ext/io_splice/io_splice_ext.c

   1 #include "ruby.h"
   2 #ifdef HAVE_RUBY_IO_H
   3 #  include "ruby/io.h"
   4 #else
   5 #  include "rubyio.h"
   6 #endif
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <assert.h>
  10 #include <sys/uio.h>
  11 #include <limits.h>
  12 #include <alloca.h>
  13 #include <unistd.h>
  14
  15 static VALUE sym_EAGAIN;
  16 #define WAITALL 0x4000000
  17
  18 /* taken from haproxy */
  19 #define MAX_AT_ONCE (1 << 30)
  20
  21 #ifndef F_LINUX_SPECIFIC_BASE
  22 #  define F_LINUX_SPECIFIC_BASE 1024
  23 #endif
  24
  25 #ifndef F_GETPIPE_SZ
  26 #  define F_SETPIPE_SZ    (F_LINUX_SPECIFIC_BASE + 7)
  27 #  define F_GETPIPE_SZ    (F_LINUX_SPECIFIC_BASE + 8)
  28 #endif
  29
  30 #if ! HAVE_RB_IO_T
  31 #  define rb_io_t OpenFile
  32 #endif
  33
  34 #ifdef GetReadFile
  35 #  define FPTR_TO_FD(fptr) (fileno(GetReadFile(fptr)))
  36 #else
  37 #  if !HAVE_RB_IO_T || (RUBY_VERSION_MAJOR == 1 && RUBY_VERSION_MINOR == 8)
  38 #    define FPTR_TO_FD(fptr) fileno(fptr->f)
  39 #  else
  40 #    define FPTR_TO_FD(fptr) fptr->fd
  41 #  endif
  42 #endif
  43
  44 #ifndef SSIZET2NUM
  45 #  define SSIZET2NUM(x) LONG2NUM(x)
  46 #endif
  47 #ifndef NUM2SSIZET
  48 #  define NUM2SSIZET(x) NUM2LONG(x)
  49 #endif
  50 #ifndef SIZET2NUM
  51 #  define SIZET2NUM(x) ULONG2NUM(x)
  52 #endif
  53 #ifndef NUM2SIZET
  54 #  define NUM2SIZET(x) NUM2ULONG(x)
  55 #endif
  56
  57 static int my_fileno(VALUE io)
  58 {
  59         rb_io_t *fptr;
  60
  61         for (;;) {
  62                 switch (TYPE(io)) {
  63                 case T_FIXNUM: return FIX2INT(io);
  64                 case T_FILE: {
  65                         GetOpenFile(io, fptr);
  66                         return FPTR_TO_FD(fptr);
  67                 }
  68                 default:
  69                         io = rb_convert_type(io, T_FILE, "IO", "to_io");
  70                         /* retry */
  71                 }
  72         }
  73 }
  74
  75 static int check_fileno(VALUE io)
  76 {
  77         int saved_errno = errno;
  78         int fd = my_fileno(io);
  79         errno = saved_errno;
  80         return fd;
  81 }
  82
  83 /* partial emulation of the 1.9 rb_thread_blocking_region under 1.8 */
  84 #if defined(HAVE_RB_THREAD_BLOCKING_REGION) && \
  85     defined(HAVE_RB_THREAD_CALL_WITHOUT_GVL)
  86 /*
  87  * Ruby 1.9 - 2.1 (we use deprecated rb_thread_blocking_region in 2.0+
  88  * because we can detect (but not use) rb_thread_blocking_region in 1.9.3
  89  */
  90 typedef VALUE (*my_blocking_fn_t)(void*);
  91 #  define WITHOUT_GVL(fn,a,ubf,b) \
  92         rb_thread_blocking_region((my_blocking_fn_t)(fn),(a),(ubf),(b))
  93 #elif defined(HAVE_RB_THREAD_CALL_WITHOUT_GVL) /* Ruby 2.2+ */
  94 #include <ruby/thread.h>
  95 #  define WITHOUT_GVL(fn,a,ubf,b) \
  96         rb_thread_call_without_gvl((fn),(a),(ubf),(b))
  97 #else /* Ruby 1.8 */
  98 #  include <rubysig.h>
  99 #  define RUBY_UBF_IO ((rb_unblock_function_t *)-1)
 100 typedef void rb_unblock_function_t(void *);
 101 typedef void * rb_blocking_function_t(void *);
 102 static void * WITHOUT_GVL(rb_blocking_function_t *func, void *data1,
 103                         rb_unblock_function_t *ubf, void *data2)
 104 {
 105         void *rv;
 106
 107         assert(RUBY_UBF_IO == ubf && "RUBY_UBF_IO required for emulation");
 108
 109         TRAP_BEG;
 110         rv = func(data1);
 111         TRAP_END;
 112
 113         return rv;
 114 }
 115 #endif /* ! HAVE_RB_THREAD_BLOCKING_REGION */
 116
