/src/compiler/android-ndk/jni/freetype/src/truetype/ttinterp.c

/***************************************************************************/
/*                                                                         */
/*  ttinterp.c                                                             */
/*                                                                         */
/*    TrueType bytecode interpreter (body).                                */
/*                                                                         */
/*  Copyright 1996-2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 by */
/*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
/*                                                                         */
/*  This file is part of the FreeType project, and may only be used,       */
/*  modified, and distributed under the terms of the FreeType project      */
/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/***************************************************************************/


#include <ft2build.h>
#include FT_INTERNAL_DEBUG_H
#include FT_INTERNAL_CALC_H
#include FT_TRIGONOMETRY_H
#include FT_SYSTEM_H

#include "ttinterp.h"

#include "tterrors.h"


#ifdef TT_USE_BYTECODE_INTERPRETER


#define TT_MULFIX           FT_MulFix
#define TT_MULDIV           FT_MulDiv
#define TT_MULDIV_NO_ROUND  FT_MulDiv_No_Round


  /*************************************************************************/
  /*                                                                       */
  /* The macro FT_COMPONENT is used in trace mode.  It is an implicit      */
  /* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log  */
  /* messages during execution.                                            */
  /*                                                                       */
#undef  FT_COMPONENT
#define FT_COMPONENT  trace_ttinterp

  /*************************************************************************/
  /*                                                                       */
  /* In order to detect infinite loops in the code, we set up a counter    */
  /* within the run loop.  A single stroke of interpretation is now        */
  /* limited to a maximal number of opcodes defined below.                 */
  /*                                                                       */
#define MAX_RUNNABLE_OPCODES  1000000L


  /*************************************************************************/
  /*                                                                       */
  /* There are two kinds of implementations:                               */
  /*                                                                       */
  /* a. static implementation                                              */
  /*                                                                       */
  /*    The current execution context is a static variable, which fields   */
  /*    are accessed directly by the interpreter during execution.  The    */
  /*    context is named `cur'.                                            */
  /*                                                                       */
  /*    This version is non-reentrant, of course.                          */
  /*                                                                       */
  /* b. indirect implementation                                            */
  /*                                                                       */
  /*    The current execution context is passed to _each_ function as its  */
  /*    first argument, and each field is thus accessed indirectly.        */
  /*                                                                       */
  /*    This version is fully re-entrant.                                  */
  /*                                                                       */
  /* The idea is that an indirect implementation may be slower to execute  */
  /* on low-end processors that are used in some systems (like 386s or     */
  /* even 486s).                                                           */
  /*                                                                       */
  /* As a consequence, the indirect implementation is now the default, as  */
  /* its performance costs can be considered negligible in our context.    */
  /* Note, however, that we kept the same source with macros because:      */
  /*                                                                       */
  /* - The code is kept very close in design to the Pascal code used for   */
  /*   development.                                                        */
  /*                                                                       */
  /* - It's much more readable that way!                                   */
  /*                                                                       */
  /* - It's still open to experimentation and tuning.                      */
  /*                                                                       */
  /*************************************************************************/


#ifndef TT_CONFIG_OPTION_STATIC_INTERPRETER     /* indirect implementation */

#define CUR  (*exc)                             /* see ttobjs.h */

  /*************************************************************************/
  /*                                                                       */
  /* This macro is used whenever `exec' is unused in a function, to avoid  */
  /* stupid warnings from pedantic compilers.                              */
  /*                                                                       */
#define FT_UNUSED_EXEC  FT_UNUSED( exc )

#else                                           /* static implementation */

#define CUR  cur

#define FT_UNUSED_EXEC  int  __dummy = __dummy

  static
  TT_ExecContextRec  cur;   /* static exec. context variable */

  /* apparently, we have a _lot_ of direct indexing when accessing  */
  /* the static `cur', which makes the code bigger (due to all the  */
  /* four bytes addresses).                                         */

#endif /* TT_CONFIG_OPTION_STATIC_INTERPRETER */


  /*************************************************************************/
  /*                                                                       */
  /* The instruction argument stack.                                       */
  /*                                                                       */
#define INS_ARG  EXEC_OP_ FT_Long*  args    /* see ttobjs.h for EXEC_OP_ */


  /*************************************************************************/
  /*                                                                       */
  /* This macro is used whenever `args' is unused in a function, to avoid  */
  /* stupid warnings from pedantic compilers.                              */
  /*                                                                       */
#define FT_UNUSED_ARG  FT_UNUSED_EXEC; FT_UNUSED( args )


  /*************************************************************************/
  /*                                                                       */
  /* The following macros hide the use of EXEC_ARG and EXEC_ARG_ to        */
  /* increase readability of the code.                                     */
  /*                                                                       */
  /*************************************************************************/


#define SKIP_Code() \
          SkipCode( EXEC_ARG )

#define GET_ShortIns() \
          GetShortIns( EXEC_ARG )

#define NORMalize( x, y, v ) \
          Normalize( EXEC_ARG_ x, y, v )

#define SET_SuperRound( scale, flags ) \
          SetSuperRound( EXEC_ARG_ scale, flags )

#define ROUND_None( d, c ) \
          Round_None( EXEC_ARG_ d, c )

#define INS_Goto_CodeRange( range, ip ) \
          Ins_Goto_CodeRange( EXEC_ARG_ range, ip )

#define CUR_Func_move( z, p, d ) \
          CUR.func_move( EXEC_ARG_ z, p, d )

#define CUR_Func_move_orig( z, p, d ) \
          CUR.func_move_orig( EXEC_ARG_ z, p, d )

#define CUR_Func_round( d, c ) \
          CUR.func_round( EXEC_ARG_ d, c )

#define CUR_Func_read_cvt( index ) \
          CUR.func_read_cvt( EXEC_ARG_ index )

#define CUR_Func_write_cvt( index, val ) \
          CUR.func_write_cvt( EXEC_ARG_ index, val )

#define CUR_Func_move_cvt( index, val ) \
          CUR.func_move_cvt( EXEC_ARG_ index, val )

#define CURRENT_Ratio() \
          Current_Ratio( EXEC_ARG )

#define CURRENT_Ppem() \
          Current_Ppem( EXEC_ARG )

#define CUR_Ppem() \
          Cur_PPEM( EXEC_ARG )

#define INS_SxVTL( a, b, c, d ) \
          Ins_SxVTL( EXEC_ARG_ a, b, c, d )

#define COMPUTE_Funcs() \
          Compute_Funcs( EXEC_ARG )

#define COMPUTE_Round( a ) \
          Compute_Round( EXEC_ARG_ a )

#define COMPUTE_Point_Displacement( a, b, c, d ) \
          Compute_Point_Displacement( EXEC_ARG_ a, b, c, d )

#define MOVE_Zp2_Point( a, b, c, t ) \
          Move_Zp2_Point( EXEC_ARG_ a, b, c, t )


