Difference between revisions of "Bitwise Operations"
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| − | Bitwise operations are used to perform an action on the bits (the 1's and 0's) of a number | + | Bitwise operations are used to perform an action on the bits (the 1's and 0's) of a number. |
In this article a "binary" formatted number (which represents the "bits" of a number) will be written with a <sup>2</sup>... and a decimal number with a <sup>10</sup> | In this article a "binary" formatted number (which represents the "bits" of a number) will be written with a <sup>2</sup>... and a decimal number with a <sup>10</sup> | ||
| + | ==Limitations== | ||
| + | |||
| + | In Sphere, numbers are stored in something called a "DWORD". The largest number a DWORD can store is constrained by the fact that a DWORD is 32 bits wide. That means the largest number it can store is 2^32-1. | ||
| + | |||
| + | * In Binary that's 11111111111111111111111111111111. | ||
| + | * In Hex it's FFFFFFFF. | ||
| + | * In Decimal that's 4294967295. | ||
| + | |||
| + | To store a 'signed' number in a DWORD (in other words, a number that can be positive or negative), the first bit is used to indicate the sign (a 1 is negative). Which means the largest 'signed' positive number is 2^31-1 | ||
| + | |||
| + | * In Binary that's 01111111111111111111111111111111. | ||
| + | * In Hex it's 7FFFFFFF. | ||
| + | * In Decimal that's 2147483647. | ||
| + | |||
| + | In sphere script language, the EVAL function outputs a signed DWORD, and the UVAL outputs an unsigned DWORD. | ||
| + | |||
| + | [FUNCTION Mathtest] | ||
| + | LOCAL.Number0=2147483647 | ||
| + | LOCAL.Number1=4294967295 | ||
| + | LOCAL.Number2=8589934588 | ||
| + | SERV.LOG eval0=<EVAL <LOCAL.Number0>> eval1=<EVAL <LOCAL.Number1>> eval2=<EVAL <LOCAL.Number2>> | ||
| + | SERV.LOG uval0=<UVAL <LOCAL.Number0>> uval1=<UVAL <LOCAL.Number1>> uval2=<UVAL <LOCAL.Number2>> | ||
| + | |||
| + | The output of this test is: | ||
| + | |||
| + | 13:37:(test.scp,10)eval0=2147483647 eval1=-1 eval2=-4 | ||
| + | 13:37:(test.scp,11)uval0=2147483647 uval1=4294967295 uval2=4294967292 | ||
| + | |||
| + | Notes: | ||
| + | |||
| + | * The output is limited to align with the limitation of the DWORD itself. | ||
| + | * Since there are 32 "bits" in a DWORD, there can only be 32 flags in a set. | ||
| + | * Be careful when manipulating flags using EVAL, because the 32nd flag could get lost. | ||
| + | |||
| + | ==Flags== | ||
| + | |||
| + | In the Sphere server, quite a few concepts are implemented using "flags". You can see examples of flags being defined in the Sphere.ini file, or the sphere_defs.scp files. For example: | ||
| + | |||
| + | [DEFNAME attr_flags] | ||
| + | attr_identified 01 | ||
| + | attr_decay 02 | ||
| + | attr_newbie 04 | ||
| + | attr_move_always 08 | ||
| + | attr_move_never 010 | ||
| + | attr_magic 020 | ||
| + | attr_owned 040 | ||
| + | attr_invis 080 | ||
| + | attr_cursed 0100 | ||
| + | attr_cursed2 0200 | ||
| + | attr_blessed 0400 | ||
| + | attr_blessed2 0800 | ||
| + | attr_forsale 01000 | ||
| + | attr_stolen 02000 | ||
| + | attr_can_decay 04000 | ||
| + | attr_static 08000 | ||
| + | attr_exceptional 010000 | ||
| + | attr_enchanted 020000 | ||
| + | attr_imbued 040000 | ||
| + | attr_questitem 080000 | ||
| + | attr_insured 0100000 | ||
| + | attr_nodrop 0200000 | ||
| + | attr_notrade 0400000 | ||
| + | attr_lockeddown 0800000 | ||
| + | attr_secure 01000000 | ||
| + | |||
| + | Notice a pattern? Let's tip it on it's side and chart the first 8 flags: | ||
| + | |||
| + | {|border=1 cellpadding=5 | ||
| + | |- | ||
| + | |Flag Name: || attr_invis|| attr_owned|| attr_magic||attr_move_never||attr_move_always|| attr_newbie|| attr_decay||attr_identified | ||
| + | |- | ||
| + | |Binary Number: || 10000000|| 01000000|| 00100000|| 00010000|| 00001000|| 00000100|| 00000010|| 00000001 | ||
