From 857ec382cf2a220748e11d6bed28c8b006282589 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Wed, 29 Oct 2025 15:53:12 +0400
Subject: [PATCH v5 2/2] Add base32hex encoding support to encode() and
 decode()

Implement base32hex encoding/decoding per RFC 4648 Section 7 for
encode() and decode() functions. This encoding uses the extended hex
alphabet (0-9, A-V) which preserves sort order.

The encode() function produces padded output, while decode() accepts
both padded and unpadded input. Decoding is case-insensitive.

Author: Andrey Borodin <x4mmm@yandex-team.ru>
Author: Aleksander Alekseev <aleksander@tigerdata.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Suggested-by: Sergey Prokhorenko <sergeyprokhorenko@yahoo.com.au>
Discussion: https://postgr.es/m/CAJ7c6TOramr1UTLcyB128LWMqita1Y7%3Darq3KHaU%3Dqikf5yKOQ%40mail.gmail.com
---
 doc/src/sgml/func/func-binarystring.sgml |  25 ++++
 src/backend/utils/adt/encode.c           | 158 +++++++++++++++++++++++
 src/test/regress/expected/strings.out    | 107 ++++++++++++++-
 src/test/regress/expected/uuid.out       |  16 +++
 src/test/regress/sql/strings.sql         |  29 ++++-
 src/test/regress/sql/uuid.sql            |   9 ++
 6 files changed, 342 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/func/func-binarystring.sgml b/doc/src/sgml/func/func-binarystring.sgml
index b256381e01f..51be0463eec 100644
--- a/doc/src/sgml/func/func-binarystring.sgml
+++ b/doc/src/sgml/func/func-binarystring.sgml
@@ -729,6 +729,7 @@
        <parameter>format</parameter> values are:
        <link linkend="encode-format-base64"><literal>base64</literal></link>,
        <link linkend="encode-format-base64url"><literal>base64url</literal></link>,
+       <link linkend="encode-format-base32hex"><literal>base32hex</literal></link>,
        <link linkend="encode-format-escape"><literal>escape</literal></link>,
        <link linkend="encode-format-hex"><literal>hex</literal></link>.
       </para>
@@ -804,6 +805,30 @@
      </listitem>
     </varlistentry>
 
+    <varlistentry id="encode-format-base32hex">
+     <term>base32hex
+      <indexterm>
+       <primary>base32hex format</primary>
+      </indexterm></term>
+     <listitem>
+      <para>
+       The <literal>base32hex</literal> format is that of
+       <ulink url="https://datatracker.ietf.org/doc/html/rfc4648#section-7">
+       RFC 4648 Section 7</ulink>.  It uses the extended hex alphabet
+       (0-9, A-V) which preserves sort order when encoding binary data.
+       The <function>encode</function> function produces padded output,
+       while <function>decode</function> accepts both padded and unpadded
+       input. Decoding is case-insensitive and ignores whitespace characters.
+      </para>
+      <para>
+       This format can be used for encoding UUIDs in a compact, sortable format:
+       <literal>substring(encode(uuid_value :: bytea, 'base32hex') from 1 for 26)</literal>
+       produces a 26-character string compared to the standard 36-character
+       UUID representation.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry id="encode-format-escape">
      <term>escape
      <indexterm>
diff --git a/src/backend/utils/adt/encode.c b/src/backend/utils/adt/encode.c
index f5f835e944a..6153a5cb5f2 100644
--- a/src/backend/utils/adt/encode.c
+++ b/src/backend/utils/adt/encode.c
@@ -825,6 +825,158 @@ esc_dec_len(const char *src, size_t srclen)
 	return len;
 }
 
