net/base/nss_memio.c

   1 // Copyright (c) 2008 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4 // Written in NSPR style to also be suitable for adding to the NSS demo suite
   5
   6 /* memio is a simple NSPR I/O layer that lets you decouple NSS from
   7  * the real network.  It's rather like openssl's memory bio,
   8  * and is useful when your app absolutely, positively doesn't
   9  * want to let NSS do its own networking.
  10  */
  11
  12 #include <stdlib.h>
  13 #include <string.h>
  14
  15 #include <prerror.h>
  16 #include <prinit.h>
  17 #include <prlog.h>
  18
  19 #include "nss_memio.h"
  20
  21 /*--------------- private memio types -----------------------*/
  22
  23 /*----------------------------------------------------------------------
  24  Simple private circular buffer class.  Size cannot be changed once allocated.
  25 ----------------------------------------------------------------------*/
  26
  27 struct memio_buffer {
  28     int head;     /* where to take next byte out of buf */
  29     int tail;     /* where to put next byte into buf */
  30     int bufsize;  /* number of bytes allocated to buf */
  31     /* TODO(port): error handling is pessimistic right now.
  32      * Once an error is set, the socket is considered broken
  33      * (PR_WOULD_BLOCK_ERROR not included).
  34      */
  35     PRErrorCode last_err;
  36     char *buf;
  37 };
  38
  39
  40 /* The 'secret' field of a PRFileDesc created by memio_CreateIOLayer points
  41  * to one of these.
  42  * In the public header, we use struct memio_Private as a typesafe alias
  43  * for this.  This causes a few ugly typecasts in the private file, but
  44  * seems safer.
  45  */
  46 struct PRFilePrivate {
  47     /* read requests are satisfied from this buffer */
  48     struct memio_buffer readbuf;
  49
  50     /* write requests are satisfied from this buffer */
  51     struct memio_buffer writebuf;
  52
  53     /* SSL needs to know socket peer's name */
  54     PRNetAddr peername;
  55
  56     /* if set, empty I/O returns EOF instead of EWOULDBLOCK */
  57     int eof;
  58
  59     /* if set, the number of bytes requested from readbuf that were not
  60      * fulfilled (due to readbuf being empty) */
  61     int read_requested;
  62 };
  63
  64 /*--------------- private memio_buffer functions ---------------------*/
  65
  66 /* Forward declarations.  */
  67
  68 /* Allocate a memio_buffer of given size. */
  69 static void memio_buffer_new(struct memio_buffer *mb, int size);
  70
  71 /* Deallocate a memio_buffer allocated by memio_buffer_new. */
  72 static void memio_buffer_destroy(struct memio_buffer *mb);
  73
  74 /* How many bytes can be read out of the buffer without wrapping */
  75 static int memio_buffer_used_contiguous(const struct memio_buffer *mb);
  76
  77 /* How many bytes exist after the wrap? */
  78 static int memio_buffer_wrapped_bytes(const struct memio_buffer *mb);
  79
  80 /* How many bytes can be written into the buffer without wrapping */
  81 static int memio_buffer_unused_contiguous(const struct memio_buffer *mb);
  82
  83 /* Write n bytes into the buffer.  Returns number of bytes written. */
  84 static int memio_buffer_put(struct memio_buffer *mb, const char *buf, int n);
  85
  86 /* Read n bytes from the buffer.  Returns number of bytes read. */
  87 static int memio_buffer_get(struct memio_buffer *mb, char *buf, int n);
  88
  89 /* Allocate a memio_buffer of given size. */
  90 static void memio_buffer_new(struct memio_buffer *mb, int size)
  91 {
  92     mb->head = 0;
  93     mb->tail = 0;
  94     mb->bufsize = size;
  95     mb->buf = malloc(size);
  96 }
  97
  98 /* Deallocate a memio_buffer allocated by memio_buffer_new. */
