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diff mupdf-source/thirdparty/harfbuzz/src/hb-sanitize.hh @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/harfbuzz/src/hb-sanitize.hh	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,430 @@
+/*
+ * 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_SANITIZE_HH
+#define HB_SANITIZE_HH
+
+#include "hb.hh"
+#include "hb-blob.hh"
+#include "hb-dispatch.hh"
+
+
+/*
+ * 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 64
+#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
+#ifndef HB_SANITIZE_MAX_SUBTABLES
+#define HB_SANITIZE_MAX_SUBTABLES 0x4000
+#endif
+
+struct hb_sanitize_context_t :
+       hb_dispatch_context_t<hb_sanitize_context_t, bool, HB_DEBUG_SANITIZE>
+{
+  hb_sanitize_context_t () :
+	start (nullptr), end (nullptr),
+	max_ops (0), max_subtables (0),
+        recursion_depth (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); }
+  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; }
+
+  bool visit_subtables (unsigned count)
+  {
+    max_subtables += count;
+    return max_subtables < HB_SANITIZE_MAX_SUBTABLES;
+  }
+
+  private:
+  template <typename T, typename ...Ts> auto
+  _dispatch (const T &obj, hb_priority<1>, Ts&&... ds) HB_AUTO_RETURN
+  ( obj.sanitize (this, std::forward<Ts> (ds)...) )
+  template <typename T, typename ...Ts> auto
+  _dispatch (const T &obj, hb_priority<0>, Ts&&... ds) HB_AUTO_RETURN
+  ( obj.dispatch (this, std::forward<Ts> (ds)...) )
+  public:
+  template <typename T, typename ...Ts> auto
+  dispatch (const T &obj, Ts&&... ds) HB_AUTO_RETURN
+  ( _dispatch (obj, hb_prioritize, std::forward<Ts> (ds)...) )
+
+
+  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 + hb_min (size_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 ();
+    unsigned m;
+    if (unlikely (hb_unsigned_mul_overflows (this->end - this->start, HB_SANITIZE_MAX_OPS_FACTOR, &m)))
+      this->max_ops = HB_SANITIZE_MAX_OPS_MAX;
+    else
+      this->max_ops = hb_clamp (m,
+				(unsigned) HB_SANITIZE_MAX_OPS_MIN,
+				(unsigned) HB_SANITIZE_MAX_OPS_MAX);
+    this->edit_count = 0;
+    this->debug_depth = 0;
+    this->recursion_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;
+  }
+
+  unsigned get_edit_count () { return edit_count; }
+
+  bool check_range (const void *base,
+		    unsigned int len) const
+  {
+    const char *p = (const char *) base;
+    bool ok = !len ||
+	      (this->start <= p &&
+	       p <= this->end &&
+	       (unsigned int) (this->end - p) >= len &&
+	       (this->max_ops -= len) > 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
+  {
+    unsigned m;
+    return !hb_unsigned_mul_overflows (a, b, &m) &&
+	   this->check_range (base, m);
+  }
+
+  template <typename T>
+  bool check_range (const T *base,
+		    unsigned int a,
+		    unsigned int b,
+		    unsigned int c) const
+  {
+    unsigned m;
+    return !hb_unsigned_mul_overflows (a, b, &m) &&
+	   this->check_range (base, m, 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));
+  }
+
+  bool check_start_recursion (int max_depth)
+  {
+    if (unlikely (recursion_depth >= max_depth)) return false;
+    return ++recursion_depth;
+  }
+
+  bool end_recursion (bool result)
+  {
+    recursion_depth--;
+    return result;
+  }
+
+  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)))
+    {
+      * 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 = reinterpret_cast<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));
+  }
+
+  const char *start, *end;
+  mutable int max_ops, max_subtables;
+  private:
+  int recursion_depth;
+  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;
+};
+
+
+#endif /* HB_SANITIZE_HH */