| + | |- | ||
| + | |Hex Number: || 080|| 040|| 020|| 010|| 08|| 04|| 02|| 01 | ||
| + | |- | ||
| + | |Decimal Number:|| 128|| 64|| 32|| 16|| 8|| 4|| 2|| 1 | ||
| + | |} | ||
| + | |||
| + | ==The OR Operator (inclusive OR)== | ||
| + | ==The AND Operator== | ||
| + | ==The XOR Operator (exclusive OR)== | ||
| + | ==The NOT Operator== | ||
| + | ==Left and right shift== | ||
| + | |||
| + | |||
| + | |||
| + | |||
| + | <!-- | ||
==Converting from decimal to binary and from binary to decimal== | ==Converting from decimal to binary and from binary to decimal== | ||
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# Therefore, the negative binary number 1111111111010011<sup>2</sup> is equal to the decimal number -45<sup>10</sup> | # Therefore, the negative binary number 1111111111010011<sup>2</sup> is equal to the decimal number -45<sup>10</sup> | ||
| − | + | --> | |
| − | |||
| − | |||
| − | |||
| − | |||
Revision as of 22:46, 28 November 2013
Bitwise operations are used to perform an action on the bits (the 1's and 0's) of a number.
In this article a "binary" formatted number (which represents the "bits" of a number) will be written with a 2... and a decimal number with a 10
Contents
Limitations
In Sphere, numbers are stored in something called a "DWORD". The largest number a DWORD can store is constrained by the fact that a DWORD is 32 bits wide. That means the largest number it can store is 2^32-1.
- In Binary that's 11111111111111111111111111111111.
- In Hex it's FFFFFFFF.
- In Decimal that's 4294967295.
To store a 'signed' number in a DWORD (in other words, a number that can be positive or negative), the first bit is used to indicate the sign (a 1 is negative). Which means the largest 'signed' positive number is 2^31-1
- In Binary that's 01111111111111111111111111111111.
- In Hex it's 7FFFFFFF.
- In Decimal that's 2147483647.
In sphere script language, the EVAL function outputs a signed DWORD, and the UVAL outputs an unsigned DWORD.
[FUNCTION Mathtest] LOCAL.Number0=2147483647 LOCAL.Number1=4294967295 LOCAL.Number2=8589934588 SERV.LOG eval0=<EVAL <LOCAL.Number0>> eval1=<EVAL <LOCAL.Number1>> eval2=<EVAL <LOCAL.Number2>> SERV.LOG uval0=<UVAL <LOCAL.Number0>> uval1=<UVAL <LOCAL.Number1>> uval2=<UVAL <LOCAL.Number2>>
The output of this test is:
13:37:(test.scp,10)eval0=2147483647 eval1=-1 eval2=-4 13:37:(test.scp,11)uval0=2147483647 uval1=4294967295 uval2=4294967292
Notes:
- The output is limited to align with the limitation of the DWORD itself.
- Since there are 32 "bits" in a DWORD, there can only be 32 flags in a set.
- Be careful when manipulating flags using EVAL, because the 32nd flag could get lost.
Flags
In the Sphere server, quite a few concepts are implemented using "flags". You can see examples of flags being defined in the Sphere.ini file, or the sphere_defs.scp files. For example:
[DEFNAME attr_flags] attr_identified 01 attr_decay 02 attr_newbie 04 attr_move_always 08 attr_move_never 010 attr_magic 020 attr_owned 040 attr_invis 080 attr_cursed 0100 attr_cursed2 0200 attr_blessed 0400 attr_blessed2 0800 attr_forsale 01000 attr_stolen 02000 attr_can_decay 04000 attr_static 08000 attr_exceptional 010000 attr_enchanted 020000 attr_imbued 040000 attr_questitem 080000 attr_insured 0100000 attr_nodrop 0200000 attr_notrade 0400000 attr_lockeddown 0800000 attr_secure 01000000
Notice a pattern? Let's tip it on it's side and chart the first 8 flags:
| Flag Name: | attr_invis | attr_owned | attr_magic | attr_move_never | attr_move_always | attr_newbie | attr_decay | attr_identified |
| Binary Number: | 10000000 | 01000000 | 00100000 | 00010000 | 00001000 | 00000100 | 00000010 | 00000001 |
| Hex Number: | 080 | 040 | 020 | 010 | 08 | 04 | 02 | 01 |
| Decimal Number: | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