 117 #ifndef RSTRING_PTR
 118 #  define RSTRING_PTR(s) (RSTRING(s)->ptr)
 119 #endif
 120 #ifndef RSTRING_LEN
 121 #  define RSTRING_LEN(s) (RSTRING(s)->len)
 122 #endif
 123 #ifndef RARRAY_LEN
 124 #  define RARRAY_LEN(s) (RARRAY(s)->len)
 125 #endif
 126
 127 #define io_run(fn,data) WITHOUT_GVL((fn),(data),RUBY_UBF_IO,0)
 128
 129 struct splice_args {
 130         int fd_in;
 131         off_t *off_in;
 132         int fd_out;
 133         off_t *off_out;
 134         size_t len;
 135         unsigned flags;
 136 };
 137
 138 static void * nogvl_splice(void *ptr)
 139 {
 140         struct splice_args *a = ptr;
 141
 142         if (a->len > MAX_AT_ONCE)
 143                 a->len = MAX_AT_ONCE;
 144
 145         return (void *)splice(a->fd_in, a->off_in, a->fd_out, a->off_out,
 146                              a->len, a->flags);
 147 }
 148
 149 static ssize_t do_splice(int argc, VALUE *argv, unsigned dflags)
 150 {
 151         off_t i = 0, o = 0;
 152         VALUE io_in, off_in, io_out, off_out, len, flags;
 153         struct splice_args a;
 154         ssize_t bytes;
 155         ssize_t total = 0;
 156         unsigned waitall;
 157
 158         rb_scan_args(argc, argv, "51",
 159                      &io_in, &off_in, &io_out, &off_out, &len, &flags);
 160
 161         a.off_in = NIL_P(off_in) ? NULL : (i = NUM2OFFT(off_in), &i);
 162         a.off_out = NIL_P(off_out) ? NULL : (o = NUM2OFFT(off_out), &o);
 163         a.len = NUM2SIZET(len);
 164         a.flags = NIL_P(flags) ? dflags : NUM2UINT(flags) | dflags;
 165         waitall = a.flags & WAITALL;
 166         if (waitall)
 167                 a.flags ^= WAITALL;
 168
 169         for (;;) {
 170                 a.fd_in = check_fileno(io_in);
 171                 a.fd_out = check_fileno(io_out);
 172                 bytes = (ssize_t)io_run(nogvl_splice, &a);
 173                 if (bytes == -1) {
 174                         if (errno == EINTR)
 175                                 continue;
 176                         if (waitall && errno == EAGAIN) {
 177                                 rb_io_wait_readable(check_fileno(io_in));
 178                                 errno = EAGAIN;
 179                                 rb_io_wait_writable(check_fileno(io_out));
 180                                 continue;
 181                         }
 182                         if (total > 0)
 183                                 return total;
 184                         return bytes;
 185                 } else if (bytes == 0) {
 186                         break;
 187                 } else if (waitall) {
 188                         total += bytes;
 189                         if ((a.len -= bytes) == 0)
 190                                 return total;
 191                         i += bytes;
 192                         o += bytes;
 193                 } else {
 194                         return bytes;
 195                 }
 196         }
 197
 198         return total;
 199 }
 200
 201 /*
 202  * call-seq:
 203  *    IO.splice(io_in, off_in, io_out, off_out, len) => integer
 204  *    IO.splice(io_in, off_in, io_out, off_out, len, flags) => integer
 205  *
 206  * Splice +len+ bytes from/to a pipe.  Either +io_in+ or +io_out+
 207  * MUST be a pipe.  +io_in+ and +io_out+ may BOTH be pipes as of
 208  * Linux 2.6.31 or later.
 209  *
 210  * +off_in+ and +off_out+ if non-nil may be used to
 211  * specify an offset for the non-pipe file descriptor.
 212  *
 213  * +flags+ defaults to zero if unspecified.
