misc/libfreetype/src/gxvalid/gxvkern.c
changeset 5172 88f2e05288ba
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/misc/libfreetype/src/gxvalid/gxvkern.c	Mon Apr 25 01:46:54 2011 +0200
@@ -0,0 +1,876 @@
+/***************************************************************************/
+/*                                                                         */
+/*  gxvkern.c                                                              */
+/*                                                                         */
+/*    TrueTypeGX/AAT kern table validation (body).                         */
+/*                                                                         */
+/*  Copyright 2004, 2005, 2006, 2007                                       */
+/*  by suzuki toshiya, Masatake YAMATO, Red Hat K.K.,                      */
+/*  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.                                        */
+/*                                                                         */
+/***************************************************************************/
+
+/***************************************************************************/
+/*                                                                         */
+/* gxvalid is derived from both gxlayout module and otvalid module.        */
+/* Development of gxlayout is supported by the Information-technology      */
+/* Promotion Agency(IPA), Japan.                                           */
+/*                                                                         */
+/***************************************************************************/
+
+
+#include "gxvalid.h"
+#include "gxvcommn.h"
+
+#include FT_SFNT_NAMES_H
+#include FT_SERVICE_GX_VALIDATE_H
+
+
+  /*************************************************************************/
+  /*                                                                       */
+  /* 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_gxvkern
+
+
+  /*************************************************************************/
+  /*************************************************************************/
+  /*****                                                               *****/
+  /*****                      Data and Types                           *****/
+  /*****                                                               *****/
+  /*************************************************************************/
+  /*************************************************************************/
+
+  typedef enum  GXV_kern_Version_
+  {
+    KERN_VERSION_CLASSIC = 0x0000,
+    KERN_VERSION_NEW     = 0x0001
+
+  } GXV_kern_Version;
+
+
+  typedef enum GXV_kern_Dialect_
+  {
+    KERN_DIALECT_UNKNOWN = 0,
+    KERN_DIALECT_MS      = FT_VALIDATE_MS,
+    KERN_DIALECT_APPLE   = FT_VALIDATE_APPLE,
+    KERN_DIALECT_ANY     = FT_VALIDATE_CKERN
+
+  } GXV_kern_Dialect;
+
+
+  typedef struct  GXV_kern_DataRec_
+  {
+    GXV_kern_Version  version;
+    void             *subtable_data;
+    GXV_kern_Dialect  dialect_request;
+
+  } GXV_kern_DataRec, *GXV_kern_Data;
+
+
+#define GXV_KERN_DATA( field )  GXV_TABLE_DATA( kern, field )
+
+#define KERN_IS_CLASSIC( valid )                               \
+          ( KERN_VERSION_CLASSIC == GXV_KERN_DATA( version ) )
+#define KERN_IS_NEW( valid )                                   \
+          ( KERN_VERSION_NEW     == GXV_KERN_DATA( version ) )
+
