diff --git a/src/backend/replication/backup_manifest.c b/src/backend/replication/backup_manifest.c
index 8af94610b3..0cefd181b5 100644
--- a/src/backend/replication/backup_manifest.c
+++ b/src/backend/replication/backup_manifest.c
@@ -13,11 +13,11 @@
 #include "postgres.h"
 
 #include "access/timeline.h"
+#include "common/hex.h"
 #include "libpq/libpq.h"
 #include "libpq/pqformat.h"
 #include "mb/pg_wchar.h"
 #include "replication/backup_manifest.h"
-#include "utils/builtins.h"
 #include "utils/json.h"
 
 static void AppendStringToManifest(backup_manifest_info *manifest, char *s);
@@ -150,10 +150,12 @@ AddFileToBackupManifest(backup_manifest_info *manifest, const char *spcoid,
 	}
 	else
 	{
+		uint64		dstlen = pg_hex_enc_len(pathlen);
+
 		appendStringInfoString(&buf, "{ \"Encoded-Path\": \"");
-		enlargeStringInfo(&buf, 2 * pathlen);
-		buf.len += hex_encode(pathname, pathlen,
-							  &buf.data[buf.len]);
+		enlargeStringInfo(&buf, dstlen);
+		buf.len += pg_hex_encode(pathname, pathlen,
+								 &buf.data[buf.len], dstlen);
 		appendStringInfoString(&buf, "\", ");
 	}
 
@@ -176,6 +178,7 @@ AddFileToBackupManifest(backup_manifest_info *manifest, const char *spcoid,
 	{
 		uint8		checksumbuf[PG_CHECKSUM_MAX_LENGTH];
 		int			checksumlen;
+		uint64		dstlen;
 
 		checksumlen = pg_checksum_final(checksum_ctx, checksumbuf);
 		if (checksumlen < 0)
@@ -185,9 +188,10 @@ AddFileToBackupManifest(backup_manifest_info *manifest, const char *spcoid,
 		appendStringInfo(&buf,
 						 ", \"Checksum-Algorithm\": \"%s\", \"Checksum\": \"",
 						 pg_checksum_type_name(checksum_ctx->type));
-		enlargeStringInfo(&buf, 2 * checksumlen);
-		buf.len += hex_encode((char *) checksumbuf, checksumlen,
-							  &buf.data[buf.len]);
+		dstlen = pg_hex_enc_len(checksumlen);
+		enlargeStringInfo(&buf, dstlen);
+		buf.len += pg_hex_encode((char *) checksumbuf, checksumlen,
+								 &buf.data[buf.len], dstlen);
 		appendStringInfoChar(&buf, '"');
 	}
 
@@ -307,8 +311,9 @@ SendBackupManifest(backup_manifest_info *manifest)
 {
 	StringInfoData protobuf;
 	uint8		checksumbuf[PG_SHA256_DIGEST_LENGTH];
-	char		checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH];
+	char	   *checksumstringbuf;
 	size_t		manifest_bytes_done = 0;
+	uint64		dstlen;
 
 	if (!IsManifestEnabled(manifest))
 		return;
@@ -328,8 +333,11 @@ SendBackupManifest(backup_manifest_info *manifest)
 	if (pg_cryptohash_final(manifest->manifest_ctx, checksumbuf) < 0)
 		elog(ERROR, "failed to finalize checksum of backup manifest");
 	AppendStringToManifest(manifest, "\"Manifest-Checksum\": \"");
-	hex_encode((char *) checksumbuf, sizeof checksumbuf, checksumstringbuf);
-	checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH - 1] = '\0';
+	dstlen = pg_hex_enc_len(PG_SHA256_DIGEST_LENGTH);
+	checksumstringbuf = palloc0(dstlen + 1);	/* includes \0 */
+	pg_hex_encode((char *) checksumbuf, sizeof checksumbuf,
+				  checksumstringbuf, dstlen);
+	checksumstringbuf[dstlen] = '\0';
 	AppendStringToManifest(manifest, checksumstringbuf);
 	AppendStringToManifest(manifest, "\"}\n");
 
diff --git a/src/backend/utils/adt/encode.c b/src/backend/utils/adt/encode.c
index 4759be25e9..8449aaac56 100644
--- a/src/backend/utils/adt/encode.c
+++ b/src/backend/utils/adt/encode.c
@@ -15,7 +15,7 @@
 
