  If no errors 
 * encoured then the File objects will still point to the original file.
 *
 * While silc_config_main() will take care of destroying Entities before
 * returning, you need to take care that the File object you created is freed
 * with the silc_config_close() function.
 *
 * The SILC Config library won't take care about storing the values contained
 * in the config file.  You must take care about it with the callback
 * functions.
 *
 * The config file syntax is pretty straightforward.  All lines starting
 * with `#' will be skipped, while sub-blocks are delimited by braces (see
 * the example below).
 *
 * Options with argument must have the `=' character between the option
 * name and the value.  Simple words and numbers does not require quoting.
 * There is a special built-in directive "Include" which allows you to include
 * another config file in the point the directive is.  You can also Include
 * inside a sub-block body, in this case when parsing the included config file
 * it will be assumed that we are within this block, and the included file
 * won't be allowed to close his root block.
 *
 * Example:
 *
 *    cipher {
 *       name = aes-256-cbc;
 *       module = "aes.sim.so";
 *       key_length = 32;       # usually the default is just fine
 *       block_length = 16;
 *    };
 *    Include "/etc/silc/hash_funcs.conf";
 *
 ***/

#ifndef SILCCONFIG_H
#define SILCCONFIG_H

/****d* silcutil/SilcConfigAPI/SilcConfigErrno
 *
 * NAME
 *
 *    enum { ... } - describe a SILC Config error
 *
 * DESCRIPTION
 *
 *    The virtual integer `errno' is returned by the silc_config_main()
 *    function and indicates what went wrong.
 *    You can convert it to the corresponding error string with the function
 *    silc_config_strerror().
 *
 * SOURCE
 */
enum {
  SILC_CONFIG_OK,		/* OK */
  SILC_CONFIG_ESILENT,		/* Error defined by callback function */
  SILC_CONFIG_EPRINTLINE,	/* Error defined by callback function */
  SILC_CONFIG_EGENERIC,		/* Invalid syntax */
  SILC_CONFIG_EINTERNAL,	/* Internal Error (caused by developer) */
  SILC_CONFIG_ECANTOPEN,	/* Can't open specified file */
  SILC_CONFIG_EOPENBRACE,	/* Expected open-brace '{' */
  SILC_CONFIG_ECLOSEBRACE,	/* Missing close-brace '}' */
  SILC_CONFIG_ETYPE,		/* Invalid data type */
  SILC_CONFIG_EBADOPTION,	/* Unknown option */
  SILC_CONFIG_EINVALIDTEXT,	/* Invalid text */
  SILC_CONFIG_EDOUBLE,		/* Double option specification */
  SILC_CONFIG_EEXPECTED,	/* Expected data but not found */
  SILC_CONFIG_EEXPECTEDEQUAL,	/* Expected '=' */
  SILC_CONFIG_EUNEXPECTED,	/* Unexpected data */
  SILC_CONFIG_EMISSFIELDS,	/* Missing mandatory fields */
  SILC_CONFIG_EMISSCOLON,	/* Missing ';' */
};
/***/

/****d* silcutil/SilcConfigAPI/SilcConfigType
 *
 * NAME
 *
 *    typedef enum { ... } SilcConfigType;
 *
 * DESCRIPTION
 *
 *    This identifies the parameter type that an option has. This parameter
 *    is very important because the callback's *val pointer points to a
 *    memory location containing the previously specified data type.
 *    For example, if you specified an option with an integer parameter
 *    callback's *val will be a pointer to an integer.
 *
 * SOURCE
 */
typedef enum {
  SILC_CONFIG_ARG_TOGGLE,	/* TOGGLE on,off; yes,no; true, false; */
  SILC_CONFIG_ARG_INT,		/* callback wants an integer */
  SILC_CONFIG_ARG_STR,		/* callback expects \0-terminated str */
  SILC_CONFIG_ARG_STRE,		/* same as above, but can also be empty */
  SILC_CONFIG_ARG_BLOCK,	/* this is a sub-block */
  SILC_CONFIG_ARG_SIZE,		/* like int, but accepts suffixes kMG */
  SILC_CONFIG_ARG_NONE,		/* does not expect any args */
} SilcConfigType;
/***/

/****f* silcutil/SilcConfigAPI/SilcConfigCallback
 *
 * SYNOPSIS
 *
 *    typedef int (*SilcConfigCallback)(SilcConfigType type, const char *name,
 *                                      SilcUInt32 line, void *val,
 *                                      void *context);
 * DESCRIPTION
 *
 *    This is the callback prototype for the options handler.  The pointer
 *    `val' points to a location of type described by `type'.  `name' points
 *    to a null-terminated string with the name of the option which triggered
 *    this callback, that is stated at line `line'.  `context' is the
 *    user-specified context provided when this option was registered.
 *
 ***/
typedef int (*SilcConfigCallback)(SilcConfigType type, const char *name,
				  SilcUInt32 line, void *val, void *context);

