Meta File Format

1. Introduction

This specification defines a user-level file format that allows items of meta
data to be stored in the same physical file as the content to which it relates.

2. Member Format

All numbers used in the file format will be unsigned integers of either 16 or
32 bits in length. These numbers will be stored in a big endian, "twos
compliment" binary format.

Conversions from host to big endian (or network) numbers can be performed using
the htonl and htons standard library functions.

Conversions from big endian (or network) to host numbers can be performed using
the ntohl and ntols standard library functions.

3. File Format

3.1. Header

  1   2   3   4
+---+---+---+---+
|VERNO  |ISIZE  |
+---+---+---+---+

VERNO
Unsigned, 16 bit integer: The version number of the Meta Archive file format,
will be 1 when conforming to this specification.

ISIZE
Unsigned, 16 bit integer: Specifies the number of items of meta data stored in
the index section of the file.

3.2. Index

  1    ...   38  39  40
+---+-- / --+---+---+---+
|KEY1         \0|MSIZE1 |
+---+-- / --+---+---+---+
|  ...          |  ...  |
+---+-- / --+---+---+---+
|KEYn*        \0|MSIZEn*|
+---+-- / --+---+---+---+
*  Where n is less than or equal to 2^16

KEY
Zero terminated ASCII string upto 38 bytes in length (including terminator):
used as a key for addressing an item of Meta Data, see section 3.4.

MSIZE
Unsigned, 16 bit integer: The size of the Meta Data item that follows.

3.3. User Data

  1   2   3   4    ...  4+n*
+---+---+---+---+===========+
|USIZE          |UDATA      |
+---+---+---+---+===========+
*  Where n is less than or equal to 2^32

USIZE
Unsigned, 32 bit integer: The size of the User Data that follows.

UDATA
Array of bytes upto 2 ^ 32 in length: The User Data.

3.4. Meta Data

    ...   a    ...  a+b   ... a+b+c*
+===========+===========+===========+
|MDATA1     |    ...    |MDATAn**   |
+===========+===========+===========+
*  Where a, b and c are less than or equal to 2^16
** Where n is less than or equal to 2^16

MDATA
Array of bytes upto 2 ^ 16 in length: The Meta Data.