Imported Upstream version 2.3.1upstream/2.3.1

1 files changed, 931 insertions, 0 deletions

diff --git a/src/hb-machinery.hh b/src/hb-machinery.hh
new file mode 100644
index 0000000..b22c238
--- /dev/null
+++ b/src/hb-machinery.hh
@@ -0,0 +1,931 @@
+/*
+ * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
+ * Copyright © 2012,2018  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Red Hat Author(s): Behdad Esfahbod
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#ifndef HB_MACHINERY_HH
+#define HB_MACHINERY_HH
+
+#include "hb.hh"
+#include "hb-blob.hh"
+
+#include "hb-array.hh"
+#include "hb-vector.hh"
+
+
+/*
+ * Casts
+ */
+
+/* Cast to struct T, reference to reference */
+template<typename Type, typename TObject>
+static inline const Type& CastR(const TObject &X)
+{ return reinterpret_cast<const Type&> (X); }
+template<typename Type, typename TObject>
+static inline Type& CastR(TObject &X)
+{ return reinterpret_cast<Type&> (X); }
+
+/* Cast to struct T, pointer to pointer */
+template<typename Type, typename TObject>
+static inline const Type* CastP(const TObject *X)
+{ return reinterpret_cast<const Type*> (X); }
+template<typename Type, typename TObject>
+static inline Type* CastP(TObject *X)
+{ return reinterpret_cast<Type*> (X); }
+
+/* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
+ * location pointed to by P plus Ofs bytes. */
+template<typename Type>
+static inline const Type& StructAtOffset(const void *P, unsigned int offset)
+{ return * reinterpret_cast<const Type*> ((const char *) P + offset); }
+template<typename Type>
+static inline Type& StructAtOffset(void *P, unsigned int offset)
+{ return * reinterpret_cast<Type*> ((char *) P + offset); }
+template<typename Type>
+static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
+{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-align"
+  return * reinterpret_cast<Type*> ((char *) P + offset);
+#pragma GCC diagnostic pop
+}
+template<typename Type>
+static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
+{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-align"
+  return * reinterpret_cast<Type*> ((char *) P + offset);
+#pragma GCC diagnostic pop
+}
+
+/* StructAfter<T>(X) returns the struct T& that is placed after X.
+ * Works with X of variable size also.  X must implement get_size() */
+template<typename Type, typename TObject>
+static inline const Type& StructAfter(const TObject &X)
+{ return StructAtOffset<Type>(&X, X.get_size()); }
+template<typename Type, typename TObject>
+static inline Type& StructAfter(TObject &X)
+{ return StructAtOffset<Type>(&X, X.get_size()); }
+
+
+/*
+ * Size checking
+ */
+
+/* Check _assertion in a method environment */
+#define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
+  void _instance_assertion_on_line_##_line () const \
+  { static_assert ((_assertion), ""); }
+# define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
+# define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)
+
+/* Check that _code compiles in a method environment */
+#define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
+  void _compiles_assertion_on_line_##_line () const \
+  { _code; }
+# define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
+# define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)
+
+
+#define DEFINE_SIZE_STATIC(size) \
+  DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
+  unsigned int get_size () const { return (size); } \
+  static constexpr unsigned null_size = (size); \
+  static constexpr unsigned min_size = (size); \
+  static constexpr unsigned static_size = (size)
+
+#define DEFINE_SIZE_UNION(size, _member) \
+  DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
+  DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
+  static constexpr unsigned null_size = (size); \
+  static constexpr unsigned min_size = (size)
+
+#define DEFINE_SIZE_MIN(size) \
+  DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
+  static constexpr unsigned null_size = (size); \
+  static constexpr unsigned min_size = (size)
+
+#define DEFINE_SIZE_UNBOUNDED(size) \
+  DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
+  static constexpr unsigned min_size = (size)
+