  99 static void memio_buffer_destroy(struct memio_buffer *mb)
 100 {
 101     free(mb->buf);
 102     mb->buf = NULL;
 103     mb->bufsize = 0;
 104     mb->head = 0;
 105     mb->tail = 0;
 106 }
 107
 108 /* How many bytes can be read out of the buffer without wrapping */
 109 static int memio_buffer_used_contiguous(const struct memio_buffer *mb)
 110 {
 111     return (((mb->tail >= mb->head) ? mb->tail : mb->bufsize) - mb->head);
 112 }
 113
 114 /* How many bytes exist after the wrap? */
 115 static int memio_buffer_wrapped_bytes(const struct memio_buffer *mb)
 116 {
 117     return (mb->tail >= mb->head) ? 0 : mb->tail;
 118 }
 119
 120 /* How many bytes can be written into the buffer without wrapping */
 121 static int memio_buffer_unused_contiguous(const struct memio_buffer *mb)
 122 {
 123     if (mb->head > mb->tail) return mb->head - mb->tail - 1;
 124     return mb->bufsize - mb->tail - (mb->head == 0);
 125 }
 126
 127 /* Write n bytes into the buffer.  Returns number of bytes written. */
 128 static int memio_buffer_put(struct memio_buffer *mb, const char *buf, int n)
 129 {
 130     int len;
 131     int transferred = 0;
 132
 133     /* Handle part before wrap */
 134     len = PR_MIN(n, memio_buffer_unused_contiguous(mb));
 135     if (len > 0) {
 136         /* Buffer not full */
 137         memcpy(&mb->buf[mb->tail], buf, len);
 138         mb->tail += len;
 139         if (mb->tail == mb->bufsize)
 140             mb->tail = 0;
 141         n -= len;
 142         buf += len;
 143         transferred += len;
 144
 145         /* Handle part after wrap */
 146         len = PR_MIN(n, memio_buffer_unused_contiguous(mb));
 147         if (len > 0) {
 148             /* Output buffer still not full, input buffer still not empty */
 149             memcpy(&mb->buf[mb->tail], buf, len);
 150             mb->tail += len;
 151             if (mb->tail == mb->bufsize)
 152                 mb->tail = 0;
 153             transferred += len;
 154         }
 155     }
 156
 157     return transferred;
 158 }
 159
 160
 161 /* Read n bytes from the buffer.  Returns number of bytes read. */
 162 static int memio_buffer_get(struct memio_buffer *mb, char *buf, int n)
 163 {
 164     int len;
 165     int transferred = 0;
 166
 167     /* Handle part before wrap */
 168     len = PR_MIN(n, memio_buffer_used_contiguous(mb));
 169     if (len) {
 170         memcpy(buf, &mb->buf[mb->head], len);
 171         mb->head += len;
 172         if (mb->head == mb->bufsize)
 173             mb->head = 0;
 174         n -= len;
 175         buf += len;
 176         transferred += len;
 177
 178         /* Handle part after wrap */
 179         len = PR_MIN(n, memio_buffer_used_contiguous(mb));
 180         if (len) {
 181             memcpy(buf, &mb->buf[mb->head], len);
 182             mb->head += len;
 183             if (mb->head == mb->bufsize)
 184                 mb->head = 0;
 185             transferred += len;
 186         }
 187     }
 188
 189     return transferred;
 190 }
 191
 192 /*--------------- private memio functions -----------------------*/
 193
 194 static PRStatus PR_CALLBACK memio_Close(PRFileDesc *fd)
 195 {
 196     struct PRFilePrivate *secret = fd->secret;
 197     memio_buffer_destroy(&secret->readbuf);
 198     memio_buffer_destroy(&secret->writebuf);
 199     free(secret);
 200     fd->dtor(fd);
 201     return PR_SUCCESS;
 202 }
 203
 204 static PRStatus PR_CALLBACK memio_Shutdown(PRFileDesc *fd, PRIntn how)
 205 {
 206     /* TODO: pass shutdown status to app somehow */
 207     return PR_SUCCESS;
 208 }
 209
 210 /* If there was a network error in the past taking bytes
 211  * out of the buffer, return it to the next call that
 212  * tries to read from an empty buffer.
