Re: Re: About GNU Ghostscript 707

Apologies, I meant to say InDesign 2.0 and not Illustrator 10.
Here is a PS file that crashes Ghostscript, and demonstrates the issue 
described below.
thanks.



On Thursday, September 11, 2003, at 11:59  pm, Russell Lang wrote:

> Yannis,
>
> Could please provide a small PostScript file with DSC comments
> that triggers this problem?  I don't have AI10.
>
> Adding nulls to the end of the buffer should not be needed.
>
> Russell
>
> On 11 Sep 2003 at 0:53, Yannis Calotychos wrote:
>
>> Ghostscript : all versions
>> file        : dscparse.c
>> function    : dsc_scan_data()
>> system      : Apple PowerBook G4 800/Mac OS X 1.2.6
>> remarks     :
>> the buffer kept by ghostscript is getting refilled when reading the ps
>> file.
>> occasionally the new data combined with the data already in the buffer
>> causes the parser to enter an infinite loop.
>> for example the buffer may look like:
>> ABCDEFGH
>>
>> after token H is parsed, the buffer may be refilled to
>> IJKLEFGH
>>
>> the new buffer can cause the parser to enter an infinite loop whereby
>> all tokens in "IJKLEFGH" are parsed.
>> a simple fix that zeros trailing parts of the buffer (to IJKL0000)
>> fixes this issue.
>> this issue crashes GS with most sample files provided by the latest
>> Adobe Illustrator installation (AI10 for Mac OS X).
>>
>> I hope this makes sense,
>> Please review, and possibly incorporate the code shown below (change 
>> is
>> bracketed in comments /* Y.Calotychos - iView Multimedia Ltd. */)
>>
>> We have a few more changes regarding functions mac_find_font_family()
>> and mac_get_font_encoding() that coould be used to load the correct
>> fonts. however we are still trying to understand how gs calculates the
>> metrics of strings as, altgough our corrections work in therms of the
>> font that is used, the character spacing/kerning is not correct.
>> I would be glad to send sample code.
>>
>>
>> ------------------------------------
>>
>>
>> int
>> dsc_scan_data(CDSC *dsc, const char *data, int length)
>> {
>>      int bytes_read;
>>      int code = 0;
>>
>>      if (dsc == NULL)
>> 	return CDSC_ERROR;
>>
>>      if (dsc->id == CDSC_NOTDSC)
>> 	return CDSC_NOTDSC;
>>      dsc->id = CDSC_OK;
>>      if (dsc->eof)
>> 	return CDSC_OK;	/* ignore */
>>
>>      if (length == 0) {
>> 	/* EOF, so process what remains */
>> 	dsc->eof = TRUE;
>>      }
>>
>>      do {
>> 	if (dsc->id == CDSC_NOTDSC)
>> 	    break;
>>
>> 	if (length != 0) {
>> 		/* Y.Calotychos - iView Multimedia Ltd. */
>> 		
>> 		/* OLD CODE --------------
>> 	    if (dsc->data_length > CDSC_DATA_LENGTH/2) {
>> 		memmove(dsc->data, dsc->data + dsc->data_index,
>> 		    dsc->data_length - dsc->data_index);
>> 		dsc->data_offset += dsc->data_index;
>> 		dsc->data_length -= dsc->data_index;
>> 		dsc->data_index = 0;
>> 	    } END OF OLD CODE -------- */
>> 	
>> 	
>> 	    if (dsc->data_length > CDSC_DATA_LENGTH/2)
>> 	    {
>> 	    	// copy the remaining data to the top of the buffer.
>> 	    	// we really nead to clear this array as parsers can get 
>> confused
>> as to where
>> 	    	// this line breaks
>> 	    	long l = dsc->data_length - dsc->data_index;
>> 			memmove(dsc->data, dsc->data + dsc->data_index, l);
>> 			memset(dsc->data+l, 0, CDSC_DATA_LENGTH-l);
>>
>>
>> 			dsc->data_offset += dsc->data_index;
>> 			dsc->data_length -= dsc->data_index;
>> 			dsc->data_index = 0;
>> 	    }