/****s* silcutil/SilcConfigAPI/SilcConfigTable
 *
 * SYNOPSIS
 *
 *    typedef struct { ... } SilcConfigTable;
 *
 * DESCRIPTION
 *
 *    SILC Config table defines an easy and quick way of registering options
 *    in an entity. The function silc_config_register_table() will take as
 *    argument a SilcConfigTable array terminated by a NULL struct, it is
 *    important thus, that the `name' field of the terminating struct is set
 *    to NULL.
 *
 *    char *name
 *
 *       The option name lowercase. The matching is always case-insensitive,
 *       but for convention the option specification must always be lowercase.
 *
 *    SilcConfigType type
 *
 *       This specifies what kind of parameter this option expects.  The
 *       special cases SILC_CONFIG_ARG_BLOCK tells SILC Config that this is
 *       not a normal option but the name of a sub-block of the current
 *       block (there is no limit to the number of nested blocks allowed).
 *
 *    SilcConfigCallback callback
 *
 *       Normally this is the value handler of the current option. If this
 *       field is set to NULL then the value is silently discarded. Useful
 *       for example to support deprecated options.
 *
 *    SilcConfigTable *subtable
 *
 *       If the `type' field is set to SILC_CONFIG_ARG_BLOCK, then this field
 *       must point to a valid sub-table NULL-terminated array. If `type' is
 *       something else, this valued is unused.
 *
 ***/
typedef struct SilcConfigTableStruct {
  char *name;
  SilcConfigType type;
  SilcConfigCallback callback;
  const struct SilcConfigTableStruct *subtable;
} SilcConfigTable;

/****s* silcutil/SilcConfigAPI/SilcConfigFile
 *
 * SYNOPSIS
 *
 *    typedef struct SilcConfigFileObject SilcConfigFile;
 *
 * DESCRIPTION
 *
 *    A File object holds the data contained in a previously loaded file by
 *    the silc_config_open() function.
 *    This is an internally allocated struct and must be used only with the
 *    helper functions.
 *
 ***/
typedef struct SilcConfigFileObject SilcConfigFile;

/****s* silcutil/SilcConfigAPI/SilcConfigEntity
 *
 * SYNOPSIS
 *
 *    typedef struct SilcConfigEntityObject *SilcConfigEntity;
 *
 * DESCRIPTION
 *
 *    The SILC Config is based on config entities.  An entity contains the
 *    SilcConfigFile object we are parsing and the registered options.
 *
 ***/
typedef struct SilcConfigEntityObject *SilcConfigEntity;

/* Macros */

/****d* silcutil/SilcConfigAPI/SILC_CONFIG_CALLBACK
 *
 * NAME
 *
 *    #define SILC_CONFIG_CALLBACK ...
 *
 * DESCRIPTION
 *
 *    Generic macro to define SilcConfigCallback functions. This defines a
 *    static function with name `func' as a config callback function.
 *
 * SOURCE
 */
#define SILC_CONFIG_CALLBACK(func)				\
static int func(SilcConfigType type, const char *name,		\
		SilcUInt32 line, void *val, void *context)
/***/

/* Prototypes */

/****f* silcutil/SilcConfigAPI/silc_config_open
 *
 * SYNOPSIS
 *
 *    SilcConfigFile *silc_config_open(char *configfile);
 *
 * DESCRIPTION
 *
 *    Tries to open the config file `configfile' and returns a valid File
 *    object on success, or NULL on failure.
 *    An File object created this way must be destroyed with the function
 *    silc_config_close().
 *
 ***/
SilcConfigFile *silc_config_open(const char *configfile);

/****f* silcutil/SilcConfigAPI/silc_config_close
 *
 * SYNOPSIS
 *
 *    void silc_config_close(SilcConfigFile *file);
 *
 * DESCRIPTION
 *
 *    Closes and frees the File object `file', which must have been returned
 *    by a previous call to silc_config_open().  Otherwise, or if
 *    this function has already been called before for the same File object,
 *    undefined behaviour occurs.
 *    If `file' is NULL, no operation is performed.
 *
 ***/
void silc_config_close(SilcConfigFile *file);

/****f* silcutil/SilcConfigAPI/silc_config_init
 *
 * SYNOPSIS
 *
 *    SilcConfigEntity silc_config_init(SilcConfigFile *file);
 *
 * DESCRIPTION
 *
 *    Creates an Entity pointing to the valid File object `file', which must
 *    be returned by a previous call to silc_config_open(), otherwise NULL
 *    is returned.
 *    Entities will be automatically destroyed after the call to the
 *    silc_config_main() function, because of this no uninit functions are
 *    provided.
 *
 ***/
SilcConfigEntity silc_config_init(SilcConfigFile *file);