#define CUR_Func_project( v1, v2 )  \
          CUR.func_project( EXEC_ARG_ (v1)->x - (v2)->x, (v1)->y - (v2)->y )

#define CUR_Func_dualproj( v1, v2 )  \
          CUR.func_dualproj( EXEC_ARG_ (v1)->x - (v2)->x, (v1)->y - (v2)->y )

#define CUR_fast_project( v ) \
          CUR.func_project( EXEC_ARG_ (v)->x, (v)->y )

#define CUR_fast_dualproj( v ) \
          CUR.func_dualproj( EXEC_ARG_ (v)->x, (v)->y )


  /*************************************************************************/
  /*                                                                       */
  /* Instruction dispatch function, as used by the interpreter.            */
  /*                                                                       */
  typedef void  (*TInstruction_Function)( INS_ARG );


  /*************************************************************************/
  /*                                                                       */
  /* A simple bounds-checking macro.                                       */
  /*                                                                       */
#define BOUNDS( x, n )  ( (FT_UInt)(x) >= (FT_UInt)(n) )

#undef  SUCCESS
#define SUCCESS  0

#undef  FAILURE
#define FAILURE  1

#ifdef TT_CONFIG_OPTION_UNPATENTED_HINTING
#define GUESS_VECTOR( V )                                         \
  if ( CUR.face->unpatented_hinting )                             \
  {                                                               \
    CUR.GS.V.x = (FT_F2Dot14)( CUR.GS.both_x_axis ? 0x4000 : 0 ); \
    CUR.GS.V.y = (FT_F2Dot14)( CUR.GS.both_x_axis ? 0 : 0x4000 ); \
  }
#else
#define GUESS_VECTOR( V )
#endif

  /*************************************************************************/
  /*                                                                       */
  /*                        CODERANGE FUNCTIONS                            */
  /*                                                                       */
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Goto_CodeRange                                                  */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Switches to a new code range (updates the code related elements in */
  /*    `exec', and `IP').                                                 */
  /*                                                                       */
  /* <Input>                                                               */
  /*    range :: The new execution code range.                             */
  /*                                                                       */
  /*    IP    :: The new IP in the new code range.                         */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    exec  :: The target execution context.                             */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Goto_CodeRange( TT_ExecContext  exec,
                     FT_Int          range,
                     FT_Long         IP )
  {
    TT_CodeRange*  coderange;


    FT_ASSERT( range >= 1 && range <= 3 );

    coderange = &exec->codeRangeTable[range - 1];

    FT_ASSERT( coderange->base != NULL );

    /* NOTE: Because the last instruction of a program may be a CALL */
    /*       which will return to the first byte *after* the code    */
    /*       range, we test for IP <= Size instead of IP < Size.     */
    /*                                                               */
    FT_ASSERT( (FT_ULong)IP <= coderange->size );

    exec->code     = coderange->base;
    exec->codeSize = coderange->size;
    exec->IP       = IP;
    exec->curRange = range;

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Set_CodeRange                                                   */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Sets a code range.                                                 */
  /*                                                                       */
  /* <Input>                                                               */
  /*    range  :: The code range index.                                    */
  /*                                                                       */
  /*    base   :: The new code base.                                       */
  /*                                                                       */
  /*    length :: The range size in bytes.                                 */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    exec   :: The target execution context.                            */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Set_CodeRange( TT_ExecContext  exec,
                    FT_Int          range,
                    void*           base,
                    FT_Long         length )
  {
    FT_ASSERT( range >= 1 && range <= 3 );

    exec->codeRangeTable[range - 1].base = (FT_Byte*)base;
    exec->codeRangeTable[range - 1].size = length;

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Clear_CodeRange                                                 */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Clears a code range.                                               */
  /*                                                                       */
  /* <Input>                                                               */
  /*    range :: The code range index.                                     */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    exec  :: The target execution context.                             */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Does not set the Error variable.                                   */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Clear_CodeRange( TT_ExecContext  exec,
                      FT_Int          range )
  {
    FT_ASSERT( range >= 1 && range <= 3 );

    exec->codeRangeTable[range - 1].base = NULL;
    exec->codeRangeTable[range - 1].size = 0;

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /*                   EXECUTION CONTEXT ROUTINES                          */
  /*                                                                       */
  /*************************************************************************/


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Done_Context                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Destroys a given context.                                          */
  /*                                                                       */
  /* <Input>                                                               */
  /*    exec   :: A handle to the target execution context.                */
  /*                                                                       */
  /*    memory :: A handle to the parent memory object.                    */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Only the glyph loader and debugger should call this function.      */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Done_Context( TT_ExecContext  exec )
  {
    FT_Memory  memory = exec->memory;


    /* points zone */
    exec->maxPoints   = 0;
    exec->maxContours = 0;

    /* free stack */
    FT_FREE( exec->stack );
    exec->stackSize = 0;

    /* free call stack */
    FT_FREE( exec->callStack );
    exec->callSize = 0;
    exec->callTop  = 0;

    /* free glyph code range */
    FT_FREE( exec->glyphIns );
    exec->glyphSize = 0;

    exec->size = NULL;
    exec->face = NULL;

    FT_FREE( exec );

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Init_Context                                                       */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Initializes a context object.                                      */
  /*                                                                       */
  /* <Input>                                                               */
  /*    memory :: A handle to the parent memory object.                    */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    exec   :: A handle to the target execution context.                */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  static FT_Error
  Init_Context( TT_ExecContext  exec,
                FT_Memory       memory )
  {
    FT_Error  error;


    FT_TRACE1(( "Init_Context: new object at 0x%08p\n", exec ));

    exec->memory   = memory;
    exec->callSize = 32;

    if ( FT_NEW_ARRAY( exec->callStack, exec->callSize ) )
      goto Fail_Memory;

    /* all values in the context are set to 0 already, but this is */
    /* here as a remainder                                         */
    exec->maxPoints   = 0;
    exec->maxContours = 0;

    exec->stackSize = 0;
    exec->glyphSize = 0;

    exec->stack     = NULL;
    exec->glyphIns  = NULL;

    exec->face = NULL;
    exec->size = NULL;

    return TT_Err_Ok;

  Fail_Memory:
    FT_ERROR(( "Init_Context: not enough memory for 0x%08lx\n",
               (FT_Long)exec ));
    TT_Done_Context( exec );

    return error;
 }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Update_Max                                                         */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Checks the size of a buffer and reallocates it if necessary.       */
  /*                                                                       */
  /* <Input>                                                               */
  /*    memory     :: A handle to the parent memory object.                */
  /*                                                                       */
  /*    multiplier :: The size in bytes of each element in the buffer.     */
  /*                                                                       */
  /*    new_max    :: The new capacity (size) of the buffer.               */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    size       :: The address of the buffer's current size expressed   */
  /*                  in elements.                                         */
  /*                                                                       */
  /*    buff       :: The address of the buffer base pointer.              */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  static FT_Error
  Update_Max( FT_Memory  memory,
              FT_ULong*  size,
              FT_Long    multiplier,
              void*      _pbuff,
              FT_ULong   new_max )
  {
    FT_Error  error;
    void**    pbuff = (void**)_pbuff;


    if ( *size < new_max )
    {
      if ( FT_REALLOC( *pbuff, *size * multiplier, new_max * multiplier ) )
        return error;
      *size = new_max;
    }

