From 6da469badaffec32f8a804181cca279561467378 Mon Sep 17 00:00:00 2001
From: Dean Rasheed
Date: Fri, 7 Mar 2025 09:31:18 +0000
Subject: Allow casting between bytea and integer types.

This allows smallint, integer, and bigint values to be cast to and
from bytea. The bytea value is the two's complement representation of
the integer, with the most significant byte first. For example:

  1234::bytea -> \x000004d2
  (-1234)::bytea -> \xfffffb2e

Author: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Joel Jacobson <joel@compiler.org>
Reviewed-by: Yugo Nagata <nagata@sraoss.co.jp>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/CAJ7c6TPtOp6%2BkFX5QX3fH1SVr7v65uHr-7yEJ%3DGMGQi5uhGtcA%40mail.gmail.com
---
 src/backend/utils/adt/varlena.c | 96 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)

(limited to 'src/backend/utils')

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index e4556571703..cdf185ea00b 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -4057,6 +4057,102 @@ bytea_sortsupport(PG_FUNCTION_ARGS)
 	PG_RETURN_VOID();
 }
 
+/* Cast bytea -> int2 */
+Datum
+bytea_int2(PG_FUNCTION_ARGS)
+{
+	bytea	   *v = PG_GETARG_BYTEA_PP(0);
+	int			len = VARSIZE_ANY_EXHDR(v);
+	uint16		result;
+
+	/* Check that the byte array is not too long */
+	if (len > sizeof(result))
+		ereport(ERROR,
+				errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				errmsg("smallint out of range"));
+
+	/* Convert it to an integer; most significant bytes come first */
+	result = 0;
+	for (int i = 0; i < len; i++)
+	{
+		result <<= BITS_PER_BYTE;
+		result |= ((unsigned char *) VARDATA_ANY(v))[i];
+	}
+
+	PG_RETURN_INT16(result);
+}
+
+/* Cast bytea -> int4 */
+Datum
+bytea_int4(PG_FUNCTION_ARGS)
+{
+	bytea	   *v = PG_GETARG_BYTEA_PP(0);
+	int			len = VARSIZE_ANY_EXHDR(v);
+	uint32		result;
+
+	/* Check that the byte array is not too long */
+	if (len > sizeof(result))
+		ereport(ERROR,
+				errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				errmsg("integer out of range"));
+
+	/* Convert it to an integer; most significant bytes come first */
+	result = 0;
+	for (int i = 0; i < len; i++)
+	{
+		result <<= BITS_PER_BYTE;
+		result |= ((unsigned char *) VARDATA_ANY(v))[i];
+	}
+
+	PG_RETURN_INT32(result);
+}
+
+/* Cast bytea -> int8 */
+Datum
+bytea_int8(PG_FUNCTION_ARGS)
+{
+	bytea	   *v = PG_GETARG_BYTEA_PP(0);
+	int			len = VARSIZE_ANY_EXHDR(v);
+	uint64		result;
+
+	/* Check that the byte array is not too long */
+	if (len > sizeof(result))
+		ereport(ERROR,
+				errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				errmsg("bigint out of range"));
+
+	/* Convert it to an integer; most significant bytes come first */
+	result = 0;
+	for (int i = 0; i < len; i++)
+	{
+		result <<= BITS_PER_BYTE;
+		result |= ((unsigned char *) VARDATA_ANY(v))[i];
+	}
+
+	PG_RETURN_INT64(result);
+}
+
+/* Cast int2 -> bytea; can just use int2send() */
+Datum
+int2_bytea(PG_FUNCTION_ARGS)
+{
+	return int2send(fcinfo);
+}
+
+/* Cast int4 -> bytea; can just use int4send() */
+Datum
+int4_bytea(PG_FUNCTION_ARGS)
+{
+	return int4send(fcinfo);
+}
+
+/* Cast int8 -> bytea; can just use int8send() */
+Datum
+int8_bytea(PG_FUNCTION_ARGS)
+{
+	return int8send(fcinfo);
+}
+
 /*
  * appendStringInfoText
  *
-- 
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