+#define KERN_DIALECT( valid )              \
+          GXV_KERN_DATA( dialect_request )
+#define KERN_ALLOWS_MS( valid )                       \
+          ( KERN_DIALECT( valid ) & KERN_DIALECT_MS )
+#define KERN_ALLOWS_APPLE( valid )                       \
+          ( KERN_DIALECT( valid ) & KERN_DIALECT_APPLE )
+
+#define GXV_KERN_HEADER_SIZE           ( KERN_IS_NEW( valid ) ? 8 : 4 )
+#define GXV_KERN_SUBTABLE_HEADER_SIZE  ( KERN_IS_NEW( valid ) ? 8 : 6 )
+
+
+  /*************************************************************************/
+  /*************************************************************************/
+  /*****                                                               *****/
+  /*****                      SUBTABLE VALIDATORS                      *****/
+  /*****                                                               *****/
+  /*************************************************************************/
+  /*************************************************************************/
+
+
+  /* ============================= format 0 ============================== */
+
+  static void
+  gxv_kern_subtable_fmt0_pairs_validate( FT_Bytes       table,
+                                         FT_Bytes       limit,
+                                         FT_UShort      nPairs,
+                                         GXV_Validator  valid )
+  {
+    FT_Bytes   p = table;
+    FT_UShort  i;
+
+    FT_UShort  last_gid_left  = 0;
+    FT_UShort  last_gid_right = 0;
+
+    FT_UNUSED( limit );
+
+
+    GXV_NAME_ENTER( "kern format 0 pairs" );
+
+    for ( i = 0; i < nPairs; i++ )
+    {
+      FT_UShort  gid_left;
+      FT_UShort  gid_right;
+      FT_Short   kernValue;
+
+
+      /* left */
+      gid_left  = FT_NEXT_USHORT( p );
+      gxv_glyphid_validate( gid_left, valid );
+
+      /* right */
+      gid_right = FT_NEXT_USHORT( p );
+      gxv_glyphid_validate( gid_right, valid );
+
+      /* Pairs of left and right GIDs must be unique and sorted. */
+      GXV_TRACE(( "left gid = %u, right gid = %u\n", gid_left, gid_right ));
+      if ( gid_left == last_gid_left )
+      {
+        if ( last_gid_right < gid_right )
+          last_gid_right = gid_right;
+        else
+          FT_INVALID_DATA;
+      }
+      else if ( last_gid_left < gid_left )
+      {
+        last_gid_left  = gid_left;
+        last_gid_right = gid_right;
+      }
+      else
+        FT_INVALID_DATA;
+
+      /* skip the kern value */
+      kernValue = FT_NEXT_SHORT( p );
+    }
+
+    GXV_EXIT;
+  }
+
+  static void
+  gxv_kern_subtable_fmt0_validate( FT_Bytes       table,
+                                   FT_Bytes       limit,
+                                   GXV_Validator  valid )
+  {
+    FT_Bytes   p = table + GXV_KERN_SUBTABLE_HEADER_SIZE;
+
+    FT_UShort  nPairs;
+    FT_UShort  unitSize;
+
+
+    GXV_NAME_ENTER( "kern subtable format 0" );
+
+    unitSize = 2 + 2 + 2;
+    nPairs   = 0;
+
+    /* nPairs, searchRange, entrySelector, rangeShift */
+    GXV_LIMIT_CHECK( 2 + 2 + 2 + 2 );
+    gxv_BinSrchHeader_validate( p, limit, &unitSize, &nPairs, valid );
+    p += 2 + 2 + 2 + 2;
+
+    gxv_kern_subtable_fmt0_pairs_validate( p, limit, nPairs, valid );
+
+    GXV_EXIT;
+  }
+
+
+  /* ============================= format 1 ============================== */
+
+
+  typedef struct  GXV_kern_fmt1_StateOptRec_
+  {
+    FT_UShort  valueTable;
+    FT_UShort  valueTable_length;
+