 #include <ctype.h>
 
-#include "common/hex_decode.h"
+#include "common/hex.h"
 #include "mb/pg_wchar.h"
 #include "utils/builtins.h"
 #include "utils/memutils.h"
@@ -32,10 +32,12 @@
  */
 struct pg_encoding
 {
-	uint64		(*encode_len) (const char *data, size_t dlen);
-	uint64		(*decode_len) (const char *data, size_t dlen);
-	uint64		(*encode) (const char *data, size_t dlen, char *res);
-	uint64		(*decode) (const char *data, size_t dlen, char *res);
+	uint64		(*encode_len) (const char *src, size_t srclen);
+	uint64		(*decode_len) (const char *src, size_t srclen);
+	uint64		(*encode) (const char *src, size_t srclen,
+						   char *dst, size_t dstlen);
+	uint64		(*decode) (const char *src, size_t srclen,
+						   char *dst, size_t dstlen);
 };
 
 static const struct pg_encoding *pg_find_encoding(const char *name);
@@ -81,11 +83,7 @@ binary_encode(PG_FUNCTION_ARGS)
 
 	result = palloc(VARHDRSZ + resultlen);
 
-	res = enc->encode(dataptr, datalen, VARDATA(result));
-
-	/* Make this FATAL 'cause we've trodden on memory ... */
-	if (res > resultlen)
-		elog(FATAL, "overflow - encode estimate too small");
+	res = enc->encode(dataptr, datalen, VARDATA(result), resultlen);
 
 	SET_VARSIZE(result, VARHDRSZ + res);
 
@@ -129,11 +127,7 @@ binary_decode(PG_FUNCTION_ARGS)
 
 	result = palloc(VARHDRSZ + resultlen);
 
-	res = enc->decode(dataptr, datalen, VARDATA(result));
-
-	/* Make this FATAL 'cause we've trodden on memory ... */
-	if (res > resultlen)
-		elog(FATAL, "overflow - decode estimate too small");
+	res = enc->decode(dataptr, datalen, VARDATA(result), resultlen);
 
 	SET_VARSIZE(result, VARHDRSZ + res);
 
@@ -145,32 +139,20 @@ binary_decode(PG_FUNCTION_ARGS)
  * HEX
  */
 
-static const char hextbl[] = "0123456789abcdef";
-
-uint64
-hex_encode(const char *src, size_t len, char *dst)
-{
-	const char *end = src + len;
-
-	while (src < end)
-	{
-		*dst++ = hextbl[(*src >> 4) & 0xF];
-		*dst++ = hextbl[*src & 0xF];
-		src++;
-	}
-	return (uint64) len * 2;
-}
-
+/*
+ * Those two wrappers are still needed to match with the layer of
+ * src/common/.
+ */
 static uint64
 hex_enc_len(const char *src, size_t srclen)
 {
-	return (uint64) srclen << 1;
+	return pg_hex_enc_len(srclen);
 }
 
 static uint64
 hex_dec_len(const char *src, size_t srclen)
 {
-	return (uint64) srclen >> 1;
+	return pg_hex_dec_len(srclen);
 }
 
 /*
@@ -192,12 +174,12 @@ static const int8 b64lookup[128] = {
 };
 
 static uint64
-pg_base64_encode(const char *src, size_t len, char *dst)
+pg_base64_encode(const char *src, size_t srclen, char *dst, size_t dstlen)
 {
 	char	   *p,
 			   *lend = dst + 76;
 	const char *s,
-			   *end = src + len;
+			   *end = src + srclen;
 	int			pos = 2;
 	uint32		buf = 0;
 
@@ -213,6 +195,8 @@ pg_base64_encode(const char *src, size_t len, char *dst)
 		/* write it out */
 		if (pos < 0)
 		{
+			if ((p - dst + 4) > dstlen)
+				elog(ERROR, "overflow of destination buffer in base64 encoding");
 			*p++ = _base64[(buf >> 18) & 0x3f];
 			*p++ = _base64[(buf >> 12) & 0x3f];
 			*p++ = _base64[(buf >> 6) & 0x3f];
@@ -223,25 +207,30 @@ pg_base64_encode(const char *src, size_t len, char *dst)
 		}
 		if (p >= lend)
 		{
+			if ((p - dst + 1) > dstlen)
+				elog(ERROR, "overflow of destination buffer in base64 encoding");
 			*p++ = '\n';
 			lend = p + 76;
 		}
 	}
 	if (pos != 2)
 	{
+		if ((p - dst + 4) > dstlen)
+			elog(ERROR, "overflow of destination buffer in base64 encoding");
 		*p++ = _base64[(buf >> 18) & 0x3f];
 		*p++ = _base64[(buf >> 12) & 0x3f];
 		*p++ = (pos == 0) ? _base64[(buf >> 6) & 0x3f] : '=';
 		*p++ = '=';
 	}
 