 213  */
 214 static int PR_CALLBACK memio_Recv(PRFileDesc *fd, void *buf, PRInt32 len,
 215                                   PRIntn flags, PRIntervalTime timeout)
 216 {
 217     struct PRFilePrivate *secret;
 218     struct memio_buffer *mb;
 219     int rv;
 220
 221     if (flags) {
 222         PR_SetError(PR_NOT_IMPLEMENTED_ERROR, 0);
 223         return -1;
 224     }
 225
 226     secret = fd->secret;
 227     mb = &secret->readbuf;
 228     PR_ASSERT(mb->bufsize);
 229     rv = memio_buffer_get(mb, buf, len);
 230     if (rv == 0 && !secret->eof) {
 231         secret->read_requested = len;
 232         /* If there is no more data in the buffer, report any pending errors
 233          * that were previously observed. Note that both the readbuf and the
 234          * writebuf are checked for errors, since the application may have
 235          * encountered a socket error while writing that would otherwise not
 236          * be reported until the application attempted to write again - which
 237          * it may never do.
 238          */
 239         if (mb->last_err)
 240             PR_SetError(mb->last_err, 0);
 241         else if (secret->writebuf.last_err)
 242             PR_SetError(secret->writebuf.last_err, 0);
 243         else
 244             PR_SetError(PR_WOULD_BLOCK_ERROR, 0);
 245         return -1;
 246     }
 247
 248     secret->read_requested = 0;
 249     return rv;
 250 }
 251
 252 static int PR_CALLBACK memio_Read(PRFileDesc *fd, void *buf, PRInt32 len)
 253 {
 254     /* pull bytes from buffer */
 255     return memio_Recv(fd, buf, len, 0, PR_INTERVAL_NO_TIMEOUT);
 256 }
 257
 258 static int PR_CALLBACK memio_Send(PRFileDesc *fd, const void *buf, PRInt32 len,
 259                                   PRIntn flags, PRIntervalTime timeout)
 260 {
 261     struct PRFilePrivate *secret;
 262     struct memio_buffer *mb;
 263     int rv;
 264
 265     secret = fd->secret;
 266     mb = &secret->writebuf;
 267     PR_ASSERT(mb->bufsize);
 268
 269     /* Note that the read error state is not reported, because it cannot be
 270      * reported until all buffered data has been read. If there is an error
 271      * with the next layer, attempting to call Send again will report the
 272      * error appropriately.
 273      */
 274     if (mb->last_err) {
 275         PR_SetError(mb->last_err, 0);
 276         return -1;
 277     }
 278     rv = memio_buffer_put(mb, buf, len);
 279     if (rv == 0) {
 280         PR_SetError(PR_WOULD_BLOCK_ERROR, 0);
 281         return -1;
 282     }
 283     return rv;
 284 }
 285
 286 static int PR_CALLBACK memio_Write(PRFileDesc *fd, const void *buf, PRInt32 len)
 287 {
 288     /* append bytes to buffer */
 289     return memio_Send(fd, buf, len, 0, PR_INTERVAL_NO_TIMEOUT);
 290 }
 291
 292 static PRStatus PR_CALLBACK memio_GetPeerName(PRFileDesc *fd, PRNetAddr *addr)
 293 {
 294     /* TODO: fail if memio_SetPeerName has not been called */
 295     struct PRFilePrivate *secret = fd->secret;
 296     *addr = secret->peername;
 297     return PR_SUCCESS;
 298 }
 299
 300 static PRStatus memio_GetSocketOption(PRFileDesc *fd, PRSocketOptionData *data)
 301 {
 302     /*
 303      * Even in the original version for real tcp sockets,
 304      * PR_SockOpt_Nonblocking is a special case that does not
 305      * translate to a getsockopt() call
 306      */
 307     if (PR_SockOpt_Nonblocking == data->option) {
 308         data->value.non_blocking = PR_TRUE;
 309         return PR_SUCCESS;
 310     }
 311     PR_SetError(PR_OPERATION_NOT_SUPPORTED_ERROR, 0);
 312     return PR_FAILURE;
 313 }
 314
 315 /*--------------- private memio data -----------------------*/
 316
 317 /*
 318  * Implement just the bare minimum number of methods needed to make ssl happy.
 319  *
 320  * Oddly, PR_Recv calls ssl_Recv calls ssl_SocketIsBlocking calls
 321  * PR_GetSocketOption, so we have to provide an implementation of
 322  * PR_GetSocketOption that just says "I'm nonblocking".
