2.2.2.4 FOUR_BYTE_SIGNED_INTEGER

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The FOUR_BYTE_SIGNED_INTEGER structure is used to encode a value in the range -0x1FFFFFFF to 0x1FFFFFFF by using a variable number of bytes. For example, -0x001A1B1C is encoded as {0xBA, 0x1B, 0x1C}, and -0x00000002 is encoded as {0x22}. The three most significant bits of the first byte encode the number of bytes in the structure and the sign.


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c

s

val1

val2 (optional)

val3 (optional)

val4 (optional)

c (2 bits):  A 2-bit unsigned integer field containing an encoded representation of the number of bytes in this structure.

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 field is 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.

s (1 bit):  A 1-bit unsigned integer field containing an encoded representation of whether the value is positive or negative.

Value

Meaning

POSITIVE_VAL

0

Implies that the value represented by this structure is positive.

NEGATIVE_VAL

1

Implies that the value represented by this structure is negative.

val1 (5 bits):  A 5-bit unsigned integer field containing the most significant 5 bits of the value represented by this structure.

val2 (1 byte, optional):  An 8-bit unsigned integer containing the second most significant bits of the value represented by this structure.

val3 (1 byte, optional):  An 8-bit unsigned integer containing the third most significant bits of the value represented by this structure.

val4 (1 byte, optional):  An 8-bit unsigned integer containing the least significant bits of the value represented by this structure.