 214  * +flags+ may be a bitmask of the following flags:
 215  *
 216  * * IO::Splice::F_MOVE
 217  * * IO::Splice::F_NONBLOCK
 218  * * IO::Splice::F_MORE
 219  * * IO::Splice::WAITALL
 220  *
 221  * Returns the number of bytes spliced.
 222  * Raises EOFError when +io_in+ has reached end of file.
 223  * Raises Errno::EAGAIN if the IO::Splice::F_NONBLOCK flag is set
 224  * and the pipe has no data to read from or space to write to.  May
 225  * also raise Errno::EAGAIN if the non-pipe descriptor has no data
 226  * to read from or space to write to.
 227  *
 228  * As splice never exposes buffers to userspace, it will not take
 229  * into account userspace buffering done by Ruby or stdio.  It is
 230  * also not subject to encoding/decoding filters under Ruby 1.9.
 231  *
 232  * Consider using IO.trysplice if +io_out+ is a pipe or if you are using
 233  * non-blocking I/O on both descriptors as it avoids the cost of raising
 234  * common Errno::EAGAIN exceptions.
 235  *
 236  * See manpage for full documentation:
 237  * http://kernel.org/doc/man-pages/online/pages/man2/splice.2.html
 238  */
 239 static VALUE my_splice(int argc, VALUE *argv, VALUE self)
 240 {
 241         ssize_t n = do_splice(argc, argv, 0);
 242
 243         if (n == 0)
 244                 rb_eof_error();
 245         if (n == -1)
 246                 rb_sys_fail("splice");
 247         return SSIZET2NUM(n);
 248 }
 249
 250 /*
 251  * call-seq:
 252  *    IO.trysplice(io_in, off_in, io_out, off_out, len) => integer
 253  *    IO.trysplice(io_in, off_in, io_out, off_out, len, flags) => integer
 254  *
 255  * Exactly like IO.splice, except +:EAGAIN+ is returned when either
 256  * the read or write end would block instead of raising Errno::EAGAIN.
 257  *
 258  * IO::Splice::F_NONBLOCK is always passed for the pipe descriptor,
 259  * but this can still block if the non-pipe descriptor is blocking.
 260  *
 261  * See IO.splice documentation for more details.
 262  *
 263  * This method is recommended whenever +io_out+ is a pipe.
 264  */
 265 static VALUE trysplice(int argc, VALUE *argv, VALUE self)
 266 {
 267         ssize_t n = do_splice(argc, argv, SPLICE_F_NONBLOCK);
 268
 269         if (n == 0)
 270                 return Qnil;
 271         if (n == -1) {
 272                 if (errno == EAGAIN)
 273                         return sym_EAGAIN;
 274                 rb_sys_fail("splice");
 275         }
 276         return SSIZET2NUM(n);
 277 }
 278
 279 struct tee_args {
 280         int fd_in;
 281         int fd_out;
 282         size_t len;
 283         unsigned flags;
 284 };
 285
 286 /* runs without GVL */
 287 static void * nogvl_tee(void *ptr)
 288 {
 289         struct tee_args *a = ptr;
 290
 291         if (a->len > MAX_AT_ONCE)
 292                 a->len = MAX_AT_ONCE;
 293
 294         return (void *)tee(a->fd_in, a->fd_out, a->len, a->flags);
 295 }
 296
 297 static ssize_t do_tee(int argc, VALUE *argv, unsigned dflags)
 298 {
 299         VALUE io_in, io_out, len, flags;
 300         struct tee_args a;
 301         ssize_t bytes;
 302         ssize_t total = 0;
 303         unsigned waitall;
 304
 305         rb_scan_args(argc, argv, "31", &io_in, &io_out, &len, &flags);
 306         a.len = (size_t)NUM2SIZET(len);
 307         a.flags = NIL_P(flags) ? dflags : NUM2UINT(flags) | dflags;
 308         waitall = a.flags & WAITALL;
 309         if (waitall)
 310                 a.flags ^= WAITALL;
 311
 312         for (;;) {
 313                 a.fd_in = check_fileno(io_in);
 314                 a.fd_out = check_fileno(io_out);
 315                 bytes = (ssize_t)io_run(nogvl_tee, &a);
 316                 if (bytes == -1) {
 317                         if (errno == EINTR)
 318                                 continue;
 319                         if (waitall && errno == EAGAIN) {
 320                                 rb_io_wait_readable(check_fileno(io_in));
 321                                 errno = EAGAIN;
 322                                 rb_io_wait_writable(check_fileno(io_out));
 323                                 continue;
 324                         }
 325                         if (total > 0)
 326                                 return total;
 327                         return bytes;
 328                 } else if (bytes == 0) {
 329                         break;
 330                 } else if (waitall) {
 331                         total += bytes;
 332                         if ((a.len -= bytes) == 0)
 333                                 return total;
 334                 } else {
 335                         return bytes;
 336                 }
 337         }
 338
 339         return total;
 340 }
 341
 342 /*
 343  * call-seq:
 344  *   IO.tee(io_in, io_out, len) => integer
 345  *   IO.tee(io_in, io_out, len, flags) => integer
 346  *
 347  * Copies up to +len+ bytes of data from +io_in+ to +io_out+.  +io_in+
 348  * and +io_out+ must both refer to pipe descriptors.  +io_in+ and +io_out+
 349  * may not be endpoints of the same pipe.