+	Assert((p - dst) <= dstlen);
 	return p - dst;
 }
 
 static uint64
-pg_base64_decode(const char *src, size_t len, char *dst)
+pg_base64_decode(const char *src, size_t srclen, char *dst, size_t dstlen)
 {
-	const char *srcend = src + len,
+	const char *srcend = src + srclen,
 			   *s = src;
 	char	   *p = dst;
 	char		c;
@@ -289,11 +278,21 @@ pg_base64_decode(const char *src, size_t len, char *dst)
 		pos++;
 		if (pos == 4)
 		{
+			if ((p - dst + 1) > dstlen)
+				elog(ERROR, "overflow of destination buffer in base64 decoding");
 			*p++ = (buf >> 16) & 255;
 			if (end == 0 || end > 1)
+			{
+				if ((p - dst + 1) > dstlen)
+					elog(ERROR, "overflow of destination buffer in base64 decoding");
 				*p++ = (buf >> 8) & 255;
+			}
 			if (end == 0 || end > 2)
+			{
+				if ((p - dst + 1) > dstlen)
+					elog(ERROR, "overflow of destination buffer in base64 decoding");
 				*p++ = buf & 255;
+			}
 			buf = 0;
 			pos = 0;
 		}
@@ -305,6 +304,7 @@ pg_base64_decode(const char *src, size_t len, char *dst)
 				 errmsg("invalid base64 end sequence"),
 				 errhint("Input data is missing padding, is truncated, or is otherwise corrupted.")));
 
+	Assert((p - dst) <= dstlen);
 	return p - dst;
 }
 
@@ -340,7 +340,7 @@ pg_base64_dec_len(const char *src, size_t srclen)
 #define DIG(VAL)		((VAL) + '0')
 
 static uint64
-esc_encode(const char *src, size_t srclen, char *dst)
+esc_encode(const char *src, size_t srclen, char *dst, size_t dstlen)
 {
 	const char *end = src + srclen;
 	char	   *rp = dst;
@@ -352,6 +352,8 @@ esc_encode(const char *src, size_t srclen, char *dst)
 
 		if (c == '\0' || IS_HIGHBIT_SET(c))
 		{
+			if ((rp - dst + 4) > dstlen)
+				elog(ERROR, "overflow of destination buffer in escape encoding");
 			rp[0] = '\\';
 			rp[1] = DIG(c >> 6);
 			rp[2] = DIG((c >> 3) & 7);
@@ -361,6 +363,8 @@ esc_encode(const char *src, size_t srclen, char *dst)
 		}
 		else if (c == '\\')
 		{
+			if ((rp - dst + 2) > dstlen)
+				elog(ERROR, "overflow of destination buffer in escape encoding");
 			rp[0] = '\\';
 			rp[1] = '\\';
 			rp += 2;
@@ -368,6 +372,8 @@ esc_encode(const char *src, size_t srclen, char *dst)
 		}
 		else
 		{
+			if ((rp - dst + 1) > dstlen)
+				elog(ERROR, "overflow of destination buffer in escape encoding");
 			*rp++ = c;
 			len++;
 		}
@@ -375,11 +381,12 @@ esc_encode(const char *src, size_t srclen, char *dst)
 		src++;
 	}
 
+	Assert((rp - dst) <= dstlen);
 	return len;
 }
 
 static uint64
-esc_decode(const char *src, size_t srclen, char *dst)
+esc_decode(const char *src, size_t srclen, char *dst, size_t dstlen)
 {
 	const char *end = src + srclen;
 	char	   *rp = dst;
@@ -388,7 +395,11 @@ esc_decode(const char *src, size_t srclen, char *dst)
 	while (src < end)
 	{
 		if (src[0] != '\\')
+		{
+			if ((rp - dst + 1) > dstlen)
+				elog(ERROR, "overflow of destination buffer in escape decoding");
 			*rp++ = *src++;
+		}
 		else if (src + 3 < end &&
 				 (src[1] >= '0' && src[1] <= '3') &&
 				 (src[2] >= '0' && src[2] <= '7') &&
@@ -400,12 +411,16 @@ esc_decode(const char *src, size_t srclen, char *dst)
 			val <<= 3;
 			val += VAL(src[2]);
 			val <<= 3;
+			if ((rp - dst + 1) > dstlen)
+				elog(ERROR, "overflow of destination buffer in escape decoding");
 			*rp++ = val + VAL(src[3]);
 			src += 4;
 		}
 		else if (src + 1 < end &&
 				 (src[1] == '\\'))
 		{
+			if ((rp - dst + 1) > dstlen)
+				elog(ERROR, "overflow of destination buffer in escape decoding");
 			*rp++ = '\\';
 			src += 2;
 		}
@@ -423,6 +438,7 @@ esc_decode(const char *src, size_t srclen, char *dst)
 		len++;
 	}
 
