`RightB$` Function

The RightB$ function in Visual Basic 6 returns a string containing a specified number of bytes from the right side (end) of a string. Unlike Right$ which works with characters, RightB$ operates at the byte level, making it essential for binary data processing and working with DBCS (Double-Byte Character Set) strings.

Syntax

RightB$(string, length)

Parameters

string - Required. String expression from which the rightmost bytes are returned. If string contains Null, Null is returned.
length - Required. Numeric expression indicating how many bytes to return. If 0, a zero-length string ("") is returned. If greater than or equal to the number of bytes in string, the entire string is returned.

Return Value

Returns a String containing the rightmost length bytes of string.

Behavior and Characteristics

Byte vs. Character Operation

RightB$ counts bytes, not characters
In VB6, each character is stored as 2 bytes (UCS-2/Unicode)
Extracting an odd number of bytes from Unicode text may split a character
DBCS characters (e.g., Japanese, Chinese) may require 2 bytes per character

Length Handling

If length = 0: Returns an empty string ("")
If length >= LenB(string): Returns the entire string
If length < 0: Generates a runtime error (Invalid procedure call or argument)
If string is empty (""): Returns an empty string regardless of length

Character Set Considerations

VB6 stores strings internally as Unicode (UCS-2)
Each character typically occupies 2 bytes
Extracting an odd number of bytes can result in incomplete characters
Use Right$ for character-based extraction in most cases

Common Usage Patterns

1. Extract Binary Data Suffix

Function GetBinarySuffix(data As String, numBytes As Integer) As String
GetBinarySuffix = RightB$(data, numBytes)
End Function

Dim suffix As String
suffix = GetBinarySuffix(binaryData, 4)  ' Get last 4 bytes

2. Read File Trailer

Function ReadFileTrailer(fileData As String) As String
' Get last 8 bytes of file (e.g., signature or checksum)
ReadFileTrailer = RightB$(fileData, 8)
End Function

Function GetProtocolFooter(packet As String) As String
' Get 2-byte footer from network packet
GetProtocolFooter = RightB$(packet, 2)
End Function

4. Process Binary Structures

Type FileHeader
signature As String * 4
version As String * 2
End Type

Function GetVersion(headerData As String) As String
' Extract last 2 bytes as version info
GetVersion = RightB$(headerData, 2)
End Function

5. Network Packet Checksum

Function ExtractChecksum(packet As String) As String
' Network packets often have 2-4 byte checksums at end
ExtractChecksum = RightB$(packet, 4)
End Function

6. GUID/UUID Component Extraction

Function GetGuidSuffix(guidData As String) As String
' Extract last 6 bytes of GUID (node portion)
GetGuidSuffix = RightB$(guidData, 6)
End Function

7. File Format Magic Bytes (Trailer)

Function CheckFileTrailer(fileData As String, expectedTrailer As String) As Boolean
Dim trailer As String
trailer = RightB$(fileData, LenB(expectedTrailer))
CheckFileTrailer = (trailer = expectedTrailer)
End Function

8. Extract Record Suffix

Function GetRecordSuffix(record As String) As String
' Fixed-length binary record with 4-byte suffix
GetRecordSuffix = RightB$(record, 4)
End Function

Function GetImageFooter(imageData As String) As String
' Some image formats have trailers (e.g., JPEG end marker)
GetImageFooter = RightB$(imageData, 2)
End Function

10. Database Record Alignment

Function AlignRecordEnd(record As String, alignment As Integer) As String
' Get aligned portion from end of record
Dim alignedSize As Integer
alignedSize = (LenB(record) \ alignment) * alignment
If alignedSize > 0 Then
AlignRecordEnd = RightB$(record, alignedSize)
Else
AlignRecordEnd = record
End If
End Function

Right$() - Returns a specified number of characters from the right (character-based)
LeftB$() - Returns a specified number of bytes from the left side of a string
MidB$() - Returns a specified number of bytes from any position in a string
LenB() - Returns the number of bytes used to represent a string in memory
RightB() - Variant version that can return Null
InStrB() - Finds the byte position of a substring
AscB() - Returns the byte value of the first byte in a string
ChrB$() - Returns a string containing a single-byte character

Best Practices

When to Use `RightB$` vs `Right$`

' Use Right$ for text/character operations
Dim fileExt As String
fileExt = Right$(fileName, 3)  ' Get last 3 characters

' Use RightB$ for binary data operations
Dim checksum As String
checksum = RightB$(binaryData, 4)  ' Get last 4 bytes

Validate Byte Count

Function SafeRightB(data As String, numBytes As Integer) As String
If numBytes < 0 Then
SafeRightB = ""
ElseIf numBytes >= LenB(data) Then
SafeRightB = data
Else
SafeRightB = RightB$(data, numBytes)
End If
End Function

Use with `LenB` for Byte Counting

' Always use LenB when working with RightB$
Dim totalBytes As Long
Dim footer As String
totalBytes = LenB(binaryData)
footer = RightB$(binaryData, 8)

Combine with `AscB` for Byte Values

Function GetLastByte(data As String) As Byte
Dim lastByte As String
lastByte = RightB$(data, 1)
GetLastByte = AscB(lastByte)
End Function

Binary Structure Parsing

' Extract multiple fields from end of structure
Dim checksum As String
Dim version As String
checksum = RightB$(structData, 4)
version = RightB$(LeftB$(structData, LenB(structData) - 4), 2)

Performance Considerations

RightB$ is efficient for binary data operations
Slightly faster than Right$ for byte-aligned operations
Avoid using in tight loops with string concatenation
Consider byte arrays for large binary data processing

' Less efficient: multiple RightB$ calls
For i = 1 To 1000
result = result & RightB$(data, 4)
Next i