+  } GXV_kern_fmt1_StateOptRec, *GXV_kern_fmt1_StateOptRecData;
+
+
+  static void
+  gxv_kern_subtable_fmt1_valueTable_load( FT_Bytes       table,
+                                          FT_Bytes       limit,
+                                          GXV_Validator  valid )
+  {
+    FT_Bytes                       p = table;
+    GXV_kern_fmt1_StateOptRecData  optdata =
+      (GXV_kern_fmt1_StateOptRecData)valid->statetable.optdata;
+
+
+    GXV_LIMIT_CHECK( 2 );
+    optdata->valueTable = FT_NEXT_USHORT( p );
+  }
+
+
+  /*
+   * passed tables_size covers whole StateTable, including kern fmt1 header
+   */
+  static void
+  gxv_kern_subtable_fmt1_subtable_setup( FT_UShort      table_size,
+                                         FT_UShort      classTable,
+                                         FT_UShort      stateArray,
+                                         FT_UShort      entryTable,
+                                         FT_UShort*     classTable_length_p,
+                                         FT_UShort*     stateArray_length_p,
+                                         FT_UShort*     entryTable_length_p,
+                                         GXV_Validator  valid )
+  {
+    FT_UShort  o[4];
+    FT_UShort  *l[4];
+    FT_UShort  buff[5];
+
+    GXV_kern_fmt1_StateOptRecData  optdata =
+      (GXV_kern_fmt1_StateOptRecData)valid->statetable.optdata;
+
+
+    o[0] = classTable;
+    o[1] = stateArray;
+    o[2] = entryTable;
+    o[3] = optdata->valueTable;
+    l[0] = classTable_length_p;
+    l[1] = stateArray_length_p;
+    l[2] = entryTable_length_p;
+    l[3] = &(optdata->valueTable_length);
+
+    gxv_set_length_by_ushort_offset( o, l, buff, 4, table_size, valid );
+  }
+
+
+  /*
+   * passed table & limit are of whole StateTable, not including subtables
+   */
+  static void
+  gxv_kern_subtable_fmt1_entry_validate(
+    FT_Byte                         state,
+    FT_UShort                       flags,
+    GXV_StateTable_GlyphOffsetCPtr  glyphOffset_p,
+    FT_Bytes                        table,
+    FT_Bytes                        limit,
+    GXV_Validator                   valid )
+  {
+    FT_UShort  push;
+    FT_UShort  dontAdvance;
+    FT_UShort  valueOffset;
+    FT_UShort  kernAction;
+    FT_UShort  kernValue;
+
+    FT_UNUSED( state );
+    FT_UNUSED( glyphOffset_p );
+
+
+    push        = (FT_UShort)( ( flags >> 15 ) & 1      );
+    dontAdvance = (FT_UShort)( ( flags >> 14 ) & 1      );
+    valueOffset = (FT_UShort)(   flags         & 0x3FFF );
+
+    {
+      GXV_kern_fmt1_StateOptRecData  vt_rec =
+        (GXV_kern_fmt1_StateOptRecData)valid->statetable.optdata;
+      FT_Bytes  p;
+
+
+      if ( valueOffset < vt_rec->valueTable )
+        FT_INVALID_OFFSET;
+
+      p     = table + valueOffset;
+      limit = table + vt_rec->valueTable + vt_rec->valueTable_length;
+
+      GXV_LIMIT_CHECK( 2 + 2 );
+      kernAction = FT_NEXT_USHORT( p );
+      kernValue  = FT_NEXT_USHORT( p );
+    }
+  }
+
+
+  static void
+  gxv_kern_subtable_fmt1_validate( FT_Bytes       table,
+                                   FT_Bytes       limit,
+                                   GXV_Validator  valid )
+  {
+    FT_Bytes                   p = table;
+    GXV_kern_fmt1_StateOptRec  vt_rec;
+
+
+    GXV_NAME_ENTER( "kern subtable format 1" );
+
+    valid->statetable.optdata =
+      &vt_rec;
+    valid->statetable.optdata_load_func =
+      gxv_kern_subtable_fmt1_valueTable_load;