+	Assert((rp - dst) <= dstlen);
 	return len;
 }
 
@@ -504,7 +520,7 @@ static const struct
 	{
 		"hex",
 		{
-			hex_enc_len, hex_dec_len, hex_encode, hex_decode
+			hex_enc_len, hex_dec_len, pg_hex_encode, pg_hex_decode
 		}
 	},
 	{
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 4838bfb4ff..479ed9ae54 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -21,8 +21,8 @@
 #include "catalog/pg_collation.h"
 #include "catalog/pg_type.h"
 #include "common/hashfn.h"
+#include "common/hex.h"
 #include "common/int.h"
-#include "common/hex_decode.h"
 #include "common/unicode_norm.h"
 #include "lib/hyperloglog.h"
 #include "libpq/pqformat.h"
@@ -304,10 +304,12 @@ byteain(PG_FUNCTION_ARGS)
 	if (inputText[0] == '\\' && inputText[1] == 'x')
 	{
 		size_t		len = strlen(inputText);
+		uint64		dstlen = pg_hex_dec_len(len - 2);
 
-		bc = (len - 2) / 2 + VARHDRSZ;	/* maximum possible length */
+		bc = dstlen + VARHDRSZ;	/* maximum possible length */
 		result = palloc(bc);
-		bc = hex_decode(inputText + 2, len - 2, VARDATA(result));
+
+		bc = pg_hex_decode(inputText + 2, len - 2, VARDATA(result), dstlen);
 		SET_VARSIZE(result, bc + VARHDRSZ); /* actual length */
 
 		PG_RETURN_BYTEA_P(result);
@@ -396,11 +398,15 @@ byteaout(PG_FUNCTION_ARGS)
 
