2.2.2.2.1.2.1.4 Four-Byte Unsigned Encoding (FOUR_BYTE_UNSIGNED_ENCODING)
The FOUR_BYTE_UNSIGNED_ENCODING structure is used to encode a value in the range 0x00000000 to 0x3FFFFFFF by using a variable number of bytes. For example, 0x001A1B1C is encoded as { 0x9A, 0x1B, 0x1C }. The two most significant bits of the first byte encode the number of bytes in the structure.
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c |
val1 |
val2 (optional) |
val3 (optional) |
val4 (optional) |
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c (2 bits): A 2-bit, unsigned integer field containing an encoded representation of the number of bytes in this structure.
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Value
Meaning
ONE_BYTE_VAL
0
Implies that the optional val2, val3, and val4 fields are not present. Hence, the structure is 1 byte in size.
TWO_BYTE_VAL
1
Implies that the optional val2 field is present while the optional val3 and val4 fields are not present. Hence, the structure is 2 bytes in size.
THREE_BYTE_VAL
2
Implies that the optional val2 and val3 fields are present while the optional val4 fields are not present. Hence, the structure is 3 bytes in size.
FOUR_BYTE_VAL
3
Implies that the optional val2, val3, and val4 fields are all present. Hence, the structure is 4 bytes in size.
val1 (6 bits): A 6-bit, unsigned integer field containing the most significant 6 bits of the value represented by this structure.
val2 (1 byte): An 8-bit, unsigned integer containing the second most significant bits of the value represented by this structure.
val3 (1 byte): An 8-bit, unsigned integer containing the third most significant bits of the value represented by this structure.
val4 (1 byte): An 8-bit, unsigned integer containing the least significant bits of the value represented by this structure.