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Make text <=> char conversion functions convert zero character to and

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from an empty text string.  This makes them consistent with the de facto
behavior of type char's I/O conversion functions, and avoids generating
text values with embedded nulls, which confuse many text operators.
This commit is contained in:
Tom Lane 2001-05-28 21:58:32 +00:00
parent a056f14be0
commit 8a3b80deb0
1 changed files with 33 additions and 5 deletions
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38
src/backend/utils/adt/char.c
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@ -9,7 +9,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/char.c,v 1.30 2001/01/24 19:43:13 momjian Exp $ * $Header: /cvsroot/pgsql/src/backend/utils/adt/char.c,v 1.31 2001/05/28 21:58:32 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -23,6 +23,8 @@
/* /*
* charin - converts "x" to 'x' * charin - converts "x" to 'x'
*
* Note that an empty input string will implicitly be converted to \0.
*/ */
Datum Datum
charin(PG_FUNCTION_ARGS) charin(PG_FUNCTION_ARGS)
@ -34,6 +36,10 @@ charin(PG_FUNCTION_ARGS)
/* /*
* charout - converts 'x' to "x" * charout - converts 'x' to "x"
*
* Note that if the char value is \0, the resulting string will appear
* to be empty (null-terminated after zero characters). So this is the
* inverse of the charin() function for such data.
*/ */
Datum Datum
charout(PG_FUNCTION_ARGS) charout(PG_FUNCTION_ARGS)
@ -147,13 +153,24 @@ chardiv(PG_FUNCTION_ARGS)
PG_RETURN_CHAR((int8) arg1 / (int8) arg2); PG_RETURN_CHAR((int8) arg1 / (int8) arg2);
} }
Datum Datum
text_char(PG_FUNCTION_ARGS) text_char(PG_FUNCTION_ARGS)
{ {
text *arg1 = PG_GETARG_TEXT_P(0); text *arg1 = PG_GETARG_TEXT_P(0);
char result;
/* XXX what if arg1 has length zero? */ /*
PG_RETURN_CHAR(*(VARDATA(arg1))); * An empty input string is converted to \0 (for consistency with charin).
* If the input is longer than one character, the excess data is silently
* discarded.
*/
if (VARSIZE(arg1) > VARHDRSZ)
result = *(VARDATA(arg1));
else
result = '\0';
PG_RETURN_CHAR(result);
} }
Datum Datum
@ -162,8 +179,19 @@ char_text(PG_FUNCTION_ARGS)
char arg1 = PG_GETARG_CHAR(0); char arg1 = PG_GETARG_CHAR(0);
text *result = palloc(VARHDRSZ + 1); text *result = palloc(VARHDRSZ + 1);
VARATT_SIZEP(result) = VARHDRSZ + 1; /*
*(VARDATA(result)) = arg1; * Convert \0 to an empty string, for consistency with charout (and
* because the text stuff doesn't like embedded nulls all that well).
*/
if (arg1 != '\0')
{
VARATT_SIZEP(result) = VARHDRSZ + 1;
*(VARDATA(result)) = arg1;
}
else
{
VARATT_SIZEP(result) = VARHDRSZ;
}
PG_RETURN_TEXT_P(result); PG_RETURN_TEXT_P(result);
} }