+    valid->statetable.subtable_setup_func =
+      gxv_kern_subtable_fmt1_subtable_setup;
+    valid->statetable.entry_glyphoffset_fmt =
+      GXV_GLYPHOFFSET_NONE;
+    valid->statetable.entry_validate_func =
+      gxv_kern_subtable_fmt1_entry_validate;
+
+    gxv_StateTable_validate( p, limit, valid );
+
+    GXV_EXIT;
+  }
+
+
+  /* ================ Data for Class-Based Subtables 2, 3 ================ */
+
+  typedef enum  GXV_kern_ClassSpec_
+  {
+    GXV_KERN_CLS_L = 0,
+    GXV_KERN_CLS_R
+
+  } GXV_kern_ClassSpec;
+
+
+  /* ============================= format 2 ============================== */
+
+  /* ---------------------- format 2 specific data ----------------------- */
+
+  typedef struct  GXV_kern_subtable_fmt2_DataRec_
+  {
+    FT_UShort         rowWidth;
+    FT_UShort         array;
+    FT_UShort         offset_min[2];
+    FT_UShort         offset_max[2];
+    const FT_String*  class_tag[2];
+    GXV_odtect_Range  odtect;
+
+  } GXV_kern_subtable_fmt2_DataRec, *GXV_kern_subtable_fmt2_Data;
+
+
+#define GXV_KERN_FMT2_DATA( field )                         \
+        ( ( (GXV_kern_subtable_fmt2_DataRec *)              \
+              ( GXV_KERN_DATA( subtable_data ) ) )->field )
+
+
+  /* -------------------------- utility functions ----------------------- */
+
+  static void
+  gxv_kern_subtable_fmt2_clstbl_validate( FT_Bytes            table,
+                                          FT_Bytes            limit,
+                                          GXV_kern_ClassSpec  spec,
+                                          GXV_Validator       valid )
+  {
+    const FT_String*  tag    = GXV_KERN_FMT2_DATA( class_tag[spec] );
+    GXV_odtect_Range  odtect = GXV_KERN_FMT2_DATA( odtect );
+
+    FT_Bytes   p = table;
+    FT_UShort  firstGlyph;
+    FT_UShort  nGlyphs;
+
+
+    GXV_NAME_ENTER( "kern format 2 classTable" );
+
+    GXV_LIMIT_CHECK( 2 + 2 );
+    firstGlyph = FT_NEXT_USHORT( p );
+    nGlyphs    = FT_NEXT_USHORT( p );
+    GXV_TRACE(( " %s firstGlyph=%d, nGlyphs=%d\n",
+                tag, firstGlyph, nGlyphs ));
+
+    gxv_glyphid_validate( firstGlyph, valid );
+    gxv_glyphid_validate( (FT_UShort)( firstGlyph + nGlyphs - 1 ), valid );
+
+    gxv_array_getlimits_ushort( p, p + ( 2 * nGlyphs ),
+                                &( GXV_KERN_FMT2_DATA( offset_min[spec] ) ),
+                                &( GXV_KERN_FMT2_DATA( offset_max[spec] ) ),
+                                valid );
+
+    gxv_odtect_add_range( table, 2 * nGlyphs, tag, odtect );
+
+    GXV_EXIT;
+  }
+
+
+  static void
+  gxv_kern_subtable_fmt2_validate( FT_Bytes       table,
+                                   FT_Bytes       limit,
+                                   GXV_Validator  valid )
+  {
+    GXV_ODTECT( 3, odtect );
+    GXV_kern_subtable_fmt2_DataRec  fmt2_rec =
+      { 0, 0, { 0, 0 }, { 0, 0 }, { "leftClass", "rightClass" }, NULL };
+
+    FT_Bytes   p = table + GXV_KERN_SUBTABLE_HEADER_SIZE;
+    FT_UShort  leftOffsetTable;
+    FT_UShort  rightOffsetTable;
+
+
+    GXV_NAME_ENTER( "kern subtable format 2" );
+
+    GXV_ODTECT_INIT( odtect );
+    fmt2_rec.odtect = odtect;
+    GXV_KERN_DATA( subtable_data ) = &fmt2_rec;
+
+    GXV_LIMIT_CHECK( 2 + 2 + 2 + 2 );
+    GXV_KERN_FMT2_DATA( rowWidth ) = FT_NEXT_USHORT( p );
+    leftOffsetTable                = FT_NEXT_USHORT( p );
+    rightOffsetTable               = FT_NEXT_USHORT( p );
+    GXV_KERN_FMT2_DATA( array )    = FT_NEXT_USHORT( p );
+
