/*-------------------------------------------------------------------------
 *
 * compat.c
 *	  Compatibility routines to let the JSON module work in PostgreSQL 8.4
 *
 * Copyright (c) 2011, PostgreSQL Global Development Group
 * Arranged by Joey Adams <joeyadams3.14159@gmail.com>.
 *
 *-------------------------------------------------------------------------
 */

#include "compat.h"

#if PG_VERSION_NUM < 90100

/*
 * Lifted from 9.1devel
 *
 * Convert a UTF-8 character to a Unicode code point.
 * This is a one-character version of pg_utf2wchar_with_len.
 *
 * No error checks here, c must point to a long-enough string.
 */
pg_wchar
json_compat_utf8_to_unicode(const unsigned char *c)
{
	if ((*c & 0x80) == 0)
		return (pg_wchar) c[0];
	else if ((*c & 0xe0) == 0xc0)
		return (pg_wchar) (((c[0] & 0x1f) << 6) |
						   (c[1] & 0x3f));
	else if ((*c & 0xf0) == 0xe0)
		return (pg_wchar) (((c[0] & 0x0f) << 12) |
						   ((c[1] & 0x3f) << 6) |
						   (c[2] & 0x3f));
	else if ((*c & 0xf8) == 0xf0)
		return (pg_wchar) (((c[0] & 0x07) << 18) |
						   ((c[1] & 0x3f) << 12) |
						   ((c[2] & 0x3f) << 6) |
						   (c[3] & 0x3f));
	else
		/* that is an invalid code on purpose */
		return 0xffffffff;
}

#endif