Most common C bitwise operations on enums

Question

For the life of me  I can t remember how to set  delete  toggle or test a bit in a bitfield  Either I m unsure or I mix them up because I rarely need these  So a  bit-cheat-sheet  would be nice to have   For example    flags   flags   FlagsEnum Bit4      Set bit 4    or  if   flags  amp  FlagsEnum Bit4      FlagsEnum Bit4     Is there a less verbose way    Can you give examples of all the other common operations  preferably in C  syntax using a  Flags  enum

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C   operations are   amp         for and  or  xor and not bitwise operations   Also of interest are    and  lt  lt   which are bitshift operations   So  to test for a bit being set in a flag  you would use      if  flags  amp  8    tests bit 4 has been set

User · Answer

C   operations are   amp         for and  or  xor and not bitwise operations   Also of interest are    and  lt  lt   which are bitshift operations   So  to test for a bit being set in a flag  you would use      if  flags  amp  8    tests bit 4 has been set

User · Answer

C   syntax  assuming bit 0 is LSB  assuming flags is unsigned long   Check if Set   flags  amp   1UL  lt  lt   bit to test  - 1     Check if not set   invert test   flag  amp           Set   flag     1UL  lt  lt   bit to set  - 1     Clear   flag  amp     1UL  lt  lt   bit to clear  - 1     Toggle   flag     1UL  lt  lt   bit to set  - 1

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The idiom is to use the bitwise or-equal operator to set bits   flags    0x04    To clear a bit  the idiom is to use bitwise and with negation   flags  amp    0x04    Sometimes you have an offset that identifies your bit  and then the idiom is to use these combined with left-shift   flags    1  lt  lt  offset  flags  amp     1  lt  lt  offset

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To test a bit you would do the following   assuming flags is a 32 bit number   Test Bit    if  flags  amp  0x08     0x08   If bit 4 is set then its true  Toggle Back  1 - 0 or 0 - 1   flags   flags   0x08  Reset Bit 4 to Zero  flags   flags  amp  0xFFFFFF7F

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For the best performance and zero garbage  use this   using System  using T   MyNamespace MyFlags   namespace MyNamespace        Flags      public enum MyFlags               None   0          Flag1   1          Flag2   2            static class MyFlagsEx               public static bool Has this T type  T value                        return  type  amp  value     value                     public static bool Is this T type  T value                        return type    value                     public static T Add this T type  T value                        return type   value                     public static T Remove this T type  T value                        return type  amp   value

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C   syntax  assuming bit 0 is LSB  assuming flags is unsigned long   Check if Set   flags  amp   1UL  lt  lt   bit to test  - 1     Check if not set   invert test   flag  amp           Set   flag     1UL  lt  lt   bit to set  - 1     Clear   flag  amp     1UL  lt  lt   bit to clear  - 1     Toggle   flag     1UL  lt  lt   bit to set  - 1

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This was inspired by using Sets as indexers in Delphi  way back when       Example of using a Boolean indexed property     to manipulate a  Flags  enum   public class BindingFlagsIndexer     BindingFlags flags   BindingFlags Default     public BindingFlagsIndexer              public BindingFlagsIndexer  BindingFlags value            this flags   value         public bool this BindingFlags index          get             return  this flags  amp  index     index            set  bool value               if  value           this flags    index        else         this flags  amp    index               public BindingFlags Value          get              return flags             set  BindingFlags value                this flags   value               public static implicit operator BindingFlags  BindingFlagsIndexer src            return src    null   src Value   BindingFlags Default         public static implicit operator BindingFlagsIndexer  BindingFlags src            return new BindingFlagsIndexer  src            public static class Class1     public static void Example           BindingFlagsIndexer myFlags   new BindingFlagsIndexer            Sets the flag s  passed as the indexer       myFlags BindingFlags ExactBinding    true          Indexer can specify multiple flags at once       myFlags BindingFlags Instance   BindingFlags Static    true          Get boolean indicating if specified flag s  are set       bool flatten   myFlags BindingFlags FlattenHierarchy           use   to test if multiple flags are set       bool isProtected     myFlags BindingFlags Public   BindingFlags NonPublic

