src/util/blob.h

   1 /*
   2  * Copyright © 2014 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #ifndef BLOB_H
  25 #define BLOB_H
  26
  27 #include <stdbool.h>
  28 #include <stddef.h>
  29 #include <stdint.h>
  30 #include <stdlib.h>
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 /* The blob functions implement a simple, low-level API for serializing and
  37  * deserializing.
  38  *
  39  * All objects written to a blob will be serialized directly, (without any
  40  * additional meta-data to describe the data written). Therefore, it is the
  41  * caller's responsibility to ensure that any data can be read later, (either
  42  * by knowing exactly what data is expected, or by writing to the blob
  43  * sufficient meta-data to describe what has been written).
  44  *
  45  * A blob is efficient in that it dynamically grows by doubling in size, so
  46  * allocation costs are logarithmic.
  47  */
  48
  49 struct blob {
  50    /* The data actually written to the blob. */
  51    uint8_t *data;
  52
  53    /** Number of bytes that have been allocated for \c data. */
  54    size_t allocated;
  55
  56    /** The number of bytes that have actual data written to them. */
  57    size_t size;
  58
  59    /** True if \c data a fixed allocation that we cannot resize
  60     *
  61     * \see blob_init_fixed
  62     */
  63    bool fixed_allocation;
  64
  65    /**
  66     * True if we've ever failed to realloc or if we go pas the end of a fixed
  67     * allocation blob.
  68     */
  69    bool out_of_memory;
  70 };
  71
  72 /* When done reading, the caller can ensure that everything was consumed by
  73  * checking the following:
  74  *
  75  *   1. blob->current should be equal to blob->end, (if not, too little was
  76  *      read).
  77  *
  78  *   2. blob->overrun should be false, (otherwise, too much was read).
  79  */
  80 struct blob_reader {
  81    const uint8_t *data;
  82    const uint8_t *end;
  83    const uint8_t *current;
  84    bool overrun;
  85 };
  86
  87 /**
  88  * Init a new, empty blob.
  89  */
  90 void
  91 blob_init(struct blob *blob);
  92
  93 /**
  94  * Init a new, fixed-size blob.
  95  *
  96  * A fixed-size blob has a fixed block of data that will not be freed on
  97  * blob_finish and will never be grown.  If we hit the end, we simply start
  98  * returning false from the write functions.
  99  *
 100  * If a fixed-size blob has a NULL data pointer then the data is written but
 101  * it otherwise operates normally.  This can be used to determine the size
 102  * that will be required to write a given data structure.
 103  */
 104 void
 105 blob_init_fixed(struct blob *blob, void *data, size_t size);
 106
 107 /**
 108  * Finish a blob and free its memory.
 109  *
 110  * If \blob was initialized with blob_init_fixed, the data pointer is
 111  * considered to be owned by the user and will not be freed.
 112  */
 113 static inline void
 114 blob_finish(struct blob *blob)
 115 {
 116    if (!blob->fixed_allocation)
 117       free(blob->data);
 118 }
 119
 120 void
 121 blob_finish_get_buffer(struct blob *blob, void **buffer, size_t *size);
 122
 123 /**
 124  * Add some unstructured, fixed-size data to a blob.
 125  *
 126  * \return True unless allocation failed.
 127  */
 128 bool
 129 blob_write_bytes(struct blob *blob, const void *bytes, size_t to_write);
 130
 131 /**
 132  * Reserve space in \blob for a number of bytes.
 133  *
 134  * Space will be allocated within the blob for these byes, but the bytes will
 135  * be left uninitialized. The caller is expected to use \sa
 136  * blob_overwrite_bytes to write to these bytes.
 137  *
 138  * \return An offset to space allocated within \blob to which \to_write bytes
 139  * can be written, (or -1 in case of any allocation error).
 140  */
 141 intptr_t
 142 blob_reserve_bytes(struct blob *blob, size_t to_write);
 143
 144 /**
 145  * Similar to \sa blob_reserve_bytes, but only reserves an uint32_t worth of
 146  * space. Note that this must be used if later reading with \sa
 147  * blob_read_uint32, since it aligns the offset correctly.
 148  */
 149 intptr_t
 150 blob_reserve_uint32(struct blob *blob);
 151
 152 /**
 153  * Similar to \sa blob_reserve_bytes, but only reserves an intptr_t worth of
 154  * space. Note that this must be used if later reading with \sa
 155  * blob_read_intptr, since it aligns the offset correctly.
 156  */
 157 intptr_t
 158 blob_reserve_intptr(struct blob *blob);
 159
 160 /**
 161  * Overwrite some data previously written to the blob.
 162  *
 163  * Writes data to an existing portion of the blob at an offset of \offset.
 164  * This data range must have previously been written to the blob by one of the
 165  * blob_write_* calls.
 166  *
 167  * For example usage, see blob_overwrite_uint32
 168  *
 169  * \return True unless the requested offset or offset+to_write lie outside
 170  * the current blob's size.
 171  */
 172 bool
 173 blob_overwrite_bytes(struct blob *blob,
 174                      size_t offset,
 175                      const void *bytes,
 176                      size_t to_write);
 177
 178 /**
 179  * Add a uint32_t to a blob.
 180  *
 181  * \note This function will only write to a uint32_t-aligned offset from the
 182  * beginning of the blob's data, so some padding bytes may be added to the
 183  * blob if this write follows some unaligned write (such as
 184  * blob_write_string).
 185  *
 186  * \return True unless allocation failed.
 187  */
 188 bool
 189 blob_write_uint32(struct blob *blob, uint32_t value);
 190
 191 /**
 192  * Overwrite a uint32_t previously written to the blob.
 193  *
 194  * Writes a uint32_t value to an existing portion of the blob at an offset of
 195  * \offset.  This data range must have previously been written to the blob by
 196  * one of the blob_write_* calls.
