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    /**
  60     * True if we've ever failed to realloc or if we go pas the end of a fixed
  61     * allocation blob.
  62     */
  63    bool out_of_memory;
  64 };
  65
  66 /* When done reading, the caller can ensure that everything was consumed by
  67  * checking the following:
  68  *
  69  *   1. blob->current should be equal to blob->end, (if not, too little was
  70  *      read).
  71  *
  72  *   2. blob->overrun should be false, (otherwise, too much was read).
  73  */
  74 struct blob_reader {
  75    uint8_t *data;
  76    uint8_t *end;
  77    uint8_t *current;
  78    bool overrun;
  79 };
  80
  81 /**
  82  * Create a new, empty blob.
  83  *
  84  * \return The new blob, (or NULL in case of allocation failure).
  85  */
  86 struct blob *
  87 blob_create(void);
  88
  89 /**
  90  * Destroy a blob and free its memory.
  91  */
  92 static inline void
  93 blob_destroy(struct blob *blob)
  94 {
  95    free(blob->data);
  96    free(blob);
  97 }
  98
  99 /**
 100  * Add some unstructured, fixed-size data to a blob.
 101  *
 102  * \return True unless allocation failed.
 103  */
 104 bool
 105 blob_write_bytes(struct blob *blob, const void *bytes, size_t to_write);
 106
 107 /**
 108  * Reserve space in \blob for a number of bytes.
 109  *
 110  * Space will be allocated within the blob for these byes, but the bytes will
 111  * be left uninitialized. The caller is expected to use the return value to
 112  * write directly (and immediately) to these bytes.
 113  *
 114  * \note The return value is valid immediately upon return, but can be
 115  * invalidated by any other call to a blob function. So the caller should call
 116  * blob_reserve_byes immediately before writing through the returned pointer.
 117  *
 118  * This function is intended to be used when interfacing with an existing API
 119  * that is not aware of the blob API, (so that blob_write_bytes cannot be
 120  * called).
 121  *
 122  * \return A pointer to space allocated within \blob to which \to_write bytes
 123  * can be written, (or NULL in case of any allocation error).
 124  */
 125 uint8_t *
 126 blob_reserve_bytes(struct blob *blob, size_t to_write);
 127
 128 /**
 129  * Overwrite some data previously written to the blob.
 130  *
 131  * Writes data to an existing portion of the blob at an offset of \offset.
 132  * This data range must have previously been written to the blob by one of the
 133  * blob_write_* calls.
 134  *
 135  * For example usage, see blob_overwrite_uint32
 136  *
 137  * \return True unless the requested offset or offset+to_write lie outside
 138  * the current blob's size.
 139  */
 140 bool
 141 blob_overwrite_bytes(struct blob *blob,
 142                      size_t offset,
 143                      const void *bytes,
 144                      size_t to_write);
 145
 146 /**
 147  * Add a uint32_t to a blob.
 148  *
 149  * \note This function will only write to a uint32_t-aligned offset from the
 150  * beginning of the blob's data, so some padding bytes may be added to the
 151  * blob if this write follows some unaligned write (such as
 152  * blob_write_string).
 153  *
 154  * \return True unless allocation failed.
 155  */
 156 bool
 157 blob_write_uint32(struct blob *blob, uint32_t value);
 158
 159 /**
 160  * Overwrite a uint32_t previously written to the blob.
 161  *
 162  * Writes a uint32_t value to an existing portion of the blob at an offset of
 163  * \offset.  This data range must have previously been written to the blob by
 164  * one of the blob_write_* calls.
 165  *
 166  *
 167  * The expected usage is something like the following pattern:
 168  *
 169  *      size_t offset;
 170  *
 171  *      offset = blob->size;
 172  *      blob_write_uint32 (blob, 0); // placeholder
 173  *      ... various blob write calls, writing N items ...
 174  *      blob_overwrite_uint32 (blob, offset, N);
 175  *
 176  * \return True unless the requested position or position+to_write lie outside
 177  * the current blob's size.
 178  */
 179 bool
 180 blob_overwrite_uint32(struct blob *blob,
 181                       size_t offset,
 182                       uint32_t value);
 183
 184 /**
 185  * Add a uint64_t to a blob.
