Attached are the C-routines that implement a BIT and BIT VARYING type.

Adriaan Joubert

contrib/bit/README

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+A set of C routines to implement an SQL-compliant bitstring type.
+
+The file varbit.c contains the c-functions to implement both BIT and
+BIT VARYING. Both types are implemented in essentially the same way,
+except that BIT is zero padded to a specified length. I've tried to
+make this code as independent as possible of the byte length, but it
+is quite possible that there may be problems on machines that don't
+have 8 bits/byte (are there still any around?).
+
+In the input routines I have assumed that the parser eats the quotes
+in B'...' or X'...'.
+
+The SQL standard only defines comparison, SUBSTR and concatenation
+operators, and these have been implemented. In addition all logical
+operators have been implemented, i.e. ~,|,&,^,<< and >>. This is
+useful if one wants to build bit masks. If the two strings are not of
+the same length the longer string is truncated (truncation was the
+only real option, as padding with zeros could give unintuitive results
+for ^) and the result has the length of the shorter string. If there
+is a requirement for any other functions, let me know, and I will have
+a look.
+
+My knowledge of postgres is not up to integrating a type, so I'm hoping
+that somebody can integrate this type for me, or give me some hints as
+to what needs to be done. These routines were developed outside the
+postgres source tree, with a hacked version of postgres.h. The header
+files probably need some ammending.
+
+The included files are 
+
+varbit.h       -- bit string header type
+varbit.c       -- the routines
+vartest.c      -- a few calls to the routines to 
+
+The following routines are available. 
+
+char * zpbitin(char *s, int dummy,  int32 atttypmod);
+	Read in a zero padded bit string of the form X'...' or B'...'
+    
+char * zpbitout(char *s);
+	Print a zero padded bit string in hex X'...'
+
+char * zpbitsout(char *s);
+	Print a zero padded bit string in binary B'...'
+
+char * varbitin(char *s, int dummy,  int32 atttypmod);
+	Read in a varying length bit string of the form X'...' or B'...'
+
+[There is no need for separate output functions for varying bit, as 
+ zpbitout will print them out correctly]
+
+char * bitcat (char *arg1, char *arg2);
+	Bit concatenation. 
+
+char * bitsubstr (char *arg, int32 s, int32 l);
+	Substring of a bit string.
+
+bool biteq (char *arg1, char *arg2);
+bool bitne (char *arg1, char *arg2);
+bool bitge (char *arg1, char *arg2);
+bool bitgt (char *arg1, char *arg2);
+bool bitle (char *arg1, char *arg2);
+bool bitlt (char *arg1, char *arg2);
+int bitcmp (char *arg1, char *arg2);
+	Comparison operators
+
+char * bitand (char * arg1, char * arg2);
+char * bitor (char * arg1, char * arg2);
+char * bitxor (char * arg1, char * arg2);
+char * bitnot (char * arg);
+char * bitshiftright (char * arg, int shft);
+char * bitshiftleft (char * arg, int shft);
+	Bit operations.
+
+If anything else needs to be done, please let me know.
+
+Adriaan (adriaan@albourne.com)