>> 		/* Y.Calotychos - iView Multimedia Ltd. */
>>
>>
>> 	    /* append to buffer */
>> 	    bytes_read = min(length, (int)(CDSC_DATA_LENGTH -
>> dsc->data_length));
>> 	    memcpy(dsc->data + dsc->data_length, data, bytes_read);
>> 	    dsc->data_length += bytes_read;
>> 	    data += bytes_read;
>> 	    length -= bytes_read;
>> 	}
>> 	if (dsc->scan_section == scan_none) {
>> 	    code = dsc_scan_type(dsc);
>> 	    if (code == CDSC_NEEDMORE) {
>> 		/* need more characters before we can identify type */
>> 		code = CDSC_OK;
>> 		break;
>> 	    }
>> 	    dsc->id = code;
>> 	}
>>
>>          if (code == CDSC_NOTDSC) {
>> 	    dsc->id = CDSC_NOTDSC;
>> 	    break;
>> 	}
>>
>> 	while ((code = dsc_read_line(dsc)) > 0) {
>> 	    if (dsc->id == CDSC_NOTDSC)
>> 		break;
>> 	    if (dsc->file_length &&
>> 		(dsc->data_offset + dsc->data_index > dsc->file_length)) {
>> 		/* have read past end of where we need to parse. */
>> 		return CDSC_OK;	/* ignore */
>> 	    }
>> 	    if (dsc->doseps_end &&
>> 		(dsc->data_offset + dsc->data_index > dsc->doseps_end)) {
>> 		/* have read past end of DOS EPS PostScript section */
>> 		return CDSC_OK;	/* ignore */
>> 	    }
>> 	    if (dsc->eof)
>> 		return CDSC_OK;
>> 	    if (dsc->skip_document)
>> 		continue;	/* embedded document */
>> 	    if (dsc->skip_lines)
>> 		continue;	/* embedded lines */
>> 	    if (IS_DSC(dsc->line, "%%BeginData:"))
>> 		continue;
>> 	    if (IS_DSC(dsc->line, "%%BeginBinary:"))
>> 		continue;
>> 	    if (IS_DSC(dsc->line, "%%EndDocument"))
>> 		continue;
>> 	    if (IS_DSC(dsc->line, "%%EndData"))
>> 		continue;
>> 	    if (IS_DSC(dsc->line, "%%EndBinary"))
>> 		continue;
>>
>> 	    do {
>> 		switch (dsc->scan_section) {
>> 		    case scan_comments:
>> 			code = dsc_scan_comments(dsc);
>> 			break;
>> 		    case scan_pre_preview:
>> 		    case scan_preview:
>> 			code = dsc_scan_preview(dsc);
>> 			break;
>> 		    case scan_pre_defaults:
>> 		    case scan_defaults:
>> 			code = dsc_scan_defaults(dsc);
>> 			break;
>> 		    case scan_pre_prolog:
>> 		    case scan_prolog:
>> 			code = dsc_scan_prolog(dsc);
>> 			break;
>> 		    case scan_pre_setup:
>> 		    case scan_setup:
>> 			code = dsc_scan_setup(dsc);
>> 			break;
>> 		    case scan_pre_pages:
>> 		    case scan_pages:
>> 			code = dsc_scan_page(dsc);
>> 			break;
>> 		    case scan_pre_trailer:
>> 		    case scan_trailer:
>> 			code = dsc_scan_trailer(dsc);
>> 			break;
>> 		    case scan_eof:
>> 			code = CDSC_OK;
>> 			break;
>> 		    default:
>> 			/* invalid state */
>> 			code = CDSC_ERROR;
>> 		}
>> 		/* repeat if line is start of next section */
>> 	    } while (code == CDSC_PROPAGATE);
>>
>> 	    /* if DOS EPS header not complete, ask for more */
>> 	    if (code == CDSC_NEEDMORE) {
>> 		code = CDSC_OK;
>> 		break;
>> 	    }
>> 	    if (code == CDSC_NOTDSC) {
>> 		dsc->id = CDSC_NOTDSC;
>> 		break;
>> 	    }
>> 	}
>>      } while (length != 0);
>>
>>      return (code < 0) ? code : dsc->id;
>> }
>>
>>
>>
>> -------------------------------------
>> yannis calotychos ph.d.
>> www.iview-multimedia.com
>>
>> _______________________________________________
>> gs-code-review mailing list
>> [email protected]
>> http://www.ghostscript.com/mailman/listinfo/gs-code-review
>
>
>
> Russell Lang                   [email protected]
> Ghostgum Software Pty Ltd      http://www.ghostgum.com.au/
>
>
>
>

-------------------------------------
yannis calotychos ph.d.
www.iview-multimedia.com