 186  *
 187  * \note This function will only write to a uint64_t-aligned offset from the
 188  * beginning of the blob's data, so some padding bytes may be added to the
 189  * blob if this write follows some unaligned write (such as
 190  * blob_write_string).
 191  *
 192  * \return True unless allocation failed.
 193  */
 194 bool
 195 blob_write_uint64(struct blob *blob, uint64_t value);
 196
 197 /**
 198  * Add an intptr_t to a blob.
 199  *
 200  * \note This function will only write to an intptr_t-aligned offset from the
 201  * beginning of the blob's data, so some padding bytes may be added to the
 202  * blob if this write follows some unaligned write (such as
 203  * blob_write_string).
 204  *
 205  * \return True unless allocation failed.
 206  */
 207 bool
 208 blob_write_intptr(struct blob *blob, intptr_t value);
 209
 210 /**
 211  * Add a NULL-terminated string to a blob, (including the NULL terminator).
 212  *
 213  * \return True unless allocation failed.
 214  */
 215 bool
 216 blob_write_string(struct blob *blob, const char *str);
 217
 218 /**
 219  * Start reading a blob, (initializing the contents of \blob for reading).
 220  *
 221  * After this call, the caller can use the various blob_read_* functions to
 222  * read elements from the data array.
 223  *
 224  * For all of the blob_read_* functions, if there is insufficient data
 225  * remaining, the functions will do nothing, (perhaps returning default values
 226  * such as 0). The caller can detect this by noting that the blob_reader's
 227  * current value is unchanged before and after the call.
 228  */
 229 void
 230 blob_reader_init(struct blob_reader *blob, uint8_t *data, size_t size);
 231
 232 /**
 233  * Read some unstructured, fixed-size data from the current location, (and
 234  * update the current location to just past this data).
 235  *
 236  * \note The memory returned belongs to the data underlying the blob reader. The
 237  * caller must copy the data in order to use it after the lifetime of the data
 238  * underlying the blob reader.
 239  *
 240  * \return The bytes read (see note above about memory lifetime).
 241  */
 242 void *
 243 blob_read_bytes(struct blob_reader *blob, size_t size);
 244
 245 /**
 246  * Read some unstructured, fixed-size data from the current location, copying
 247  * it to \dest (and update the current location to just past this data)
 248  */
 249 void
 250 blob_copy_bytes(struct blob_reader *blob, uint8_t *dest, size_t size);
 251
 252 /**
 253  * Read a uint32_t from the current location, (and update the current location
 254  * to just past this uint32_t).
 255  *
 256  * \note This function will only read from a uint32_t-aligned offset from the
 257  * beginning of the blob's data, so some padding bytes may be skipped.
 258  *
 259  * \return The uint32_t read
 260  */
 261 uint32_t
 262 blob_read_uint32(struct blob_reader *blob);
 263
 264 /**
 265  * Read a uint64_t from the current location, (and update the current location
 266  * to just past this uint64_t).
 267  *
 268  * \note This function will only read from a uint64_t-aligned offset from the
 269  * beginning of the blob's data, so some padding bytes may be skipped.
 270  *
 271  * \return The uint64_t read
 272  */
 273 uint64_t
 274 blob_read_uint64(struct blob_reader *blob);
 275
 276 /**
 277  * Read an intptr_t value from the current location, (and update the
 278  * current location to just past this intptr_t).
 279  *
 280  * \note This function will only read from an intptr_t-aligned offset from the
 281  * beginning of the blob's data, so some padding bytes may be skipped.
 282  *
 283  * \return The intptr_t read
 284  */
 285 intptr_t
 286 blob_read_intptr(struct blob_reader *blob);
 287
 288 /**
 289  * Read a NULL-terminated string from the current location, (and update the
 290  * current location to just past this string).
 291  *
 292  * \note The memory returned belongs to the data underlying the blob reader. The
 293  * caller must copy the string in order to use the string after the lifetime
 294  * of the data underlying the blob reader.
 295  *
 296  * \return The string read (see note above about memory lifetime). However, if
 297  * there is no NULL byte remaining within the blob, this function returns
 298  * NULL.
 299  */
 300 char *
 301 blob_read_string(struct blob_reader *blob);
 302
 303 #ifdef __cplusplus
 304 }
 305 #endif
 306
 307 #endif /* BLOB_H */