 350  *
 351  * +flags+ may be zero (the default) or a combination of:
 352  * * IO::Splice::F_NONBLOCK
 353  * * IO::Splice::WAITALL
 354  *
 355  * Other IO::Splice flags are currently unimplemented or have no effect.
 356  *
 357  * Returns the number of bytes duplicated if successful.
 358  * Raises EOFError when +io_in+ is closed and emptied.
 359  * Raises Errno::EAGAIN when +io_in+ is empty and/or +io_out+ is full
 360  * and +flags+ contains IO::Splice::F_NONBLOCK
 361  *
 362  * Consider using IO.trytee if you are using IO::Splice::F_NONBLOCK
 363  * as it avoids the cost of raising common Errno::EAGAIN exceptions.
 364  *
 365  * See manpage for full documentation:
 366  * http://kernel.org/doc/man-pages/online/pages/man2/tee.2.html
 367  */
 368 static VALUE my_tee(int argc, VALUE *argv, VALUE self)
 369 {
 370         ssize_t n = do_tee(argc, argv, 0);
 371
 372         if (n == 0)
 373                 rb_eof_error();
 374         if (n == -1)
 375                 rb_sys_fail("tee");
 376
 377         return SSIZET2NUM(n);
 378 }
 379
 380 /*
 381  * call-seq:
 382  *    IO.trytee(io_in, io_out, len) => integer
 383  *    IO.trytee(io_in, io_out, len, flags) => integer
 384  *
 385  * Exactly like IO.tee, except +:EAGAIN+ is returned when either
 386  * the read or write end would block instead of raising Errno::EAGAIN.
 387  *
 388  * IO::Splice::F_NONBLOCK is always passed for the pipe descriptor,
 389  * but this can still block if the non-pipe descriptor is blocking.
 390  *
 391  * See IO.tee documentation for more details.
 392  */
 393 static VALUE trytee(int argc, VALUE *argv, VALUE self)
 394 {
 395         ssize_t n = do_tee(argc, argv, SPLICE_F_NONBLOCK);
 396
 397         if (n == 0)
 398                 return Qnil;
 399         if (n == -1) {
 400                 if (errno == EAGAIN)
 401                         return sym_EAGAIN;
 402                 rb_sys_fail("tee");
 403         }
 404
 405         return SSIZET2NUM(n);
 406 }
 407
 408 struct vmsplice_args {
 409         int fd;
 410         struct iovec *iov;
 411         unsigned long nr_segs;
 412         unsigned flags;
 413 };
 414
 415 static void * nogvl_vmsplice(void *ptr)
 416 {
 417         struct vmsplice_args *a = ptr;
 418
 419         return (void *)vmsplice(a->fd, a->iov, a->nr_segs, a->flags);
 420 }
 421
 422 /* this can't be a function since we use alloca() */
 423 #define ARY2IOVEC(iov,iovcnt,expect,ary) \
 424 do { \
 425         struct iovec *tmp; \
 426         unsigned long i; \
 427         iovcnt = (unsigned long)RARRAY_LEN(ary); \
 428         if (iovcnt > IOV_MAX) \
 429                 rb_raise(rb_eArgError, "array is larger than IOV_MAX"); \
 430         iov = tmp = alloca(sizeof(struct iovec) * iovcnt); \
 431         expect = 0; \
 432         for (i = 0; i < iovcnt; tmp++, i++) { \
 433                 VALUE cur = rb_ary_entry(ary, (long)i); \
 434                 Check_Type(cur, T_STRING); \
 435                 tmp->iov_base = RSTRING_PTR(cur); \
 436                 tmp->iov_len = RSTRING_LEN(cur); \
 437                 expect += tmp->iov_len; \
 438         } \
 439 } while (0)
 440
 441 static void advance_vmsplice_args(struct vmsplice_args *a, long n)
 442 {
 443         struct iovec *new_iov = a->iov;
 444         unsigned long i;
 445
 446         /* skip over iovecs we've already written completely */
 447         for (i = 0; i < a->nr_segs; i++, new_iov++) {
 448                 if (n == 0)
 449                         break;
 450                 /*
 451                  * partially written iov,
 452                  * modify and retry with current iovec in
 453                  * front
 454                  */
 455                 if (new_iov->iov_len > (size_t)n) {
 456                         VALUE base = (VALUE)new_iov->iov_base;
 457
 458                         new_iov->iov_len -= n;
 459                         new_iov->iov_base = (void *)(base + n);
 460                         break;
