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51 lines
2.4 KiB
Plaintext
51 lines
2.4 KiB
Plaintext
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== Definitions
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=== Types
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All binary types used in this specification are stored as little-endian values on the file.
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This specification follows the C syntax to denote hexadecimal values, and requires the reader have some knowledge on programming.
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=== Endianness
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Unless otherwise specified, all fields in this specification are considered to be in __Little-Endian__ format, that is the hexadecimal number `0x12345678` is stored in disk as the following sequence of bytes: `0x78 0x56 0x34 0x12`.
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=== Header identifiers
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Header identifiers are 4 `ASCII` characters stored as a sequence of bytes inside a single 32 bits pack.
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They are shown in this specification enclosed in single quotes.
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For example, the header identifier `AARU` should be stored on disk as `0x41 0x41 0x52 0x55`.
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=== Integers
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Integer values are designated in this specification if unsigned (U) and no letter for signed, continuing with `int`, the number of bits able to be stored in them, and finishing with `_t`.
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That so, the signed integers should be: `int8_t`, `int16_t`, `int32_t`, `int64_t` and `int128_t`.
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And the unsigned integers should be: `uint8_t`, `uint16_t`, `uint32_t`, `uint64_t` , `uint128_t`.
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=== Strings
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All strings are stored as a sequence of bytes, in Unicode's `UTF-16` little endian encoding and terminated and filled with `NULL` (`0x00`) bytes.
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`String8` values mean the string is stored in Unicode’s `UTF-8` encoding and terminated and filled with `NULL` (`0x00`) bytes.
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`StringA` values mean the string is stored in `ASCII` encoding and terminated and filled with `NULL` (`0x00`) bytes.
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=== Timestamp
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All timestamps used in this specification are stored as a signed 64bit integer (`int64_t`) counting the number of nanoseconds in the UTC timezone after/before the epoch of 1st January 1601 at 00:00 of the Gregorian Calendar.
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This epoch is chosen because it is when the leap-year scheme was adopted.
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=== Media tag
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A media tag is a piece of data that is physically present in the media but it’s not part of the user data.
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It can be the table of contents, some manufacturing information, sector replacement tables, etc.
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=== Sector tag
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A sector tag is a piece of data that is physically present in the media, once per each sector, but it’s not part of the user data.
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It can be addressing information, error detection or correction information, encryption metadata, etc.
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=== NULL
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NULLs are `0x00` bytes.
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