+#define DEFINE_SIZE_ARRAY(size, array) \
+  DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
+  DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + VAR * sizeof ((array)[0])) \
+  static constexpr unsigned null_size = (size); \
+  static constexpr unsigned min_size = (size)
+
+#define DEFINE_SIZE_ARRAY_SIZED(size, array) \
+  unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
+  DEFINE_SIZE_ARRAY(size, array)
+
+
+/*
+ * Dispatch
+ */
+
+template <typename Context, typename Return, unsigned int MaxDebugDepth>
+struct hb_dispatch_context_t
+{
+  static constexpr unsigned max_debug_depth = MaxDebugDepth;
+  typedef Return return_t;
+  template <typename T, typename F>
+  bool may_dispatch (const T *obj HB_UNUSED, const F *format HB_UNUSED) { return true; }
+  static return_t no_dispatch_return_value () { return Context::default_return_value (); }
+  static bool stop_sublookup_iteration (const return_t r HB_UNUSED) { return false; }
+};
+
+
+/*
+ * Sanitize
+ *
+ *
+ * === Introduction ===
+ *
+ * The sanitize machinery is at the core of our zero-cost font loading.  We
+ * mmap() font file into memory and create a blob out of it.  Font subtables
+ * are returned as a readonly sub-blob of the main font blob.  These table
+ * blobs are then sanitized before use, to ensure invalid memory access does
+ * not happen.  The toplevel sanitize API use is like, eg. to load the 'head'
+ * table:
+ *
+ *   hb_blob_t *head_blob = hb_sanitize_context_t ().reference_table<OT::head> (face);
+ *
+ * The blob then can be converted to a head table struct with:
+ *
+ *   const head *head_table = head_blob->as<head> ();
+ *
+ * What the reference_table does is, to call hb_face_reference_table() to load
+ * the table blob, sanitize it and return either the sanitized blob, or empty
+ * blob if sanitization failed.  The blob->as() function returns the null
+ * object of its template type argument if the blob is empty.  Otherwise, it
+ * just casts the blob contents to the desired type.
+ *
+ * Sanitizing a blob of data with a type T works as follows (with minor
+ * simplification):
+ *
+ *   - Cast blob content to T*, call sanitize() method of it,
+ *   - If sanitize succeeded, return blob.
+ *   - Otherwise, if blob is not writable, try making it writable,
+ *     or copy if cannot be made writable in-place,
+ *   - Call sanitize() again.  Return blob if sanitize succeeded.
+ *   - Return empty blob otherwise.
+ *
+ *
+ * === The sanitize() contract ===
+ *
+ * The sanitize() method of each object type shall return true if it's safe to
+ * call other methods of the object, and false otherwise.
+ *
+ * Note that what sanitize() checks for might align with what the specification
+ * describes as valid table data, but does not have to be.  In particular, we
+ * do NOT want to be pedantic and concern ourselves with validity checks that
+ * are irrelevant to our use of the table.  On the contrary, we want to be
+ * lenient with error handling and accept invalid data to the extent that it
+ * does not impose extra burden on us.
+ *
+ * Based on the sanitize contract, one can see that what we check for depends
+ * on how we use the data in other table methods.  Ie. if other table methods
+ * assume that offsets do NOT point out of the table data block, then that's
+ * something sanitize() must check for (GSUB/GPOS/GDEF/etc work this way).  On
+ * the other hand, if other methods do such checks themselves, then sanitize()
+ * does not have to bother with them (glyf/local work this way).  The choice
+ * depends on the table structure and sanitize() performance.  For example, to
+ * check glyf/loca offsets in sanitize() would cost O(num-glyphs).  We try hard
+ * to avoid such costs during font loading.  By postponing such checks to the
+ * actual glyph loading, we reduce the sanitize cost to O(1) and total runtime
+ * cost to O(used-glyphs).  As such, this is preferred.
+ *
+ * The same argument can be made re GSUB/GPOS/GDEF, but there, the table
+ * structure is so complicated that by checking all offsets at sanitize() time,
+ * we make the code much simpler in other methods, as offsets and referenced
+ * objects do not need to be validated at each use site.