 461                 }
 462
 463                 n -= new_iov->iov_len;
 464         }
 465
 466         /* setup to retry without the already-written iovecs */
 467         a->nr_segs -= i;
 468         a->iov = new_iov;
 469 }
 470
 471 /*
 472  * call-seq:
 473  *   IO.vmsplice(io, string_array) => integer
 474  *   IO.vmsplice(io, string_array, flags) => integer
 475  *   IO.vmsplice(io, string) => integer
 476  *   IO.vmsplice(io, string, flags) => integer
 477  *
 478  * Transfers an array of strings into the pipe descriptor given by io.
 479  * +io+ must be the writable end of a pipe.
 480  *
 481  * This may allow the kernel to avoid data copies in some cases.
 482  * but is (probably) of limited usefulness in Ruby.  If you have
 483  * use cases or ideas for making this more useful for Ruby users,
 484  * please tell us at ruby.io.splice@librelist.org!
 485  *
 486  * Also consider the "sendfile" RubyGem or IO.copy_stream in Ruby 1.9
 487  * if you want to do zero-copy file transfers to pipes or sockets.  As
 488  * of Linux 2.6.33, sendfile(2) can copy to any output descriptor,
 489  * not just sockets.
 490  *
 491  * See manpage for full documentation:
 492  * http://kernel.org/doc/man-pages/online/pages/man2/vmsplice.2.html
 493  */
 494 static VALUE my_vmsplice(int argc, VALUE * argv, VALUE self)
 495 {
 496         ssize_t rv = 0;
 497         ssize_t left;
 498         struct vmsplice_args a;
 499         struct iovec iov;
 500         ssize_t n;
 501
 502         VALUE io, data, flags;
 503
 504         rb_scan_args(argc, argv, "21", &io, &data, &flags);
 505
 506         switch (TYPE(data)) {
 507         case T_STRING:
 508                 iov.iov_base = RSTRING_PTR(data);
 509                 iov.iov_len = (size_t)(left = (ssize_t)RSTRING_LEN(data));
 510                 a.iov = &iov;
 511                 a.nr_segs = 1;
 512                 break;
 513         case T_ARRAY:
 514                 ARY2IOVEC(a.iov, a.nr_segs, left, data);
 515                 break;
 516         default:
 517                 rb_raise(rb_eTypeError, "wrong argument type %s "
 518                          "(expected a String or Array of strings)",
 519                          rb_obj_classname(data));
 520         }
 521
 522         a.flags = NIL_P(flags) ? 0 : NUM2UINT(flags);
 523
 524         for (;;) {
 525                 a.fd = check_fileno(io);
 526                 n = (ssize_t)io_run(nogvl_vmsplice, &a);
 527
 528                 if (n == -1) {
 529                         if (errno == EAGAIN) {
 530                                 if (a.flags & SPLICE_F_NONBLOCK)
 531                                         rb_sys_fail("vmsplice");
 532                                 if (rb_io_wait_writable(check_fileno(io)))
 533                                         continue;
 534                                 /* fall through on error */
 535                         }
 536                         /*
 537                          * unlikely to hit this case, return the
 538                          * already written bytes, we'll let the next
 539                          * write (or close) fail instead
 540                          */
 541                         if (rv > 0)
 542                                 break;
 543                         if (errno == EINTR)
 544                                 continue;
 545                         rb_sys_fail("vmsplice");
 546                 }
 547
 548                 rv += n;
 549                 left -= n;
 550                 if (left == 0)
 551                         break;
 552                 advance_vmsplice_args(&a, n);
 553         }
 554
 555         return SSIZET2NUM(rv);
 556 }
 557
 558 /*
 559  * call-seq:
 560  *   reader, writer = IO.pipe
 561  *   reader.pipe_size => integer
 562  *
 563  * Returns the pipe capacity of the underlying pipe in bytes.  The
 564  * default capacity is 65536 bytes since Linux 2.6.11, and 4096 bytes
 565  * in previous kernels.
