lib/ofpbuf.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "ofpbuf.h"
  19 #include <assert.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include "dynamic-string.h"
  23 #include "util.h"
  24
  25 /* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
  26  * memory starting at 'base'.
  27  *
  28  * 'base' should ordinarily be the first byte of a region obtained from
  29  * malloc(), but in circumstances where it can be guaranteed that 'b' will
  30  * never need to be expanded or freed, it can be a pointer into arbitrary
  31  * memory. */
  32 void
  33 ofpbuf_use(struct ofpbuf *b, void *base, size_t allocated)
  34 {
  35     b->base = b->data = base;
  36     b->allocated = allocated;
  37     b->size = 0;
  38     b->l2 = b->l3 = b->l4 = b->l7 = NULL;
  39     b->next = NULL;
  40     b->private_p = NULL;
  41 }
  42
  43 /* Initializes 'b' as an empty ofpbuf with an initial capacity of 'size'
  44  * bytes. */
  45 void
  46 ofpbuf_init(struct ofpbuf *b, size_t size)
  47 {
  48     ofpbuf_use(b, size ? xmalloc(size) : NULL, size);
  49 }
  50
  51 /* Frees memory that 'b' points to. */
  52 void
  53 ofpbuf_uninit(struct ofpbuf *b)
  54 {
  55     if (b) {
  56         free(b->base);
  57     }
  58 }
  59
  60 /* Frees memory that 'b' points to and allocates a new ofpbuf */
  61 void
  62 ofpbuf_reinit(struct ofpbuf *b, size_t size)
  63 {
  64     ofpbuf_uninit(b);
  65     ofpbuf_init(b, size);
  66 }
  67
  68 /* Creates and returns a new ofpbuf with an initial capacity of 'size'
  69  * bytes. */
  70 struct ofpbuf *
  71 ofpbuf_new(size_t size)
  72 {
  73     struct ofpbuf *b = xmalloc(sizeof *b);
  74     ofpbuf_init(b, size);
  75     return b;
  76 }
  77
  78 struct ofpbuf *
  79 ofpbuf_clone(const struct ofpbuf *buffer)
  80 {
  81     return ofpbuf_clone_data(buffer->data, buffer->size);
  82 }
  83
  84 struct ofpbuf *
  85 ofpbuf_clone_data(const void *data, size_t size)
  86 {
  87     struct ofpbuf *b = ofpbuf_new(size);
  88     ofpbuf_put(b, data, size);
  89     return b;
  90 }
  91
  92 /* Frees memory that 'b' points to, as well as 'b' itself. */
  93 void
  94 ofpbuf_delete(struct ofpbuf *b)
  95 {
  96     if (b) {
  97         ofpbuf_uninit(b);
  98         free(b);
  99     }
 100 }
 101
 102 /* Returns the number of bytes of headroom in 'b', that is, the number of bytes
 103  * of unused space in ofpbuf 'b' before the data that is in use.  (Most
 104  * commonly, the data in a ofpbuf is at its beginning, and thus the ofpbuf's
 105  * headroom is 0.) */
 106 size_t
 107 ofpbuf_headroom(const struct ofpbuf *b)
 108 {
 109     return (char*)b->data - (char*)b->base;
 110 }
 111
 112 /* Returns the number of bytes that may be appended to the tail end of ofpbuf
 113  * 'b' before the ofpbuf must be reallocated. */
 114 size_t
 115 ofpbuf_tailroom(const struct ofpbuf *b)
 116 {
 117     return (char*)ofpbuf_end(b) - (char*)ofpbuf_tail(b);
 118 }
 119
 120 /* Changes 'b->base' to 'new_base' and adjusts all of 'b''s internal pointers
 121  * to reflect the change. */
 122 static void
 123 ofpbuf_rebase__(struct ofpbuf *b, void *new_base)
 124 {
 125     if (b->base != new_base) {
 126         uintptr_t base_delta = (char*)new_base - (char*)b->base;
