glib/gbytes.c

   1 /*
   2  * Copyright © 2009, 2010 Codethink Limited
   3  * Copyright © 2011 Collabora Ltd.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the licence, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Ryan Lortie <desrt@desrt.ca>
  19  *         Stef Walter <stefw@collabora.co.uk>
  20  */
  21
  22 #include "config.h"
  23
  24 #include "gbytes.h"
  25
  26 #include <glib/garray.h>
  27 #include <glib/gstrfuncs.h>
  28 #include <glib/gatomic.h>
  29 #include <glib/gslice.h>
  30 #include <glib/gtestutils.h>
  31 #include <glib/gmem.h>
  32 #include <glib/gmessages.h>
  33
  34 #include <string.h>
  35
  36 /**
  37  * GBytes:
  38  *
  39  * A simple refcounted data type representing an immutable sequence of zero or
  40  * more bytes from an unspecified origin.
  41  *
  42  * The purpose of a #GBytes is to keep the memory region that it holds
  43  * alive for as long as anyone holds a reference to the bytes.  When
  44  * the last reference count is dropped, the memory is released. Multiple
  45  * unrelated callers can use byte data in the #GBytes without coordinating
  46  * their activities, resting assured that the byte data will not change or
  47  * move while they hold a reference.
  48  *
  49  * A #GBytes can come from many different origins that may have
  50  * different procedures for freeing the memory region.  Examples are
  51  * memory from g_malloc(), from memory slices, from a #GMappedFile or
  52  * memory from other allocators.
  53  *
  54  * #GBytes work well as keys in #GHashTable. Use g_bytes_equal() and
  55  * g_bytes_hash() as parameters to g_hash_table_new() or g_hash_table_new_full().
  56  * #GBytes can also be used as keys in a #GTree by passing the g_bytes_compare()
  57  * function to g_tree_new().
  58  *
  59  * The data pointed to by this bytes must not be modified. For a mutable
  60  * array of bytes see #GByteArray. Use g_bytes_unref_to_array() to create a
  61  * mutable array for a #GBytes sequence. To create an immutable #GBytes from
  62  * a mutable #GByteArray, use the g_byte_array_free_to_bytes() function.
  63  *
  64  * Since: 2.32
  65  **/
  66
  67 struct _GBytes
  68 {
  69   gconstpointer data;  /* may be NULL iff (size == 0) */
  70   gsize size;  /* may be 0 */
  71   gint ref_count;
  72   GDestroyNotify free_func;
  73   gpointer user_data;
  74 };
  75
  76 /**
  77  * g_bytes_new:
  78  * @data: (transfer none) (array length=size) (element-type guint8) (nullable):
  79  *        the data to be used for the bytes
  80  * @size: the size of @data
  81  *
  82  * Creates a new #GBytes from @data.
  83  *
  84  * @data is copied. If @size is 0, @data may be %NULL.
  85  *
  86  * Returns: (transfer full): a new #GBytes
  87  *
  88  * Since: 2.32
  89  */
  90 GBytes *
  91 g_bytes_new (gconstpointer data,
  92              gsize         size)
  93 {
  94   g_return_val_if_fail (data != NULL || size == 0, NULL);
  95
  96   return g_bytes_new_take (g_memdup (data, size), size);
  97 }
  98
  99 /**
 100  * g_bytes_new_take:
 101  * @data: (transfer full) (array length=size) (element-type guint8) (nullable):
 102           the data to be used for the bytes
 103  * @size: the size of @data
 104  *
 105  * Creates a new #GBytes from @data.
 106  *
 107  * After this call, @data belongs to the bytes and may no longer be
 108  * modified by the caller.  g_free() will be called on @data when the
 109  * bytes is no longer in use. Because of this @data must have been created by
 110  * a call to g_malloc(), g_malloc0() or g_realloc() or by one of the many
 111  * functions that wrap these calls (such as g_new(), g_strdup(), etc).
 112  *
 113  * For creating #GBytes with memory from other allocators, see
 114  * g_bytes_new_with_free_func().
 115  *
 116  * @data may be %NULL if @size is 0.