 566  *
 567  * Since the pipe is a circular buffer in the same kernel, the size
 568  * of the reader is exactly the same as the size of the writer.
 569  *
 570  * This method is only exposed on Linux 2.6.35 or later.
 571  */
 572 static VALUE pipe_size(VALUE self)
 573 {
 574         int size = fcntl(my_fileno(self),  F_GETPIPE_SZ);
 575
 576         if (size < 0)
 577                 rb_sys_fail("fcntl(F_GETPIPE_SZ)");
 578
 579         return INT2NUM(size);
 580 }
 581
 582 /*
 583  * call-seq:
 584  *   reader, writer = IO.pipe
 585  *   reader.pipe_size = integer
 586  *
 587  * Sets and returns the pipe capacity of the underlying pipe in bytes.
 588  *
 589  * This MUST be a power-of-two, or Errno::EINVAL will be raised.
 590  * Linux will silently increase this to be equal to the page size
 591  * (4096 bytes on most architectures) if the specified value is
 592  * less than the size of a page.
 593  *
 594  * For users without CAP_SYS_RESOURCE, this raises Errno::EPERM when
 595  * attempting to specify a value greater than the value in
 596  * /proc/sys/fs/pipe-max-size.
 597  *
 598  * Since the pipe is a circular buffer in the same kernel, the size
 599  * of the reader is exactly the same as the size of the writer.
 600  *
 601  * Raises Errno::EBUSY if the assigned value is less than
 602  * the currently filled portion of the pipe.
 603  *
 604  * This method is only exposed on Linux 2.6.35 or later.
 605  */
 606 static VALUE set_pipe_size(VALUE self, VALUE size)
 607 {
 608         int fd = my_fileno(self);
 609         int bytes = NUM2INT(size);
 610         int rv = fcntl(fd, F_SETPIPE_SZ, bytes);
 611
 612         if (rv < 0) {
 613                 if (errno == ENOMEM) {
 614                         rb_gc();
 615                         rv = fcntl(fd, F_SETPIPE_SZ, bytes);
 616                 }
 617                 if (rv < 0)
 618                         rb_sys_fail("fcntl(F_SETPIPE_SZ)");
 619         }
 620
 621         return size;
 622 }
 623
 624 static int can_mod_pipe_size(void)
 625 {
 626         /*
 627          * pipe2 appeared in Linux 2.6.27, F_*PIPE_SZ appeared in 2.6.35,
 628          * thus not having pipe2 automatically disqualifies us from having
 629          * F_*PIPE_SZ support
 630          */
 631 #ifdef HAVE_PIPE2
 632         int fds[2];
 633         int rc = pipe2(fds, O_CLOEXEC);
 634
 635         if (rc == 0) {
 636                 rc = fcntl(fds[0], F_GETPIPE_SZ);
 637                 rc = rc < 0 ? 0 : 1;
 638
 639                 (void)close(fds[0]);
 640                 (void)close(fds[1]);
 641         } else {
 642                 /*
 643                  * weird error, but don't raise during init, this could be
 644                  * ENOSYS, even..
 645                  */
 646                 rc = 0;
 647         }
 648         errno = 0;
 649         return rc;
 650 #else  /* ! HAVE_PIPE2 */
 651         return 0;
 652 #endif /* ! HAVE_PIPE2 */
 653 }
 654
 655 void Init_io_splice_ext(void)
 656 {
 657         VALUE mSplice = rb_define_module_under(rb_cIO, "Splice");
 658
 659         rb_define_singleton_method(rb_cIO, "splice", my_splice, -1);
 660         rb_define_singleton_method(rb_cIO, "trysplice", trysplice, -1);
 661         rb_define_singleton_method(rb_cIO, "tee", my_tee, -1);
 662         rb_define_singleton_method(rb_cIO, "trytee", trytee, -1);
 663         rb_define_singleton_method(rb_cIO, "vmsplice", my_vmsplice, -1);
 664
 665         /*
 666          * Attempt to move pages instead of copying.  This is only a hint
 667          * and support for it was removed in Linux 2.6.21.  It will be
 668          * re-added for FUSE filesystems only in Linux 2.6.35.
