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+# mruby.h
+
+Basic header of mruby.
+It includes **mrbconf.h**, **mruby/value.h**, **mruby/version.h** internally.
+
+## `mrb_state` management
+
+### mrb_open
+```C
+mrb_state* mrb_open();
+```
+Creates new `mrb_state`.
+
+### mrb_allocf
+```C
+typedef void* (*mrb_allocf) (struct mrb_state *mrb, void *ptr, size_t s, void *ud);
+```
+Function pointer type of custom allocator used in `mrb_open_allocf`.
+
+The function pointing it must behave similarly as `realloc` except:
+* If `ptr` is `NULL` it must allocate new space.
+* If `s` is `NULL`, `ptr` must be freed.
+
+### mrb_open_allocf
+```C
+mrb_state* mrb_open_allocf(mrb_allocf f, void *ud);
+```
+Create new `mrb_state` with custom allocator.
+`ud` will be passed to custom allocator `f`.
+If user data isn't required just pass `NULL`.
+Function pointer `f` must satisfy requirements of its type.
+
+### mrb_close
+```C
+void mrb_close(mrb_state *mrb);
+```
+Deletes `mrb_state`.
+
+## Method
+
+### mrb_get_args
+```C
+int mrb_get_args(mrb_state *mrb, const char *format, ...);
+```
+Retrieve arguments from `mrb_state`.
+Use it inside a function pointed by `mrb_func_t`.
+It returns number of function retrieved.
+`format` is a list of following format specifier:
+
+char|mruby type|retrieve types|note
+:---:|----------|--------------|---
+`o`|`Object`|`mrb_value`|Could be used to retreive any type of argument
+`C`|`Class`/`Module`|`mrb_value`|
+`S`|`String`|`mrb_value`|
+`A`|`Array`|`mrb_value`|
+`H`|`Hash`|`mrb_value`|
+`s`|`String`|`char*`, `mrb_int`|
+`z`|`String`|`char*`|
+`a`|`Array`|`mrb_value*`, `mrb_int`|
+`f`|`Float`|`mrb_float`|
+`i`|`Integer`|`mrb_int`|
+`b`|boolean|`mrb_bool`|
+`n`|`Symbol`|`mrb_sym`|
+`&`|block|`mrb_value`|
+`*`|rest arguments|`mrb_value*`, `mrb_int`|Receive the rest of arguments as an array.
+<code>&#124;</code>|optional||After this spec following specs would be optional.
+`?`|optional given|`mrb_bool`|True if preceding argument is given. Used to check optional argument is given.
+
+The passing variadic arguments must be a pointer of retreiving type.