 	if (bytea_output == BYTEA_OUTPUT_HEX)
 	{
+		uint64		dstlen = pg_hex_enc_len(VARSIZE_ANY_EXHDR(vlena));
+
 		/* Print hex format */
-		rp = result = palloc(VARSIZE_ANY_EXHDR(vlena) * 2 + 2 + 1);
+		rp = result = palloc(dstlen + 2 + 1);
 		*rp++ = '\\';
 		*rp++ = 'x';
-		rp += hex_encode(VARDATA_ANY(vlena), VARSIZE_ANY_EXHDR(vlena), rp);
+
+		rp += pg_hex_encode(VARDATA_ANY(vlena), VARSIZE_ANY_EXHDR(vlena), rp,
+							dstlen);
 	}
 	else if (bytea_output == BYTEA_OUTPUT_ESCAPE)
 	{
diff --git a/src/common/Makefile b/src/common/Makefile
index f624977939..93eb27a2aa 100644
--- a/src/common/Makefile
+++ b/src/common/Makefile
@@ -58,7 +58,7 @@ OBJS_COMMON = \
 	file_perm.o \
 	file_utils.o \
 	hashfn.o \
-	hex_decode.o \
+	hex.o \
 	ip.o \
 	jsonapi.o \
 	keywords.o \
diff --git a/src/common/hex.c b/src/common/hex.c
new file mode 100644
index 0000000000..e4878ba253
--- /dev/null
+++ b/src/common/hex.c
@@ -0,0 +1,192 @@
+/*-------------------------------------------------------------------------
+ *
+ * hex.c
+ *	  Encoding and decoding routines for hex.
+ *
+ * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/common/hex.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+#include "common/hex.h"
+#ifdef FRONTEND
+#include "common/logging.h"
+#endif
+#include "mb/pg_wchar.h"
+
+
+static const int8 hexlookup[128] = {
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
+	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+};
+
+static const char hextbl[] = "0123456789abcdef";
+
+static inline char
+get_hex(const char *cp)
+{
+	unsigned char c = (unsigned char) *cp;
+	int			res = -1;
+
+	if (c < 127)
+		res = hexlookup[c];
+
+	if (res < 0)
+	{
+#ifdef FRONTEND
+		pg_log_fatal("invalid hexadecimal digit");
+		exit(EXIT_FAILURE);
+#else
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid hexadecimal digit: \"%.*s\"",
+						pg_mblen(cp), cp)));
+#endif
+	}
+
+	return (char) res;
+}
+
+/*
+ * pg_hex_encode
+ *
+ * Encode into hex the given string.  Returns the length of the encoded
+ * string.
+ */
+uint64
+pg_hex_encode(const char *src, size_t srclen, char *dst, size_t dstlen)
+{
+	const char *end = src + srclen;
+	char	   *p;
+
+	p = dst;
+
+	while (src < end)
+	{
+		/*
+		 * Leave if there is an overflow in the area allocated for the encoded
+		 * string.
+		 */
+		if ((p - dst + 2) > dstlen)
+		{
+#ifdef FRONTEND
+			pg_log_fatal("overflow of destination buffer in hex encoding");
+			exit(EXIT_FAILURE);
+#else
+			elog(ERROR, "overflow of destination buffer in hex encoding");
+#endif
+		}
+
+		*p++ = hextbl[(*src >> 4) & 0xF];
+		*p++ = hextbl[*src & 0xF];
+		src++;
+	}
+
+	Assert((p - dst) <= dstlen);
+	return p - dst;
+}
+
+/*
+ * pg_hex_decode
+ *
+ * Decode the given hex string.  Returns the length of the decoded string.
+ */
+uint64
+pg_hex_decode(const char *src, size_t srclen, char *dst, size_t dstlen)
+{
+	const char *s,
+			   *srcend;
+	char		v1,
+				v2,
+			   *p;
+
+	srcend = src + srclen;
+	s = src;
+	p = dst;
+	while (s < srcend)
+	{
+		if (*s == ' ' || *s == '\n' || *s == '\t' || *s == '\r')
+		{
+			s++;
+			continue;
+		}
+		v1 = get_hex(s) << 4;
+		s++;
+
+		if (s >= srcend)
+		{
+#ifdef FRONTEND
+			pg_log_fatal("invalid hexadecimal data: odd number of digits");
+			exit(EXIT_FAILURE);
+#else
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("invalid hexadecimal data: odd number of digits")));
+#endif
+		}
+
+		v2 = get_hex(s);
+		s++;
+
+		/* overflow check */
+		if ((p - dst + 1) > dstlen)
+		{
+#ifdef FRONTEND
+			pg_log_fatal("overflow of destination buffer in hex decoding");
+			exit(EXIT_FAILURE);
+#else
+			elog(ERROR, "overflow of destination buffer in hex decoding");
+#endif
+		}
+
+		*p++ = v1 | v2;
+	}
+
+	Assert((p - dst) <= dstlen);
+	return p - dst;
+}
+
+/*
+ * pg_hex_enc_len
+ *
+ * Returns to caller the length of the string if it were encoded with
+ * hex based on the length provided by caller.  This is useful to estimate
+ * how large a buffer allocation needs to be done before doing the actual
+ * encoding.
+ */
+uint64
+pg_hex_enc_len(size_t srclen)
+{
+	return (uint64) srclen << 1;
+}
+
+/*
+ * pg_hex_dec_len
+ *
+ * Returns to caller the length of the string if it were to be decoded
+ * with hex, based on the length given by caller.  This is useful to
+ * estimate how large a buffer allocation needs to be done before doing
+ * the actual decoding.
+ */
+uint64
+pg_hex_dec_len(size_t srclen)
+{
+	return (uint64) srclen >> 1;
+}
