src/compiler/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    uint8_t *data;
  82    uint8_t *end;
  83    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 void
 101 blob_init_fixed(struct blob *blob, void *data, size_t size);
 102
 103 /**
 104  * Finish a blob and free its memory.
 105  *
 106  * If \blob was initialized with blob_init_fixed, the data pointer is
 107  * considered to be owned by the user and will not be freed.
 108  */
 109 static inline void
 110 blob_finish(struct blob *blob)
 111 {
 112    if (!blob->fixed_allocation)
 113       free(blob->data);
 114 }
 115
 116 /**
 117  * Add some unstructured, fixed-size data to a blob.
 118  *
 119  * \return True unless allocation failed.
 120  */
 121 bool
 122 blob_write_bytes(struct blob *blob, const void *bytes, size_t to_write);
 123
 124 /**
 125  * Reserve space in \blob for a number of bytes.
 126  *
 127  * Space will be allocated within the blob for these byes, but the bytes will
 128  * be left uninitialized. The caller is expected to use the return value to
 129  * write directly (and immediately) to these bytes.
 130  *
 131  * \note The return value is valid immediately upon return, but can be
 132  * invalidated by any other call to a blob function. So the caller should call
 133  * blob_reserve_byes immediately before writing through the returned pointer.
 134  *
 135  * This function is intended to be used when interfacing with an existing API
 136  * that is not aware of the blob API, (so that blob_write_bytes cannot be
 137  * called).
 138  *
 139  * \return A pointer to space allocated within \blob to which \to_write bytes
 140  * can be written, (or NULL in case of any allocation error).
 141  */
 142 uint8_t *
 143 blob_reserve_bytes(struct blob *blob, size_t to_write);
 144
 145 /**
 146  * Overwrite some data previously written to the blob.
 147  *
 148  * Writes data to an existing portion of the blob at an offset of \offset.
 149  * This data range must have previously been written to the blob by one of the
 150  * blob_write_* calls.
 151  *
 152  * For example usage, see blob_overwrite_uint32
 153  *
 154  * \return True unless the requested offset or offset+to_write lie outside
 155  * the current blob's size.
 156  */
 157 bool
 158 blob_overwrite_bytes(struct blob *blob,
 159                      size_t offset,
 160                      const void *bytes,
 161                      size_t to_write);
 162
 163 /**
 164  * Add a uint32_t to a blob.
 165  *
 166  * \note This function will only write to a uint32_t-aligned offset from the
 167  * beginning of the blob's data, so some padding bytes may be added to the
 168  * blob if this write follows some unaligned write (such as
 169  * blob_write_string).
 170  *
 171  * \return True unless allocation failed.
 172  */
 173 bool
 174 blob_write_uint32(struct blob *blob, uint32_t value);
 175
 176 /**
 177  * Overwrite a uint32_t previously written to the blob.
 178  *
 179  * Writes a uint32_t value to an existing portion of the blob at an offset of
 180  * \offset.  This data range must have previously been written to the blob by
 181  * one of the blob_write_* calls.
 182  *
 183  *
 184  * The expected usage is something like the following pattern:
 185  *
 186  *      size_t offset;
 187  *
 188  *      offset = blob->size;
 189  *      blob_write_uint32 (blob, 0); // placeholder
 190  *      ... various blob write calls, writing N items ...
 191  *      blob_overwrite_uint32 (blob, offset, N);
 192  *
 193  * \return True unless the requested position or position+to_write lie outside
 194  * the current blob's size.
 195  */
 196 bool
 197 blob_overwrite_uint32(struct blob *blob,
 198                       size_t offset,
 199                       uint32_t value);
 200
 201 /**
 202  * Add a uint64_t to a blob.
 203  *
 204  * \note This function will only write to a uint64_t-aligned offset from the
 205  * beginning of the blob's data, so some padding bytes may be added to the
 206  * blob if this write follows some unaligned write (such as
 207  * blob_write_string).
 208  *
 209  * \return True unless allocation failed.