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Load_Context                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Prepare an execution context for glyph hinting.                    */
  /*                                                                       */
  /* <Input>                                                               */
  /*    face :: A handle to the source face object.                        */
  /*                                                                       */
  /*    size :: A handle to the source size object.                        */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    exec :: A handle to the target execution context.                  */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Only the glyph loader and debugger should call this function.      */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Load_Context( TT_ExecContext  exec,
                   TT_Face         face,
                   TT_Size         size )
  {
    FT_Int          i;
    FT_ULong        tmp;
    TT_MaxProfile*  maxp;
    FT_Error        error;


    exec->face = face;
    maxp       = &face->max_profile;
    exec->size = size;

    if ( size )
    {
      exec->numFDefs   = size->num_function_defs;
      exec->maxFDefs   = size->max_function_defs;
      exec->numIDefs   = size->num_instruction_defs;
      exec->maxIDefs   = size->max_instruction_defs;
      exec->FDefs      = size->function_defs;
      exec->IDefs      = size->instruction_defs;
      exec->tt_metrics = size->ttmetrics;
      exec->metrics    = size->metrics;

      exec->maxFunc    = size->max_func;
      exec->maxIns     = size->max_ins;

      for ( i = 0; i < TT_MAX_CODE_RANGES; i++ )
        exec->codeRangeTable[i] = size->codeRangeTable[i];

      /* set graphics state */
      exec->GS = size->GS;

      exec->cvtSize = size->cvt_size;
      exec->cvt     = size->cvt;

      exec->storeSize = size->storage_size;
      exec->storage   = size->storage;

      exec->twilight  = size->twilight;
    }

    /* XXX: We reserve a little more elements on the stack to deal safely */
    /*      with broken fonts like arialbs, courbs, timesbs, etc.         */
    tmp = exec->stackSize;
    error = Update_Max( exec->memory,
                        &tmp,
                        sizeof ( FT_F26Dot6 ),
                        (void*)&exec->stack,
                        maxp->maxStackElements + 32 );
    exec->stackSize = (FT_UInt)tmp;
    if ( error )
      return error;

    tmp = exec->glyphSize;
    error = Update_Max( exec->memory,
                        &tmp,
                        sizeof ( FT_Byte ),
                        (void*)&exec->glyphIns,
                        maxp->maxSizeOfInstructions );
    exec->glyphSize = (FT_UShort)tmp;
    if ( error )
      return error;

    exec->pts.n_points   = 0;
    exec->pts.n_contours = 0;

    exec->zp1 = exec->pts;
    exec->zp2 = exec->pts;
    exec->zp0 = exec->pts;

    exec->instruction_trap = FALSE;

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Save_Context                                                    */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Saves the code ranges in a `size' object.                          */
  /*                                                                       */
  /* <Input>                                                               */
  /*    exec :: A handle to the source execution context.                  */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    size :: A handle to the target size object.                        */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Only the glyph loader and debugger should call this function.      */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Save_Context( TT_ExecContext  exec,
                   TT_Size         size )
  {
    FT_Int  i;


    /* XXXX: Will probably disappear soon with all the code range */
    /*       management, which is now rather obsolete.            */
    /*                                                            */
    size->num_function_defs    = exec->numFDefs;
    size->num_instruction_defs = exec->numIDefs;

    size->max_func = exec->maxFunc;
    size->max_ins  = exec->maxIns;

    for ( i = 0; i < TT_MAX_CODE_RANGES; i++ )
      size->codeRangeTable[i] = exec->codeRangeTable[i];

    return TT_Err_Ok;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    TT_Run_Context                                                     */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Executes one or more instructions in the execution context.        */
  /*                                                                       */
  /* <Input>                                                               */
  /*    debug :: A Boolean flag.  If set, the function sets some internal  */
  /*             variables and returns immediately, otherwise TT_RunIns()  */
  /*             is called.                                                */
  /*                                                                       */
  /*             This is commented out currently.                          */
  /*                                                                       */
  /* <Input>                                                               */
  /*    exec  :: A handle to the target execution context.                 */
  /*                                                                       */
  /* <Return>                                                              */
  /*    TrueType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    Only the glyph loader and debugger should call this function.      */
  /*                                                                       */
  FT_LOCAL_DEF( FT_Error )
  TT_Run_Context( TT_ExecContext  exec,
                  FT_Bool         debug )
  {
    FT_Error  error;


    if ( ( error = TT_Goto_CodeRange( exec, tt_coderange_glyph, 0  ) )
           != TT_Err_Ok )
      return error;

    exec->zp0 = exec->pts;
    exec->zp1 = exec->pts;
    exec->zp2 = exec->pts;

    exec->GS.gep0 = 1;
    exec->GS.gep1 = 1;
    exec->GS.gep2 = 1;

    exec->GS.projVector.x = 0x4000;
    exec->GS.projVector.y = 0x0000;

    exec->GS.freeVector = exec->GS.projVector;
    exec->GS.dualVector = exec->GS.projVector;

#ifdef TT_CONFIG_OPTION_UNPATENTED_HINTING
    exec->GS.both_x_axis = TRUE;
#endif

    exec->GS.round_state = 1;
    exec->GS.loop        = 1;

    /* some glyphs leave something on the stack. so we clean it */
    /* before a new execution.                                  */
    exec->top     = 0;
    exec->callTop = 0;

#if 1
    FT_UNUSED( debug );

    return exec->face->interpreter( exec );
#else
    if ( !debug )
      return TT_RunIns( exec );
    else
      return TT_Err_Ok;
#endif
  }


  /* The default value for `scan_control' is documented as FALSE in the */
  /* TrueType specification.  This is confusing since it implies a      */
  /* Boolean value.  However, this is not the case, thus both the       */
  /* default values of our `scan_type' and `scan_control' fields (which */
  /* the documentation's `scan_control' variable is split into) are     */
  /* zero.                                                              */

  const TT_GraphicsState  tt_default_graphics_state =
  {
    0, 0, 0,
    { 0x4000, 0 },
    { 0x4000, 0 },
    { 0x4000, 0 },

#ifdef TT_CONFIG_OPTION_UNPATENTED_HINTING
    TRUE,
#endif

    1, 64, 1,
    TRUE, 68, 0, 0, 9, 3,
    0, FALSE, 0, 1, 1, 1
  };


