kc3-lang/harfbuzz/src/hb-blob.h

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• Hash : c3ba49b6
  Author :
  Date : 2013-02-25T17:06:35
  

  Always create sub-blobs in MEMORY_MODE_READONLY
  
  This fixes a design bug with sanitize and sub-blobs that can
  cause crashes.  Jonathan and I found and debugged this issue
  when we tested a corrupt font with the md5sum / filename:
  ea395483d37af0cb933f40689ff7b60a.  Two hours of intense
  debugging we found out that the font has overlapping GSUB/GPOS
  tables, and as such, sanitizing the second table can modify
  the first one, which can cause all kinds of undefined behavior.
  
  The correct way to fix this is to make sure sub-blobs are
  always created readonly, since we consider the parent blob
  to be a shared resource and can't modify it, even if it *is*
  writable.
  
  This essentially makes the READONLY_MAY_MAKE_WRITABLE mode
  unused...  Maybe we should simply remove / deprecate it.
  

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• src/hb-blob.h

• /*
   * Copyright © 2009  Red Hat, 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
   */
  
  #ifndef HB_H_IN
  #error "Include <hb.h> instead."
  #endif
  
  #ifndef HB_BLOB_H
  #define HB_BLOB_H
  
  #include "hb-common.h"
  
  HB_BEGIN_DECLS
  
  
  /*
   * Note re various memory-modes:
   *
   * - In no case shall the HarfBuzz client modify memory
   *   that is passed to HarfBuzz in a blob.  If there is
   *   any such possibility, MODE_DUPLICATE should be used
   *   such that HarfBuzz makes a copy immediately,
   *
   * - Use MODE_READONLY otherse, unless you really really
   *   really know what you are doing,
   *
   * - MODE_WRITABLE is appropriate if you relaly made a
   *   copy of data solely for the purpose of passing to
   *   HarfBuzz and doing that just once (no reuse!),
   *
   * - If the font is mmap()ed, it's ok to use
   *   READONLY_MAY_MAKE_WRITABLE, however, there were
   *   design problems with that mode, so HarfBuzz do not
   *   really use it anymore.  If not sure, use MODE_READONLY.
   */
  typedef enum {
    HB_MEMORY_MODE_DUPLICATE,
    HB_MEMORY_MODE_READONLY,
    HB_MEMORY_MODE_WRITABLE,
    HB_MEMORY_MODE_READONLY_MAY_MAKE_WRITABLE
  } hb_memory_mode_t;
  
  typedef struct hb_blob_t hb_blob_t;
  
  hb_blob_t *
  hb_blob_create (const char        *data,
  		unsigned int       length,
  		hb_memory_mode_t   mode,
  		void              *user_data,
  		hb_destroy_func_t  destroy);
  
  /* Always creates with MEMORY_MODE_READONLY.
   * Even if the parent blob is writable, we don't
   * want the user of the sub-blob to be able to
   * modify the parent data as that data may be
   * shared among multiple sub-blobs.
   */
  hb_blob_t *
  hb_blob_create_sub_blob (hb_blob_t    *parent,
  			 unsigned int  offset,
  			 unsigned int  length);
  
  hb_blob_t *
  hb_blob_get_empty (void);
  
  hb_blob_t *
  hb_blob_reference (hb_blob_t *blob);
  
  void
  hb_blob_destroy (hb_blob_t *blob);
  
  hb_bool_t
  hb_blob_set_user_data (hb_blob_t          *blob,
  		       hb_user_data_key_t *key,
  		       void *              data,
  		       hb_destroy_func_t   destroy,
  		       hb_bool_t           replace);
  
  
  void *
  hb_blob_get_user_data (hb_blob_t          *blob,
  		       hb_user_data_key_t *key);
  
  
  void
  hb_blob_make_immutable (hb_blob_t *blob);
  
  hb_bool_t
  hb_blob_is_immutable (hb_blob_t *blob);
  
  
  unsigned int
  hb_blob_get_length (hb_blob_t *blob);
  
  const char *
  hb_blob_get_data (hb_blob_t *blob, unsigned int *length);
  
  char *
  hb_blob_get_data_writable (hb_blob_t *blob, unsigned int *length);
  
  
  HB_END_DECLS
  
  #endif /* HB_BLOB_H */
  

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