+ */
+
+/* This limits sanitizing time on really broken fonts. */
+#ifndef HB_SANITIZE_MAX_EDITS
+#define HB_SANITIZE_MAX_EDITS 32
+#endif
+#ifndef HB_SANITIZE_MAX_OPS_FACTOR
+#define HB_SANITIZE_MAX_OPS_FACTOR 8
+#endif
+#ifndef HB_SANITIZE_MAX_OPS_MIN
+#define HB_SANITIZE_MAX_OPS_MIN 16384
+#endif
+#ifndef HB_SANITIZE_MAX_OPS_MAX
+#define HB_SANITIZE_MAX_OPS_MAX 0x3FFFFFFF
+#endif
+
+struct hb_sanitize_context_t :
+       hb_dispatch_context_t<hb_sanitize_context_t, bool, HB_DEBUG_SANITIZE>
+{
+  hb_sanitize_context_t () :
+	debug_depth (0),
+	start (nullptr), end (nullptr),
+	max_ops (0),
+	writable (false), edit_count (0),
+	blob (nullptr),
+	num_glyphs (65536),
+	num_glyphs_set (false) {}
+
+  const char *get_name () { return "SANITIZE"; }
+  template <typename T, typename F>
+  bool may_dispatch (const T *obj HB_UNUSED, const F *format)
+  { return format->sanitize (this); }
+  template <typename T>
+  return_t dispatch (const T &obj) { return obj.sanitize (this); }
+  static return_t default_return_value () { return true; }
+  static return_t no_dispatch_return_value () { return false; }
+  bool stop_sublookup_iteration (const return_t r) const { return !r; }
+
+  void init (hb_blob_t *b)
+  {
+    this->blob = hb_blob_reference (b);
+    this->writable = false;
+  }
+
+  void set_num_glyphs (unsigned int num_glyphs_)
+  {
+    num_glyphs = num_glyphs_;
+    num_glyphs_set = true;
+  }
+  unsigned int get_num_glyphs () { return num_glyphs; }
+
+  void set_max_ops (int max_ops_) { max_ops = max_ops_; }
+
+  template <typename T>
+  void set_object (const T *obj)
+  {
+    reset_object ();
+
+    if (!obj) return;
+
+    const char *obj_start = (const char *) obj;
+    if (unlikely (obj_start < this->start || this->end <= obj_start))
+      this->start = this->end = nullptr;
+    else
+    {
+      this->start = obj_start;
+      this->end   = obj_start + MIN<uintptr_t> (this->end - obj_start, obj->get_size ());
+    }
+  }
+
+  void reset_object ()
+  {
+    this->start = this->blob->data;
+    this->end = this->start + this->blob->length;
+    assert (this->start <= this->end); /* Must not overflow. */
+  }
+
+  void start_processing ()
+  {
+    reset_object ();
+    this->max_ops = MAX ((unsigned int) (this->end - this->start) * HB_SANITIZE_MAX_OPS_FACTOR,
+			 (unsigned) HB_SANITIZE_MAX_OPS_MIN);
+    this->edit_count = 0;
+    this->debug_depth = 0;
+
+    DEBUG_MSG_LEVEL (SANITIZE, start, 0, +1,
+		     "start [%p..%p] (%lu bytes)",
+		     this->start, this->end,
+		     (unsigned long) (this->end - this->start));
+  }
+
+  void end_processing ()
+  {
+    DEBUG_MSG_LEVEL (SANITIZE, this->start, 0, -1,
+		     "end [%p..%p] %u edit requests",
+		     this->start, this->end, this->edit_count);
+
+    hb_blob_destroy (this->blob);
+    this->blob = nullptr;
+    this->start = this->end = nullptr;
+  }
+
+  bool check_range (const void *base,
+			   unsigned int len) const
+  {
+    const char *p = (const char *) base;
+    bool ok = this->start <= p &&
+	      p <= this->end &&
+	      (unsigned int) (this->end - p) >= len &&
+	      this->max_ops-- > 0;
+
+    DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
+       "check_range [%p..%p] (%d bytes) in [%p..%p] -> %s",
+       p, p + len, len,
+       this->start, this->end,
+       ok ? "OK" : "OUT-OF-RANGE");
+
+    return likely (ok);
+  }
+
+  template <typename T>
+  bool check_range (const T *base,
+			   unsigned int a,
+			   unsigned int b) const
+  {
+    return !hb_unsigned_mul_overflows (a, b) &&
+	   this->check_range (base, a * b);
+  }
+
+  template <typename T>
+  bool check_range (const T *base,
+			   unsigned int a,
+			   unsigned int b,
+			   unsigned int c) const
+  {
+    return !hb_unsigned_mul_overflows (a, b) &&
+	   this->check_range (base, a * b, c);
+  }
+
+  template <typename T>
+  bool check_array (const T *base, unsigned int len) const
+  {
+    return this->check_range (base, len, hb_static_size (T));
+  }
+
+  template <typename T>