  /* documentation is in ttinterp.h */

  FT_EXPORT_DEF( TT_ExecContext )
  TT_New_Context( TT_Driver  driver )
  {
    TT_ExecContext  exec;
    FT_Memory       memory;


    memory = driver->root.root.memory;
    exec   = driver->context;

    if ( !driver->context )
    {
      FT_Error  error;


      /* allocate object */
      if ( FT_NEW( exec ) )
        goto Fail;

      /* initialize it; in case of error this deallocates `exec' too */
      error = Init_Context( exec, memory );
      if ( error )
        goto Fail;

      /* store it into the driver */
      driver->context = exec;
    }

    return driver->context;

  Fail:
    return NULL;
  }


  /*************************************************************************/
  /*                                                                       */
  /* Before an opcode is executed, the interpreter verifies that there are */
  /* enough arguments on the stack, with the help of the `Pop_Push_Count'  */
  /* table.                                                                */
  /*                                                                       */
  /* For each opcode, the first column gives the number of arguments that  */
  /* are popped from the stack; the second one gives the number of those   */
  /* that are pushed in result.                                            */
  /*                                                                       */
  /* Opcodes which have a varying number of parameters in the data stream  */
  /* (NPUSHB, NPUSHW) are handled specially; they have a negative value in */
  /* the `opcode_length' table, and the value in `Pop_Push_Count' is set   */
  /* to zero.                                                              */
  /*                                                                       */
  /*************************************************************************/


#undef  PACK
#define PACK( x, y )  ( ( x << 4 ) | y )


  static
  const FT_Byte  Pop_Push_Count[256] =
  {
    /* opcodes are gathered in groups of 16 */
    /* please keep the spaces as they are   */

    /*  SVTCA  y  */  PACK( 0, 0 ),
    /*  SVTCA  x  */  PACK( 0, 0 ),
    /*  SPvTCA y  */  PACK( 0, 0 ),
    /*  SPvTCA x  */  PACK( 0, 0 ),
    /*  SFvTCA y  */  PACK( 0, 0 ),
    /*  SFvTCA x  */  PACK( 0, 0 ),
    /*  SPvTL //  */  PACK( 2, 0 ),
    /*  SPvTL +   */  PACK( 2, 0 ),
    /*  SFvTL //  */  PACK( 2, 0 ),
    /*  SFvTL +   */  PACK( 2, 0 ),
    /*  SPvFS     */  PACK( 2, 0 ),
    /*  SFvFS     */  PACK( 2, 0 ),
    /*  GPV       */  PACK( 0, 2 ),
    /*  GFV       */  PACK( 0, 2 ),
    /*  SFvTPv    */  PACK( 0, 0 ),
    /*  ISECT     */  PACK( 5, 0 ),

    /*  SRP0      */  PACK( 1, 0 ),
    /*  SRP1      */  PACK( 1, 0 ),
    /*  SRP2      */  PACK( 1, 0 ),
    /*  SZP0      */  PACK( 1, 0 ),
    /*  SZP1      */  PACK( 1, 0 ),
    /*  SZP2      */  PACK( 1, 0 ),
    /*  SZPS      */  PACK( 1, 0 ),
    /*  SLOOP     */  PACK( 1, 0 ),
    /*  RTG       */  PACK( 0, 0 ),
    /*  RTHG      */  PACK( 0, 0 ),
    /*  SMD       */  PACK( 1, 0 ),
    /*  ELSE      */  PACK( 0, 0 ),
    /*  JMPR      */  PACK( 1, 0 ),
    /*  SCvTCi    */  PACK( 1, 0 ),
    /*  SSwCi     */  PACK( 1, 0 ),
    /*  SSW       */  PACK( 1, 0 ),

    /*  DUP       */  PACK( 1, 2 ),
    /*  POP       */  PACK( 1, 0 ),
    /*  CLEAR     */  PACK( 0, 0 ),
    /*  SWAP      */  PACK( 2, 2 ),
    /*  DEPTH     */  PACK( 0, 1 ),
    /*  CINDEX    */  PACK( 1, 1 ),
    /*  MINDEX    */  PACK( 1, 0 ),
    /*  AlignPTS  */  PACK( 2, 0 ),
    /*  INS_$28   */  PACK( 0, 0 ),
    /*  UTP       */  PACK( 1, 0 ),
    /*  LOOPCALL  */  PACK( 2, 0 ),
    /*  CALL      */  PACK( 1, 0 ),
    /*  FDEF      */  PACK( 1, 0 ),
    /*  ENDF      */  PACK( 0, 0 ),
    /*  MDAP[0]   */  PACK( 1, 0 ),
    /*  MDAP[1]   */  PACK( 1, 0 ),

    /*  IUP[0]    */  PACK( 0, 0 ),
    /*  IUP[1]    */  PACK( 0, 0 ),
    /*  SHP[0]    */  PACK( 0, 0 ),
    /*  SHP[1]    */  PACK( 0, 0 ),
    /*  SHC[0]    */  PACK( 1, 0 ),
    /*  SHC[1]    */  PACK( 1, 0 ),
    /*  SHZ[0]    */  PACK( 1, 0 ),
    /*  SHZ[1]    */  PACK( 1, 0 ),
    /*  SHPIX     */  PACK( 1, 0 ),
    /*  IP        */  PACK( 0, 0 ),
    /*  MSIRP[0]  */  PACK( 2, 0 ),
    /*  MSIRP[1]  */  PACK( 2, 0 ),
    /*  AlignRP   */  PACK( 0, 0 ),
    /*  RTDG      */  PACK( 0, 0 ),
    /*  MIAP[0]   */  PACK( 2, 0 ),
    /*  MIAP[1]   */  PACK( 2, 0 ),

    /*  NPushB    */  PACK( 0, 0 ),
    /*  NPushW    */  PACK( 0, 0 ),
    /*  WS        */  PACK( 2, 0 ),
    /*  RS        */  PACK( 1, 1 ),
    /*  WCvtP     */  PACK( 2, 0 ),
    /*  RCvt      */  PACK( 1, 1 ),
    /*  GC[0]     */  PACK( 1, 1 ),
    /*  GC[1]     */  PACK( 1, 1 ),
    /*  SCFS      */  PACK( 2, 0 ),
    /*  MD[0]     */  PACK( 2, 1 ),
    /*  MD[1]     */  PACK( 2, 1 ),
    /*  MPPEM     */  PACK( 0, 1 ),
    /*  MPS       */  PACK( 0, 1 ),
    /*  FlipON    */  PACK( 0, 0 ),
    /*  FlipOFF   */  PACK( 0, 0 ),
    /*  DEBUG     */  PACK( 1, 0 ),