 117  *
 118  * Returns: (transfer full): a new #GBytes
 119  *
 120  * Since: 2.32
 121  */
 122 GBytes *
 123 g_bytes_new_take (gpointer data,
 124                   gsize    size)
 125 {
 126   return g_bytes_new_with_free_func (data, size, g_free, data);
 127 }
 128
 129
 130 /**
 131  * g_bytes_new_static: (skip)
 132  * @data: (transfer full) (array length=size) (element-type guint8) (nullable):
 133           the data to be used for the bytes
 134  * @size: the size of @data
 135  *
 136  * Creates a new #GBytes from static data.
 137  *
 138  * @data must be static (ie: never modified or freed). It may be %NULL if @size
 139  * is 0.
 140  *
 141  * Returns: (transfer full): a new #GBytes
 142  *
 143  * Since: 2.32
 144  */
 145 GBytes *
 146 g_bytes_new_static (gconstpointer data,
 147                     gsize         size)
 148 {
 149   return g_bytes_new_with_free_func (data, size, NULL, NULL);
 150 }
 151
 152 /**
 153  * g_bytes_new_with_free_func: (skip)
 154  * @data: (array length=size) (element-type guint8) (nullable):
 155           the data to be used for the bytes
 156  * @size: the size of @data
 157  * @free_func: the function to call to release the data
 158  * @user_data: data to pass to @free_func
 159  *
 160  * Creates a #GBytes from @data.
 161  *
 162  * When the last reference is dropped, @free_func will be called with the
 163  * @user_data argument.
 164  *
 165  * @data must not be modified after this call is made until @free_func has
 166  * been called to indicate that the bytes is no longer in use.
 167  *
 168  * @data may be %NULL if @size is 0.
 169  *
 170  * Returns: (transfer full): a new #GBytes
 171  *
 172  * Since: 2.32
 173  */
 174 GBytes *
 175 g_bytes_new_with_free_func (gconstpointer  data,
 176                             gsize          size,
 177                             GDestroyNotify free_func,
 178                             gpointer       user_data)
 179 {
 180   GBytes *bytes;
 181
 182   g_return_val_if_fail (data != NULL || size == 0, NULL);
 183
 184   bytes = g_slice_new (GBytes);
 185   bytes->data = data;
 186   bytes->size = size;
 187   bytes->free_func = free_func;
 188   bytes->user_data = user_data;
 189   bytes->ref_count = 1;
 190
 191   return (GBytes *)bytes;
 192 }
 193
 194 /**
 195  * g_bytes_new_from_bytes:
 196  * @bytes: a #GBytes
 197  * @offset: offset which subsection starts at
 198  * @length: length of subsection
 199  *
 200  * Creates a #GBytes which is a subsection of another #GBytes. The @offset +
 201  * @length may not be longer than the size of @bytes.
 202  *
 203  * A reference to @bytes will be held by the newly created #GBytes until
 204  * the byte data is no longer needed.
 205  *
 206  * Returns: (transfer full): a new #GBytes
 207  *
 208  * Since: 2.32
 209  */
 210 GBytes *
 211 g_bytes_new_from_bytes (GBytes  *bytes,
 212                         gsize    offset,
 213                         gsize    length)
 214 {
 215   /* Note that length may be 0. */
 216   g_return_val_if_fail (bytes != NULL, NULL);
 217   g_return_val_if_fail (offset <= bytes->size, NULL);
 218   g_return_val_if_fail (offset + length <= bytes->size, NULL);
 219
 220   return g_bytes_new_with_free_func ((gchar *)bytes->data + offset, length,
 221                                      (GDestroyNotify)g_bytes_unref, g_bytes_ref (bytes));
 222 }
 223
 224 /**
 225  * g_bytes_get_data:
 226  * @bytes: a #GBytes
 227  * @size: (out) (optional): location to return size of byte data
 228  *
 229  * Get the byte data in the #GBytes. This data should not be modified.
 230  *
 231  * This function will always return the same pointer for a given #GBytes.
 232  *
 233  * %NULL may be returned if @size is 0. This is not guaranteed, as the #GBytes
 234  * may represent an empty string with @data non-%NULL and @size as 0. %NULL will
 235  * not be returned if @size is non-zero.
 236  *
 237  * Returns: (transfer none) (array length=size) (element-type guint8) (nullable):
 238  *          a pointer to the byte data, or %NULL
 239  *
 240  * Since: 2.32
 241  */
 242 gconstpointer
 243 g_bytes_get_data (GBytes *bytes,
 244                   gsize *size)
 245 {
 246   g_return_val_if_fail (bytes != NULL, NULL);
 247   if (size)
 248     *size = bytes->size;
 249   return bytes->data;
 250 }
 251
 252 /**
 253  * g_bytes_get_size:
 254  * @bytes: a #GBytes
 255  *
 256  * Get the size of the byte data in the #GBytes.
