config2c is a tool that generates a C parser of a configure file.
Compared to existing prjects, config2c generates the C structure itself,
thus users can directly use the fields instead of a second parsing.
config2c also supports customed types so user can directly parse a string
into a struct. The fomat spec and the config file mostly follow C gramar.


Concepts:

For configure files:

Basic types: char, integer, float, string, identifier
These types are parsed mostly following spec of the C programming language,
excepting:
  1. numbers (integers and floats) has a optional '+' and '-' sign,
    and suffices like L, u, etc are ignored.
  2. char and strings do not accept octal escape strings, and unicode are
    not tested yet. wchar_t is not implemented

Composed data types:
These types are parsed like C, we use following notation for an array:
'[' element ',' element ',' ... element ',' ']'
For a struct / union, config writer is requested to provide field name:
'{' '.' name '=' value ',' ...  '.' name '=' value ',' '}''

The content of a configure file is a struct.

For configre spec:
User-defined types:
mapped to a list of C types. Users are required to
provide parse, free and dump functions. The types of arguments shall be
the same as the type list.
example/prim_funcs.c is a good example.

enum:
similar to C enums. 'as' is provided to define an alias of an enum
constant. If the parser sees an alias, it automatically converts it to
the corresponding constant.

struct:
mapped to c struct.
Following types are supported:
user-defined types, struct, union, enum, unnamed union
Members of user-defined types are mapped to a list of C variables, the type
of each is defined by the mapped types list of the user-defined type.
enum and struct are directly mapped.
unions are mapped to a union and an enum, which specifies the selected
member.

all values except unnamed union can be a scale value, a fixed length array,
or a variable length array.
Both scale value and fixed length array are mapped. The length of a fixed
length array is checked. A variable length array is mapped to a pointer and
a length field.

A struct can optionally have an export attribute, the corresponding
functions would be exported.

union:
A union is mapped to a C union and a C enum. The latter is used to specify
the field set. A field in a union can be a value of user-defined type,
enum, struct or an unnamed struct. A field of user-defined type in a union
cannot be mapped to multiple fields. A field in a union can not be a
variable length array.

Note:
A unnamed member cannot have its unnamed member.


Install:
You need to run following commands to install config2c:
1.  make
2.  make install
By default, config2c would be installed into /usr/local/, you can use
make install DESTDIR=<prefix> to change the install location.
Requirement: GCC, bison, flex


Usage:
1. Write config spec
2. Write functions for user-defined types, example/prim_funcs is an
   example
3. Write prelude to include necessary headers, etc. Prelude would be copied
   to the header of generated .h file.
4. run following command:
       config2c --spec_path=... \
    		--prim_path=... \
    		--prelude_path=... \
    		--hdr_path=... \
    		--src_path=... \
    		--include_guard=...
   This command generates a .c file and a .h file. The .h file includes
definitions of the data types. For each exported struct, following
functions are provided:
   A function that parses a file into a struct.
   A function that frees a struct.
   A function that dumps a struct.
5. If you want to compile the project, you need following files:
        supplement/parser.c
        supplement/parser.h
        supplement/parsery.tab.c
        supplement/parsery.tab.h
        supplement/parserl.lex.c
   Please put these files into your project