 197  *
 198  *
 199  * The expected usage is something like the following pattern:
 200  *
 201  *      size_t offset;
 202  *
 203  *      offset = blob_reserve_uint32(blob);
 204  *      ... various blob write calls, writing N items ...
 205  *      blob_overwrite_uint32 (blob, offset, N);
 206  *
 207  * \return True unless the requested position or position+to_write lie outside
 208  * the current blob's size.
 209  */
 210 bool
 211 blob_overwrite_uint32(struct blob *blob,
 212                       size_t offset,
 213                       uint32_t value);
 214
 215 /**
 216  * Add a uint64_t to a blob.
 217  *
 218  * \note This function will only write to a uint64_t-aligned offset from the
 219  * beginning of the blob's data, so some padding bytes may be added to the
 220  * blob if this write follows some unaligned write (such as
 221  * blob_write_string).
 222  *
 223  * \return True unless allocation failed.
 224  */
 225 bool
 226 blob_write_uint64(struct blob *blob, uint64_t value);
 227
 228 /**
 229  * Add an intptr_t to a blob.
 230  *
 231  * \note This function will only write to an intptr_t-aligned offset from the
 232  * beginning of the blob's data, so some padding bytes may be added to the
 233  * blob if this write follows some unaligned write (such as
 234  * blob_write_string).
 235  *
 236  * \return True unless allocation failed.
 237  */
 238 bool
 239 blob_write_intptr(struct blob *blob, intptr_t value);
 240
 241 /**
 242  * Overwrite an intptr_t previously written to the blob.
 243  *
 244  * Writes a intptr_t value to an existing portion of the blob at an offset of
 245  * \offset.  This data range must have previously been written to the blob by
 246  * one of the blob_write_* calls.
 247  *
 248  * For example usage, see blob_overwrite_uint32
 249  *
 250  * \return True unless the requested position or position+to_write lie outside
 251  * the current blob's size.
 252  */
 253 bool
 254 blob_overwrite_intptr(struct blob *blob,
 255                       size_t offset,
 256                       intptr_t value);
 257
 258 /**
 259  * Add a NULL-terminated string to a blob, (including the NULL terminator).
 260  *
 261  * \return True unless allocation failed.
 262  */
 263 bool
 264 blob_write_string(struct blob *blob, const char *str);
 265
 266 /**
 267  * Start reading a blob, (initializing the contents of \blob for reading).
 268  *
 269  * After this call, the caller can use the various blob_read_* functions to
 270  * read elements from the data array.
 271  *
 272  * For all of the blob_read_* functions, if there is insufficient data
 273  * remaining, the functions will do nothing, (perhaps returning default values
 274  * such as 0). The caller can detect this by noting that the blob_reader's
 275  * current value is unchanged before and after the call.
 276  */
 277 void
 278 blob_reader_init(struct blob_reader *blob, const void *data, size_t size);
 279
 280 /**
 281  * Read some unstructured, fixed-size data from the current location, (and
 282  * update the current location to just past this data).
 283  *
 284  * \note The memory returned belongs to the data underlying the blob reader. The
 285  * caller must copy the data in order to use it after the lifetime of the data
 286  * underlying the blob reader.
 287  *
 288  * \return The bytes read (see note above about memory lifetime).
 289  */
 290 const void *
 291 blob_read_bytes(struct blob_reader *blob, size_t size);
 292
 293 /**
 294  * Read some unstructured, fixed-size data from the current location, copying
 295  * it to \dest (and update the current location to just past this data)
 296  */
 297 void
 298 blob_copy_bytes(struct blob_reader *blob, void *dest, size_t size);
 299
 300 /**
 301  * Skip \size bytes within the blob.
 302  */
 303 void
 304 blob_skip_bytes(struct blob_reader *blob, size_t size);
 305
 306 /**
 307  * Read a uint32_t from the current location, (and update the current location
 308  * to just past this uint32_t).
 309  *
 310  * \note This function will only read from a uint32_t-aligned offset from the
 311  * beginning of the blob's data, so some padding bytes may be skipped.
 312  *
 313  * \return The uint32_t read
 314  */
 315 uint32_t
 316 blob_read_uint32(struct blob_reader *blob);
 317
 318 /**
 319  * Read a uint64_t from the current location, (and update the current location
 320  * to just past this uint64_t).
 321  *
 322  * \note This function will only read from a uint64_t-aligned offset from the
 323  * beginning of the blob's data, so some padding bytes may be skipped.
 324  *
 325  * \return The uint64_t read
 326  */
 327 uint64_t
 328 blob_read_uint64(struct blob_reader *blob);
 329
 330 /**
 331  * Read an intptr_t value from the current location, (and update the
 332  * current location to just past this intptr_t).
 333  *
 334  * \note This function will only read from an intptr_t-aligned offset from the
 335  * beginning of the blob's data, so some padding bytes may be skipped.
 336  *
 337  * \return The intptr_t read
 338  */
 339 intptr_t
 340 blob_read_intptr(struct blob_reader *blob);
 341
 342 /**
 343  * Read a NULL-terminated string from the current location, (and update the
 344  * current location to just past this string).
 345  *
 346  * \note The memory returned belongs to the data underlying the blob reader. The
 347  * caller must copy the string in order to use the string after the lifetime
 348  * of the data underlying the blob reader.
 349  *
 350  * \return The string read (see note above about memory lifetime). However, if
 351  * there is no NULL byte remaining within the blob, this function returns
 352  * NULL.
 353  */
 354 char *
 355 blob_read_string(struct blob_reader *blob);
 356
 357 #ifdef __cplusplus
 358 }
 359 #endif
 360
 361 #endif /* BLOB_H */