Opt: Introduced contexts

[libucw.git] / ucw / conf.h

diff --git a/ucw/conf.h b/ucw/conf.h
index a387f274d57966818aa0c9e76d3bb6c36ae886ab..0ff991309f146bfb1505c77ed7fa9a2d23219239 100644 (file)
--- a/ucw/conf.h
+++ b/ucw/conf.h
@@ -24,7 +24,7 @@ struct mempool;
  * One such context is automatically created during initialization of the library
  * and you need not care about more, as long as you use a single configuration file.
  *
- * In full generality, you can define as many context as you wish and switch
+ * In full generality, you can define as many contexts as you wish and switch
  * between them. Each thread has its own pointer to the current context, which
  * must not be shared with other threads.
  ***/
@@ -41,7 +41,7 @@ struct cf_context *cf_new_context(void);
  * of the context is freed, which includes memory obtained by calls to
  * cf_malloc().
  **/
-void cf_free_context(struct cf_context *cc);
+void cf_delete_context(struct cf_context *cc);
 
 /**
  * Make the given configuration context current and return the previously
@@ -63,6 +63,7 @@ struct cf_context *cf_switch_context(struct cf_context *cc);
  * configuration specified in the file are undone.
  **/
 int cf_load(const char *file);
+
 /**
  * Reload configuration from @file, replace the old one.
  * If @file is NULL, reload all loaded configuration files and re-apply
@@ -71,6 +72,7 @@ int cf_load(const char *file);
  * settings are rolled back to the state before calling this function.
  **/
 int cf_reload(const char *file);
+
 /**
  * Parse some part of configuration passed in @string.
  * The syntax is the same as in the <<config:,configuration file>>.
@@ -97,6 +99,12 @@ void cf_open_group(void);
  **/
 int cf_close_group(void);
 
+/**
+ * Return all configuration items to their initial state before loading the
+ * configuration file. If journalling is disabled, it does nothing.
+ **/
+void cf_revert(void);
+
 /*** === Data types [[conf_types]] ***/
 
 enum cf_class {                                /** Class of the configuration item. **/
@@ -400,6 +408,9 @@ struct cf_section {                 /** A section. **/
  * reloaded or rolled back, or the context is deleted, it gets lost).
  *
  * Memory allocated from within custom parsers should be allocated from the pools.
+ *
+ * Please note that the pool is not guaranteed to exist before you call cf_load(),
+ * cf_set(), or cf_getopt() on the particular context.
  ***/
 struct mempool *cf_get_pool(void); /** Return a pointer to the current configuration pool. **/
 void *cf_malloc(uns size);     /** Returns @size bytes of memory allocated from the current configuration pool. **/
@@ -412,16 +423,21 @@ char *cf_printf(const char *fmt, ...) FORMAT_CHECK(printf,1,2); /** printf() int
  * Undo journal
  * ~~~~~~~~~~~~
  *
- * The configuration system uses journaling to safely reload
- * configuration. It begins a transaction and tries to load the
- * configuration. If it fails, it restores the original state.
+ * The configuration system uses a simple journaling mechanism, which makes
+ * it possible to undo changes to configuration. A typical example is loading
+ * of configuration by cf_load(): internally, it creates a transaction, applies
+ * all changes specified by the configuration and if one of them fails, the whole
+ * journal is replayed to restore the whole original state. Similarly, cf_reload()
+ * uses the journal to switch between configurations.
  *
- * The behaviour of journal is described in <<reload,reloading configuration>>.
+ * In most cases, you need not care about the journal, except when you need
+ * to change some data from a <<hooks,hook>>, or if you want to call cf_modify_item() and then
+ * undo the changes.
  ***/
 /**
- * By default, the configuration mechanism remembers all changes in a journal,
- * so that the configuration can be rolled back or reloaded. This function
- * can be used to disable journalling, which saves some memory.
+ * This function can be used to disable the whole journalling mechanism.
+ * It saves some memory, but it makes undoing of configuration changes impossible,
+ * which breaks for example cf_reload().
  **/
 void cf_set_journalling(int enable);
 /**
@@ -432,7 +448,7 @@ void cf_set_journalling(int enable);
  * before them.
  **/
 void cf_journal_block(void *ptr, uns len);
-#define CF_JOURNAL_VAR(var) cf_journal_block(&(var), sizeof(var))      // Store single value into journal.
+#define CF_JOURNAL_VAR(var) cf_journal_block(&(var), sizeof(var))      // Store a single value into the journal
 
 struct cf_journal_item;                /** Opaque identifier of the journal state. **/
 /**
@@ -472,8 +488,17 @@ void cf_journal_rollback_transaction(uns new_pool, struct cf_journal_item *oldj)
  * If @allow_unknown is set to 0 and a variable not described in @sec
  * is found in the configuration file, it produces an error.
  * If you set it to 1, all such variables are ignored.
+ *
+ * Please note that a single section definition cannot be used in multiple
+ * configuration contexts simultaneously.
  **/
 void cf_declare_section(const char *name, struct cf_section *sec, uns allow_unknown);
+/**
+ * Like @cf_declare_section(), but instead of item pointers, the section
+ * contains offsets relative to @ptr. In other words, it does the same
+ * as `CF_SECTION`, but for top-level sections.
+ **/
+void cf_declare_rel_section(const char *name, struct cf_section *sec, void *ptr, uns allow_unknown);
 /**
  * If you have a section in a structure and you want to initialize it
  * (eg. if you want a copy of default values outside the configuration),
@@ -504,7 +529,8 @@ char *cf_parse_ip(const char *p, u32 *varp);                /** Parser for IP addresses. **/
  * ~~~~~~~~~~~~~
  *
  * Direct access to configuration items.
- * You probably should not need this.
+ * You probably should not need this, but in your do, you have to handle
+ * <<journal,journalling>> yourself.
  ***/
 
 /**
@@ -545,7 +571,7 @@ char *cf_modify_item(struct cf_item *item, enum cf_operation op, int number, cha
 
 struct fastbuf;
 /**
- * Take everything and write it into @fb.
+ * Write the current state of all configuration items into @fb.
  **/
 void cf_dump_sections(struct fastbuf *fb);