FreeTDS Development Group

[<camber AT ais.org>]

Hi Bob,

Thanks for the patches, I'll try to get them merged in tonight.

On Sun, 4 Jun 2000, Bob Kline wrote:

> On Sun, 4 Jun 2000, Bob Kline wrote:
> 
> > On Sat, 3 Jun 2000, Bob Kline wrote:
> > 
> > So I made a set of diffs against the 0.50 sources.  [snip ...]
> 
> I'm having a public conversation with myself. :->} 
> 
> The patches I sent in earlier this morning were flawed. Here are the
> flaws:
> 
> 1. I was mistaken in my observation that the gcc wcslen() is calculating
>    lengths correctly for UTF-16 strings.  It doesn't, because in the
>    gcc world, wide characters are four bytes wide, not two.
> 2. I had hoped that I would be able to avoid touching anything but the
>    tds layer, but Microsoft isn't null-terminating the NTEXT data that
>    it sends.  The tds layer is obtaining the correct length from the tds
>    stream, but the dblib layer was discarding this information.  So the
>    tds conversion code can't calculate the length and it can't get the
>    length without some modifications to dblib.c.
dblib layer should really care about the length.  The application is
responsible for ensure 1) there is a max length (in bytes) 2) there is
sufficient space for the returning text.  MS must introduce a new binding
type to handle unicode right? (Something like NSTRINGBIND instead of
STRINGBIND???) Does anyone know what this might be?  I believe ctlib
support multichar codes.

> 3. I believe I guessed incorrectly about the return value from 
>    tds_convert(), thinking that for string values it should represent
>    the number of characters.  It seems more likely that it is supposed
>    to represent the number of bytes converted for all types.  Haven't
>    been able to find the comments documenting what the real answer is.
The return from tds_convert() is the size of converted data...ie it
includes the null.

> 4. The upper layers don't provide any way to bind to a wide-character
>    string variable, so the destination type comes through as -1 when
>    I pass through the data type byte for NTEXT (99).  The real fix 
>    for this, of course, is to extend all the upper layers to fill
>    this gap, but I'm reluctant to disturb any layers above tds more
>    than I have to, so as a stopgap solution, I've added -1 to the
>    switch statement in the new tds_convert_ntext() function, preserving
>    the 16-bit characters from the original transmission.
again, a new bind type is needed.  We need to know if MS has put one it
their dblib, otherwise I nominate NSTRINGBIND and NTBNSTRINGBIND.