+    GXV_TRACE(( "rowWidth = %d\n", GXV_KERN_FMT2_DATA( rowWidth ) ));
+
+
+    GXV_LIMIT_CHECK( leftOffsetTable );
+    GXV_LIMIT_CHECK( rightOffsetTable );
+    GXV_LIMIT_CHECK( GXV_KERN_FMT2_DATA( array ) );
+
+    gxv_kern_subtable_fmt2_clstbl_validate( table + leftOffsetTable, limit,
+                                            GXV_KERN_CLS_L, valid );
+
+    gxv_kern_subtable_fmt2_clstbl_validate( table + rightOffsetTable, limit,
+                                            GXV_KERN_CLS_R, valid );
+
+    if ( GXV_KERN_FMT2_DATA( offset_min[GXV_KERN_CLS_L] ) +
+           GXV_KERN_FMT2_DATA( offset_min[GXV_KERN_CLS_R] )
+         < GXV_KERN_FMT2_DATA( array )                      )
+      FT_INVALID_OFFSET;
+
+    gxv_odtect_add_range( table + GXV_KERN_FMT2_DATA( array ),
+                          GXV_KERN_FMT2_DATA( offset_max[GXV_KERN_CLS_L] )
+                            + GXV_KERN_FMT2_DATA( offset_max[GXV_KERN_CLS_R] )
+                            - GXV_KERN_FMT2_DATA( array ),
+                          "array", odtect );
+
+    gxv_odtect_validate( odtect, valid );
+
+    GXV_EXIT;
+  }
+
+
+  /* ============================= format 3 ============================== */
+
+  static void
+  gxv_kern_subtable_fmt3_validate( FT_Bytes       table,
+                                   FT_Bytes       limit,
+                                   GXV_Validator  valid )
+  {
+    FT_Bytes   p = table + GXV_KERN_SUBTABLE_HEADER_SIZE;
+    FT_UShort  glyphCount;
+    FT_Byte    kernValueCount;
+    FT_Byte    leftClassCount;
+    FT_Byte    rightClassCount;
+    FT_Byte    flags;
+
+
+    GXV_NAME_ENTER( "kern subtable format 3" );
+
+    GXV_LIMIT_CHECK( 2 + 1 + 1 + 1 + 1 );
+    glyphCount      = FT_NEXT_USHORT( p );
+    kernValueCount  = FT_NEXT_BYTE( p );
+    leftClassCount  = FT_NEXT_BYTE( p );
+    rightClassCount = FT_NEXT_BYTE( p );
+    flags           = FT_NEXT_BYTE( p );
+
+    if ( valid->face->num_glyphs != glyphCount )
+    {
+      GXV_TRACE(( "maxGID=%d, but glyphCount=%d\n",
+                  valid->face->num_glyphs, glyphCount ));
+      if ( valid->root->level >= FT_VALIDATE_PARANOID )
+        FT_INVALID_GLYPH_ID;
+    }
+
+    /*
+     * just skip kernValue[kernValueCount]
+     */
+    GXV_LIMIT_CHECK( 2 * kernValueCount );
+    p += 2 * kernValueCount;
+
+    /*
+     * check leftClass[gid] < leftClassCount
+     */
+    {
+      FT_Byte  min, max;
+
+
+      GXV_LIMIT_CHECK( glyphCount );
+      gxv_array_getlimits_byte( p, p + glyphCount, &min, &max, valid );
+      p += valid->subtable_length;
+
+      if ( leftClassCount < max )
+        FT_INVALID_DATA;
+    }
+
+    /*
+     * check rightClass[gid] < rightClassCount
+     */
+    {
+      FT_Byte  min, max;
+
+
+      GXV_LIMIT_CHECK( glyphCount );
+      gxv_array_getlimits_byte( p, p + glyphCount, &min, &max, valid );
+      p += valid->subtable_length;
+
+      if ( rightClassCount < max )
+        FT_INVALID_DATA;
+    }
+
+    /*
+     * check kernIndex[i, j] < kernValueCount
+     */
+    {
+      FT_UShort  i, j;
+
+
+      for ( i = 0; i < leftClassCount; i++ )
+      {
+        for ( j = 0; j < rightClassCount; j++ )
+        {
+          GXV_LIMIT_CHECK( 1 );
+          if ( kernValueCount < FT_NEXT_BYTE( p ) )
+            FT_INVALID_OFFSET;
+        }
+      }
+    }
+
+    valid->subtable_length = p - table;
+
+    GXV_EXIT;
+  }
+
+
+  static FT_Bool
+  gxv_kern_coverage_new_apple_validate( FT_UShort      coverage,
