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handling_20unsigned_2032-bit_20values

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handling_20unsigned_2032-bit_20values [2018/03/31 13:19] 127.0.0.1 external edit |
handling_20unsigned_2032-bit_20values [2018/04/17 16:31] (current) tbest3112 Added syntax highlighting |
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//by Richard Russell, October 2006//\\ \\ BBC BASIC's 32-bit integers are all signed, i.e. they represent values between -2147483648 (&80000000) and +2147483647 (&7FFFFFFF); values outside this range can only be represented by floating-point numbers. Occasionally you may want to treat a 32-bit integer as if it was unsigned, i.e. representing a value between zero (&00000000) and +4294967295 (&FFFFFFFF), for example this could be necessary when interpreting a UINT value returned from a Windows API function.\\ \\ The function listed below performs the necessary conversion. It takes as a parameter a normal 32-bit integer and returns the equivalent unsigned value:\\ | //by Richard Russell, October 2006//\\ \\ BBC BASIC's 32-bit integers are all signed, i.e. they represent values between -2147483648 (&80000000) and +2147483647 (&7FFFFFFF); values outside this range can only be represented by floating-point numbers. Occasionally you may want to treat a 32-bit integer as if it was unsigned, i.e. representing a value between zero (&00000000) and +4294967295 (&FFFFFFFF), for example this could be necessary when interpreting a UINT value returned from a Windows API function.\\ \\ The function listed below performs the necessary conversion. It takes as a parameter a normal 32-bit integer and returns the equivalent unsigned value:\\ | ||

+ | <code bb4w> | ||

DEF FNuint(N%) = (N% >>> 1)*2 + (N% AND 1) | DEF FNuint(N%) = (N% >>> 1)*2 + (N% AND 1) | ||

+ | </code> | ||

This function is equivalent, but it is slightly slower and somewhat bigger than the previous one:\\ | This function is equivalent, but it is slightly slower and somewhat bigger than the previous one:\\ | ||

+ | <code bb4w> | ||

DEF FNuint(N%) = (N% AND &7FFFFFFF) - (N% < 0)*2147483648 | DEF FNuint(N%) = (N% AND &7FFFFFFF) - (N% < 0)*2147483648 | ||

+ | </code> | ||

\\ The function below performs the reverse conversion, that is it takes an unsigned value (0 <= N < 2^32) and converts it to the equivalent 32-bit integer:\\ | \\ The function below performs the reverse conversion, that is it takes an unsigned value (0 <= N < 2^32) and converts it to the equivalent 32-bit integer:\\ | ||

+ | <code bb4w> | ||

DEF FNintu(N) = ((N / 2) << 1) - (INT(N / 2) <> N / 2) | DEF FNintu(N) = ((N / 2) << 1) - (INT(N / 2) <> N / 2) | ||

+ | </code> | ||

Alternatively:\\ | Alternatively:\\ | ||

+ | <code bb4w> | ||

DEF FNintu(N) IF N > &7FFFFFFF THEN = N - 2^32 ELSE = N | DEF FNintu(N) IF N > &7FFFFFFF THEN = N - 2^32 ELSE = N | ||

+ | </code> |

handling_20unsigned_2032-bit_20values.txt ยท Last modified: 2018/04/17 16:31 by tbest3112

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