+  bool check_array (const T *base,
+		    unsigned int a,
+		    unsigned int b) const
+  {
+    return this->check_range (base, a, b, hb_static_size (T));
+  }
+
+  template <typename Type>
+  bool check_struct (const Type *obj) const
+  { return likely (this->check_range (obj, obj->min_size)); }
+
+  bool may_edit (const void *base, unsigned int len)
+  {
+    if (this->edit_count >= HB_SANITIZE_MAX_EDITS)
+      return false;
+
+    const char *p = (const char *) base;
+    this->edit_count++;
+
+    DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
+       "may_edit(%u) [%p..%p] (%d bytes) in [%p..%p] -> %s",
+       this->edit_count,
+       p, p + len, len,
+       this->start, this->end,
+       this->writable ? "GRANTED" : "DENIED");
+
+    return this->writable;
+  }
+
+  template <typename Type, typename ValueType>
+  bool try_set (const Type *obj, const ValueType &v)
+  {
+    if (this->may_edit (obj, hb_static_size (Type)))
+    {
+      hb_assign (* const_cast<Type *> (obj), v);
+      return true;
+    }
+    return false;
+  }
+
+  template <typename Type>
+  hb_blob_t *sanitize_blob (hb_blob_t *blob)
+  {
+    bool sane;
+
+    init (blob);
+
+  retry:
+    DEBUG_MSG_FUNC (SANITIZE, start, "start");
+
+    start_processing ();
+
+    if (unlikely (!start))
+    {
+      end_processing ();
+      return blob;
+    }
+
+    Type *t = CastP<Type> (const_cast<char *> (start));
+
+    sane = t->sanitize (this);
+    if (sane)
+    {
+      if (edit_count)
+      {
+	DEBUG_MSG_FUNC (SANITIZE, start, "passed first round with %d edits; going for second round", edit_count);
+
+        /* sanitize again to ensure no toe-stepping */
+        edit_count = 0;
+	sane = t->sanitize (this);
+	if (edit_count) {
+	  DEBUG_MSG_FUNC (SANITIZE, start, "requested %d edits in second round; FAILLING", edit_count);
+	  sane = false;
+	}
+      }
+    }
+    else
+    {
+      if (edit_count && !writable) {
+        start = hb_blob_get_data_writable (blob, nullptr);
+	end = start + blob->length;
+
+	if (start)
+	{
+	  writable = true;
+	  /* ok, we made it writable by relocating.  try again */
+	  DEBUG_MSG_FUNC (SANITIZE, start, "retry");
+	  goto retry;
+	}
+      }
+    }
+
+    end_processing ();
+
+    DEBUG_MSG_FUNC (SANITIZE, start, sane ? "PASSED" : "FAILED");
+    if (sane)
+    {
+      hb_blob_make_immutable (blob);
+      return blob;
+    }
+    else
+    {
+      hb_blob_destroy (blob);
+      return hb_blob_get_empty ();
+    }
+  }
+
+  template <typename Type>
+  hb_blob_t *reference_table (const hb_face_t *face, hb_tag_t tableTag = Type::tableTag)
+  {
+    if (!num_glyphs_set)
+      set_num_glyphs (hb_face_get_glyph_count (face));
+    return sanitize_blob<Type> (hb_face_reference_table (face, tableTag));
+  }
+
+  mutable unsigned int debug_depth;
+  const char *start, *end;
+  mutable int max_ops;
+  private:
+  bool writable;
+  unsigned int edit_count;
+  hb_blob_t *blob;
+  unsigned int num_glyphs;
+  bool  num_glyphs_set;
+};
+
+struct hb_sanitize_with_object_t
+{
+  template <typename T>
+  hb_sanitize_with_object_t (hb_sanitize_context_t *c,
+				    const T& obj) : c (c)
+  { c->set_object (obj); }
+  ~hb_sanitize_with_object_t ()
+  { c->reset_object (); }
+
+  private:
+  hb_sanitize_context_t *c;
+};
+
+
+/*
+ * Serialize
+ */
+
+struct hb_serialize_context_t
+{
+  hb_serialize_context_t (void *start_, unsigned int size)
+  {
+    this->start = (char *) start_;
+    this->end = this->start + size;
+    reset ();
+  }
+
+  bool in_error () const { return !this->successful; }
+
+  void reset ()
+  {
+    this->successful = true;
+    this->head = this->start;
+    this->debug_depth = 0;
+  }
+
+  bool propagate_error (bool e)
+  { return this->successful = this->successful && e; }
+  template <typename T> bool propagate_error (const T &obj)
+  { return this->successful = this->successful && !obj.in_error (); }
+  template <typename T> bool propagate_error (const T *obj)
+  { return this->successful = this->successful && !obj->in_error (); }