+                                        FT_UShort*     format,
+                                        GXV_Validator  valid )
+  {
+    /* new Apple-dialect */
+    FT_Bool  kernVertical;
+    FT_Bool  kernCrossStream;
+    FT_Bool  kernVariation;
+
+    FT_UNUSED( valid );
+
+
+    /* reserved bits = 0 */
+    if ( coverage & 0x1FFC )
+      return 0;
+
+    kernVertical    = FT_BOOL( ( coverage >> 15 ) & 1 );
+    kernCrossStream = FT_BOOL( ( coverage >> 14 ) & 1 );
+    kernVariation   = FT_BOOL( ( coverage >> 13 ) & 1 );
+
+    *format = (FT_UShort)( coverage & 0x0003 );
+
+    GXV_TRACE(( "new Apple-dialect: "
+                "horizontal=%d, cross-stream=%d, variation=%d, format=%d\n",
+                 !kernVertical, kernCrossStream, kernVariation, *format ));
+
+    GXV_TRACE(( "kerning values in Apple format subtable are ignored\n" ));
+
+    return 1;
+  }
+
+
+  static FT_Bool
+  gxv_kern_coverage_classic_apple_validate( FT_UShort      coverage,
+                                            FT_UShort*     format,
+                                            GXV_Validator  valid )
+  {
+    /* classic Apple-dialect */
+    FT_Bool  horizontal;
+    FT_Bool  cross_stream;
+
+
+    /* check expected flags, but don't check if MS-dialect is impossible */
+    if ( !( coverage & 0xFD00 ) && KERN_ALLOWS_MS( valid ) )
+      return 0;
+
+    /* reserved bits = 0 */
+    if ( coverage & 0x02FC )
+      return 0;
+
+    horizontal   = FT_BOOL( ( coverage >> 15 ) & 1 );
+    cross_stream = FT_BOOL( ( coverage >> 13 ) & 1 );
+
+    *format = (FT_UShort)( coverage & 0x0003 );
+
+    GXV_TRACE(( "classic Apple-dialect: "
+                "horizontal=%d, cross-stream=%d, format=%d\n",
+                 horizontal, cross_stream, *format ));
+
+    /* format 1 requires GX State Machine, too new for classic */
+    if ( *format == 1 )
+      return 0;
+
+    GXV_TRACE(( "kerning values in Apple format subtable are ignored\n" ));
+
+    return 1;
+  }
+
+
+  static FT_Bool
+  gxv_kern_coverage_classic_microsoft_validate( FT_UShort      coverage,
+                                                FT_UShort*     format,
+                                                GXV_Validator  valid )
+  {
+    /* classic Microsoft-dialect */
+    FT_Bool  horizontal;
+    FT_Bool  minimum;
+    FT_Bool  cross_stream;
+    FT_Bool  override;
+
+    FT_UNUSED( valid );
+
+
+    /* reserved bits = 0 */
+    if ( coverage & 0xFDF0 )
+      return 0;
+
+    horizontal   = FT_BOOL(   coverage        & 1 );
+    minimum      = FT_BOOL( ( coverage >> 1 ) & 1 );
+    cross_stream = FT_BOOL( ( coverage >> 2 ) & 1 );
+    override     = FT_BOOL( ( coverage >> 3 ) & 1 );
+
+    *format = (FT_UShort)( ( coverage >> 8 ) & 0x0003 );
+
+    GXV_TRACE(( "classic Microsoft-dialect: "
+                "horizontal=%d, minimum=%d, cross-stream=%d, "
+                "override=%d, format=%d\n",
+                horizontal, minimum, cross_stream, override, *format ));
+
+    if ( *format == 2 )
+      GXV_TRACE((
+        "kerning values in Microsoft format 2 subtable are ignored\n" ));
+
+    return 1;
+  }
+
+
+  /*************************************************************************/
+  /*************************************************************************/
+  /*****                                                               *****/
+  /*****                            MAIN                               *****/
