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