> 
> The replacement patches below fix all of these flaws.  Please use them
> instead of those sent in earlier today.  Sorry for the premature
> submission.
> 
> 
> *** dblib.c.orig      Tue Nov 30 22:20:34 1999
> --- dblib.c   Sun Jun  4 21:05:45 2000
> ***************
> *** 325,332 ****
> --- 325,334 ----
>            }
>            else
>            {
> +             DBINT srclen = -1;
>       
>               if (is_blob_type(curcol->column_type)) {
> +                srclen = curcol->column_textsize;
>               src =  curcol->column_textvalue;
>               } else {
>                  src = ((char*)buffer_row_address(buf, index)) 
> ***************
> *** 339,345 ****
>               dbconvert(dbproc,
>                         srctype,                      /* srctype  */
>                         src,                          /* src      */
> !                       -1,                           /* srclen   */
>                         desttype,                     /* desttype */
>                         curcol->varaddr,              /* dest     */
>                         curcol->column_bindlen);      /* destlen  */
> --- 341,347 ----
>               dbconvert(dbproc,
>                         srctype,                      /* srctype  */
>                         src,                          /* src      */
> !                       srclen,                       /* srclen   */
>                         desttype,                     /* desttype */
>                         curcol->varaddr,              /* dest     */
>                         curcol->column_bindlen);      /* destlen  */
> 
> 
> *** tds.h.orig        Sun Jun  4 08:28:18 2000
> --- tds.h     Sun Jun  4 08:24:39 2000
> ***************
> *** 155,160 ****
> --- 155,161 ----
>   #define SYBDATETIME  61   /* 0x3D */
>   #define SYBBIT       50   /* 0x32 */
>   #define SYBTEXT      35   /* 0x23 */
> + #define SYBNTEXT     99   /* 0x63 */
>   #define SYBIMAGE     34   /* 0x22 */
>   #define SYBMONEY4    122  /* 0x7A */
>   #define SYBMONEY     60   /* 0x3C */
> ***************
> *** 196,203 ****
>                       x==SYBVARBINARY || \
>                       x==SYBMONEYN    || \
>                       x==SYBTEXT      || \
> !                     x==SYBIMAGE)
> ! #define is_blob_type(x) (x==SYBTEXT || x==SYBIMAGE)
>   /* large type means it has a two byte size field */
>   #define is_large_type(x) (x>128)
>   #define is_numeric_type(x) (x==SYBNUMERIC || x==SYBDECIMAL)
> --- 197,205 ----
>                       x==SYBVARBINARY || \
>                       x==SYBMONEYN    || \
>                       x==SYBTEXT      || \
> !                     x==SYBIMAGE || \
> !                     x==SYBNTEXT)
> ! #define is_blob_type(x) (x==SYBTEXT || x==SYBIMAGE || x==SYBNTEXT)
>   /* large type means it has a two byte size field */
>   #define is_large_type(x) (x>128)
>   #define is_numeric_type(x) (x==SYBNUMERIC || x==SYBDECIMAL)
> 
> *** convert.c.orig    Fri Dec  3 20:06:07 1999
> --- convert.c Sun Jun  4 20:42:59 2000
> ***************
> *** 23,28 ****
> --- 23,29 ----
>   #include <stdlib.h>
>   #include <unistd.h>
>   #include <time.h>
> + #include <assert.h>
>   
>   
>   static char  software_version[]   = "$Id: convert.c,v 1.35 1999/12/04 
> 01:06:07 camber Exp $";
> ***************
> *** 103,108 ****
> --- 104,167 ----
>            return cplen;
>      }
>   }
> + 
> + typedef unsigned short utf16_t;
> + 
> + static TDS_UINT utf16len(const utf16_t* s)
> + {
> +     const utf16_t* p = s;
> +     while (*p++)
> +             ;
> +     return p - s;
> + }
> + 
> + TDS_INT tds_convert_ntext(int srctype,unsigned char *src,TDS_UINT srclen,
> +     int desttype,unsigned char *dest,TDS_UINT destlen)
> + {
> +     /* 
> +      * XXX Limit of 255 + 1 needs to be fixed by determining what the 
> +      *     real limit of [N][VAR]CHAR columns is.
> +      * XXX What about NCHAR?  Don't see a constant for it in tds.h.
> +      * XXX Case for -1 in switch statement because upper levels don't
> +      *     have a way to bind to wide-character types.
> +      */
> +     TDS_UINT i, cplen, char_limit = 255;
> +     utf16_t* wsrc  = (utf16_t*)src;
> +     utf16_t* wdest = (utf16_t*)dest;
> +     assert(sizeof(utf16_t) == 2);
> +     switch (desttype) {
> +             case SYBNVARCHAR:
> +                     if (destlen > char_limit * sizeof(utf16_t))
> +                             destlen = char_limit * sizeof(utf16_t);
> +                     /* Fall through ... */
> +             case SYBNTEXT:
> +             case -1:
> +                     cplen = srclen > destlen ? destlen : srclen;
> +                     memcpy(dest, src, cplen);
> +                     if (destlen < srclen + sizeof(utf16_t)) {
> +                             size_t term_pos  = destlen - sizeof(utf16_t);
> +                             size_t odd_bytes = term_pos % sizeof(utf16_t);
> +                             term_pos -= odd_bytes;
> +                             wdest[term_pos / sizeof(utf16_t)] = 0;
> +                     }
> +             else
> +                             wdest[cplen / sizeof(utf16_t)] = 0;
> +                     return utf16len(wdest) * 2;
> +             default:
> +                     /* Assume caller wants conversion to narrow string. */
> +                     if (destlen > char_limit && desttype != SYBTEXT)
> +                             destlen = char_limit;
> +                     cplen = srclen > destlen ? destlen : srclen;
> +                     for (i = 0; i < cplen; ++i)
> +                             dest[i] = (unsigned char)wsrc[i];
> +                     if (destlen < srclen)
> +                             dest[destlen - 1] = 0;
> +                     else
> +                             dest[cplen] = 0;
> +                     return strlen(dest);
> +     }
> + }
> + 
>   TDS_INT tds_convert_binary(int srctype,unsigned char *src,TDS_INT srclen,
>       int desttype,unsigned char *dest,TDS_INT destlen)
>   {
> ***************
> *** 678,683 ****
> --- 737,746 ----
>                       break;
>               case SYBTEXT:
>                       return tds_convert_text(srctype,src,srclen,
> +                             desttype,dest,destlen);
> +                     break;
> +             case SYBNTEXT:
> +                     return tds_convert_ntext(srctype,src,srclen,
>                               desttype,dest,destlen);
>                       break;
>               default:
> 
> 
> -- 
> Bob Kline
> mailto:bkline AT rksystems.com
> http://www.rksystems.com
> 
>