+  /*****                                                               *****/
+  /*************************************************************************/
+  /*************************************************************************/
+
+  static GXV_kern_Dialect
+  gxv_kern_coverage_validate( FT_UShort      coverage,
+                              FT_UShort*     format,
+                              GXV_Validator  valid )
+  {
+    GXV_kern_Dialect  result = KERN_DIALECT_UNKNOWN;
+
+
+    GXV_NAME_ENTER( "validating coverage" );
+
+    GXV_TRACE(( "interprete coverage 0x%04x by Apple style\n", coverage ));
+
+    if ( KERN_IS_NEW( valid ) )
+    {
+      if ( gxv_kern_coverage_new_apple_validate( coverage,
+                                                 format,
+                                                 valid ) )
+      {
+        result = KERN_DIALECT_APPLE;
+        goto Exit;
+      }
+    }
+
+    if ( KERN_IS_CLASSIC( valid ) && KERN_ALLOWS_APPLE( valid ) )
+    {
+      if ( gxv_kern_coverage_classic_apple_validate( coverage,
+                                                     format,
+                                                     valid ) )
+      {
+        result = KERN_DIALECT_APPLE;
+        goto Exit;
+      }
+    }
+
+    if ( KERN_IS_CLASSIC( valid ) && KERN_ALLOWS_MS( valid ) )
+    {
+      if ( gxv_kern_coverage_classic_microsoft_validate( coverage,
+                                                         format,
+                                                         valid ) )
+      {
+        result = KERN_DIALECT_MS;
+        goto Exit;
+      }
+    }
+
+    GXV_TRACE(( "cannot interprete coverage, broken kern subtable\n" ));
+
+  Exit:
+    GXV_EXIT;
+    return result;
+  }
+
+
+  static void
+  gxv_kern_subtable_validate( FT_Bytes       table,
+                              FT_Bytes       limit,
+                              GXV_Validator  valid )
+  {
+    FT_Bytes   p = table;
+    FT_UShort  version = 0;    /* MS only: subtable version, unused */
+    FT_ULong   length;         /* MS: 16bit, Apple: 32bit*/
+    FT_UShort  coverage;
+    FT_UShort  tupleIndex = 0; /* Apple only */
+    FT_UShort  u16[2];
+    FT_UShort  format = 255;   /* subtable format */
+
+
+    GXV_NAME_ENTER( "kern subtable" );
+
+    GXV_LIMIT_CHECK( 2 + 2 + 2 );
+    u16[0]   = FT_NEXT_USHORT( p ); /* Apple: length_hi MS: version */
+    u16[1]   = FT_NEXT_USHORT( p ); /* Apple: length_lo MS: length */
+    coverage = FT_NEXT_USHORT( p );
+
+    switch ( gxv_kern_coverage_validate( coverage, &format, valid ) )
+    {
+    case KERN_DIALECT_MS:
+      version    = u16[0];
+      length     = u16[1];
+      tupleIndex = 0;
+      GXV_TRACE(( "Subtable version = %d\n", version ));
+      GXV_TRACE(( "Subtable length = %d\n", length ));
+      break;
+
+    case KERN_DIALECT_APPLE:
+      version    = 0;
+      length     = ( u16[0] << 16 ) + u16[1];
+      tupleIndex = 0;
+      GXV_TRACE(( "Subtable length = %d\n", length ));
+
+      if ( KERN_IS_NEW( valid ) )
+      {
+        GXV_LIMIT_CHECK( 2 );
+        tupleIndex = FT_NEXT_USHORT( p );
+        GXV_TRACE(( "Subtable tupleIndex = %d\n", tupleIndex ));
+      }
+      break;
+
+    default:
+      length = u16[1];
+      GXV_TRACE(( "cannot detect subtable dialect, "
+                  "just skip %d byte\n", length ));
+      goto Exit;
+    }
+
+    /* formats 1, 2, 3 require the position of the start of this subtable */
+    if ( format == 0 )