 257  *
 258  * This function will always return the same value for a given #GBytes.
 259  *
 260  * Returns: the size
 261  *
 262  * Since: 2.32
 263  */
 264 gsize
 265 g_bytes_get_size (GBytes *bytes)
 266 {
 267   g_return_val_if_fail (bytes != NULL, 0);
 268   return bytes->size;
 269 }
 270
 271
 272 /**
 273  * g_bytes_ref:
 274  * @bytes: a #GBytes
 275  *
 276  * Increase the reference count on @bytes.
 277  *
 278  * Returns: the #GBytes
 279  *
 280  * Since: 2.32
 281  */
 282 GBytes *
 283 g_bytes_ref (GBytes *bytes)
 284 {
 285   g_return_val_if_fail (bytes != NULL, NULL);
 286
 287   g_atomic_int_inc (&bytes->ref_count);
 288
 289   return bytes;
 290 }
 291
 292 /**
 293  * g_bytes_unref:
 294  * @bytes: (nullable): a #GBytes
 295  *
 296  * Releases a reference on @bytes.  This may result in the bytes being
 297  * freed.
 298  *
 299  * Since: 2.32
 300  */
 301 void
 302 g_bytes_unref (GBytes *bytes)
 303 {
 304   if (bytes == NULL)
 305     return;
 306
 307   if (g_atomic_int_dec_and_test (&bytes->ref_count))
 308     {
 309       if (bytes->free_func != NULL)
 310         bytes->free_func (bytes->user_data);
 311       g_slice_free (GBytes, bytes);
 312     }
 313 }
 314
 315 /**
 316  * g_bytes_equal:
 317  * @bytes1: (type GLib.Bytes): a pointer to a #GBytes
 318  * @bytes2: (type GLib.Bytes): a pointer to a #GBytes to compare with @bytes1
 319  *
 320  * Compares the two #GBytes values being pointed to and returns
 321  * %TRUE if they are equal.
 322  *
 323  * This function can be passed to g_hash_table_new() as the @key_equal_func
 324  * parameter, when using non-%NULL #GBytes pointers as keys in a #GHashTable.
 325  *
 326  * Returns: %TRUE if the two keys match.
 327  *
 328  * Since: 2.32
 329  */
 330 gboolean
 331 g_bytes_equal (gconstpointer bytes1,
 332                gconstpointer bytes2)
 333 {
 334   const GBytes *b1 = bytes1;
 335   const GBytes *b2 = bytes2;
 336
 337   g_return_val_if_fail (bytes1 != NULL, FALSE);
 338   g_return_val_if_fail (bytes2 != NULL, FALSE);
 339
 340   return b1->size == b2->size &&
 341          memcmp (b1->data, b2->data, b1->size) == 0;
 342 }
 343
 344 /**
 345  * g_bytes_hash:
 346  * @bytes: (type GLib.Bytes): a pointer to a #GBytes key
 347  *
 348  * Creates an integer hash code for the byte data in the #GBytes.
 349  *
 350  * This function can be passed to g_hash_table_new() as the @key_hash_func
 351  * parameter, when using non-%NULL #GBytes pointers as keys in a #GHashTable.
 352  *
 353  * Returns: a hash value corresponding to the key.
 354  *
 355  * Since: 2.32
 356  */
 357 guint
 358 g_bytes_hash (gconstpointer bytes)
 359 {
 360   const GBytes *a = bytes;
 361   const signed char *p, *e;
 362   guint32 h = 5381;
 363
 364   g_return_val_if_fail (bytes != NULL, 0);
 365
 366   for (p = (signed char *)a->data, e = (signed char *)a->data + a->size; p != e; p++)
 367     h = (h << 5) + h + *p;
 368
 369   return h;
 370 }
 371
 372 /**
 373  * g_bytes_compare:
 374  * @bytes1: (type GLib.Bytes): a pointer to a #GBytes
 375  * @bytes2: (type GLib.Bytes): a pointer to a #GBytes to compare with @bytes1
 376  *
 377  * Compares the two #GBytes values.