+/*
+ * BASE32HEX
+ */
+
+static const char base32hex_table[] = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
+
+static uint64
+base32hex_enc_len(const char *src, size_t srclen)
+{
+	/* 5 bytes encode to 8 characters, round up to multiple of 8 for padding */
+	return ((uint64) srclen + 4) / 5 * 8;
+}
+
+static uint64
+base32hex_dec_len(const char *src, size_t srclen)
+{
+	/* Decode length is (srclen * 5) / 8, but we may have padding */
+	return ((uint64) srclen * 5) / 8;
+}
+
+static uint64
+base32hex_encode(const char *src, size_t srclen, char *dst)
+{
+	const unsigned char *data = (const unsigned char *) src;
+	uint64		bits_buffer = 0;
+	int			bits_in_buffer = 0;
+	uint64		output_pos = 0;
+	size_t		i;
+
+	for (i = 0; i < srclen; i++)
+	{
+		/* Add 8 bits to the buffer */
+		bits_buffer = (bits_buffer << 8) | data[i];
+		bits_in_buffer += 8;
+
+		/* Extract 5-bit chunks while we have enough bits */
+		while (bits_in_buffer >= 5)
+		{
+			bits_in_buffer -= 5;
+			/* Extract top 5 bits */
+			dst[output_pos++] = base32hex_table[(bits_buffer >> bits_in_buffer) & 0x1F];
+			/* Clear the extracted bits by masking */
+			bits_buffer &= ((1ULL << bits_in_buffer) - 1);
+		}
+	}
+
+	/* Handle remaining bits (if any) */
+	if (bits_in_buffer > 0)
+	{
+		dst[output_pos++] = base32hex_table[(bits_buffer << (5 - bits_in_buffer)) & 0x1F];
+	}
+
+	/* Add padding to make length a multiple of 8 (per RFC 4648) */
+	while (output_pos % 8 != 0)
+	{
+		dst[output_pos++] = '=';
+	}
+
+	return output_pos;
+}
+
+static uint64
+base32hex_decode(const char *src, size_t srclen, char *dst)
+{
+	const unsigned char *data = (const unsigned char *) src;
+	uint64		bits_buffer = 0;
+	int			bits_in_buffer = 0;
+	uint64		output_pos = 0;
+	size_t		i;
+	int			pos = 0;		/* position within 8-character group (0-7) */
+	bool		end = false;	/* have we seen padding? */
+
+	for (i = 0; i < srclen; i++)
+	{
+		unsigned char c = data[i];
+		int			val;
+
+		/* Skip whitespace */
+		if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
+			continue;
+
+		if (c == '=')
+		{
+			/*
+			 * Padding is only valid at positions 2, 4, 5, or 7 within an
+			 * 8-character group (corresponding to 1, 2, 3, or 4 input bytes).
+			 * We only check the position for the first '=' character.
+			 */
+			if (!end)
+			{
+				if (pos != 2 && pos != 4 && pos != 5 && pos != 7)
+					ereport(ERROR,
+							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+							 errmsg("unexpected \"=\" while decoding %s sequence",
+									"base32hex")));
+				end = true;
+			}
+			pos++;
+			continue;
+		}
+
+		/* No data characters allowed after padding */
+		if (end)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("invalid symbol \"%.*s\" found while decoding %s sequence",
+							pg_mblen((const char *) &c), (const char *) &c,
+							"base32hex")));
+
+		/* Decode base32hex character (0-9, A-V, case-insensitive) */
+		if (c >= '0' && c <= '9')
+			val = c - '0';
+		else if (c >= 'A' && c <= 'V')
+			val = c - 'A' + 10;
+		else if (c >= 'a' && c <= 'v')
+			val = c - 'a' + 10;
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("invalid symbol \"%.*s\" found while decoding %s sequence",
+							pg_mblen((const char *) &c), (const char *) &c,
+							"base32hex")));
+
+		/* Add 5 bits to buffer */
+		bits_buffer = (bits_buffer << 5) | val;
+		bits_in_buffer += 5;
+		pos++;
+
+		/* Extract 8-bit bytes when we have enough bits */
+		while (bits_in_buffer >= 8)
+		{
+			bits_in_buffer -= 8;
+			dst[output_pos++] = (unsigned char) (bits_buffer >> bits_in_buffer);
+			/* Clear the extracted bits */
+			bits_buffer &= ((1ULL << bits_in_buffer) - 1);
+		}
+
+		/* Reset position after each complete 8-character group */
+		if (pos == 8)
+			pos = 0;
+	}
+
+	/* Verify no extra bits remain (padding bits should be zero) */
+	if (bits_in_buffer > 0 && (bits_buffer & ((1ULL << bits_in_buffer) - 1)) != 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid base32hex end sequence"),
+				 errhint("Input data has non-zero padding bits.")));
+
+	return output_pos;
+}
+
 /*
  * Common
  */
@@ -854,6 +1006,12 @@ static const struct
 			pg_base64url_enc_len, pg_base64url_dec_len, pg_base64url_encode, pg_base64url_decode
 		}
 	},
+	{
+		"base32hex",
+		{
+			base32hex_enc_len, base32hex_dec_len, base32hex_encode, base32hex_decode
+		}
+	},
 	{
 		"escape",
 		{
diff --git a/src/test/regress/expected/strings.out b/src/test/regress/expected/strings.out
index f38688b5c37..910757537e7 100644
--- a/src/test/regress/expected/strings.out
+++ b/src/test/regress/expected/strings.out
@@ -2605,9 +2605,114 @@ SELECT decode('00', 'invalid');           -- error
 ERROR:  unrecognized encoding: "invalid"
 HINT:  Valid encodings are "base64", "base64url", "escape", and "hex".
 --
--- base64url encoding/decoding
+-- base32hex encoding/decoding
 --
 SET bytea_output TO hex;
+SELECT encode('', 'base32hex');  -- ''
+ encode 
+--------
+ 
+(1 row)
+
+SELECT encode('\x11', 'base32hex');  -- '24======'
+  encode  
+----------
+ 24======
+(1 row)
+
+SELECT encode('\x1122', 'base32hex');  -- '24H0===='
+  encode  
+----------
+ 24H0====
+(1 row)
+
+SELECT encode('\x112233', 'base32hex');  -- '24H36==='
+  encode  
+----------
+ 24H36===
+(1 row)
+
+SELECT encode('\x11223344', 'base32hex');  -- '24H36H0='
+  encode  
+----------
+ 24H36H0=
+(1 row)
+
+SELECT encode('\x1122334455', 'base32hex');  -- '24H36H2L'
+  encode  
+----------
+ 24H36H2L
+(1 row)
+
+SELECT encode('\x112233445566', 'base32hex');  -- '24H36H2LCO======'
+      encode      
+------------------
+ 24H36H2LCO======
+(1 row)
+
+SELECT decode('', 'base32hex');  -- ''
+ decode 
+--------
+ \x
+(1 row)
+
+SELECT decode('24======', 'base32hex');  -- \x11
+ decode 
+--------
+ \x11
+(1 row)
+
+SELECT decode('24H0====', 'base32hex');  -- \x1122
+ decode 
+--------
+ \x1122
+(1 row)
+
+SELECT decode('24H36===', 'base32hex');  -- \x112233
+  decode  
+----------
+ \x112233
+(1 row)
+
+SELECT decode('24H36H0=', 'base32hex');  -- \x11223344
+   decode   
+------------
+ \x11223344
+(1 row)
+
+SELECT decode('24H36H2L', 'base32hex');  -- \x1122334455
+    decode    
+--------------
+ \x1122334455
+(1 row)
+
+SELECT decode('24H36H2LCO======', 'base32hex');  -- \x112233445566
+     decode     
+----------------
+ \x112233445566
+(1 row)
+
+SELECT decode('24', 'base32hex');  -- OK, padding `=` are optional
+ decode 
+--------
+ \x11
+(1 row)
+
+SELECT decode('24h36h2lco', 'base32hex');  -- OK, the encoding is case-insensitive
+     decode     
+----------------
+ \x112233445566
+(1 row)
+
+SELECT decode('=', 'base32hex');  -- error
+ERROR:  unexpected "=" while decoding base32hex sequence
+SELECT decode('W', 'base32hex');  -- error
+ERROR:  invalid symbol "W" found while decoding base32hex sequence
+SELECT decode('24H36H0=24', 'base32hex'); -- error
+ERROR:  invalid symbol "2" found while decoding base32hex sequence
+--
+-- base64url encoding/decoding
+--
 -- Simple encoding/decoding
 SELECT encode('\x69b73eff', 'base64url');  -- abc-_w
  encode 
diff --git a/src/test/regress/expected/uuid.out b/src/test/regress/expected/uuid.out
index d157ef7d0b3..df25a6aa5c5 100644
--- a/src/test/regress/expected/uuid.out
+++ b/src/test/regress/expected/uuid.out
@@ -327,5 +327,21 @@ SELECT v = v::bytea::uuid as matched FROM gen_random_uuid() v;
  t
 (1 row)
 