+  template <typename T1, typename T2> bool propagate_error (T1 &o1, T2 &o2)
+  { return propagate_error (o1) && propagate_error (o2); }
+  template <typename T1, typename T2> bool propagate_error (T1 *o1, T2 *o2)
+  { return propagate_error (o1) && propagate_error (o2); }
+  template <typename T1, typename T2, typename T3>
+  bool propagate_error (T1 &o1, T2 &o2, T3 &o3)
+  { return propagate_error (o1) && propagate_error (o2, o3); }
+  template <typename T1, typename T2, typename T3>
+  bool propagate_error (T1 *o1, T2 *o2, T3 *o3)
+  { return propagate_error (o1) && propagate_error (o2, o3); }
+
+  /* To be called around main operation. */
+  template <typename Type>
+  Type *start_serialize ()
+  {
+    DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, +1,
+		     "start [%p..%p] (%lu bytes)",
+		     this->start, this->end,
+		     (unsigned long) (this->end - this->start));
+
+    return start_embed<Type> ();
+  }
+  void end_serialize ()
+  {
+    DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, -1,
+		     "end [%p..%p] serialized %d bytes; %s",
+		     this->start, this->end,
+		     (int) (this->head - this->start),
+		     this->successful ? "successful" : "UNSUCCESSFUL");
+  }
+
+  unsigned int length () const { return this->head - this->start; }
+
+  void align (unsigned int alignment)
+  {
+    unsigned int l = length () % alignment;
+    if (l)
+      allocate_size<void> (alignment - l);
+  }
+
+  template <typename Type>
+  Type *start_embed (const Type *_ HB_UNUSED = nullptr) const
+  {
+    Type *ret = reinterpret_cast<Type *> (this->head);
+    return ret;
+  }
+
+  template <typename Type>
+  Type *allocate_size (unsigned int size)
+  {
+    if (unlikely (!this->successful || this->end - this->head < ptrdiff_t (size))) {
+      this->successful = false;
+      return nullptr;
+    }
+    memset (this->head, 0, size);
+    char *ret = this->head;
+    this->head += size;
+    return reinterpret_cast<Type *> (ret);
+  }
+
+  template <typename Type>
+  Type *allocate_min ()
+  {
+    return this->allocate_size<Type> (Type::min_size);
+  }
+
+  template <typename Type>
+  Type *embed (const Type &obj)
+  {
+    unsigned int size = obj.get_size ();
+    Type *ret = this->allocate_size<Type> (size);
+    if (unlikely (!ret)) return nullptr;
+    memcpy (ret, &obj, size);
+    return ret;
+  }
+  template <typename Type>
+  hb_serialize_context_t &operator << (const Type &obj) { embed (obj); return *this; }
+
+  template <typename Type>
+  Type *extend_size (Type &obj, unsigned int size)
+  {
+    assert (this->start <= (char *) &obj);
+    assert ((char *) &obj <= this->head);
+    assert ((char *) &obj + size >= this->head);
+    if (unlikely (!this->allocate_size<Type> (((char *) &obj) + size - this->head))) return nullptr;
+    return reinterpret_cast<Type *> (&obj);
+  }
+
+  template <typename Type>
+  Type *extend_min (Type &obj) { return extend_size (obj, obj.min_size); }
+
+  template <typename Type>
+  Type *extend (Type &obj) { return extend_size (obj, obj.get_size ()); }
+
+  /* Output routines. */
+  template <typename Type>
+  Type *copy () const
+  {
+    assert (this->successful);
+    unsigned int len = this->head - this->start;
+    void *p = malloc (len);
+    if (p)
+      memcpy (p, this->start, len);
+    return reinterpret_cast<Type *> (p);
+  }
+  hb_bytes_t copy_bytes () const
+  {
+    assert (this->successful);
+    unsigned int len = this->head - this->start;
+    void *p = malloc (len);
+    if (p)
+      memcpy (p, this->start, len);
+    else
+      return hb_bytes_t ();
+    return hb_bytes_t ((char *) p, len);
+  }
+  hb_blob_t *copy_blob () const
+  {
+    assert (this->successful);
+    return hb_blob_create (this->start,
+			   this->head - this->start,
+			   HB_MEMORY_MODE_DUPLICATE,
+			   nullptr, nullptr);
+  }
+
+  public:
+  unsigned int debug_depth;
+  char *start, *end, *head;
+  bool successful;
+};
+
+
+
+/*
+ * Big-endian integers.
