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Base256 to int

TiborKi
TiborKi asked
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Medium Priority
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Last Modified: 2008-02-01
Does anybody know how to convert a string (base 256 number) to integer?
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Top Expert 2007
Commented:

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Top Expert 2014

Commented:
How big is the string?
The ciuly link is probably the easiest solution.

Author

Commented:
the string is 4 bytes
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Top Expert 2014

Commented:
The only problem you are likely to encounter is signed versus unsigned integer values.  If the high-order bit of the high-order byte = 1 then a signed integer will be negative.

Is this a performance critical function or do you simply need to know how it can be done?

Author

Commented:
well, it must be fast...
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Top Expert 2014
Commented:
"fast" is relative.  The best course of action will be to try the ciuly linked solution and determine if it suits your needs as far as functionality and speed.  If it doesn't, then ask us for more help.

===================================
For future readers, there are several approaches available to do this conversion.
* character->ord add and shiftLeft 8 (three statement pairs followed by simple add)
* similar to above, but using For iteration construct
* Delphi Copy function or API call to copy bytes directly into integer variable.  May require additional ntohl API call to reverse the byte order to accomodate Little-endian Windows environment.  This solution can get really tricky, depending on the nature of the 'string variable'.  Due to complexity, this should be solution approach of last resort.
* ASM solution (see the FastCode project)
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