From 73874a06f02691b32c07318e543d83e7947efa51 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Tue, 31 Oct 2000 10:22:13 +0000
Subject: Change the parser to convert SQL "position" and "substring" syntax to
 position() and substring() functions, so that it works transparently for bit
 types as well.  Alias the text functions appropriately.

Add position() for bit types.

Add new constant node T_BitString that represents literals of the form
B'1001 and pass those to zpbit type.
---
 src/backend/utils/adt/varbit.c | 102 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 99 insertions(+), 3 deletions(-)

(limited to 'src/backend/utils/adt/varbit.c')

diff --git a/src/backend/utils/adt/varbit.c b/src/backend/utils/adt/varbit.c
index 04717dbf17e..741ef3f924b 100644
--- a/src/backend/utils/adt/varbit.c
+++ b/src/backend/utils/adt/varbit.c
@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/varbit.c,v 1.9 2000/08/26 21:53:41 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/varbit.c,v 1.10 2000/10/31 10:22:11 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1053,8 +1053,8 @@ bitshiftright(PG_FUNCTION_ARGS)
 	/* Negative shift is a shift to the left */
 	if (shft < 0)
 		PG_RETURN_DATUM(DirectFunctionCall2(bitshiftleft,
-											VarBitPGetDatum(arg),
-											Int32GetDatum(-shft)));
+						    VarBitPGetDatum(arg),
+						    Int32GetDatum(-shft)));
 
 	result = (VarBit *) palloc(VARSIZE(arg));
 	VARATT_SIZEP(result) = VARSIZE(arg);
@@ -1146,3 +1146,99 @@ bittoint4(PG_FUNCTION_ARGS)
 
 	PG_RETURN_INT32(result);
 }
+
+
+
+/* Determines the position of S2 in the bitstring S1 (1-based string).
+ * If S2 does not appear in S1 this function returns 0.
+ * If S2 is of length 0 this function returns 1.
+ */
+Datum
+bitposition(PG_FUNCTION_ARGS)
+{
+	VarBit		*substr = PG_GETARG_VARBIT_P(1);
+	VarBit		*arg = PG_GETARG_VARBIT_P(0);
+	int			substr_length, 
+				arg_length,
+				i,
+				is;
+	bits8		*s,				/* pointer into substring */
+				*p;				/* pointer into arg */
+	bits8		cmp,			/* shifted substring byte to compare */ 
+				mask1,          /* mask for substring byte shifted right */
+				mask2,          /* mask for substring byte shifted left */
+				end_mask,       /* pad mask for last substring byte */
+				arg_mask;		/* pad mask for last argument byte */
+	bool		is_match;
+
+	/* Get the substring length */
+	substr_length = VARBITLEN(substr);
+	arg_length = VARBITLEN(arg);
+
+	/* Argument has 0 length or substring longer than argument, return 0 */
+	if (arg_length == 0 || substr_length > arg_length)
+		PG_RETURN_INT32(0);	
+	
+	/* 0-length means return 1 */
+	if (substr_length == 0)
+		PG_RETURN_INT32(1);
+
+	/* Initialise the padding masks */
+	end_mask = BITMASK << VARBITPAD(substr);
+	arg_mask = BITMASK << VARBITPAD(arg);
+	for (i = 0; i < VARBITBYTES(arg) - VARBITBYTES(substr) + 1; i++) 
+	{
+		for (is = 0; is < BITS_PER_BYTE; is++) {
+			is_match = true;
+			p = VARBITS(arg) + i;
+			mask1 = BITMASK >> is;
+			mask2 = ~mask1;
+			for (s = VARBITS(substr); 
+				 is_match && s < VARBITEND(substr); s++) 
+			{
+				cmp = *s >> is;
+				if (s == VARBITEND(substr) - 1) 
+				{
+					mask1 &= end_mask >> is;
+					if (p == VARBITEND(arg) - 1) {
+						/* Check that there is enough of arg left */
+						if (mask1 & ~arg_mask) {
+							is_match = false;
+							break;
+						}
+						mask1 &= arg_mask;
+					}
+				}
+				is_match = ((cmp ^ *p) & mask1) == 0;
+				if (!is_match)
+					break;
+				// Move on to the next byte
+				p++;
+				if (p == VARBITEND(arg)) {
+					mask2 = end_mask << (BITS_PER_BYTE - is);
+					is_match = mask2 == 0;
+					elog(NOTICE,"S. %d %d em=%2x sm=%2x r=%d",
+						 i,is,end_mask,mask2,is_match);
+					break;
+				}
+				cmp = *s << (BITS_PER_BYTE - is);
+				if (s == VARBITEND(substr) - 1) 
+				{
+					mask2 &= end_mask << (BITS_PER_BYTE - is);
+					if (p == VARBITEND(arg) - 1) {
+						if (mask2 & ~arg_mask) {
+							is_match = false;
+							break;
+						}
+						mask2 &= arg_mask;
+					}
+				}
+				is_match = ((cmp ^ *p) & mask2) == 0;
+			}
+			/* Have we found a match */
+			if (is_match)
+				PG_RETURN_INT32(i*BITS_PER_BYTE + is + 1);
+		}
+	}
+	PG_RETURN_INT32(0);
+}
-- 
cgit v1.2.3