 669          */
 670         rb_define_const(mSplice, "F_MOVE", UINT2NUM(SPLICE_F_MOVE));
 671         assert(WAITALL != SPLICE_F_MOVE && "WAITALL == F_MOVE");
 672
 673         /*
 674          * Do not block on pipe I/O.  This flag only affects the pipe(s)
 675          * being spliced from/to and has no effect on the non-pipe
 676          * descriptor (which requires non-blocking operation to be set
 677          * explicitly).
 678          *
 679          * The non-blocking flag (O_NONBLOCK) on the pipe descriptors
 680          * themselves are ignored by this family of functions, and
 681          * using this flag is the only way to get non-blocking operation
 682          * out of them.
 683          *
 684          * It is highly recommended this flag be set (or IO.trysplice used)
 685          * whenever splicing from a socket into a pipe unless there is
 686          * another (native) thread or process doing a blocking read on that
 687          * pipe.  Otherwise it is possible to block a single-threaded process
 688          * if the socket buffers are larger than the pipe buffers.
 689          */
 690         rb_define_const(mSplice, "F_NONBLOCK", UINT2NUM(SPLICE_F_NONBLOCK));
 691         assert(WAITALL != SPLICE_F_NONBLOCK && "WAITALL == F_NONBLOCK");
 692
 693         /*
 694          * Indicate that there may be more data coming into the outbound
 695          * descriptor.  This can allow the kernel to avoid sending partial
 696          * frames from sockets.  Currently only used with splice.
 697          */
 698         rb_define_const(mSplice, "F_MORE", UINT2NUM(SPLICE_F_MORE));
 699         assert(WAITALL != SPLICE_F_MORE && "WAITALL == F_MORE");
 700
 701         /*
 702          * Only usable by vmsplice.  This flag probably not useful in the
 703          * context of Ruby applications which cannot control alignment.
 704          */
 705         rb_define_const(mSplice, "F_GIFT", UINT2NUM(SPLICE_F_GIFT));
 706         assert(WAITALL != SPLICE_F_GIFT && "WAITALL == F_GIFT");
 707
 708         /*
 709          * Retry until the requested transfer is complete, this will
 710          * cause IO.splice/IO.tee to never return less than the requested
 711          * transfer size unless an error occored.
 712          *
 713          * IO.vmsplice always defaults to this behavior.
 714          */
 715         rb_define_const(mSplice, "WAITALL", UINT2NUM(WAITALL));
 716
 717         /*
 718          * The maximum size of an atomic write to a pipe
 719          * POSIX requires this to be at least 512 bytes.
 720          * Under Linux, this is 4096 bytes.
 721          */
 722         rb_define_const(mSplice, "PIPE_BUF", UINT2NUM(PIPE_BUF));
 723
 724         /*
 725          * The maximum size we're allowed to splice at once.  Larger
 726          * sizes will be broken up and retried if the WAITALL flag or
 727          * IO::Splice.copy_stream is used.
 728          */
 729         rb_define_const(mSplice, "MAX_AT_ONCE", SIZET2NUM(MAX_AT_ONCE));
 730
 731         if (can_mod_pipe_size()) {
 732                 rb_define_method(rb_cIO, "pipe_size", pipe_size, 0);
 733                 rb_define_method(rb_cIO, "pipe_size=", set_pipe_size, 1);
 734
 735                 /*
 736                  * fcntl() command constant used to return the size of a pipe.
 737                  * This constant is only defined when running Linux 2.6.35
 738                  * or later.  For convenience, use IO#pipe_size instead.
 739                  */
 740                 rb_define_const(mSplice, "F_GETPIPE_SZ",
 741                                 UINT2NUM(F_GETPIPE_SZ));
 742
 743                 /*
 744                  * fcntl() command constant used to set the size of a pipe.
 745                  * This constant is only defined when running Linux 2.6.35
 746                  * or later.  For convenience, use IO#pipe_size= instead.
 747                  */
 748                 rb_define_const(mSplice, "F_SETPIPE_SZ",
 749                                 UINT2NUM(F_SETPIPE_SZ));
 750         }
 751
 752         sym_EAGAIN = ID2SYM(rb_intern("EAGAIN"));
 753 }