    /*  LT        */  PACK( 2, 1 ),
    /*  LTEQ      */  PACK( 2, 1 ),
    /*  GT        */  PACK( 2, 1 ),
    /*  GTEQ      */  PACK( 2, 1 ),
    /*  EQ        */  PACK( 2, 1 ),
    /*  NEQ       */  PACK( 2, 1 ),
    /*  ODD       */  PACK( 1, 1 ),
    /*  EVEN      */  PACK( 1, 1 ),
    /*  IF        */  PACK( 1, 0 ),
    /*  EIF       */  PACK( 0, 0 ),
    /*  AND       */  PACK( 2, 1 ),
    /*  OR        */  PACK( 2, 1 ),
    /*  NOT       */  PACK( 1, 1 ),
    /*  DeltaP1   */  PACK( 1, 0 ),
    /*  SDB       */  PACK( 1, 0 ),
    /*  SDS       */  PACK( 1, 0 ),

    /*  ADD       */  PACK( 2, 1 ),
    /*  SUB       */  PACK( 2, 1 ),
    /*  DIV       */  PACK( 2, 1 ),
    /*  MUL       */  PACK( 2, 1 ),
    /*  ABS       */  PACK( 1, 1 ),
    /*  NEG       */  PACK( 1, 1 ),
    /*  FLOOR     */  PACK( 1, 1 ),
    /*  CEILING   */  PACK( 1, 1 ),
    /*  ROUND[0]  */  PACK( 1, 1 ),
    /*  ROUND[1]  */  PACK( 1, 1 ),
    /*  ROUND[2]  */  PACK( 1, 1 ),
    /*  ROUND[3]  */  PACK( 1, 1 ),
    /*  NROUND[0] */  PACK( 1, 1 ),
    /*  NROUND[1] */  PACK( 1, 1 ),
    /*  NROUND[2] */  PACK( 1, 1 ),
    /*  NROUND[3] */  PACK( 1, 1 ),

    /*  WCvtF     */  PACK( 2, 0 ),
    /*  DeltaP2   */  PACK( 1, 0 ),
    /*  DeltaP3   */  PACK( 1, 0 ),
    /*  DeltaCn[0] */ PACK( 1, 0 ),
    /*  DeltaCn[1] */ PACK( 1, 0 ),
    /*  DeltaCn[2] */ PACK( 1, 0 ),
    /*  SROUND    */  PACK( 1, 0 ),
    /*  S45Round  */  PACK( 1, 0 ),
    /*  JROT      */  PACK( 2, 0 ),
    /*  JROF      */  PACK( 2, 0 ),
    /*  ROFF      */  PACK( 0, 0 ),
    /*  INS_$7B   */  PACK( 0, 0 ),
    /*  RUTG      */  PACK( 0, 0 ),
    /*  RDTG      */  PACK( 0, 0 ),
    /*  SANGW     */  PACK( 1, 0 ),
    /*  AA        */  PACK( 1, 0 ),

    /*  FlipPT    */  PACK( 0, 0 ),
    /*  FlipRgON  */  PACK( 2, 0 ),
    /*  FlipRgOFF */  PACK( 2, 0 ),
    /*  INS_$83   */  PACK( 0, 0 ),
    /*  INS_$84   */  PACK( 0, 0 ),
    /*  ScanCTRL  */  PACK( 1, 0 ),
    /*  SDVPTL[0] */  PACK( 2, 0 ),
    /*  SDVPTL[1] */  PACK( 2, 0 ),
    /*  GetINFO   */  PACK( 1, 1 ),
    /*  IDEF      */  PACK( 1, 0 ),
    /*  ROLL      */  PACK( 3, 3 ),
    /*  MAX       */  PACK( 2, 1 ),
    /*  MIN       */  PACK( 2, 1 ),
    /*  ScanTYPE  */  PACK( 1, 0 ),
    /*  InstCTRL  */  PACK( 2, 0 ),
    /*  INS_$8F   */  PACK( 0, 0 ),

    /*  INS_$90  */   PACK( 0, 0 ),
    /*  INS_$91  */   PACK( 0, 0 ),
    /*  INS_$92  */   PACK( 0, 0 ),
    /*  INS_$93  */   PACK( 0, 0 ),
    /*  INS_$94  */   PACK( 0, 0 ),
    /*  INS_$95  */   PACK( 0, 0 ),
    /*  INS_$96  */   PACK( 0, 0 ),
    /*  INS_$97  */   PACK( 0, 0 ),
    /*  INS_$98  */   PACK( 0, 0 ),
    /*  INS_$99  */   PACK( 0, 0 ),
    /*  INS_$9A  */   PACK( 0, 0 ),
    /*  INS_$9B  */   PACK( 0, 0 ),
    /*  INS_$9C  */   PACK( 0, 0 ),
    /*  INS_$9D  */   PACK( 0, 0 ),
    /*  INS_$9E  */   PACK( 0, 0 ),
    /*  INS_$9F  */   PACK( 0, 0 ),

    /*  INS_$A0  */   PACK( 0, 0 ),
    /*  INS_$A1  */   PACK( 0, 0 ),
    /*  INS_$A2  */   PACK( 0, 0 ),
    /*  INS_$A3  */   PACK( 0, 0 ),
    /*  INS_$A4  */   PACK( 0, 0 ),
    /*  INS_$A5  */   PACK( 0, 0 ),
    /*  INS_$A6  */   PACK( 0, 0 ),
    /*  INS_$A7  */   PACK( 0, 0 ),
    /*  INS_$A8  */   PACK( 0, 0 ),
    /*  INS_$A9  */   PACK( 0, 0 ),
    /*  INS_$AA  */   PACK( 0, 0 ),
    /*  INS_$AB  */   PACK( 0, 0 ),
    /*  INS_$AC  */   PACK( 0, 0 ),
    /*  INS_$AD  */   PACK( 0, 0 ),
    /*  INS_$AE  */   PACK( 0, 0 ),
    /*  INS_$AF  */   PACK( 0, 0 ),

    /*  PushB[0]  */  PACK( 0, 1 ),
    /*  PushB[1]  */  PACK( 0, 2 ),
    /*  PushB[2]  */  PACK( 0, 3 ),
    /*  PushB[3]  */  PACK( 0, 4 ),
    /*  PushB[4]  */  PACK( 0, 5 ),
    /*  PushB[5]  */  PACK( 0, 6 ),
    /*  PushB[6]  */  PACK( 0, 7 ),
    /*  PushB[7]  */  PACK( 0, 8 ),
    /*  PushW[0]  */  PACK( 0, 1 ),
    /*  PushW[1]  */  PACK( 0, 2 ),
    /*  PushW[2]  */  PACK( 0, 3 ),
    /*  PushW[3]  */  PACK( 0, 4 ),
    /*  PushW[4]  */  PACK( 0, 5 ),
    /*  PushW[5]  */  PACK( 0, 6 ),
    /*  PushW[6]  */  PACK( 0, 7 ),
    /*  PushW[7]  */  PACK( 0, 8 ),