+ */
+
+template <typename Type, int Bytes> struct BEInt;
+
+template <typename Type>
+struct BEInt<Type, 1>
+{
+  public:
+  void set (Type V)      { v = V; }
+  operator Type () const { return v; }
+  private: uint8_t v;
+};
+template <typename Type>
+struct BEInt<Type, 2>
+{
+  public:
+  void set (Type V)
+  {
+    v[0] = (V >>  8) & 0xFF;
+    v[1] = (V      ) & 0xFF;
+  }
+  operator Type () const
+  {
+#if ((defined(__GNUC__) && __GNUC__ >= 5) || defined(__clang__)) && \
+    defined(__BYTE_ORDER) && \
+    (__BYTE_ORDER == __LITTLE_ENDIAN || __BYTE_ORDER == __BIG_ENDIAN)
+    /* Spoon-feed the compiler a big-endian integer with alignment 1.
+     * https://github.com/harfbuzz/harfbuzz/pull/1398 */
+    struct __attribute__((packed)) packed_uint16_t { uint16_t v; };
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+    return __builtin_bswap16 (((packed_uint16_t *) this)->v);
+#else /* __BYTE_ORDER == __BIG_ENDIAN */
+    return ((packed_uint16_t *) this)->v;
+#endif
+#endif
+    return (v[0] <<  8)
+         + (v[1]      );
+  }
+  private: uint8_t v[2];
+};
+template <typename Type>
+struct BEInt<Type, 3>
+{
+  public:
+  void set (Type V)
+  {
+    v[0] = (V >> 16) & 0xFF;
+    v[1] = (V >>  8) & 0xFF;
+    v[2] = (V      ) & 0xFF;
+  }
+  operator Type () const
+  {
+    return (v[0] << 16)
+         + (v[1] <<  8)
+         + (v[2]      );
+  }
+  private: uint8_t v[3];
+};
+template <typename Type>
+struct BEInt<Type, 4>
+{
+  public:
+  typedef Type type;
+  void set (Type V)
+  {
+    v[0] = (V >> 24) & 0xFF;
+    v[1] = (V >> 16) & 0xFF;
+    v[2] = (V >>  8) & 0xFF;
+    v[3] = (V      ) & 0xFF;
+  }
+  operator Type () const
+  {
+    return (v[0] << 24)
+         + (v[1] << 16)
+         + (v[2] <<  8)
+         + (v[3]      );
+  }
+  private: uint8_t v[4];
+};
+
+
+/*
+ * Lazy loaders.
