src/hb-blob.cc

/*
 * 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
 */

/* http://www.oracle.com/technetwork/articles/servers-storage-dev/standardheaderfiles-453865.html */
#ifndef _POSIX_C_SOURCE
#define _POSIX_C_SOURCE 200809L
#endif

#include "hb-private.hh"
#include "hb-debug.hh"

#include "hb-object-private.hh"

#ifdef HAVE_SYS_MMAN_H
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
#include <sys/mman.h>
#endif /* HAVE_SYS_MMAN_H */

#include <stdio.h>
#include <errno.h>


struct hb_blob_t {
  hb_object_header_t header;
  ASSERT_POD ();

  bool immutable;

  const char *data;
  unsigned int length;
  hb_memory_mode_t mode;

  void *user_data;
  hb_destroy_func_t destroy;
};


static bool _try_writable (hb_blob_t *blob);

static void
_hb_blob_destroy_user_data (hb_blob_t *blob)
{
  if (blob->destroy) {
    blob->destroy (blob->user_data);
    blob->user_data = nullptr;
    blob->destroy = nullptr;
  }
}

/**
 * hb_blob_create: (skip)
 * @data: Pointer to blob data.
 * @length: Length of @data in bytes.
 * @mode: Memory mode for @data.
 * @user_data: Data parameter to pass to @destroy.
 * @destroy: Callback to call when @data is not needed anymore.
 *
 * Creates a new "blob" object wrapping @data.  The @mode parameter is used
 * to negotiate ownership and lifecycle of @data.
 *
 * Return value: New blob, or the empty blob if something failed or if @length is
 * zero.  Destroy with hb_blob_destroy().
 *
 * Since: 0.9.2
 **/
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)
{
  hb_blob_t *blob;

  if (!length ||
      length >= 1u << 31 ||
      !(blob = hb_object_create<hb_blob_t> ())) {
    if (destroy)
      destroy (user_data);
    return hb_blob_get_empty ();
  }

  blob->data = data;
  blob->length = length;
  blob->mode = mode;

  blob->user_data = user_data;
  blob->destroy = destroy;

  if (blob->mode == HB_MEMORY_MODE_DUPLICATE) {
    blob->mode = HB_MEMORY_MODE_READONLY;
    if (!_try_writable (blob)) {
      hb_blob_destroy (blob);
      return hb_blob_get_empty ();
    }
  }

  return blob;
}

static void
_hb_blob_destroy (void *data)
{
  hb_blob_destroy ((hb_blob_t *) data);
}

/**
 * hb_blob_create_sub_blob:
 * @parent: Parent blob.
 * @offset: Start offset of sub-blob within @parent, in bytes.
 * @length: Length of sub-blob.
 *
 * Returns a blob that represents a range of bytes in @parent.  The new
 * blob is always created with %HB_MEMORY_MODE_READONLY, meaning that it
 * will never modify data in the parent blob.  The parent data is not
 * expected to be modified, and will result in undefined behavior if it
 * is.
 *
 * Makes @parent immutable.
 *
 * Return value: New blob, or the empty blob if something failed or if
 * @length is zero or @offset is beyond the end of @parent's data.  Destroy
 * with hb_blob_destroy().
 *
 * Since: 0.9.2
 **/
hb_blob_t *
hb_blob_create_sub_blob (hb_blob_t    *parent,
			 unsigned int  offset,
			 unsigned int  length)
{
  hb_blob_t *blob;

  if (!length || offset >= parent->length)
    return hb_blob_get_empty ();

  hb_blob_make_immutable (parent);

  blob = hb_blob_create (parent->data + offset,
			 MIN (length, parent->length - offset),
			 HB_MEMORY_MODE_READONLY,
			 hb_blob_reference (parent),
			 _hb_blob_destroy);