 127         b->base = new_base;
 128         b->data = (char*)b->data + base_delta;
 129         if (b->l2) {
 130             b->l2 = (char*)b->l2 + base_delta;
 131         }
 132         if (b->l3) {
 133             b->l3 = (char*)b->l3 + base_delta;
 134         }
 135         if (b->l4) {
 136             b->l4 = (char*)b->l4 + base_delta;
 137         }
 138         if (b->l7) {
 139             b->l7 = (char*)b->l7 + base_delta;
 140         }
 141     }
 142 }
 143
 144 /* Reallocates 'b' so that it has exactly 'new_tailroom' bytes of tailroom. */
 145 static void
 146 ofpbuf_resize_tailroom__(struct ofpbuf *b, size_t new_tailroom)
 147 {
 148     b->allocated = ofpbuf_headroom(b) + b->size + new_tailroom;
 149     ofpbuf_rebase__(b, xrealloc(b->base, b->allocated));
 150 }
 151
 152 /* Ensures that 'b' has room for at least 'size' bytes at its tail end,
 153  * reallocating and copying its data if necessary.  Its headroom, if any, is
 154  * preserved. */
 155 void
 156 ofpbuf_prealloc_tailroom(struct ofpbuf *b, size_t size)
 157 {
 158     if (size > ofpbuf_tailroom(b)) {
 159         ofpbuf_resize_tailroom__(b, MAX(size, 64));
 160     }
 161 }
 162
 163 void
 164 ofpbuf_prealloc_headroom(struct ofpbuf *b, size_t size)
 165 {
 166     assert(size <= ofpbuf_headroom(b));
 167 }
 168
 169 /* Trims the size of 'b' to fit its actual content, reducing its tailroom to
 170  * 0.  Its headroom, if any, is preserved. */
 171 void
 172 ofpbuf_trim(struct ofpbuf *b)
 173 {
 174     if (ofpbuf_tailroom(b) > 0) {
 175         ofpbuf_resize_tailroom__(b, 0);
 176     }
 177 }
 178
 179 /* Appends 'size' bytes of data to the tail end of 'b', reallocating and
 180  * copying its data if necessary.  Returns a pointer to the first byte of the
 181  * new data, which is left uninitialized. */
 182 void *
 183 ofpbuf_put_uninit(struct ofpbuf *b, size_t size)
 184 {
 185     void *p;
 186     ofpbuf_prealloc_tailroom(b, size);
 187     p = ofpbuf_tail(b);
 188     b->size += size;
 189     return p;
 190 }
 191
 192 /* Appends 'size' zeroed bytes to the tail end of 'b'.  Data in 'b' is
 193  * reallocated and copied if necessary.  Returns a pointer to the first byte of
 194  * the data's location in the ofpbuf. */
 195 void *
 196 ofpbuf_put_zeros(struct ofpbuf *b, size_t size)
 197 {
 198     void *dst = ofpbuf_put_uninit(b, size);
 199     memset(dst, 0, size);
 200     return dst;
 201 }
 202
 203 /* Appends the 'size' bytes of data in 'p' to the tail end of 'b'.  Data in 'b'
 204  * is reallocated and copied if necessary.  Returns a pointer to the first
 205  * byte of the data's location in the ofpbuf. */
 206 void *
 207 ofpbuf_put(struct ofpbuf *b, const void *p, size_t size)
 208 {
 209     void *dst = ofpbuf_put_uninit(b, size);
 210     memcpy(dst, p, size);
 211     return dst;
 212 }
 213
 214 /* Reserves 'size' bytes of headroom so that they can be later allocated with
 215  * ofpbuf_push_uninit() without reallocating the ofpbuf. */
 216 void
 217 ofpbuf_reserve(struct ofpbuf *b, size_t size)
 218 {
 219     assert(!b->size);
 220     ofpbuf_prealloc_tailroom(b, size);
 221     b->data = (char*)b->data + size;
 222 }
 223
 224 void *
 225 ofpbuf_push_uninit(struct ofpbuf *b, size_t size)
 226 {