 323  */
 324
 325 static struct PRIOMethods  memio_layer_methods = {
 326     PR_DESC_LAYERED,
 327     memio_Close,
 328     memio_Read,
 329     memio_Write,
 330     NULL,
 331     NULL,
 332     NULL,
 333     NULL,
 334     NULL,
 335     NULL,
 336     NULL,
 337     NULL,
 338     NULL,
 339     NULL,
 340     NULL,
 341     NULL,
 342     memio_Shutdown,
 343     memio_Recv,
 344     memio_Send,
 345     NULL,
 346     NULL,
 347     NULL,
 348     NULL,
 349     NULL,
 350     NULL,
 351     memio_GetPeerName,
 352     NULL,
 353     NULL,
 354     memio_GetSocketOption,
 355     NULL,
 356     NULL,
 357     NULL,
 358     NULL,
 359     NULL,
 360     NULL,
 361     NULL,
 362 };
 363
 364 static PRDescIdentity memio_identity = PR_INVALID_IO_LAYER;
 365
 366 static PRStatus memio_InitializeLayerName(void)
 367 {
 368     memio_identity = PR_GetUniqueIdentity("memio");
 369     return PR_SUCCESS;
 370 }
 371
 372 /*--------------- public memio functions -----------------------*/
 373
 374 PRFileDesc *memio_CreateIOLayer(int readbufsize, int writebufsize)
 375 {
 376     PRFileDesc *fd;
 377     struct PRFilePrivate *secret;
 378     static PRCallOnceType once;
 379
 380     PR_CallOnce(&once, memio_InitializeLayerName);
 381
 382     fd = PR_CreateIOLayerStub(memio_identity, &memio_layer_methods);
 383     secret = malloc(sizeof(struct PRFilePrivate));
 384     memset(secret, 0, sizeof(*secret));
 385
 386     memio_buffer_new(&secret->readbuf, readbufsize);
 387     memio_buffer_new(&secret->writebuf, writebufsize);
 388     fd->secret = secret;
 389     return fd;
 390 }
 391
 392 void memio_SetPeerName(PRFileDesc *fd, const PRNetAddr *peername)
 393 {
 394     PRFileDesc *memiofd = PR_GetIdentitiesLayer(fd, memio_identity);
 395     struct PRFilePrivate *secret = memiofd->secret;
 396     secret->peername = *peername;
 397 }
 398
 399 memio_Private *memio_GetSecret(PRFileDesc *fd)
 400 {
 401     PRFileDesc *memiofd = PR_GetIdentitiesLayer(fd, memio_identity);
 402     struct PRFilePrivate *secret =  memiofd->secret;
 403     return (memio_Private *)secret;
 404 }
 405
 406 int memio_GetReadRequest(memio_Private *secret)
 407 {
 408     return ((PRFilePrivate *)secret)->read_requested;
 409 }
 410
 411 int memio_GetReadParams(memio_Private *secret, char **buf)
 412 {
 413     struct memio_buffer* mb = &((PRFilePrivate *)secret)->readbuf;
 414     PR_ASSERT(mb->bufsize);
 415
 416     *buf = &mb->buf[mb->tail];
 417     return memio_buffer_unused_contiguous(mb);
 418 }
 419
 420 int memio_GetReadableBufferSize(memio_Private *secret)
 421 {
 422     struct memio_buffer* mb = &((PRFilePrivate *)secret)->readbuf;
 423     PR_ASSERT(mb->bufsize);
 424
 425     return memio_buffer_used_contiguous(mb);
 426 }
 427
 428 void memio_PutReadResult(memio_Private *secret, int bytes_read)
 429 {
 430     struct memio_buffer* mb = &((PRFilePrivate *)secret)->readbuf;
 431     PR_ASSERT(mb->bufsize);
 432
 433     if (bytes_read > 0) {
 434         mb->tail += bytes_read;
 435         if (mb->tail == mb->bufsize)
 436             mb->tail = 0;
 437     } else if (bytes_read == 0) {
 438         /* Record EOF condition and report to caller when buffer runs dry */
