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{{DISPLAYTITLE: _ADLER32}} | {{DISPLAYTITLE: _ADLER32}} | ||
The '''_ADLER32''' function returns the [[Wikipedia:Adler-32|Adler-32]] checksum of | The '''_ADLER32''' function returns the [[Wikipedia:Adler-32|Adler-32]] checksum of any arbitrary string. | ||
| Line 8: | Line 8: | ||
{{PageParameters}} | {{PageParameters}} | ||
* {{Parameter|chksum~&}} is the [[_UNSIGNED]][[LONG]] checksum returned (zero, if the given {{Parameter|dataString$}} was empty). | * {{Parameter|chksum~&}} is the [[_UNSIGNED]] [[LONG]] checksum returned (zero, if the given {{Parameter|dataString$}} was empty). | ||
* {{Parameter|dataString$}} is any literal or variable [[STRING]] to build the checksum from. | * {{Parameter|dataString$}} is any literal or variable [[STRING]] to build the checksum from. | ||
{{PageDescription}} | {{PageDescription}} | ||
* 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 [file:///C:/Users/Herzlich%20Willkommen/Downloads/337373-001us-intelqatdatacompressionintegritywhitepaper.pdf Chapter 5 here]. | |||
{{PageExamples}} | {{PageExamples}} | ||
;Example: | ;Example: Showing how the Adler-32 checksum can detect differences in two strings. | ||
{{CodeStart}} | {{CodeStart}} | ||
{{Text|<nowiki>'this is the correct text</nowiki>|#919191}} | |||
t$ = {{Text|<nowiki>"QB64 Phoenix Edition"</nowiki>|#FFB100}} | |||
{{Cl|PRINT}} {{Text|<nowiki>"Correct Text: "</nowiki>|#FFB100}}; t$ | |||
{{Cl|PRINT}} {{Text|<nowiki>"Adler-32 Sum: "</nowiki>|#FFB100}}; {{Cl|RIGHT$}}({{Text|<nowiki>"00000000"</nowiki>|#FFB100}} + {{Cl|HEX$}}({{Cl|_ADLER32}}(t$)), {{Text|8|#F580B1}}) | |||
{{Cl|PRINT}} | |||
{{Text|<nowiki>'this text differs in just 1 bit from the above, by changing 4 to 5</nowiki>|#919191}} | |||
{{Text|<nowiki>'ASC("4") = 52 = &B00110100</nowiki>|#919191}} | |||
{{Text|<nowiki>'ASC("5") = 53 = &B00110101</nowiki>|#919191}} | |||
t$ = {{Text|<nowiki>"QB65 Phoenix Edition"</nowiki>|#FFB100}} | |||
{{Cl|PRINT}} {{Text|<nowiki>"Mangled Text: "</nowiki>|#FFB100}}; t$ | |||
{{Cl|PRINT}} {{Text|<nowiki>"Adler-32 Sum: "</nowiki>|#FFB100}}; {{Cl|RIGHT$}}({{Text|<nowiki>"00000000"</nowiki>|#FFB100}} + {{Cl|HEX$}}({{Cl|_ADLER32}}(t$)), {{Text|8|#F580B1}}) | |||
{{Cl|END}} | |||
{{CodeEnd}} | {{CodeEnd}} | ||
{{OutputStart}} | {{OutputStart}} | ||
Correct Text: QB64 Phoenix Edition | |||
Adler-32 Sum: 41F806E5 | |||
Mangled Text: QB65 Phoenix Edition | |||
Adler-32 Sum: 420906E6 | |||
{{OutputEnd}} | {{OutputEnd}} | ||
Revision as of 19:40, 2 February 2024
The _ADLER32 function returns the Adler-32 checksum of any arbitrary string.
Syntax
- chksum~& = _ADLER32(dataString$)
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 [file:///C:/Users/Herzlich%20Willkommen/Downloads/337373-001us-intelqatdatacompressionintegritywhitepaper.pdf 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