2.2.5.1 General Rules

Data structure encodings in TDS are defined in terms of the following fundamental definitions.

BIT: A single bit value of either 0 or 1.

 BIT = %b0 / %b1

BYTE: An unsigned single byte (8-bit) value. The range is 0 to 255.

 BYTE = 8BIT

BYTELEN: An unsigned single byte (8-bit) value representing the length of the associated data. The range is 0 to 255.

 BYTELEN = BYTE

USHORT: An unsigned 2-byte (16-bit) value. The range is 0 to 65535.

 USHORT = 2BYTE

LONG: A signed 4-byte (32-bit) value. The range is -(2^31) to (2^31)-1.

 LONG = 4BYTE

ULONG: An unsigned 4-byte (32-bit) value. The range is 0 to (2^32)-1

 ULONG = 4BYTE

DWORD: An unsigned 4-byte (32-bit) value. The range when used as a numeric value is 0 to (2^32)-1.

 DWORD = 32BIT

LONGLONG: A signed 8-byte (64-bit) value. The range is –(2^63)  to (2^63)-1.

 LONGLONG = 8BYTE

ULONGLONG: An unsigned 8-byte (64-bit) value. The range is 0 to (2^64)-1.

 ULONGLONG = 8BYTE

UCHAR: An unsigned single byte (8-bit) value representing a character. The range is 0 to 255.

 UCHAR = BYTE

USHORTLEN: An unsigned 2-byte (16-bit) value representing the length of the associated data. The range is 0 to 65535.

 USHORTLEN = 2BYTE

USHORTCHARBINLEN: An unsigned 2-byte (16-bit) value representing the length of the associated character or binary data. The range is 0 to 8000.

 USHORTCHARBINLEN = 2BYTE

LONGLEN: A signed 4-byte (32-bit) value representing the length of the associated data. The range is -(2^31) to (2^31)-1.

 LONGLEN = 4BYTE

ULONGLONGLEN: An unsigned 8-byte (64-bit) value representing the length of the associated data. The range is 0 to (2^64)-1.

 ULONGLONGLEN = 8BYTE

PRECISION: An unsigned single byte (8-bit) value representing the precision of a numeric number.

 PRECISION = 8BIT

SCALE: An unsigned single byte (8-bit) value representing the scale of a numeric number.

 SCALE = 8BIT

GEN_NULL: A single byte (8-bit) value representing a NULL value.

 GEN_NULL = %x00

CHARBIN_NULL: A 2-byte (16-bit) or 4-byte (32-bit) value representing a T-SQL NULL value for a character or binary data type. Please refer to TYPE_VARBYTE (see section 2.2.5.2.3) for additional details.

 CHARBIN_NULL = (%xFF %xFF) / (%xFF %xFF %xFF %xFF)

FRESERVEDBIT: A FRESERVEDBIT is a BIT value used for padding that does not transmit information. FRESERVEDBIT fields SHOULD be set to %b0 and MUST be ignored on receipt.

 FRESERVEDBIT = %b0

FRESERVEDBYTE: A FRESERVEDBYTE is a BYTE value used for padding that does not transmit information. FRESERVEDBYTE fields SHOULD be set to %x00 and MUST be ignored on receipt.

 FRESERVEDBYTE = %x00

UNICODECHAR: A single Unicode character in UCS-2 encoding, as specified in Unicode [UNICODE].

 UNICODECHAR = 2BYTE

Notes

  • All integer types are represented in reverse byte order (little-endian) unless otherwise specified.

  • FRESERVEDBIT and FRESERVEDBYTE are often used to pad unused parts of a byte or bytes. The value of these reserved bits SHOULD be ignored. These elements are generally set to 0.

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