FreeTDS Development Group

[Frediano Ziglio <freddyz77 AT tin.it>]

Il dom, 2002-11-17 alle 18:32, James K. Lowden ha scritto:
> On 17 Nov 2002 11:07:15 +0100, Frediano Ziglio <freddyz77 AT tin.it> wrote:
> > This type had many problems:
> > - conversions to VARBINARY was unavailable
> > - unsupported VARBINARY > 255 (mssql7+)
> > (also a bad buffer overflow was spotted)
> > This was fixed saving VARBINARY in libtds in the same way of BINARY (a
> > simple array of bytes). This has some drawbacks:
> > - conversion to VARBINARY are trivial (the good one)
> 
> All good!
> 
> > - libraries should handle "conversion" from libtds VARBINARY to library
> > VARBINARY. 
> 
> Not clear to me.  Could you point to the lines in convert.c, please?  
> 

The lack is not in convert.c but in client source
See this page (search for CS_VARBINARY). There is a binding type in
ctlib (that seem  not supported by our library). It return a structure
CS_VARBINARY. Same lack for CS_VARCHAR. ODBC haven't this problem,
dblib.. I don't know... Also libtds do not handle this structure...
http://manuals.sybase.com/onlinebooks/group-cn/cng1250e/guide/@Generic__BookTextView/4041

> > It seem that dblib/ctlib do not return VARBINARY type.. quite
> > strange.
> 
> Sybase db-lib documentation for dbcoltype:
> 
>     In a few cases, the token value returned by this routine may 
>     not correspond exactly with the column's server datatype:  
>     ·    SYBVARCHAR is returned as SYBCHAR.
>     ·    SYBVARBINARY is returned as SYBBINARY.

Strange! Does our library have same behavior?

>     ·    SYBDATETIMN is returned as SYBDATETIME.
>     ·    SYBMONEYN is returned as SYBMONEY.
>     ·    SYBFLTN is returned as SYBFLT8.
>     ·    SYBINTN is returned as SYBINT1, SYBINT2, or SYBINT4, 
>     depending on the actual type of the SYBINTN.
> 
> and dbconvert:
> 
>     A conversion to or from the datatypes SYBBINARY and SYBIMAGE is 
>     a straight bit-copy, except when the conversion involves SYBCHAR
>     or SYBTEXT. When converting SYBCHAR or SYBTEXT data to 
>     SYBBINARY or SYBIMAGE, DBCONVERT interprets the SYBCHAR or
>     SYBTEXT string as hexadecimal, whether or not the string contains
>     a leading "0x". When converting SYBBINARY or SYBIMAGE data to 
>     SYBCHAR or SYBTEXT, dbconvert creates a hexadecimal string 
>     without a leading "0x".
> 

Correct.

> 
> Frediano, do you think this will help Paul Kiela?  Were we lying about the
> length of a returned buffer?  Not that that should result in a segfault in
> PHP.  
> 

I don't remember. PHP has a bug returning binary data. It call dbconvert
using same length of buffer (but dbconvert require double of space) and
pass buffer length as -1 (there is sufficient space). So lead to a
buffer overflow...

> Chris's data have no binary types.  All numeric, char, and datetime
> AFAICT.  I think I misled you; he *does* use numeric conversion.  See my
> message to him on 14 November.  
> 

I think I should compile PHP... very strange... but problem raise after
numeric change... so...

bye
  freddy77