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This was inspired by using Sets as indexers in Delphi  way back when       Example of using a Boolean indexed property     to manipulate a  Flags  enum   public class BindingFlagsIndexer     BindingFlags flags   BindingFlags Default     public BindingFlagsIndexer              public BindingFlagsIndexer  BindingFlags value            this flags   value         public bool this BindingFlags index          get             return  this flags  amp  index     index            set  bool value               if  value           this flags    index        else         this flags  amp    index               public BindingFlags Value          get              return flags             set  BindingFlags value                this flags   value               public static implicit operator BindingFlags  BindingFlagsIndexer src            return src    null   src Value   BindingFlags Default         public static implicit operator BindingFlagsIndexer  BindingFlags src            return new BindingFlagsIndexer  src            public static class Class1     public static void Example           BindingFlagsIndexer myFlags   new BindingFlagsIndexer            Sets the flag s  passed as the indexer       myFlags BindingFlags ExactBinding    true          Indexer can specify multiple flags at once       myFlags BindingFlags Instance   BindingFlags Static    true          Get boolean indicating if specified flag s  are set       bool flatten   myFlags BindingFlags FlattenHierarchy           use   to test if multiple flags are set       bool isProtected     myFlags BindingFlags Public   BindingFlags NonPublic

User · Answer

C   syntax  assuming bit 0 is LSB  assuming flags is unsigned long   Check if Set   flags  amp   1UL  lt  lt   bit to test  - 1     Check if not set   invert test   flag  amp           Set   flag     1UL  lt  lt   bit to set  - 1     Clear   flag  amp     1UL  lt  lt   bit to clear  - 1     Toggle   flag     1UL  lt  lt   bit to set  - 1

User · Answer

C   operations are   amp         for and  or  xor and not bitwise operations   Also of interest are    and  lt  lt   which are bitshift operations   So  to test for a bit being set in a flag  you would use      if  flags  amp  8    tests bit 4 has been set

User · Answer

In  NET 4 you can now write   flags HasFlag FlagsEnum Bit4

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I did some more work on these extensions - You can find the code here  I wrote some extension methods that extend System Enum that I use often    I m not claiming that they are bulletproof  but they have helped    Comments removed     namespace Enum Extensions        public static class EnumerationExtensions            public static bool Has lt T gt  this System Enum type  T value                try                   return    int  object type  amp   int  object value      int  object value                              catch                   return false                                   public static bool Is lt T gt  this System Enum type  T value                try                   return  int  object type     int  object value                            catch                   return false                                        public static T Add lt T gt  this System Enum type  T value                try                   return  T  object    int  object type    int  object value                              catch Exception ex                    throw new ArgumentException                      string Format                           Could not append value from enumerated type   0                              typeof T  Name                            ex                                         public static T Remove lt T gt  this System Enum type  T value                try                   return  T  object    int  object type  amp    int  object value                              catch  Exception ex                    throw new ArgumentException                      string Format                           Could not remove value from enumerated type   0                              typeof T  Name                            ex                                        Then they are used like the following  SomeType value   SomeType Grapes  bool isGrapes   value Is SomeType Grapes     true bool hasGrapes   value Has SomeType Grapes     true  value   value Add SomeType Oranges   value   value Add SomeType Apples   value   value Remove SomeType Grapes    bool hasOranges   value Has SomeType Oranges     true bool isApples   value Is SomeType Apples     false bool hasGrapes   value Has SomeType Grapes     false

User · Answer

The idiom is to use the bitwise or-equal operator to set bits   flags    0x04    To clear a bit  the idiom is to use bitwise and with negation   flags  amp    0x04    Sometimes you have an offset that identifies your bit  and then the idiom is to use these combined with left-shift   flags    1  lt  lt  offset  flags  amp     1  lt  lt  offset

User · Answer

The idiom is to use the bitwise or-equal operator to set bits   flags    0x04    To clear a bit  the idiom is to use bitwise and with negation   flags  amp    0x04    Sometimes you have an offset that identifies your bit  and then the idiom is to use these combined with left-shift   flags    1  lt  lt  offset  flags  amp     1  lt  lt  offset