' More efficient: single operation or byte array
Dim parts() As String
ReDim parts(1 To 1000)
For i = 1 To 1000
parts(i) = RightB$(data, 4)
Next i
result = Join(parts, "")

Character Encoding and VB6

Unicode String Storage

VB6 stores strings internally as Unicode (UCS-2):

Dim text As String
text = "AB"
Debug.Print Len(text)   ' Prints 2 (characters)
Debug.Print LenB(text)  ' Prints 4 (bytes: 2 bytes per character)

Dim lastChar As String
lastChar = Right$(text, 1)   ' Returns "B" (1 character)
Dim lastTwoBytes As String
lastTwoBytes = RightB$(text, 2)  ' Returns "B" (last 2 bytes = 1 character)

DBCS Considerations

When working with Double-Byte Character Sets:

' Be careful with DBCS text - extracting odd number of bytes
' can split multi-byte characters
Dim japaneseText As String
japaneseText = "こんにちは"

' Right$ extracts by characters (safe)
Dim lastChar As String
lastChar = Right$(japaneseText, 1)  ' Gets last character properly

' RightB$ extracts by bytes (may split characters)
Dim lastByte As String
lastByte = RightB$(japaneseText, 1)  ' May get incomplete character!

Common Pitfalls

1. Confusing Bytes with Characters

Dim text As String
text = "Hello"

' Wrong: thinking RightB$ works like Right$
result = RightB$(text, 3)  ' Gets last 3 BYTES (not characters)
' With Unicode, 3 bytes = 1.5 characters (1 complete + half of another)

' Correct: use Right$ for character operations
result = Right$(text, 3)  ' Gets "llo"

2. Odd Byte Counts with Unicode

' Problematic: odd number of bytes splits Unicode characters
Dim text As String
text = "Test"
Dim partial As String
partial = RightB$(text, 3)  ' 3 bytes = 1 character + half a character
' Result may be unexpected or corrupted

' Better: use even byte counts for Unicode
Dim proper As String
proper = RightB$(text, 4)  ' 4 bytes = 2 complete characters

3. Not Using `LenB` for Length

' Wrong: using Len instead of LenB
If RightB$(data, Len(data) - 4) Then  ' Incorrect!

' Correct: use LenB for byte operations
If RightB$(data, LenB(data) - 4) Then

4. Negative Length Values

' Runtime error: Invalid procedure call or argument
result = RightB$("Hello", -1)  ' ERROR!

' Validate first
If numBytes >= 0 Then
result = RightB$(data, numBytes)
End If

5. Assuming ASCII/ANSI Encoding

' Wrong: assuming 1 byte = 1 character
Dim data As String
data = "ABCD"
Dim lastByte As String
lastByte = RightB$(data, 1)  ' Gets 1 byte, not last character
' In Unicode, this is half of the last character

' Correct: use Right$ or account for 2 bytes per character
Dim lastChar As String
lastChar = Right$(data, 1)   ' Gets "D"
' OR
lastChar = RightB$(data, 2)  ' Gets last 2 bytes = "D"

Limitations

Cannot handle Null values (use RightB variant function instead)
Works with bytes, not characters (can split multi-byte characters)
Negative length values cause runtime errors
Limited usefulness for Unicode text (use Right$ instead)
No built-in validation for character boundaries
Extracting odd byte counts from Unicode strings can produce invalid characters
Less intuitive than Right$ for general string processing

VB6Parse / Library / String / rightb_dollar

`RightB$` Function

Syntax

Parameters

Return Value

Behavior and Characteristics

Byte vs. Character Operation

Length Handling

Character Set Considerations

Common Usage Patterns

1. Extract Binary Data Suffix

2. Read File Trailer

3. Extract Protocol Footer

4. Process Binary Structures

5. Network Packet Checksum

6. GUID/UUID Component Extraction

7. File Format Magic Bytes (Trailer)

8. Extract Record Suffix

9. Image Data Footer

10. Database Record Alignment

Best Practices

When to Use `RightB$` vs `Right$`

Validate Byte Count

Use with `LenB` for Byte Counting

Combine with `AscB` for Byte Values

Binary Structure Parsing

Performance Considerations

Character Encoding and VB6

Unicode String Storage

DBCS Considerations

Common Pitfalls

1. Confusing Bytes with Characters

2. Odd Byte Counts with Unicode

3. Not Using `LenB` for Length

4. Negative Length Values

5. Assuming ASCII/ANSI Encoding

Limitations

RightB$ Function

Syntax

Parameters

Return Value

Behavior and Characteristics

Byte vs. Character Operation

Length Handling

Character Set Considerations

Common Usage Patterns

1. Extract Binary Data Suffix

2. Read File Trailer

3. Extract Protocol Footer

4. Process Binary Structures

5. Network Packet Checksum

6. GUID/UUID Component Extraction

7. File Format Magic Bytes (Trailer)

8. Extract Record Suffix

9. Image Data Footer

10. Database Record Alignment

Related Functions

Best Practices

When to Use RightB$ vs Right$

Validate Byte Count

Use with LenB for Byte Counting

Combine with AscB for Byte Values

Binary Structure Parsing

Performance Considerations

Character Encoding and VB6

Unicode String Storage

DBCS Considerations

Common Pitfalls

1. Confusing Bytes with Characters

2. Odd Byte Counts with Unicode

3. Not Using LenB for Length

4. Negative Length Values

5. Assuming ASCII/ANSI Encoding

Limitations

`RightB$` Function

When to Use `RightB$` vs `Right$`

Use with `LenB` for Byte Counting

Combine with `AscB` for Byte Values

3. Not Using `LenB` for Length