  return blob;
}

/**
 * hb_blob_get_empty:
 *
 * Returns the singleton empty blob.
 *
 * See TODO:link object types for more information.
 *
 * Return value: (transfer full): the empty blob.
 *
 * Since: 0.9.2
 **/
hb_blob_t *
hb_blob_get_empty (void)
{
  static const hb_blob_t _hb_blob_nil = {
    HB_OBJECT_HEADER_STATIC,

    true, /* immutable */

    nullptr, /* data */
    0, /* length */
    HB_MEMORY_MODE_READONLY, /* mode */

    nullptr, /* user_data */
    nullptr  /* destroy */
  };

  return const_cast<hb_blob_t *> (&_hb_blob_nil);
}

/**
 * hb_blob_reference: (skip)
 * @blob: a blob.
 *
 * Increases the reference count on @blob.
 *
 * See TODO:link object types for more information.
 *
 * Return value: @blob.
 *
 * Since: 0.9.2
 **/
hb_blob_t *
hb_blob_reference (hb_blob_t *blob)
{
  return hb_object_reference (blob);
}

/**
 * hb_blob_destroy: (skip)
 * @blob: a blob.
 *
 * Descreases the reference count on @blob, and if it reaches zero, destroys
 * @blob, freeing all memory, possibly calling the destroy-callback the blob
 * was created for if it has not been called already.
 *
 * See TODO:link object types for more information.
 *
 * Since: 0.9.2
 **/
void
hb_blob_destroy (hb_blob_t *blob)
{
  if (!hb_object_destroy (blob)) return;

  _hb_blob_destroy_user_data (blob);

  free (blob);
}

/**
 * hb_blob_set_user_data: (skip)
 * @blob: a blob.
 * @key: key for data to set.
 * @data: data to set.
 * @destroy: callback to call when @data is not needed anymore.
 * @replace: whether to replace an existing data with the same key.
 *
 * Return value: 
 *
 * Since: 0.9.2
 **/
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)
{
  return hb_object_set_user_data (blob, key, data, destroy, replace);
}

/**
 * hb_blob_get_user_data: (skip)
 * @blob: a blob.
 * @key: key for data to get.
 *
 * 
 *
 * Return value: (transfer none): 
 *
 * Since: 0.9.2
 **/
void *
hb_blob_get_user_data (hb_blob_t          *blob,
		       hb_user_data_key_t *key)
{
  return hb_object_get_user_data (blob, key);
}


/**
 * hb_blob_make_immutable:
 * @blob: a blob.
 *
 * 
 *
 * Since: 0.9.2
 **/
void
hb_blob_make_immutable (hb_blob_t *blob)
{
  if (hb_object_is_inert (blob))
    return;

  blob->immutable = true;
}

/**
 * hb_blob_is_immutable:
 * @blob: a blob.
 *
 * 
 *
 * Return value: TODO
 *
 * Since: 0.9.2
 **/
hb_bool_t
hb_blob_is_immutable (hb_blob_t *blob)
{
  return blob->immutable;
}


/**
 * hb_blob_get_length:
 * @blob: a blob.
 *
 * 
 *
 * Return value: the length of blob data in bytes.
 *
 * Since: 0.9.2
 **/
unsigned int
hb_blob_get_length (hb_blob_t *blob)
{
  return blob->length;
}

/**
 * hb_blob_get_data:
 * @blob: a blob.
 * @length: (out):
 *
 * 
 *
 * Returns: (transfer none) (array length=length): 
 *
 * Since: 0.9.2
 **/
const char *
hb_blob_get_data (hb_blob_t *blob, unsigned int *length)
{
  if (length)
    *length = blob->length;

  return blob->data;
}

/**
 * hb_blob_get_data_writable:
 * @blob: a blob.
 * @length: (out): output length of the writable data.
 *
 * Tries to make blob data writable (possibly copying it) and
 * return pointer to data.
 *
 * Fails if blob has been made immutable, or if memory allocation
 * fails.
 *
 * Returns: (transfer none) (array length=length): Writable blob data,
 * or %NULL if failed.
 *
 * Since: 0.9.2
 **/
char *
hb_blob_get_data_writable (hb_blob_t *blob, unsigned int *length)
{
  if (!_try_writable (blob)) {
    if (length)
      *length = 0;