 227     ofpbuf_prealloc_headroom(b, size);
 228     b->data = (char*)b->data - size;
 229     b->size += size;
 230     return b->data;
 231 }
 232
 233 /* Prefixes 'size' zeroed bytes to the head end of 'b'.  'b' must have at least
 234  * 'size' bytes of headroom.  Returns a pointer to the first byte of the data's
 235  * location in the ofpbuf. */
 236 void *
 237 ofpbuf_push_zeros(struct ofpbuf *b, size_t size)
 238 {
 239     void *dst = ofpbuf_push_uninit(b, size);
 240     memset(dst, 0, size);
 241     return dst;
 242 }
 243
 244 void *
 245 ofpbuf_push(struct ofpbuf *b, const void *p, size_t size)
 246 {
 247     void *dst = ofpbuf_push_uninit(b, size);
 248     memcpy(dst, p, size);
 249     return dst;
 250 }
 251
 252 /* If 'b' contains at least 'offset + size' bytes of data, returns a pointer to
 253  * byte 'offset'.  Otherwise, returns a null pointer. */
 254 void *
 255 ofpbuf_at(const struct ofpbuf *b, size_t offset, size_t size)
 256 {
 257     return offset + size <= b->size ? (char *) b->data + offset : NULL;
 258 }
 259
 260 /* Returns a pointer to byte 'offset' in 'b', which must contain at least
 261  * 'offset + size' bytes of data. */
 262 void *
 263 ofpbuf_at_assert(const struct ofpbuf *b, size_t offset, size_t size)
 264 {
 265     assert(offset + size <= b->size);
 266     return ((char *) b->data) + offset;
 267 }
 268
 269 /* Returns the byte following the last byte of data in use in 'b'. */
 270 void *
 271 ofpbuf_tail(const struct ofpbuf *b)
 272 {
 273     return (char *) b->data + b->size;
 274 }
 275
 276 /* Returns the byte following the last byte allocated for use (but not
 277  * necessarily in use) by 'b'. */
 278 void *
 279 ofpbuf_end(const struct ofpbuf *b)
 280 {
 281     return (char *) b->base + b->allocated;
 282 }
 283
 284 /* Clears any data from 'b'. */
 285 void
 286 ofpbuf_clear(struct ofpbuf *b)
 287 {
 288     b->data = b->base;
 289     b->size = 0;
 290 }
 291
 292 /* Removes 'size' bytes from the head end of 'b', which must contain at least
 293  * 'size' bytes of data.  Returns the first byte of data removed. */
 294 void *
 295 ofpbuf_pull(struct ofpbuf *b, size_t size)
 296 {
 297     void *data = b->data;
 298     assert(b->size >= size);
 299     b->data = (char*)b->data + size;
 300     b->size -= size;
 301     return data;
 302 }
 303
 304 /* If 'b' has at least 'size' bytes of data, removes that many bytes from the
 305  * head end of 'b' and returns the first byte removed.  Otherwise, returns a
 306  * null pointer without modifying 'b'. */
 307 void *
 308 ofpbuf_try_pull(struct ofpbuf *b, size_t size)
 309 {
 310     return b->size >= size ? ofpbuf_pull(b, size) : NULL;
 311 }
 312
 313 /* Returns a string that describes some of 'b''s metadata plus a hex dump of up
 314  * to 'maxbytes' from the start of the buffer. */
 315 char *
 316 ofpbuf_to_string(const struct ofpbuf *b, size_t maxbytes)
 317 {
 318     struct ds s;
 319
 320     ds_init(&s);
 321     ds_put_format(&s, "size=%zu, allocated=%zu, head=%zu, tail=%zu\n",
 322                   b->size, b->allocated,
 323                   ofpbuf_headroom(b), ofpbuf_tailroom(b));
 324     ds_put_hex_dump(&s, b->data, MIN(b->size, maxbytes), 0, false);
 325     return ds_cstr(&s);
 326 }