    /*  MDRP[00]  */  PACK( 1, 0 ),
    /*  MDRP[01]  */  PACK( 1, 0 ),
    /*  MDRP[02]  */  PACK( 1, 0 ),
    /*  MDRP[03]  */  PACK( 1, 0 ),
    /*  MDRP[04]  */  PACK( 1, 0 ),
    /*  MDRP[05]  */  PACK( 1, 0 ),
    /*  MDRP[06]  */  PACK( 1, 0 ),
    /*  MDRP[07]  */  PACK( 1, 0 ),
    /*  MDRP[08]  */  PACK( 1, 0 ),
    /*  MDRP[09]  */  PACK( 1, 0 ),
    /*  MDRP[10]  */  PACK( 1, 0 ),
    /*  MDRP[11]  */  PACK( 1, 0 ),
    /*  MDRP[12]  */  PACK( 1, 0 ),
    /*  MDRP[13]  */  PACK( 1, 0 ),
    /*  MDRP[14]  */  PACK( 1, 0 ),
    /*  MDRP[15]  */  PACK( 1, 0 ),

    /*  MDRP[16]  */  PACK( 1, 0 ),
    /*  MDRP[17]  */  PACK( 1, 0 ),
    /*  MDRP[18]  */  PACK( 1, 0 ),
    /*  MDRP[19]  */  PACK( 1, 0 ),
    /*  MDRP[20]  */  PACK( 1, 0 ),
    /*  MDRP[21]  */  PACK( 1, 0 ),
    /*  MDRP[22]  */  PACK( 1, 0 ),
    /*  MDRP[23]  */  PACK( 1, 0 ),
    /*  MDRP[24]  */  PACK( 1, 0 ),
    /*  MDRP[25]  */  PACK( 1, 0 ),
    /*  MDRP[26]  */  PACK( 1, 0 ),
    /*  MDRP[27]  */  PACK( 1, 0 ),
    /*  MDRP[28]  */  PACK( 1, 0 ),
    /*  MDRP[29]  */  PACK( 1, 0 ),
    /*  MDRP[30]  */  PACK( 1, 0 ),
    /*  MDRP[31]  */  PACK( 1, 0 ),

    /*  MIRP[00]  */  PACK( 2, 0 ),
    /*  MIRP[01]  */  PACK( 2, 0 ),
    /*  MIRP[02]  */  PACK( 2, 0 ),
    /*  MIRP[03]  */  PACK( 2, 0 ),
    /*  MIRP[04]  */  PACK( 2, 0 ),
    /*  MIRP[05]  */  PACK( 2, 0 ),
    /*  MIRP[06]  */  PACK( 2, 0 ),
    /*  MIRP[07]  */  PACK( 2, 0 ),
    /*  MIRP[08]  */  PACK( 2, 0 ),
    /*  MIRP[09]  */  PACK( 2, 0 ),
    /*  MIRP[10]  */  PACK( 2, 0 ),
    /*  MIRP[11]  */  PACK( 2, 0 ),
    /*  MIRP[12]  */  PACK( 2, 0 ),
    /*  MIRP[13]  */  PACK( 2, 0 ),
    /*  MIRP[14]  */  PACK( 2, 0 ),
    /*  MIRP[15]  */  PACK( 2, 0 ),

    /*  MIRP[16]  */  PACK( 2, 0 ),
    /*  MIRP[17]  */  PACK( 2, 0 ),
    /*  MIRP[18]  */  PACK( 2, 0 ),
    /*  MIRP[19]  */  PACK( 2, 0 ),
    /*  MIRP[20]  */  PACK( 2, 0 ),
    /*  MIRP[21]  */  PACK( 2, 0 ),
    /*  MIRP[22]  */  PACK( 2, 0 ),
    /*  MIRP[23]  */  PACK( 2, 0 ),
    /*  MIRP[24]  */  PACK( 2, 0 ),
    /*  MIRP[25]  */  PACK( 2, 0 ),
    /*  MIRP[26]  */  PACK( 2, 0 ),
    /*  MIRP[27]  */  PACK( 2, 0 ),
    /*  MIRP[28]  */  PACK( 2, 0 ),
    /*  MIRP[29]  */  PACK( 2, 0 ),
    /*  MIRP[30]  */  PACK( 2, 0 ),
    /*  MIRP[31]  */  PACK( 2, 0 )
  };


  static
  const FT_Char  opcode_length[256] =
  {
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,

   -1,-2, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,

    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    2, 3, 4, 5,  6, 7, 8, 9,  3, 5, 7, 9, 11,13,15,17,

    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,
    1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1,  1, 1, 1, 1
  };

#undef PACK

#if 1

  static FT_Int32
  TT_MulFix14( FT_Int32  a,
               FT_Int    b )
  {
    FT_Int32   sign;
    FT_UInt32  ah, al, mid, lo, hi;


    sign = a ^ b;

    if ( a < 0 )
      a = -a;
    if ( b < 0 )
      b = -b;

    ah = (FT_UInt32)( ( a >> 16 ) & 0xFFFFU );
    al = (FT_UInt32)( a & 0xFFFFU );

    lo    = al * b;
    mid   = ah * b;
    hi    = mid >> 16;
    mid   = ( mid << 16 ) + ( 1 << 13 ); /* rounding */
    lo   += mid;
    if ( lo < mid )
      hi += 1;

    mid = ( lo >> 14 ) | ( hi << 18 );

    return sign >= 0 ? (FT_Int32)mid : -(FT_Int32)mid;
  }

#else

  /* compute (a*b)/2^14 with maximal accuracy and rounding */
  static FT_Int32
  TT_MulFix14( FT_Int32  a,
               FT_Int    b )
  {
    FT_Int32   m, s, hi;
    FT_UInt32  l, lo;


    /* compute ax*bx as 64-bit value */
    l  = (FT_UInt32)( ( a & 0xFFFFU ) * b );
    m  = ( a >> 16 ) * b;

    lo = l + (FT_UInt32)( m << 16 );
    hi = ( m >> 16 ) + ( (FT_Int32)l >> 31 ) + ( lo < l );

    /* divide the result by 2^14 with rounding */
    s   = hi >> 31;
    l   = lo + (FT_UInt32)s;
    hi += s + ( l < lo );
    lo  = l;

    l   = lo + 0x2000U;
    hi += l < lo;

    return ( hi << 18 ) | ( l >> 14 );
  }
#endif


  /* compute (ax*bx+ay*by)/2^14 with maximal accuracy and rounding */
  static FT_Int32
  TT_DotFix14( FT_Int32  ax,
               FT_Int32  ay,
               FT_Int    bx,
               FT_Int    by )
  {
    FT_Int32   m, s, hi1, hi2, hi;
    FT_UInt32  l, lo1, lo2, lo;


