osi/include/config.h

#pragma once

// This module implements a configuration parser. Clients can query the
// contents of a configuration file through the interface provided here.
// The current implementation is read-only; mutations are only kept in
// memory. This parser supports the INI file format.

// Implementation notes:
// - Key/value pairs that are not within a section are assumed to be under
//   the |CONFIG_DEFAULT_SECTION| section.
// - Multiple sections with the same name will be merged as if they were in
//   a single section.
// - Empty sections with no key/value pairs will be treated as if they do
//   not exist. In other words, |config_has_section| will return false for
//   empty sections.
// - Duplicate keys in a section will overwrite previous values.
// - All strings are case sensitive.

#include <stdbool.h>

// The default section name to use if a key/value pair is not defined within
// a section.
#define CONFIG_DEFAULT_SECTION "Global"

typedef struct config_t config_t;
typedef struct config_section_node_t config_section_node_t;

// Creates a new config object with no entries (i.e. not backed by a file).
// This function returns a config object or NULL on error. Clients must call
// |config_free| on the returned handle when it is no longer required.
config_t* config_new_empty(void);

// Loads the specified file and returns a handle to the config file. If there
// was a problem loading the file or allocating memory, this function returns
// NULL. Clients must call |config_free| on the returned handle when it is no
// longer required. |filename| must not be NULL and must point to a readable
// file on the filesystem.
config_t* config_new(const char* filename);

// Clones |src|, including all of it's sections, keys, and values.
// Returns a new config which is a copy and separated from the original;
// changes to the new config are not reflected in any way in the original.
//
// |src| must not be NULL
// This function will not return NULL.
// Clients must call config_free on the returned object.
config_t* config_new_clone(const config_t* src);

// Frees resources associated with the config file. No further operations may
// be performed on the |config| object after calling this function. |config|
// may be NULL.
void config_free(config_t* config);

// Returns true if the config file contains a section named |section|. If
// the section has no key/value pairs in it, this function will return false.
// |config| and |section| must not be NULL.
bool config_has_section(const config_t* config, const char* section);

// Returns true if the config file has a key named |key| under |section|.
// Returns false otherwise. |config|, |section|, and |key| must not be NULL.
bool config_has_key(const config_t* config, const char* section,
                    const char* key);

// Returns the integral value for a given |key| in |section|. If |section|
// or |key| do not exist, or the value cannot be fully converted to an integer,
// this function returns |def_value|. |config|, |section|, and |key| must not
// be NULL.
int config_get_int(const config_t* config, const char* section, const char* key,
                   int def_value);

// Returns the boolean value for a given |key| in |section|. If |section|
// or |key| do not exist, or the value cannot be converted to a boolean, this
// function returns |def_value|. |config|, |section|, and |key| must not be
// NULL.
bool config_get_bool(const config_t* config, const char* section,
                     const char* key, bool def_value);

// Returns the string value for a given |key| in |section|. If |section| or
// |key| do not exist, this function returns |def_value|. The returned string
// is owned by the config module and must not be freed. |config|, |section|,
// and |key| must not be NULL. |def_value| may be NULL.
const char* config_get_string(const config_t* config, const char* section,
                              const char* key, const char* def_value);

// Sets an integral value for the |key| in |section|. If |key| or |section| do
// not already exist, this function creates them. |config|, |section|, and |key|
// must not be NULL.
void config_set_int(config_t* config, const char* section, const char* key,
                    int value);

// Sets a boolean value for the |key| in |section|. If |key| or |section| do
// not already exist, this function creates them. |config|, |section|, and |key|
// must not be NULL.
void config_set_bool(config_t* config, const char* section, const char* key,
                     bool value);

// Sets a string value for the |key| in |section|. If |key| or |section| do
// not already exist, this function creates them. |config|, |section|, |key|,
// and
// |value| must not be NULL.
void config_set_string(config_t* config, const char* section, const char* key,
                       const char* value);

// Removes |section| from the |config| (and, as a result, all keys in the
// section).
// Returns true if |section| was found and removed from |config|, false
// otherwise.
// Neither |config| nor |section| may be NULL.
bool config_remove_section(config_t* config, const char* section);

// Removes one specific |key| residing in |section| of the |config|. Returns
// true
// if the section and key were found and the key was removed, false otherwise.
// None of |config|, |section|, or |key| may be NULL.
bool config_remove_key(config_t* config, const char* section, const char* key);

// Returns an iterator to the first section in the config file. If there are no
// sections, the iterator will equal the return value of |config_section_end|.
// The returned pointer must be treated as an opaque handle and must not be
// freed.
// The iterator is invalidated on any config mutating operation. |config| may
// not be NULL.
const config_section_node_t* config_section_begin(const config_t* config);

// Returns an iterator to one past the last section in the config file. It does
// not represent a valid section, but can be used to determine if all sections
// have been iterated over. The returned pointer must be treated as an opaque
// handle and must not be freed and must not be iterated on (must not call
// |config_section_next| on it). |config| may not be NULL.
const config_section_node_t* config_section_end(const config_t* config);

// Moves |iter| to the next section. If there are no more sections, |iter| will
// equal the value of |config_section_end|. |iter| may not be NULL and must be
// a pointer returned by either |config_section_begin| or |config_section_next|.
const config_section_node_t* config_section_next(
    const config_section_node_t* iter);

// Returns the name of the section referred to by |iter|. The returned pointer
// is owned by the config module and must not be freed by the caller. The
// pointer will remain valid until |config_free| is called. |iter| may not be
// NULL and must not equal the value returned by |config_section_end|.
const char* config_section_name(const config_section_node_t* iter);

// Saves |config| to a file given by |filename|. Note that this could be a
// destructive operation: if |filename| already exists, it will be overwritten.
// The config module does not preserve comments or formatting so if a config
// file was opened with |config_new| and subsequently overwritten with
// |config_save|, all comments and special formatting in the original file will
// be lost. Neither |config| nor |filename| may be NULL.
bool config_save(const config_t* config, const char* filename);