ADLER32

The _ADLER32 function returns the Adler-32 checksum of any arbitrary string.

Syntax

chksum~& = _ADLER32(dataString$)

Parameters

• chksum~& is the _UNSIGNED LONG checksum returned (zero, if the given dataString$ was empty).
• dataString$ is any literal or variable STRING to build the checksum from.

Description

• The Adler-32 checksum uses a relative simple but very fast algorithm, it has the following known properties:
  • All single bit flips will be detected.
  • All double bit flips will be detected.
  • Burst errors up to seven bits are always detected.
• For more informations have a closer look at Chapter 5 here.

Examples

Example

Showing how the Adler-32 checksum can detect differences in two strings.

'this is the correct text t$ = "QB64 Phoenix Edition" PRINT "Correct Text: "; t$ PRINT "Adler-32 Sum: "; RIGHT$("00000000" + HEX$(_ADLER32(t$)), 8) PRINT 'this text differs in just 1 bit from the above, by changing 4 to 5 'ASC("4") = 52 = &B00110100 'ASC("5") = 53 = &B00110101 t$ = "QB65 Phoenix Edition" PRINT "Mangled Text: "; t$ PRINT "Adler-32 Sum: "; RIGHT$("00000000" + HEX$(_ADLER32(t$)), 8) END

Correct Text: QB64 Phoenix Edition Adler-32 Sum: 41F806E5 Mangled Text: QB65 Phoenix Edition Adler-32 Sum: 420906E6

See also

• _DEFLATE$, _INFLATE$
• _CRC32, _MD5$

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