;/*
SC resopt desc_MacPICT2.c nodebug opt optsize link nostrt nostkext nostkchk
quit 
*/
/* Execute this file to compile with SAS C 
 * Ex. "1.Ram:>execute desc_MacPICT2.c"
 *
 * Otherwise it must be compiled with no stack checking. 
 * It must not be linked with any startup code so that DTHook is
 * the entry point for the executable.
 *
 */

#include <exec/types.h>
#include <exec/memory.h>
#include <dos/dos.h>
#include <dos/dosextens.h>
#include <datatypes/datatypes.h>
#include <datatypes/pictureclass.h>

#include <clib/exec_protos.h>
#include <clib/dos_protos.h>
#include <clib/utility_protos.h>

#include <pragmas/exec_pragmas.h>
#include <pragmas/dos_pragmas.h>
#include <pragmas/utility_pragmas.h>

#define SysBase          dthc->dthc_SysBase
#define DOSBase          dthc->dthc_DOSBase
#define UtilityBase      dthc->dthc_UtilityBase

#define HEADER_SIZE 0x200
#define	PICT_picVersion	0x0011
#define PICT_MacPICT2 0x02ff
#define BUFSIZE 0x80
#define MAXCHECK 0x3e /* BUFSIZE/2 - 2 */

BOOL __asm DTHook (register __a0 struct DTHookContext * dthc)
{
  BOOL retval = FALSE;
  ULONG n;
  UWORD *buffer;
  BPTR fh;

  /* Make sure we have a filehandle */
  if (fh = dthc->dthc_FileHandle) {

    /* Allocate a buffer */
    if(buffer = AllocVec(BUFSIZE, MEMF_PUBLIC)) {

      Seek(fh, HEADER_SIZE, OFFSET_BEGINNING);
      if(Read(fh, buffer, BUFSIZE) == BUFSIZE) {
        n = 5;
        while((n < MAXCHECK) && (buffer[n]==0)) n++;
        if((buffer[n]==PICT_picVersion) && (buffer[n+1]==PICT_MacPICT2))
          retval = TRUE;
      }
      /* Do not steal memory */
      FreeVec(buffer);		
    }
  }
  return retval;
}