text: /*-------------------------------------------------------------------------
   *
   *	  ISO8859_1 <--> UTF8
   *
   * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
   *	  src/backend/utils/mb/conversion_procs/utf8_and_iso8859_1/utf8_and_iso8859_1.c
   *
   *-------------------------------------------------------------------------
   */
  
  #include "postgres.h"
  #include "fmgr.h"
  #include "mb/pg_wchar.h"
  
  PG_MODULE_MAGIC;
  
  PG_FUNCTION_INFO_V1(iso8859_1_to_utf8);
  PG_FUNCTION_INFO_V1(utf8_to_iso8859_1);
  
  /* ----------
   * conv_proc(
   *		INTEGER,	-- source encoding id
   *		INTEGER,	-- destination encoding id
   *		CSTRING,	-- source string (null terminated C string)
   *		CSTRING,	-- destination string (null terminated C string)
   *		INTEGER		-- source string length
   * ) returns VOID;
   * ----------
   */
  
  Datum
  iso8859_1_to_utf8(PG_FUNCTION_ARGS)
  {
  	unsigned char *src = (unsigned char *) PG_GETARG_CSTRING(2);
  	unsigned char *dest = (unsigned char *) PG_GETARG_CSTRING(3);
  	int			len = PG_GETARG_INT32(4);
  	unsigned short c;
  
  	CHECK_ENCODING_CONVERSION_ARGS(PG_LATIN1, PG_UTF8);
  
  	while (len > 0)
  	{
  		c = *src;
  		if (c == 0)
  			report_invalid_encoding(PG_LATIN1, (const char *) src, len);
  		if (!IS_HIGHBIT_SET(c))
  			*dest++ = c;
  		else
  		{
  			*dest++ = (c >> 6) | 0xc0;
  			*dest++ = (c & 0x003f) | HIGHBIT;
  		}
  		src++;
  		len--;
  	}
  	*dest = '\0';
  
  	PG_RETURN_VOID();
  }
  
  Datum
  utf8_to_iso8859_1(PG_FUNCTION_ARGS)
  {
  	unsigned char *src = (unsigned char *) PG_GETARG_CSTRING(2);
  	unsigned char *dest = (unsigned char *) PG_GETARG_CSTRING(3);
  	int			len = PG_GETARG_INT32(4);
  	unsigned short c,
  				c1;
  
  	CHECK_ENCODING_CONVERSION_ARGS(PG_UTF8, PG_LATIN1);
  
  	while (len > 0)
  	{
  		c = *src;
  		if (c == 0)
  			report_invalid_encoding(PG_UTF8, (const char *) src, len);
  		/* fast path for ASCII-subset characters */
  		if (!IS_HIGHBIT_SET(c))
  		{
  			*dest++ = c;
  			src++;
  			len--;
  		}
  		else
  		{
  			int			l = pg_utf_mblen(src);
  
  			if (l > len || !pg_utf8_islegal(src, l))
  				report_invalid_encoding(PG_UTF8, (const char *) src, len);
  			if (l != 2)
  				report_untranslatable_char(PG_UTF8, PG_LATIN1,
  										   (const char *) src, len);
  			c1 = src[1] & 0x3f;
  			c = ((c & 0x1f) << 6) | c1;
  			if (c >= 0x80 && c <= 0xff)
  			{
  				*dest++ = (unsigned char) c;
  				src += 2;
  				len -= 2;
  			}
  			else
  				report_untranslatable_char(PG_UTF8, PG_LATIN1,
  										   (const char *) src, len);
  		}
  	}
  	*dest = '\0';
  
  	PG_RETURN_VOID();
  }
  