User · Answer

To test a bit you would do the following   assuming flags is a 32 bit number   Test Bit    if  flags  amp  0x08     0x08   If bit 4 is set then its true  Toggle Back  1 - 0 or 0 - 1   flags   flags   0x08  Reset Bit 4 to Zero  flags   flags  amp  0xFFFFFF7F

User · Answer

C   operations are   amp         for and  or  xor and not bitwise operations   Also of interest are    and  lt  lt   which are bitshift operations   So  to test for a bit being set in a flag  you would use      if  flags  amp  8    tests bit 4 has been set

User · Answer

To test a bit you would do the following   assuming flags is a 32 bit number   Test Bit    if  flags  amp  0x08     0x08   If bit 4 is set then its true  Toggle Back  1 - 0 or 0 - 1   flags   flags   0x08  Reset Bit 4 to Zero  flags   flags  amp  0xFFFFFF7F

User · Answer

NET s built-in flag enum operations are unfortunately quite limited  Most of the time users are left with figuring out the bitwise operation logic   In  NET 4  the method HasFlag was added to Enum which helps simplify user s code but unfortunately there are many problems with it    HasFlag is not type-safe as it accepts any type of enum value argument  not just the given enum type  HasFlag is ambiguous as to whether it checks if the value has all or any of the flags provided by the enum value argument  It s all by the way  HasFlag is rather slow as it requires boxing which causes allocations and thus more garbage collections    Due in part to  NET s limited support for flag enums I wrote the OSS library Enums NET which addresses each of these issues and makes dealing with flag enums much easier   Below are some of the operations it provides along with their equivalent implementations using just the  NET framework   Combine Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags   otherFlags  Enums NET flags CombineFlags otherFlags     Remove Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags  amp   otherFlags  Enums NET flags RemoveFlags otherFlags     Common Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags  amp  otherFlags  Enums NET flags CommonFlags otherFlags     Toggle Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags   otherFlags  Enums NET flags ToggleFlags otherFlags     Has All Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  flags  amp  otherFlags     otherFlags or flags HasFlag otherFlags   Enums NET flags HasAllFlags otherFlags     Has Any Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  flags  amp  otherFlags     0  Enums NET flags HasAnyFlags otherFlags     Get Flags   NET  Enumerable Range 0  64     Where bit   gt    flags GetTypeCode      TypeCode UInt64    long  ulong flags   Convert ToInt64 flags    amp   1L  lt  lt  bit      0     Select bit   gt  Enum ToObject flags GetType    1L  lt  lt  bit      Enums NET flags GetFlags      I m trying to get these improvements incorporated into  NET Core and maybe eventually the full  NET Framework  You can check out my proposal here

User · Answer

Drew  Note that except in the simplest of cases  the Enum HasFlag carries a heavy performance penalty in comparison to writing out the code manually  Consider the following code    Flags  public enum TestFlags       One   1      Two   2      Three   4      Four   8      Five   16      Six   32      Seven   64      Eight   128      Nine   256      Ten   512     class Program       static void Main string   args                TestFlags f   TestFlags Five     or any other enum            bool result   false           Stopwatch s   Stopwatch StartNew            for  int i   0  i  lt  10000000  i                          result    f HasFlag TestFlags Three                     s Stop            Console WriteLine s ElapsedMilliseconds       4793 ms           s Restart            for  int i   0  i  lt  10000000  i                          result     f  amp  TestFlags Three     0                    s Stop            Console WriteLine s ElapsedMilliseconds       27 ms                   Console ReadLine              Over 10 million iterations  the HasFlags extension method takes a whopping 4793 ms  compared to the 27 ms for the standard bitwise implementation