 439         ((PRFilePrivate *)secret)->eof = PR_TRUE;
 440     } else /* if (bytes_read < 0) */ {
 441         mb->last_err = bytes_read;
 442     }
 443 }
 444
 445 int memio_GetWriteParams(memio_Private *secret,
 446                          const char **buf1, unsigned int *len1,
 447                          const char **buf2, unsigned int *len2)
 448 {
 449     struct memio_buffer* mb = &((PRFilePrivate *)secret)->writebuf;
 450     PR_ASSERT(mb->bufsize);
 451
 452     if (mb->last_err)
 453         return mb->last_err;
 454
 455     *buf1 = &mb->buf[mb->head];
 456     *len1 = memio_buffer_used_contiguous(mb);
 457     *buf2 = mb->buf;
 458     *len2 = memio_buffer_wrapped_bytes(mb);
 459     return 0;
 460 }
 461
 462 void memio_PutWriteResult(memio_Private *secret, int bytes_written)
 463 {
 464     struct memio_buffer* mb = &((PRFilePrivate *)secret)->writebuf;
 465     PR_ASSERT(mb->bufsize);
 466
 467     if (bytes_written > 0) {
 468         mb->head += bytes_written;
 469         if (mb->head >= mb->bufsize)
 470             mb->head -= mb->bufsize;
 471     } else if (bytes_written < 0) {
 472         mb->last_err = bytes_written;
 473     }
 474 }
 475
 476 /*--------------- private memio_buffer self-test -----------------*/
 477
 478 /* Even a trivial unit test is very helpful when doing circular buffers. */
 479 /*#define TRIVIAL_SELF_TEST*/
 480 #ifdef TRIVIAL_SELF_TEST
 481 #include <stdio.h>
 482
 483 #define TEST_BUFLEN 7
 484
 485 #define CHECKEQ(a, b) { \
 486     if ((a) != (b)) { \
 487         printf("%d != %d, Test failed line %d\n", a, b, __LINE__); \
 488         exit(1); \
 489     } \
 490 }
 491
 492 int main()
 493 {
 494     struct memio_buffer mb;
 495     char buf[100];
 496     int i;
 497
 498     memio_buffer_new(&mb, TEST_BUFLEN);
 499
 500     CHECKEQ(memio_buffer_unused_contiguous(&mb), TEST_BUFLEN-1);
 501     CHECKEQ(memio_buffer_used_contiguous(&mb), 0);
 502
 503     CHECKEQ(memio_buffer_put(&mb, "howdy", 5), 5);
 504
 505     CHECKEQ(memio_buffer_unused_contiguous(&mb), TEST_BUFLEN-1-5);
 506     CHECKEQ(memio_buffer_used_contiguous(&mb), 5);
 507     CHECKEQ(memio_buffer_wrapped_bytes(&mb), 0);
 508
 509     CHECKEQ(memio_buffer_put(&mb, "!", 1), 1);
 510
 511     CHECKEQ(memio_buffer_unused_contiguous(&mb), 0);
 512     CHECKEQ(memio_buffer_used_contiguous(&mb), 6);
 513     CHECKEQ(memio_buffer_wrapped_bytes(&mb), 0);
 514
 515     CHECKEQ(memio_buffer_get(&mb, buf, 6), 6);
 516     CHECKEQ(memcmp(buf, "howdy!", 6), 0);
 517
 518     CHECKEQ(memio_buffer_unused_contiguous(&mb), 1);
 519     CHECKEQ(memio_buffer_used_contiguous(&mb), 0);
 520
 521     CHECKEQ(memio_buffer_put(&mb, "01234", 5), 5);
 522
 523     CHECKEQ(memio_buffer_used_contiguous(&mb), 1);
 524     CHECKEQ(memio_buffer_wrapped_bytes(&mb), 4);
 525     CHECKEQ(memio_buffer_unused_contiguous(&mb), TEST_BUFLEN-1-5);
 526
 527     CHECKEQ(memio_buffer_put(&mb, "5", 1), 1);
 528
 529     CHECKEQ(memio_buffer_unused_contiguous(&mb), 0);
 530     CHECKEQ(memio_buffer_used_contiguous(&mb), 1);
 531
 532     /* TODO: add more cases */
 533
 534     printf("Test passed\n");
 535     exit(0);
 536 }
 537
 538 #endif