+-- make sure base32hex encoding works with UUIDs and preserves ordering
+SELECT orig, encode(orig :: bytea, 'base32hex') AS enc
+FROM unnest(ARRAY[
+    '123e4567-e89b-12d3-a456-426614174000',
+    '00000000-0000-0000-0000-000000000000',
+    '11111111-1111-1111-1111-111111111111',
+    'ffffffff-ffff-ffff-ffff-ffffffffffff'] :: uuid[]
+) AS orig ORDER BY enc;
+                 orig                 |               enc                
+--------------------------------------+----------------------------------
+ 00000000-0000-0000-0000-000000000000 | 00000000000000000000000000======
+ 11111111-1111-1111-1111-111111111111 | 248H248H248H248H248H248H24======
+ 123e4567-e89b-12d3-a456-426614174000 | 28V4APV8JC9D792M89J185Q000======
+ ffffffff-ffff-ffff-ffff-ffffffffffff | VVVVVVVVVVVVVVVVVVVVVVVVVS======
+(4 rows)
+
 -- clean up
 DROP TABLE guid1, guid2, guid3 CASCADE;
diff --git a/src/test/regress/sql/strings.sql b/src/test/regress/sql/strings.sql
index d8a09737668..b5237e85172 100644
--- a/src/test/regress/sql/strings.sql
+++ b/src/test/regress/sql/strings.sql
@@ -835,10 +835,37 @@ SELECT encode('\x01'::bytea, 'invalid');  -- error
 SELECT decode('00', 'invalid');           -- error
 
