Defining dword flags
June 13, 2002 04:24 PM
How do I create my own flag system for a certain struct?
I want to store a bunch of booleans in a single dword, but I don''t know how to define my own flags for that dword.
1,658
June 13, 2002 04:46 PM
Are you talking about bitfields ?
Which lets you pack a bunch of flags in a struct.
Or a set of binary constants;
Or a C++ bitset class (which covers most uses).
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struct foo_t{ bool a : 1; // 1 bit, treated as bool bool b : 1; // 1 bit, treated as bool unsigned int c : 1; // 1 bit, treated as unsigned int signed char d : 7; // 7 bits, treated as signed char signed long e : 10; // 10 bits, treated as unsigned long unsigned short f : 12; // 12 bits, treated as unsigned short}; // total 32 bits...foo_t foo = { true, false, 0, ''a'', -2, 1000 }; Which lets you pack a bunch of flags in a struct.
struct foo_t{ bool bit0 : 1; bool bit1 : 1; bool bit2 : 1; bool bit3 : 1; bool bit4 : 1; bool bit5 : 1; bool bit6 : 1; bool bit7 : 1;}; Or a set of binary constants;
const unsigned long BIT0 = 1 << 0;const unsigned long BIT1 = 1 << 1;const unsigned long BIT2 = 1 << 2;const unsigned long BIT3 = 1 << 3;const unsigned long BIT4 = 1 << 4;...unsigned long FOO = BIT0 | BIT4; Or a C++ bitset class (which covers most uses).
#include <bitset>typedef std::bitset<12> flag_t; // 12-bit bitsetflag_t foo1 = "110000110101";flag_t foo2 = 255;...if ( foo1[5] ) { foo2.flip( 4 ); foo2.reset( 2 ); foo1.set( 0 ); ...};if( foo1 == foo2 ) ...if( (foo1 & ~foo2).any() ) ... Documents [ GDNet | MSDN | STL | OpenGL | Formats | RTFM | Asking Smart Questions ]
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"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." — Brian W. Kernighan
June 13, 2002 06:35 PM
Umm... I mean like the .dwFlags member of structs like DDSURFACEDESC and DDBLITFX - they''re binary OR''ed together in a DWORD, and each flag represents a certain attribute.
Ex:
ddbltfx.dwFlags = DDBLT_COLORFILL;
How would I make my own set of flags for a certain struct to use? (If you''ve already shown me, forgive my blindness and point out which method would do this)
Ex:
ddbltfx.dwFlags = DDBLT_COLORFILL;
How would I make my own set of flags for a certain struct to use? (If you''ve already shown me, forgive my blindness and point out which method would do this)
1,658
June 13, 2002 06:40 PM
Ah...
You want the crude way...
*shakes his head with disgust*
Use the third code block.
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C++ Stuff [ MinGW | Loki | SDL | Boost. | STLport | FLTK | ACCU Recommended Books ]
You want the crude way...
*shakes his head with disgust*
Use the third code block.
Documents [ GDNet | MSDN | STL | OpenGL | Formats | RTFM | Asking Smart Questions ]
C++ Stuff [ MinGW | Loki | SDL | Boost. | STLport | FLTK | ACCU Recommended Books ]
"Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." — Brian W. Kernighan
122
June 13, 2002 06:45 PM
Define your flags as powers of 2
#define FLAG1 1 (0x00000001 in binary)
#define FLAG2 2 (0x00000010 in binary)
#define FLAG3 4 (0x00000100 in binary)
#define FLAG4 8 (0x00001000 in binary)
etc...
Notice the pattern, they each take their own bit
Now say you want certain flags, just OR those flags together to get the final value
Then if you want to check if a certain flag is set in a DWORD of ORed flags, just do say
DWORD Flags = FLAG1 | FLAG3
if(Flags & FLAG1) ..do stuff for flag1
hope that helps
ByteMe95::~ByteMe95()
My S(h)ite
#define FLAG1 1 (0x00000001 in binary)
#define FLAG2 2 (0x00000010 in binary)
#define FLAG3 4 (0x00000100 in binary)
#define FLAG4 8 (0x00001000 in binary)
etc...
Notice the pattern, they each take their own bit
Now say you want certain flags, just OR those flags together to get the final value
Then if you want to check if a certain flag is set in a DWORD of ORed flags, just do say
DWORD Flags = FLAG1 | FLAG3
if(Flags & FLAG1) ..do stuff for flag1
hope that helps
ByteMe95::~ByteMe95()
My S(h)ite
ByteMe95::~ByteMe95()My S(h)ite
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