= C-language like structure declaration

== Overview:

StructPacking uses "C like structure declaration" to define 
object packing byte array format.
It is mostly compatible with struct definition in C language, and
some extended notation to support byte packing function in Ruby language.

This is mainly use to genarate Ruby pack template string from C language's struct
declaration.

== Syntax:
Syntax is same as C-language variable declaration.
  [sign-modifier] <type> <variable-name> [ [array-length] ];


== Type:
* Traditional C language's types.
  * char
  * short
  * int
  * long
  * long long
  * float
  * double


* C99 types.
  * int8_t
  * int16_t
  * int32_t
  * int64_t
  * uint8_t
  * uint16_t
  * uint32_t
  * uint64_t

* Extend keyword for Ruby pack string support.
  * ascii
  * utf8
  * big
  * big16
  * big32
  * little
  * little16
  * little32
  * big float
  * little float
  * big double
  * little double

== Variable-name:
Variable-name is identifier of this variable.
This is must unique in this struct.

In StructPacking package, variable-name is used to make relation object
with struct definition.
Packing function is get value from object's attr-getter which is same name as
variable-name, and pack the value toC-like_structure_declaration.rdoc 

== Array-length
If "[]" is placed after variable-name, this variable define as array.

== Sign-modifier:
* signed 
* unsigned
are sign-modifier.

== Bit-field
* TODO


== Ruby pack template mapping:

* Signed (or not assinged)

*char*::      "c"
*int8_t*::      "c"
*short*::     "s"
*int16_t*::     "s"
*int*::       "i"
*int32_t*::     "l"
*long*::        "l"
*long* *long*:: "q"
*int64_t*::       "q"
*float*::       "f"
*double*::       "d"

* Unsigned

*unsigned* *char*::        "C"
*uint8_t*::                  "C"
*unsigned* *short*::       "S"
*uint16_t*::                 "S"
*unsigned* *int*::         "I"
*unsigned* *long*::        "L"
*uint32_t*::                 "L"
*unsigned* *long* *long*:: "Q"
*uint64_t*::                 "Q"

* Extend types

*ascii*:: "a"
*utf8*:: "U"
*big*:: "N"
*big16*:: "n"
*big32*:: "N"
*little*:: "V"
*little16*:: "v"
*little32*:: "V"
*big* *float*:: "g"
*little* *float*:: "e"
*big* *double*:: "G"
*little* *double*:: "E"