    /* compute ax*bx as 64-bit value */
    l = (FT_UInt32)( ( ax & 0xFFFFU ) * bx );
    m = ( ax >> 16 ) * bx;

    lo1 = l + (FT_UInt32)( m << 16 );
    hi1 = ( m >> 16 ) + ( (FT_Int32)l >> 31 ) + ( lo1 < l );

    /* compute ay*by as 64-bit value */
    l = (FT_UInt32)( ( ay & 0xFFFFU ) * by );
    m = ( ay >> 16 ) * by;

    lo2 = l + (FT_UInt32)( m << 16 );
    hi2 = ( m >> 16 ) + ( (FT_Int32)l >> 31 ) + ( lo2 < l );

    /* add them */
    lo = lo1 + lo2;
    hi = hi1 + hi2 + ( lo < lo1 );

    /* divide the result by 2^14 with rounding */
    s   = hi >> 31;
    l   = lo + (FT_UInt32)s;
    hi += s + ( l < lo );
    lo  = l;

    l   = lo + 0x2000U;
    hi += ( l < lo );

    return ( hi << 18 ) | ( l >> 14 );
  }


  /* return length of given vector */

#if 0

  static FT_Int32
  TT_VecLen( FT_Int32  x,
             FT_Int32  y )
  {
    FT_Int32   m, hi1, hi2, hi;
    FT_UInt32  l, lo1, lo2, lo;


    /* compute x*x as 64-bit value */
    lo = (FT_UInt32)( x & 0xFFFFU );
    hi = x >> 16;

    l  = lo * lo;
    m  = hi * lo;
    hi = hi * hi;

    lo1 = l + (FT_UInt32)( m << 17 );
    hi1 = hi + ( m >> 15 ) + ( lo1 < l );

    /* compute y*y as 64-bit value */
    lo = (FT_UInt32)( y & 0xFFFFU );
    hi = y >> 16;

    l  = lo * lo;
    m  = hi * lo;
    hi = hi * hi;

    lo2 = l + (FT_UInt32)( m << 17 );
    hi2 = hi + ( m >> 15 ) + ( lo2 < l );

    /* add them to get 'x*x+y*y' as 64-bit value */
    lo = lo1 + lo2;
    hi = hi1 + hi2 + ( lo < lo1 );

    /* compute the square root of this value */
    {
      FT_UInt32  root, rem, test_div;
      FT_Int     count;


      root = 0;

      {
        rem   = 0;
        count = 32;
        do
        {
          rem      = ( rem << 2 ) | ( (FT_UInt32)hi >> 30 );
          hi       = (  hi << 2 ) | (            lo >> 30 );
          lo     <<= 2;
          root   <<= 1;
          test_div = ( root << 1 ) + 1;

          if ( rem >= test_div )
          {
            rem  -= test_div;
            root += 1;
          }
        } while ( --count );
      }

      return (FT_Int32)root;
    }
  }

#else

  /* this version uses FT_Vector_Length which computes the same value */
  /* much, much faster..                                              */
  /*                                                                  */
  static FT_F26Dot6
  TT_VecLen( FT_F26Dot6  X,
             FT_F26Dot6  Y )
  {
    FT_Vector  v;


    v.x = X;
    v.y = Y;

    return FT_Vector_Length( &v );
  }

#endif


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Current_Ratio                                                      */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Returns the current aspect ratio scaling factor depending on the   */
  /*    projection vector's state and device resolutions.                  */
  /*                                                                       */
  /* <Return>                                                              */
  /*    The aspect ratio in 16.16 format, always <= 1.0 .                  */
  /*                                                                       */
  static FT_Long
  Current_Ratio( EXEC_OP )
  {
    if ( !CUR.tt_metrics.ratio )
    {
#ifdef TT_CONFIG_OPTION_UNPATENTED_HINTING
      if ( CUR.face->unpatented_hinting )
      {
        if ( CUR.GS.both_x_axis )
          CUR.tt_metrics.ratio = CUR.tt_metrics.x_ratio;
        else
          CUR.tt_metrics.ratio = CUR.tt_metrics.y_ratio;
      }
      else
#endif
      {
        if ( CUR.GS.projVector.y == 0 )
          CUR.tt_metrics.ratio = CUR.tt_metrics.x_ratio;

        else if ( CUR.GS.projVector.x == 0 )
          CUR.tt_metrics.ratio = CUR.tt_metrics.y_ratio;

        else
        {
          FT_Long  x, y;


          x = TT_MULDIV( CUR.GS.projVector.x,
                         CUR.tt_metrics.x_ratio, 0x4000 );
          y = TT_MULDIV( CUR.GS.projVector.y,
                         CUR.tt_metrics.y_ratio, 0x4000 );
          CUR.tt_metrics.ratio = TT_VecLen( x, y );
        }
      }
    }
    return CUR.tt_metrics.ratio;
  }


  static FT_Long
  Current_Ppem( EXEC_OP )
  {
    return TT_MULFIX( CUR.tt_metrics.ppem, CURRENT_Ratio() );
  }


  /*************************************************************************/
  /*                                                                       */
  /* Functions related to the control value table (CVT).                   */
  /*                                                                       */
  /*************************************************************************/


  FT_CALLBACK_DEF( FT_F26Dot6 )
  Read_CVT( EXEC_OP_ FT_ULong  idx )
  {
    return CUR.cvt[idx];
  }


  FT_CALLBACK_DEF( FT_F26Dot6 )
  Read_CVT_Stretched( EXEC_OP_ FT_ULong  idx )
  {
    return TT_MULFIX( CUR.cvt[idx], CURRENT_Ratio() );
  }


  FT_CALLBACK_DEF( void )
  Write_CVT( EXEC_OP_ FT_ULong    idx,
                      FT_F26Dot6  value )
  {
    CUR.cvt[idx] = value;
  }


  FT_CALLBACK_DEF( void )
  Write_CVT_Stretched( EXEC_OP_ FT_ULong    idx,
                                FT_F26Dot6  value )
  {
    CUR.cvt[idx] = FT_DivFix( value, CURRENT_Ratio() );
  }


  FT_CALLBACK_DEF( void )
  Move_CVT( EXEC_OP_ FT_ULong    idx,
                     FT_F26Dot6  value )
  {
    CUR.cvt[idx] += value;
  }