 378  *
 379  * This function can be used to sort GBytes instances in lexographical order.
 380  *
 381  * Returns: a negative value if bytes2 is lesser, a positive value if bytes2 is
 382  *          greater, and zero if bytes2 is equal to bytes1
 383  *
 384  * Since: 2.32
 385  */
 386 gint
 387 g_bytes_compare (gconstpointer bytes1,
 388                  gconstpointer bytes2)
 389 {
 390   const GBytes *b1 = bytes1;
 391   const GBytes *b2 = bytes2;
 392   gint ret;
 393
 394   g_return_val_if_fail (bytes1 != NULL, 0);
 395   g_return_val_if_fail (bytes2 != NULL, 0);
 396
 397   ret = memcmp (b1->data, b2->data, MIN (b1->size, b2->size));
 398   if (ret == 0 && b1->size != b2->size)
 399       ret = b1->size < b2->size ? -1 : 1;
 400   return ret;
 401 }
 402
 403 static gpointer
 404 try_steal_and_unref (GBytes         *bytes,
 405                      GDestroyNotify  free_func,
 406                      gsize          *size)
 407 {
 408   gpointer result;
 409
 410   if (bytes->free_func != free_func || bytes->data == NULL)
 411     return NULL;
 412
 413   /* Are we the only reference? */
 414   if (g_atomic_int_get (&bytes->ref_count) == 1)
 415     {
 416       *size = bytes->size;
 417       result = (gpointer)bytes->data;
 418       g_slice_free (GBytes, bytes);
 419       return result;
 420     }
 421
 422   return NULL;
 423 }
 424
 425
 426 /**
 427  * g_bytes_unref_to_data:
 428  * @bytes: (transfer full): a #GBytes
 429  * @size: (out): location to place the length of the returned data
 430  *
 431  * Unreferences the bytes, and returns a pointer the same byte data
 432  * contents.
 433  *
 434  * As an optimization, the byte data is returned without copying if this was
 435  * the last reference to bytes and bytes was created with g_bytes_new(),
 436  * g_bytes_new_take() or g_byte_array_free_to_bytes(). In all other cases the
 437  * data is copied.
 438  *
 439  * Returns: (transfer full) (array length=size) (element-type guint8)
 440  *          (not nullable): a pointer to the same byte data, which should be
 441  *          freed with g_free()
 442  *
 443  * Since: 2.32
 444  */
 445 gpointer
 446 g_bytes_unref_to_data (GBytes *bytes,
 447                        gsize  *size)
 448 {
 449   gpointer result;
 450
 451   g_return_val_if_fail (bytes != NULL, NULL);
 452   g_return_val_if_fail (size != NULL, NULL);
 453
 454   /*
 455    * Optimal path: if this is was the last reference, then we can return
 456    * the data from this GBytes without copying.
 457    */
 458
 459   result = try_steal_and_unref (bytes, g_free, size);
 460   if (result == NULL)
 461     {
 462       /*
 463        * Copy: Non g_malloc (or compatible) allocator, or static memory,
 464        * so we have to copy, and then unref.
 465        */
 466       result = g_memdup (bytes->data, bytes->size);
 467       *size = bytes->size;
 468       g_bytes_unref (bytes);
 469     }
 470
 471   return result;
 472 }
 473
 474 /**
 475  * g_bytes_unref_to_array:
 476  * @bytes: (transfer full): a #GBytes
 477  *
 478  * Unreferences the bytes, and returns a new mutable #GByteArray containing
 479  * the same byte data.
 480  *
 481  * As an optimization, the byte data is transferred to the array without copying
 482  * if this was the last reference to bytes and bytes was created with
 483  * g_bytes_new(), g_bytes_new_take() or g_byte_array_free_to_bytes(). In all
 484  * other cases the data is copied.
 485  *
 486  * Returns: (transfer full): a new mutable #GByteArray containing the same byte data
 487  *
 488  * Since: 2.32
 489  */
 490 GByteArray *
 491 g_bytes_unref_to_array (GBytes *bytes)
 492 {
 493   gpointer data;
 494   gsize size;
 495
 496   g_return_val_if_fail (bytes != NULL, NULL);
 497
 498   data = g_bytes_unref_to_data (bytes, &size);
 499   return g_byte_array_new_take (data, size);
 500 }