+ */
+
+template <typename Data, unsigned int WheresData>
+struct hb_data_wrapper_t
+{
+  static_assert (WheresData > 0, "");
+
+  Data * get_data () const
+  { return *(((Data **) (void *) this) - WheresData); }
+
+  bool is_inert () const { return !get_data (); }
+
+  template <typename Stored, typename Subclass>
+  Stored * call_create () const { return Subclass::create (get_data ()); }
+};
+template <>
+struct hb_data_wrapper_t<void, 0>
+{
+  bool is_inert () const { return false; }
+
+  template <typename Stored, typename Funcs>
+  Stored * call_create () const { return Funcs::create (); }
+};
+
+template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
+template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };
+
+template <typename Returned,
+	  typename Subclass = void,
+	  typename Data = void,
+	  unsigned int WheresData = 0,
+	  typename Stored = Returned>
+struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
+{
+  typedef typename hb_non_void_t<Subclass,
+				 hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
+				>::value Funcs;
+
+  void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
+  void init ()  { instance.set_relaxed (nullptr); }
+  void fini ()  { do_destroy (instance.get ()); }
+
+  void free_instance ()
+  {
+  retry:
+    Stored *p = instance.get ();
+    if (unlikely (p && !cmpexch (p, nullptr)))
+      goto retry;
+    do_destroy (p);
+  }
+
+  static void do_destroy (Stored *p)
+  {
+    if (p && p != const_cast<Stored *> (Funcs::get_null ()))
+      Funcs::destroy (p);
+  }
+
+  const Returned * operator -> () const { return get (); }
+  const Returned & operator * () const  { return *get (); }
+  explicit_operator bool () const
+  { return get_stored () != Funcs::get_null (); }
+  template <typename C> operator const C * () const { return get (); }
+
+  Stored * get_stored () const
+  {
+  retry:
+    Stored *p = this->instance.get ();
+    if (unlikely (!p))
+    {
+      if (unlikely (this->is_inert ()))
+	return const_cast<Stored *> (Funcs::get_null ());
+
+      p = this->template call_create<Stored, Funcs> ();
+      if (unlikely (!p))
+	p = const_cast<Stored *> (Funcs::get_null ());
+
+      if (unlikely (!cmpexch (nullptr, p)))
+      {
+        do_destroy (p);
+	goto retry;
+      }
+    }
+    return p;
+  }
+  Stored * get_stored_relaxed () const
+  {
+    return this->instance.get_relaxed ();
+  }
+
+  bool cmpexch (Stored *current, Stored *value) const
+  {
+    /* This *must* be called when there are no other threads accessing. */
+    return this->instance.cmpexch (current, value);
+  }
+
+  const Returned * get () const { return Funcs::convert (get_stored ()); }
+  const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
+  Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }
+
+  /* To be possibly overloaded by subclasses. */
+  static Returned* convert (Stored *p) { return p; }
+
+  /* By default null/init/fini the object. */
+  static const Stored* get_null () { return &Null(Stored); }
+  static Stored *create (Data *data)
+  {
+    Stored *p = (Stored *) calloc (1, sizeof (Stored));
+    if (likely (p))
+      p->init (data);
+    return p;
+  }
+  static Stored *create ()
+  {
+    Stored *p = (Stored *) calloc (1, sizeof (Stored));
+    if (likely (p))
+      p->init ();
+    return p;
+  }
+  static void destroy (Stored *p)
+  {
+    p->fini ();
+    free (p);
+  }
+
+//  private:
+  /* Must only have one pointer. */
+  hb_atomic_ptr_t<Stored *> instance;
+};
+
+/* Specializations. */
+
+template <typename T, unsigned int WheresFace>
+struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
+						hb_face_lazy_loader_t<T, WheresFace>,
+						hb_face_t, WheresFace> {};
+
+template <typename T, unsigned int WheresFace>
+struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
+						 hb_table_lazy_loader_t<T, WheresFace>,
+						 hb_face_t, WheresFace,
+						 hb_blob_t>
+{
+  static hb_blob_t *create (hb_face_t *face)
+  { return hb_sanitize_context_t ().reference_table<T> (face); }
+  static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }
+
+  static const hb_blob_t *get_null ()
+  { return hb_blob_get_empty (); }
+
+  static const T* convert (const hb_blob_t *blob)
+  { return blob->as<T> (); }
+
+  hb_blob_t* get_blob () const { return this->get_stored (); }
+};
+
+template <typename Subclass>
+struct hb_font_funcs_lazy_loader_t : hb_lazy_loader_t<hb_font_funcs_t, Subclass>
+{
+  static void destroy (hb_font_funcs_t *p)
+  { hb_font_funcs_destroy (p); }
+  static const hb_font_funcs_t *get_null ()
+  { return hb_font_funcs_get_empty (); }
+};
+template <typename Subclass>
+struct hb_unicode_funcs_lazy_loader_t : hb_lazy_loader_t<hb_unicode_funcs_t, Subclass>
+{
+  static void destroy (hb_unicode_funcs_t *p)
+  { hb_unicode_funcs_destroy (p); }
+  static const hb_unicode_funcs_t *get_null ()
+  { return hb_unicode_funcs_get_empty (); }
+};
+
+
+#endif /* HB_MACHINERY_HH */