_ADLER32

From QB64 Phoenix Edition Wiki
Revision as of 22:39, 25 May 2024 by RhoSigma (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

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


Syntax

chksum~& = _ADLER32(dataString$)


Parameters

  • chksum~& is the _UNSIGNED LONG checksum returned (one (1), 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 Chapters 5-7 here.


Availability


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
Example by RhoSigma
Correct Text: QB64 Phoenix Edition
Adler-32 Sum: 41F806E5

Mangled Text: QB65 Phoenix Edition
Adler-32 Sum: 420906E6


See also



Navigation:
Main Page with Articles and Tutorials
Keyword Reference - Alphabetical
Keyword Reference - By usage
Report a broken link