/****f* silcutil/SilcConfigAPI/silc_config_strerror
 *
 * SYNOPSIS
 *
 *    char *silc_config_strerror(int errnum);
 *
 * DESCRIPTION
 *
 *    The silc_config_strerror() function returns a string describing the
 *    error code passed in the argument `errnum'.
 *
 ***/
char *silc_config_strerror(int errnum);

/****f* silcutil/SilcConfigAPI/silc_config_get_filename
 *
 * SYNOPSIS
 *
 *    char *silc_config_get_filename(SilcConfigFile *file);
 *
 * DESCRIPTION
 *
 *    Returns the original filename of the object file.
 *    The returned pointer points to internally allocated storage and must
 *    not be freed, modified or stored.
 *
 ***/
char *silc_config_get_filename(SilcConfigFile *file);

/****f* silcutil/SilcConfigAPI/silc_config_get_line
 *
 * SYNOPSIS
 *
 *    SilcUInt32 silc_config_get_line(SilcConfigFile *file);
 *
 * DESCRIPTION
 *
 *    Returns the current line that file parsing arrived at.
 *
 ***/
SilcUInt32 silc_config_get_line(SilcConfigFile *file);

/****f* silcutil/SilcConfigAPI/silc_config_read_line
 *
 * SYNOPSIS
 *
 *    char *silc_config_read_line(SilcConfigFile *file, SilcUInt32 line);
 *
 * DESCRIPTION
 *
 *    Returns a dynamically allocated null-terminated buffer containing the
 *    line `line' of `file'.
 *    The returned pointer must be freed when it's not needed any longer.
 *
 * SEE ALSO
 *    silc_config_read_current_line
 *
 ***/
char *silc_config_read_line(SilcConfigFile *file, SilcUInt32 line);

/****f* silcutil/SilcConfigAPI/silc_config_read_current_line
 *
 * SYNOPSIS
 *
 *    char *silc_config_read_current_line(SilcConfigFile *file);
 *
 * DESCRIPTION
 *
 *    Returns a dynamically allocated buffer containing the line that the
 *    parser stopped at.  This is a convenience function for
 *    silc_config_read_line.
 *    The returned pointer must be freed when it's not needed any longer.
 *
 ***/
char *silc_config_read_current_line(SilcConfigFile *file);

/****f* silcutil/SilcConfigAPI/silc_config_register
 *
 * SYNOPSIS
 *
 *    bool silc_config_register(SilcConfigEntity ent, const char *name,
 *                              SilcConfigType type, SilcConfigCallback cb,
 *                              const SilcConfigTable *subtable,
 *                              void *context);
 *
 * DESCRIPTION
 *
 *    Register option `name' in the entity `ent'. If `cb' is not NULL, it
 *    will be called with the *val pointer pointing to an internally
 *    allocated storage of type described by `type'.
 *
 *    If `type' is SILC_CONFIG_ARG_BLOCK, then `subtable' must be a valid
 *    pointer to a SilcConfigTable array specifying the options in the
 *    sub-block.
 *
 *    If the option `name' was already registered in this sub-block or it
 *    matches the reserved word "Include", then this function returns FALSE,
 *    otherwise it returns TRUE.
 *
 * SEE ALSO
 *    silc_config_register_table
 *
 ***/
bool silc_config_register(SilcConfigEntity ent, const char *name,
			  SilcConfigType type, SilcConfigCallback cb,
			  const SilcConfigTable *subtable, void *context);

/****f* silcutil/SilcConfigAPI/silc_config_register_table
 *
 * SYNOPSIS
 *
 *    bool silc_config_register_table(SilcConfigEntity ent,
 *                                    const SilcConfigTable table[],
 *                                    void *context);
 *
 * DESCRIPTION
 *
 *    Register the tableset of options `table' automatically in the entity
 *    `ent'.  If defined in the table, the callback functions will be called
 *    all with the same context `context'.
 *
 *    The `table' array must be terminated with an entry with the name field
 *    set to NULL.
 *
 *    If the table contains invalid data this function returns FALSE, otherwise
 *    it returns TRUE.  If a calling to this function failed, you must destroy
 *    and recreate the entity before retrying, as it's impossible to detect
 *    the point at the function stopped the registering process.
 *
 * SEE ALSO
 *    SilcConfigTable
 *
 ***/
bool silc_config_register_table(SilcConfigEntity ent,
				const SilcConfigTable table[], void *context);

/****f* silcutil/SilcConfigAPI/silc_config_main
 *
 * SYNOPSIS
 *
 *    int silc_config_main(SilcConfigEntity ent);
 *
 * DESCRIPTION
 *
 *    Enter the main parsing loop. When this function returns the parsing
 *    is finished in the current block (and sub-blocks).
 *
 *    When this function exits, the entity is already destroyed, because
 *    of this you should set it to NULL right after the function call.
 *
 ***/
int silc_config_main(SilcConfigEntity ent);

#endif	/* !SILCCONFIG_H */