Add codec for jsonpath type

PostgreSQL 12 added the `jsonpath` type to represent SQL/JSON values.
Add a codec to handle that.

Author: elprans

codecs/__init__.pxd

@@ -101,6 +101,11 @@ cdef jsonb_encode(CodecContext settings, WriteBuffer buf, obj)
 cdef jsonb_decode(CodecContext settings, FRBuffer * buf)
 
 
+# JSON path
+cdef jsonpath_encode(CodecContext settings, WriteBuffer buf, obj)
+cdef jsonpath_decode(CodecContext settings, FRBuffer * buf)
+
+
 # Text
 cdef as_pg_string_and_size(
         CodecContext settings, obj, char **cstr, ssize_t *size)

codecs/jsonpath.pyx

@@ -0,0 +1,29 @@
+# Copyright (C) 2016-present the asyncpg authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of asyncpg and is released under
+# the Apache 2.0 License: http://www.apache.org/licenses/LICENSE-2.0
+
+
+cdef jsonpath_encode(CodecContext settings, WriteBuffer buf, obj):
+    cdef:
+        char *str
+        ssize_t size
+
+    as_pg_string_and_size(settings, obj, &str, &size)
+
+    if size > 0x7fffffff - 1:
+        raise ValueError('string too long')
+
+    buf.write_int32(<int32_t>size + 1)
+    buf.write_byte(1)  # jsonpath format version
+    buf.write_cstr(str, size)
+
+
+cdef jsonpath_decode(CodecContext settings, FRBuffer *buf):
+    cdef uint8_t format = <uint8_t>(frb_read(buf, 1)[0])
+
+    if format != 1:
+        raise ValueError('unexpected jsonpath format: {}'.format(format))
+
+    return text_decode(settings, buf)

pgproto.pyx

@@ -37,6 +37,7 @@ include "./codecs/datetime.pyx"
 include "./codecs/float.pyx"
 include "./codecs/int.pyx"
 include "./codecs/json.pyx"
+include "./codecs/jsonpath.pyx"
 include "./codecs/uuid.pyx"
 include "./codecs/numeric.pyx"
 include "./codecs/bits.pyx"