  FT_CALLBACK_DEF( void )
  Move_CVT_Stretched( EXEC_OP_ FT_ULong    idx,
                               FT_F26Dot6  value )
  {
    CUR.cvt[idx] += FT_DivFix( value, CURRENT_Ratio() );
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    GetShortIns                                                        */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Returns a short integer taken from the instruction stream at       */
  /*    address IP.                                                        */
  /*                                                                       */
  /* <Return>                                                              */
  /*    Short read at code[IP].                                            */
  /*                                                                       */
  /* <Note>                                                                */
  /*    This one could become a macro.                                     */
  /*                                                                       */
  static FT_Short
  GetShortIns( EXEC_OP )
  {
    /* Reading a byte stream so there is no endianess (DaveP) */
    CUR.IP += 2;
    return (FT_Short)( ( CUR.code[CUR.IP - 2] << 8 ) +
                         CUR.code[CUR.IP - 1]      );
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Ins_Goto_CodeRange                                                 */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Goes to a certain code range in the instruction stream.            */
  /*                                                                       */
  /* <Input>                                                               */
  /*    aRange :: The index of the code range.                             */
  /*                                                                       */
  /*    aIP    :: The new IP address in the code range.                    */
  /*                                                                       */
  /* <Return>                                                              */
  /*    SUCCESS or FAILURE.                                                */
  /*                                                                       */
  static FT_Bool
  Ins_Goto_CodeRange( EXEC_OP_ FT_Int    aRange,
                               FT_ULong  aIP )
  {
    TT_CodeRange*  range;


    if ( aRange < 1 || aRange > 3 )
    {
      CUR.error = TT_Err_Bad_Argument;
      return FAILURE;
    }

    range = &CUR.codeRangeTable[aRange - 1];

    if ( range->base == NULL )     /* invalid coderange */
    {
      CUR.error = TT_Err_Invalid_CodeRange;
      return FAILURE;
    }

    /* NOTE: Because the last instruction of a program may be a CALL */
    /*       which will return to the first byte *after* the code    */
    /*       range, we test for AIP <= Size, instead of AIP < Size.  */

    if ( aIP > range->size )
    {
      CUR.error = TT_Err_Code_Overflow;
      return FAILURE;
    }

    CUR.code     = range->base;
    CUR.codeSize = range->size;
    CUR.IP       = aIP;
    CUR.curRange = aRange;

    return SUCCESS;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Direct_Move                                                        */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Moves a point by a given distance along the freedom vector.  The   */
  /*    point will be `touched'.                                           */
  /*                                                                       */
  /* <Input>                                                               */
  /*    point    :: The index of the point to move.                        */
  /*                                                                       */
  /*    distance :: The distance to apply.                                 */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    zone     :: The affected glyph zone.                               */
  /*                                                                       */
  static void
  Direct_Move( EXEC_OP_ TT_GlyphZone  zone,
                        FT_UShort     point,
                        FT_F26Dot6    distance )
  {
    FT_F26Dot6  v;


#ifdef TT_CONFIG_OPTION_UNPATENTED_HINTING
    FT_ASSERT( !CUR.face->unpatented_hinting );
#endif

    v = CUR.GS.freeVector.x;

    if ( v != 0 )
    {
      zone->cur[point].x += TT_MULDIV( distance,
                                       v * 0x10000L,
                                       CUR.F_dot_P );

      zone->tags[point] |= FT_CURVE_TAG_TOUCH_X;
    }

    v = CUR.GS.freeVector.y;

    if ( v != 0 )
    {
      zone->cur[point].y += TT_MULDIV( distance,
                                       v * 0x10000L,
                                       CUR.F_dot_P );

      zone->tags[point] |= FT_CURVE_TAG_TOUCH_Y;
    }
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Direct_Move_Orig                                                   */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Moves the *original* position of a point by a given distance along */
  /*    the freedom vector.  Obviously, the point will not be `touched'.   */
  /*                                                                       */
  /* <Input>                                                               */
  /*    point    :: The index of the point to move.                        */
  /*                                                                       */
  /*    distance :: The distance to apply.                                 */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    zone     :: The affected glyph zone.                               */
  /*                                                                       */
  static void
  Direct_Move_Orig( EXEC_OP_ TT_GlyphZone  zone,
                             FT_UShort     point,
                             FT_F26Dot6    distance )
  {
    FT_F26Dot6  v;


#ifdef TT_CONFIG_OPTION_UNPATENTED_HINTING
    FT_ASSERT( !CUR.face->unpatented_hinting );
#endif

    v = CUR.GS.freeVector.x;

    if ( v != 0 )
      zone->org[point].x += TT_MULDIV( distance,
                                       v * 0x10000L,
                                       CUR.F_dot_P );

    v = CUR.GS.freeVector.y;

    if ( v != 0 )
      zone->org[point].y += TT_MULDIV( distance,
                                       v * 0x10000L,
                                       CUR.F_dot_P );
  }


  /*************************************************************************/
  /*                                                                       */
  /* Special versions of Direct_Move()                                     */
  /*                                                                       */
  /*   The following versions are used whenever both vectors are both      */
  /*   along one of the coordinate unit vectors, i.e. in 90% of the cases. */
  /*                                                                       */
  /*************************************************************************/


  static void
  Direct_Move_X( EXEC_OP_ TT_GlyphZone  zone,
                          FT_UShort     point,
                          FT_F26Dot6    distance )
  {
    FT_UNUSED_EXEC;

    zone->cur[point].x += distance;
    zone->tags[point]  |= FT_CURVE_TAG_TOUCH_X;
  }


  static void
  Direct_Move_Y( EXEC_OP_ TT_GlyphZone  zone,
                          FT_UShort     point,
                          FT_F26Dot6    distance )
  {
    FT_UNUSED_EXEC;

    zone->cur[point].y += distance;
    zone->tags[point]  |= FT_CURVE_TAG_TOUCH_Y;
  }


  /*************************************************************************/
  /*                                                                       */
  /* Special versions of Direct_Move_Orig()                                */
  /*                                                                       */
  /*   The following versions are used whenever both vectors are both      */
  /*   along one of the coordinate unit vectors, i.e. in 90% of the cases. */
  /*                                                                       */
  /*************************************************************************/


  static void
  Direct_Move_Orig_X( EXEC_OP_ TT_GlyphZone  zone,
                               FT_UShort     point,
                               FT_F26Dot6    distance )
  {
    FT_UNUSED_EXEC;

    zone->org[point].x += distance;
  }


  static void
  Direct_Move_Orig_Y( EXEC_OP_ TT_GlyphZone  zone,
                               FT_UShort     point,
                               FT_F26Dot6    distance )
  {
    FT_UNUSED_EXEC;

    zone->org[point].y += distance;
  }


  /*************************************************************************/
  /*                                                                       */
  /* <Function>                                                            */
  /*    Round_None                                                         */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Does not round, but adds engine compensation.                      */
  /*                                                                       */
  /* <Input>                                                               */
  /*    distance     :: The distance (not) to round.                       */
  /*                                                                       */
  /*    compensation :: The engine compensation.                           */
  /*                                                                       */
  /* <Return>                                                              */
  /*    The compensated distance.                                          */
  /*                                                                       */
  /* <Note>                                                                */
  /*    The TrueType specification says very few about the relationship    */
  /*    between rounding and engine compensation.  However, it seems from  */
  /*    the description of super round that we should add the compensation */
  /*    before rounding.