User · Answer

I did some more work on these extensions - You can find the code here  I wrote some extension methods that extend System Enum that I use often    I m not claiming that they are bulletproof  but they have helped    Comments removed     namespace Enum Extensions        public static class EnumerationExtensions            public static bool Has lt T gt  this System Enum type  T value                try                   return    int  object type  amp   int  object value      int  object value                              catch                   return false                                   public static bool Is lt T gt  this System Enum type  T value                try                   return  int  object type     int  object value                            catch                   return false                                        public static T Add lt T gt  this System Enum type  T value                try                   return  T  object    int  object type    int  object value                              catch Exception ex                    throw new ArgumentException                      string Format                           Could not append value from enumerated type   0                              typeof T  Name                            ex                                         public static T Remove lt T gt  this System Enum type  T value                try                   return  T  object    int  object type  amp    int  object value                              catch  Exception ex                    throw new ArgumentException                      string Format                           Could not remove value from enumerated type   0                              typeof T  Name                            ex                                        Then they are used like the following  SomeType value   SomeType Grapes  bool isGrapes   value Is SomeType Grapes     true bool hasGrapes   value Has SomeType Grapes     true  value   value Add SomeType Oranges   value   value Add SomeType Apples   value   value Remove SomeType Grapes    bool hasOranges   value Has SomeType Oranges     true bool isApples   value Is SomeType Apples     false bool hasGrapes   value Has SomeType Grapes     false

User · Answer

Drew  Note that except in the simplest of cases  the Enum HasFlag carries a heavy performance penalty in comparison to writing out the code manually  Consider the following code    Flags  public enum TestFlags       One   1      Two   2      Three   4      Four   8      Five   16      Six   32      Seven   64      Eight   128      Nine   256      Ten   512     class Program       static void Main string   args                TestFlags f   TestFlags Five     or any other enum            bool result   false           Stopwatch s   Stopwatch StartNew            for  int i   0  i  lt  10000000  i                          result    f HasFlag TestFlags Three                     s Stop            Console WriteLine s ElapsedMilliseconds       4793 ms           s Restart            for  int i   0  i  lt  10000000  i                          result     f  amp  TestFlags Three     0                    s Stop            Console WriteLine s ElapsedMilliseconds       27 ms                   Console ReadLine              Over 10 million iterations  the HasFlags extension method takes a whopping 4793 ms  compared to the 27 ms for the standard bitwise implementation

User · Answer

In  NET 4 you can now write   flags HasFlag FlagsEnum Bit4

User · Answer

For the best performance and zero garbage  use this   using System  using T   MyNamespace MyFlags   namespace MyNamespace        Flags      public enum MyFlags               None   0          Flag1   1          Flag2   2            static class MyFlagsEx               public static bool Has this T type  T value                        return  type  amp  value     value                     public static bool Is this T type  T value                        return type    value                     public static T Add this T type  T value                        return type   value                     public static T Remove this T type  T value                        return type  amp   value

User · Answer

The idiom is to use the bitwise or-equal operator to set bits   flags    0x04    To clear a bit  the idiom is to use bitwise and with negation   flags  amp    0x04    Sometimes you have an offset that identifies your bit  and then the idiom is to use these combined with left-shift   flags    1  lt  lt  offset  flags  amp     1  lt  lt  offset

User · Answer

C   syntax  assuming bit 0 is LSB  assuming flags is unsigned long   Check if Set   flags  amp   1UL  lt  lt   bit to test  - 1     Check if not set   invert test   flag  amp           Set   flag     1UL  lt  lt   bit to set  - 1     Clear   flag  amp     1UL  lt  lt   bit to clear  - 1     Toggle   flag     1UL  lt  lt   bit to set  - 1

User · Answer

To test a bit you would do the following   assuming flags is a 32 bit number   Test Bit    if  flags  amp  0x08     0x08   If bit 4 is set then its true  Toggle Back  1 - 0 or 0 - 1   flags   flags   0x08  Reset Bit 4 to Zero  flags   flags  amp  0xFFFFFF7F