 210  */
 211 bool
 212 blob_write_uint64(struct blob *blob, uint64_t value);
 213
 214 /**
 215  * Add an intptr_t to a blob.
 216  *
 217  * \note This function will only write to an intptr_t-aligned offset from the
 218  * beginning of the blob's data, so some padding bytes may be added to the
 219  * blob if this write follows some unaligned write (such as
 220  * blob_write_string).
 221  *
 222  * \return True unless allocation failed.
 223  */
 224 bool
 225 blob_write_intptr(struct blob *blob, intptr_t value);
 226
 227 /**
 228  * Add a NULL-terminated string to a blob, (including the NULL terminator).
 229  *
 230  * \return True unless allocation failed.
 231  */
 232 bool
 233 blob_write_string(struct blob *blob, const char *str);
 234
 235 /**
 236  * Start reading a blob, (initializing the contents of \blob for reading).
 237  *
 238  * After this call, the caller can use the various blob_read_* functions to
 239  * read elements from the data array.
 240  *
 241  * For all of the blob_read_* functions, if there is insufficient data
 242  * remaining, the functions will do nothing, (perhaps returning default values
 243  * such as 0). The caller can detect this by noting that the blob_reader's
 244  * current value is unchanged before and after the call.
 245  */
 246 void
 247 blob_reader_init(struct blob_reader *blob, uint8_t *data, size_t size);
 248
 249 /**
 250  * Read some unstructured, fixed-size data from the current location, (and
 251  * update the current location to just past this data).
 252  *
 253  * \note The memory returned belongs to the data underlying the blob reader. The
 254  * caller must copy the data in order to use it after the lifetime of the data
 255  * underlying the blob reader.
 256  *
 257  * \return The bytes read (see note above about memory lifetime).
 258  */
 259 void *
 260 blob_read_bytes(struct blob_reader *blob, size_t size);
 261
 262 /**
 263  * Read some unstructured, fixed-size data from the current location, copying
 264  * it to \dest (and update the current location to just past this data)
 265  */
 266 void
 267 blob_copy_bytes(struct blob_reader *blob, uint8_t *dest, size_t size);
 268
 269 /**
 270  * Read a uint32_t from the current location, (and update the current location
 271  * to just past this uint32_t).
 272  *
 273  * \note This function will only read from a uint32_t-aligned offset from the
 274  * beginning of the blob's data, so some padding bytes may be skipped.
 275  *
 276  * \return The uint32_t read
 277  */
 278 uint32_t
 279 blob_read_uint32(struct blob_reader *blob);
 280
 281 /**
 282  * Read a uint64_t from the current location, (and update the current location
 283  * to just past this uint64_t).
 284  *
 285  * \note This function will only read from a uint64_t-aligned offset from the
 286  * beginning of the blob's data, so some padding bytes may be skipped.
 287  *
 288  * \return The uint64_t read
 289  */
 290 uint64_t
 291 blob_read_uint64(struct blob_reader *blob);
 292
 293 /**
 294  * Read an intptr_t value from the current location, (and update the
 295  * current location to just past this intptr_t).
 296  *
 297  * \note This function will only read from an intptr_t-aligned offset from the
 298  * beginning of the blob's data, so some padding bytes may be skipped.
 299  *
 300  * \return The intptr_t read
 301  */
 302 intptr_t
 303 blob_read_intptr(struct blob_reader *blob);
 304
 305 /**
 306  * Read a NULL-terminated string from the current location, (and update the
 307  * current location to just past this string).
 308  *
 309  * \note The memory returned belongs to the data underlying the blob reader. The
 310  * caller must copy the string in order to use the string after the lifetime
 311  * of the data underlying the blob reader.
 312  *
 313  * \return The string read (see note above about memory lifetime). However, if
 314  * there is no NULL byte remaining within the blob, this function returns
 315  * NULL.
 316  */
 317 char *
 318 blob_read_string(struct blob_reader *blob);
 319
 320 #ifdef __cplusplus
 321 }
 322 #endif
 323
 324 #endif /* BLOB_H */