+      gxv_kern_subtable_fmt0_validate( table, table + length, valid );
+    else if ( format == 1 )
+      gxv_kern_subtable_fmt1_validate( table, table + length, valid );
+    else if ( format == 2 )
+      gxv_kern_subtable_fmt2_validate( table, table + length, valid );
+    else if ( format == 3 )
+      gxv_kern_subtable_fmt3_validate( table, table + length, valid );
+    else
+      FT_INVALID_DATA;
+
+  Exit:
+    valid->subtable_length = length;
+    GXV_EXIT;
+  }
+
+
+  /*************************************************************************/
+  /*************************************************************************/
+  /*****                                                               *****/
+  /*****                         kern TABLE                            *****/
+  /*****                                                               *****/
+  /*************************************************************************/
+  /*************************************************************************/
+
+  static void
+  gxv_kern_validate_generic( FT_Bytes          table,
+                             FT_Face           face,
+                             FT_Bool           classic_only,
+                             GXV_kern_Dialect  dialect_request,
+                             FT_Validator      ftvalid )
+  {
+    GXV_ValidatorRec   validrec;
+    GXV_Validator      valid = &validrec;
+
+    GXV_kern_DataRec   kernrec;
+    GXV_kern_Data      kern = &kernrec;
+
+    FT_Bytes           p     = table;
+    FT_Bytes           limit = 0;
+
+    FT_ULong           nTables = 0;
+    FT_UInt            i;
+
+
+    valid->root       = ftvalid;
+    valid->table_data = kern;
+    valid->face       = face;
+
+    FT_TRACE3(( "validating `kern' table\n" ));
+    GXV_INIT;
+    KERN_DIALECT( valid ) = dialect_request;
+
+    GXV_LIMIT_CHECK( 2 );
+    GXV_KERN_DATA( version ) = (GXV_kern_Version)FT_NEXT_USHORT( p );
+    GXV_TRACE(( "version 0x%04x (higher 16bit)\n",
+                GXV_KERN_DATA( version ) ));
+
+    if ( 0x0001 < GXV_KERN_DATA( version ) )
+      FT_INVALID_FORMAT;
+    else if ( KERN_IS_CLASSIC( valid ) )
+    {
+      GXV_LIMIT_CHECK( 2 );
+      nTables = FT_NEXT_USHORT( p );
+    }
+    else if ( KERN_IS_NEW( valid ) )
+    {
+      if ( classic_only )
+        FT_INVALID_FORMAT;
+
+      if ( 0x0000 != FT_NEXT_USHORT( p ) )
+        FT_INVALID_FORMAT;
+
+      GXV_LIMIT_CHECK( 4 );
+      nTables = FT_NEXT_ULONG( p );
+    }
+
+    for ( i = 0; i < nTables; i++ )
+    {
+      GXV_TRACE(( "validating subtable %d/%d\n", i, nTables ));
+      /* p should be 32bit-aligned? */
+      gxv_kern_subtable_validate( p, 0, valid );
+      p += valid->subtable_length;
+    }
+
+    FT_TRACE4(( "\n" ));
+  }
+
+
+  FT_LOCAL_DEF( void )
+  gxv_kern_validate( FT_Bytes      table,
+                     FT_Face       face,
+                     FT_Validator  ftvalid )
+  {
+    gxv_kern_validate_generic( table, face, 0, KERN_DIALECT_ANY, ftvalid );
+  }
+
+
+  FT_LOCAL_DEF( void )
+  gxv_kern_validate_classic( FT_Bytes      table,
+                             FT_Face       face,
+                             FT_Int        dialect_flags,
+                             FT_Validator  ftvalid )
+  {
+    GXV_kern_Dialect  dialect_request;
+
+
+    dialect_request = (GXV_kern_Dialect)dialect_flags;
+    gxv_kern_validate_generic( table, face, 1, dialect_request, ftvalid );
+  }
+
+
+/* END */