    return nullptr;
  }

  if (length)
    *length = blob->length;

  return const_cast<char *> (blob->data);
}


static hb_bool_t
_try_make_writable_inplace_unix (hb_blob_t *blob)
{
#if defined(HAVE_SYS_MMAN_H) && defined(HAVE_MPROTECT)
  uintptr_t pagesize = -1, mask, length;
  const char *addr;

#if defined(HAVE_SYSCONF) && defined(_SC_PAGE_SIZE)
  pagesize = (uintptr_t) sysconf (_SC_PAGE_SIZE);
#elif defined(HAVE_SYSCONF) && defined(_SC_PAGESIZE)
  pagesize = (uintptr_t) sysconf (_SC_PAGESIZE);
#elif defined(HAVE_GETPAGESIZE)
  pagesize = (uintptr_t) getpagesize ();
#endif

  if ((uintptr_t) -1L == pagesize) {
    DEBUG_MSG_FUNC (BLOB, blob, "failed to get pagesize: %s", strerror (errno));
    return false;
  }
  DEBUG_MSG_FUNC (BLOB, blob, "pagesize is %lu", (unsigned long) pagesize);

  mask = ~(pagesize-1);
  addr = (const char *) (((uintptr_t) blob->data) & mask);
  length = (const char *) (((uintptr_t) blob->data + blob->length + pagesize-1) & mask)  - addr;
  DEBUG_MSG_FUNC (BLOB, blob,
		  "calling mprotect on [%p..%p] (%lu bytes)",
		  addr, addr+length, (unsigned long) length);
  if (-1 == mprotect ((void *) addr, length, PROT_READ | PROT_WRITE)) {
    DEBUG_MSG_FUNC (BLOB, blob, "mprotect failed: %s", strerror (errno));
    return false;
  }

  blob->mode = HB_MEMORY_MODE_WRITABLE;

  DEBUG_MSG_FUNC (BLOB, blob,
		  "successfully made [%p..%p] (%lu bytes) writable\n",
		  addr, addr+length, (unsigned long) length);
  return true;
#else
  return false;
#endif
}

static bool
_try_writable_inplace (hb_blob_t *blob)
{
  DEBUG_MSG_FUNC (BLOB, blob, "making writable inplace\n");

  if (_try_make_writable_inplace_unix (blob))
    return true;

  DEBUG_MSG_FUNC (BLOB, blob, "making writable -> FAILED\n");

  /* Failed to make writable inplace, mark that */
  blob->mode = HB_MEMORY_MODE_READONLY;
  return false;
}

static bool
_try_writable (hb_blob_t *blob)
{
  if (blob->immutable)
    return false;

  if (blob->mode == HB_MEMORY_MODE_WRITABLE)
    return true;

  if (blob->mode == HB_MEMORY_MODE_READONLY_MAY_MAKE_WRITABLE && _try_writable_inplace (blob))
    return true;

  if (blob->mode == HB_MEMORY_MODE_WRITABLE)
    return true;


  DEBUG_MSG_FUNC (BLOB, blob, "current data is -> %p\n", blob->data);

  char *new_data;

  new_data = (char *) malloc (blob->length);
  if (unlikely (!new_data))
    return false;

  DEBUG_MSG_FUNC (BLOB, blob, "dupped successfully -> %p\n", blob->data);

  memcpy (new_data, blob->data, blob->length);
  _hb_blob_destroy_user_data (blob);
  blob->mode = HB_MEMORY_MODE_WRITABLE;
  blob->data = new_data;
  blob->user_data = new_data;
  blob->destroy = free;

  return true;
}