diff --git a/src/common/hex_decode.c b/src/common/hex_decode.c
deleted file mode 100644
index dbc0e1c30a..0000000000
--- a/src/common/hex_decode.c
+++ /dev/null
@@ -1,106 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * hex_decode.c
- *		hex decoding
- *
- *
- * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- *	  src/common/hex_decode.c
- *
- *-------------------------------------------------------------------------
- */
-
-
-#ifndef FRONTEND
-#include "postgres.h"
-#else
-#include "postgres_fe.h"
-#endif
-
-#ifdef FRONTEND
-#include "common/logging.h"
-#else
-#include "mb/pg_wchar.h"
-#endif
-#include "common/hex_decode.h"
-
-
-static const int8 hexlookup[128] = {
-	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-};
-
-static inline char
-get_hex(const char *cp)
-{
-	unsigned char c = (unsigned char) *cp;
-	int			res = -1;
-
-	if (c < 127)
-		res = hexlookup[c];
-
-	if (res < 0)
-	{
-#ifdef FRONTEND
-		pg_log_fatal("invalid hexadecimal digit");
-		exit(EXIT_FAILURE);
-#else
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("invalid hexadecimal digit: \"%.*s\"",
-						pg_mblen(cp), cp)));
-#endif
-	}
-
-	return (char) res;
-}
-
-uint64
-hex_decode(const char *src, size_t len, char *dst)
-{
-	const char *s,
-			   *srcend;
-	char		v1,
-				v2,
-			   *p;
-
-	srcend = src + len;
-	s = src;
-	p = dst;
-	while (s < srcend)
-	{
-		if (*s == ' ' || *s == '\n' || *s == '\t' || *s == '\r')
-		{
-			s++;
-			continue;
-		}
-		v1 = get_hex(s) << 4;
-		s++;
-		if (s >= srcend)
-		{
-#ifdef FRONTEND
-			pg_log_fatal("invalid hexadecimal data: odd number of digits");
-			exit(EXIT_FAILURE);
-#else
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("invalid hexadecimal data: odd number of digits")));
-#endif
-		}
-		v2 = get_hex(s);
-		s++;
-		*p++ = v1 | v2;
-	}
-
-	return p - dst;
-}
diff --git a/src/include/common/hex.h b/src/include/common/hex.h
new file mode 100644
index 0000000000..3c3c956bb6
--- /dev/null
+++ b/src/include/common/hex.h
@@ -0,0 +1,25 @@
+/*------------------------------------------------------------------------
+ *
+ *	hex.h
+ *	  Encoding and decoding routines for hex strings.
+ *
+ *	Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+ *	Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *		  src/include/common/hex.h
+ *
+ *------------------------------------------------------------------------
+ */
+
+#ifndef COMMON_HEX_H
+#define COMMON_HEX_H
+
+extern uint64 pg_hex_decode(const char *src, size_t srclen,
+							char *dst, size_t dstlen);
+extern uint64 pg_hex_encode(const char *src, size_t srclen,
+							char *dst, size_t dstlen);
+extern uint64 pg_hex_enc_len(size_t srclen);
+extern uint64 pg_hex_dec_len(size_t srclen);
+
+#endif							/* COMMON_HEX_H */
diff --git a/src/include/common/hex_decode.h b/src/include/common/hex_decode.h
deleted file mode 100644
index 29ab248458..0000000000
--- a/src/include/common/hex_decode.h
+++ /dev/null
@@ -1,16 +0,0 @@
-/*
- *	hex_decode.h
- *		hex decoding
- *
- *	Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
- *	Portions Copyright (c) 1994, Regents of the University of California
- *
- *	src/include/common/hex_decode.h
- */
-#ifndef COMMON_HEX_DECODE_H
-#define COMMON_HEX_DECODE_H
-
-extern uint64 hex_decode(const char *src, size_t len, char *dst);
-
-
-#endif							/* COMMON_HEX_DECODE_H */
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 6f739a8822..27d2f2ffb3 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -31,9 +31,6 @@ extern void domain_check(Datum value, bool isnull, Oid domainType,
 extern int	errdatatype(Oid datatypeOid);
 extern int	errdomainconstraint(Oid datatypeOid, const char *conname);
 
-/* encode.c */
-extern uint64 hex_encode(const char *src, size_t len, char *dst);
-
 /* int.c */
 extern int2vector *buildint2vector(const int16 *int2s, int n);
 
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 535b67e668..5634b2d40c 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -121,7 +121,7 @@ sub mkvcbuild
 	our @pgcommonallfiles = qw(
 	  archive.c base64.c checksum_helper.c
 	  config_info.c controldata_utils.c d2s.c encnames.c exec.c
-	  f2s.c file_perm.c file_utils.c hashfn.c hex_decode.c ip.c jsonapi.c
+	  f2s.c file_perm.c file_utils.c hashfn.c hex.c ip.c jsonapi.c
 	  keywords.c kwlookup.c link-canary.c md5_common.c
 	  pg_get_line.c pg_lzcompress.c pgfnames.c psprintf.c relpath.c rmtree.c
 	  saslprep.c scram-common.c string.c stringinfo.c unicode_norm.c username.c