User · Answer

NET s built-in flag enum operations are unfortunately quite limited  Most of the time users are left with figuring out the bitwise operation logic   In  NET 4  the method HasFlag was added to Enum which helps simplify user s code but unfortunately there are many problems with it    HasFlag is not type-safe as it accepts any type of enum value argument  not just the given enum type  HasFlag is ambiguous as to whether it checks if the value has all or any of the flags provided by the enum value argument  It s all by the way  HasFlag is rather slow as it requires boxing which causes allocations and thus more garbage collections    Due in part to  NET s limited support for flag enums I wrote the OSS library Enums NET which addresses each of these issues and makes dealing with flag enums much easier   Below are some of the operations it provides along with their equivalent implementations using just the  NET framework   Combine Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags   otherFlags  Enums NET flags CombineFlags otherFlags     Remove Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags  amp   otherFlags  Enums NET flags RemoveFlags otherFlags     Common Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags  amp  otherFlags  Enums NET flags CommonFlags otherFlags     Toggle Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp flags   otherFlags  Enums NET flags ToggleFlags otherFlags     Has All Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  flags  amp  otherFlags     otherFlags or flags HasFlag otherFlags   Enums NET flags HasAllFlags otherFlags     Has Any Flags   NET  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  flags  amp  otherFlags     0  Enums NET flags HasAnyFlags otherFlags     Get Flags   NET  Enumerable Range 0  64     Where bit   gt    flags GetTypeCode      TypeCode UInt64    long  ulong flags   Convert ToInt64 flags    amp   1L  lt  lt  bit      0     Select bit   gt  Enum ToObject flags GetType    1L  lt  lt  bit      Enums NET flags GetFlags      I m trying to get these improvements incorporated into  NET Core and maybe eventually the full  NET Framework  You can check out my proposal here

User · Answer

I did some more work on these extensions - You can find the code here  I wrote some extension methods that extend System Enum that I use often    I m not claiming that they are bulletproof  but they have helped    Comments removed     namespace Enum Extensions        public static class EnumerationExtensions            public static bool Has lt T gt  this System Enum type  T value                try                   return    int  object type  amp   int  object value      int  object value                              catch                   return false                                   public static bool Is lt T gt  this System Enum type  T value                try                   return  int  object type     int  object value                            catch                   return false                                        public static T Add lt T gt  this System Enum type  T value                try                   return  T  object    int  object type    int  object value                              catch Exception ex                    throw new ArgumentException                      string Format                           Could not append value from enumerated type   0                              typeof T  Name                            ex                                         public static T Remove lt T gt  this System Enum type  T value                try                   return  T  object    int  object type  amp    int  object value                              catch  Exception ex                    throw new ArgumentException                      string Format                           Could not remove value from enumerated type   0                              typeof T  Name                            ex                                        Then they are used like the following  SomeType value   SomeType Grapes  bool isGrapes   value Is SomeType Grapes     true bool hasGrapes   value Has SomeType Grapes     true  value   value Add SomeType Oranges   value   value Add SomeType Apples   value   value Remove SomeType Grapes    bool hasOranges   value Has SomeType Oranges     true bool isApples   value Is SomeType Apples     false bool hasGrapes   value Has SomeType Grapes     false

User · Answer

I did some more work on these extensions - You can find the code here  I wrote some extension methods that extend System Enum that I use often    I m not claiming that they are bulletproof  but they have helped    Comments removed     namespace Enum Extensions        public static class EnumerationExtensions            public static bool Has lt T gt  this System Enum type  T value                try                   return    int  object type  amp   int  object value      int  object value                              catch                   return false                                   public static bool Is lt T gt  this System Enum type  T value                try                   return  int  object type     int  object value                            catch                   return false                                        public static T Add lt T gt  this System Enum type  T value                try                   return  T  object    int  object type    int  object value                              catch Exception ex                    throw new ArgumentException                      string Format                           Could not append value from enumerated type   0                              typeof T  Name                            ex                                         public static T Remove lt T gt  this System Enum type  T value                try                   return  T  object    int  object type  amp    int  object value                              catch  Exception ex                    throw new ArgumentException                      string Format                           Could not remove value from enumerated type   0                              typeof T  Name                            ex                                        Then they are used like the following  SomeType value   SomeType Grapes  bool isGrapes   value Is SomeType Grapes     true bool hasGrapes   value Has SomeType Grapes     true  value   value Add SomeType Oranges   value   value Add SomeType Apples   value   value Remove SomeType Grapes    bool hasOranges   value Has SomeType Oranges     true bool isApples   value Is SomeType Apples     false bool hasGrapes   value Has SomeType Grapes     false

[c#] Most common C# bitwise operations on enums

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