 --
--- base64url encoding/decoding
+-- base32hex encoding/decoding
 --
 SET bytea_output TO hex;
 
+SELECT encode('', 'base32hex');  -- ''
+SELECT encode('\x11', 'base32hex');  -- '24======'
+SELECT encode('\x1122', 'base32hex');  -- '24H0===='
+SELECT encode('\x112233', 'base32hex');  -- '24H36==='
+SELECT encode('\x11223344', 'base32hex');  -- '24H36H0='
+SELECT encode('\x1122334455', 'base32hex');  -- '24H36H2L'
+SELECT encode('\x112233445566', 'base32hex');  -- '24H36H2LCO======'
+
+SELECT decode('', 'base32hex');  -- ''
+SELECT decode('24======', 'base32hex');  -- \x11
+SELECT decode('24H0====', 'base32hex');  -- \x1122
+SELECT decode('24H36===', 'base32hex');  -- \x112233
+SELECT decode('24H36H0=', 'base32hex');  -- \x11223344
+SELECT decode('24H36H2L', 'base32hex');  -- \x1122334455
+SELECT decode('24H36H2LCO======', 'base32hex');  -- \x112233445566
+
+SELECT decode('24', 'base32hex');  -- OK, padding `=` are optional
+SELECT decode('24h36h2lco', 'base32hex');  -- OK, the encoding is case-insensitive
+SELECT decode('=', 'base32hex');  -- error
+SELECT decode('W', 'base32hex');  -- error
+SELECT decode('24H36H0=24', 'base32hex'); -- error
+
+
+--
+-- base64url encoding/decoding
+--
+
 -- Simple encoding/decoding
 SELECT encode('\x69b73eff', 'base64url');  -- abc-_w
 SELECT decode('abc-_w', 'base64url');      -- \x69b73eff
diff --git a/src/test/regress/sql/uuid.sql b/src/test/regress/sql/uuid.sql
index f512f4dea1d..278a5773ada 100644
--- a/src/test/regress/sql/uuid.sql
+++ b/src/test/regress/sql/uuid.sql
@@ -152,5 +152,14 @@ SELECT '\x019a2f859ced7225b99d9c55044a2563'::bytea::uuid;
 SELECT '\x1234567890abcdef'::bytea::uuid; -- error
 SELECT v = v::bytea::uuid as matched FROM gen_random_uuid() v;
 
+-- make sure base32hex encoding works with UUIDs and preserves ordering
+SELECT orig, encode(orig :: bytea, 'base32hex') AS enc
+FROM unnest(ARRAY[
+    '123e4567-e89b-12d3-a456-426614174000',
+    '00000000-0000-0000-0000-000000000000',
+    '11111111-1111-1111-1111-111111111111',
+    'ffffffff-ffff-ffff-ffff-ffffffffffff'] :: uuid[]
+) AS orig ORDER BY enc;
+
 -- clean up
 DROP TABLE guid1, guid2, guid3 CASCADE;
-- 
2.43.0

