implement linux_sendfile support

This will also allow non-Linux users to use sendfile
if it is not available.

5 files changed, 170 insertions, 0 deletions

diff --git a/ext/sleepy_penguin/extconf.rb b/ext/sleepy_penguin/extconf.rb
index b1a95c4..e07f5d2 100644
--- a/ext/sleepy_penguin/extconf.rb
+++ b/ext/sleepy_penguin/extconf.rb
@@ -6,6 +6,7 @@ if have_header('sys/event.h')
 end
 have_header('sys/mount.h')
 have_header('sys/eventfd.h')
+have_header('sys/sendfile.h')
 
 # it's impossible to use signalfd reliably with Ruby since Ruby currently
 # manages # (and overrides) all signal handling
diff --git a/ext/sleepy_penguin/init.c b/ext/sleepy_penguin/init.c
index 0a1458b..8295073 100644
--- a/ext/sleepy_penguin/init.c
+++ b/ext/sleepy_penguin/init.c
@@ -54,6 +54,7 @@ void sleepy_penguin_init_signalfd(void);
 
 void sleepy_penguin_init_splice(void);
 void sleepy_penguin_init_cfr(void);
+void sleepy_penguin_init_sendfile(void);
 
 static size_t l1_cache_line_size_detect(void)
 {
@@ -132,4 +133,5 @@ void Init_sleepy_penguin_ext(void)
         sleepy_penguin_init_signalfd();
         sleepy_penguin_init_splice();
         sleepy_penguin_init_cfr();
+        sleepy_penguin_init_sendfile();
 }
diff --git a/ext/sleepy_penguin/sendfile.c b/ext/sleepy_penguin/sendfile.c
new file mode 100644
index 0000000..887dfb6
--- /dev/null
+++ b/ext/sleepy_penguin/sendfile.c
@@ -0,0 +1,120 @@
+#include "sleepy_penguin.h"
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+
+#if defined(HAVE_SYS_SENDFILE_H) && !defined(HAVE_BSD_SENDFILE)
+#  include <sys/sendfile.h>
+#endif
+
+#if defined(__linux__) && defined(HAVE_SENDFILE)
+#  define linux_sendfile(in_fd, out_fd, offset, count) \
+                sendfile((in_fd),(out_fd),(offset),(count))
+
+/* all good */
+#elif defined(HAVE_SENDFILE) && \
+      (defined(__FreeBSD__) || defined(__DragonFly__))
+/*
+ * make BSD sendfile look like Linux for now...
+ * we can support SF_NODISKIO later
+ */
+static ssize_t linux_sendfile(int sockfd, int filefd, off_t *off, size_t count)
+{
+        off_t sbytes = 0;
+        off_t offset = off ? *off : lseek(filefd, 0, SEEK_CUR);
+
+        int rc = sendfile(filefd, sockfd, offset, count, NULL, &sbytes, 0);
+        if (sbytes > 0) {
+                if (off)
+                        *off += sbytes;
+                else
+                        lseek(filefd, sbytes, SEEK_CUR);
+                return (ssize_t)sbytes;
+        }
+
+        return (ssize_t)rc;
+}
+#else /* emulate sendfile using (read|pread) + write */
+static ssize_t pread_sendfile(int sockfd, int filefd, off_t *off, size_t count)
+{
+        size_t max_read = 16384;
+        void *buf;
+        ssize_t r;
+        ssize_t w;
+
+        max_read = count > max_read ? max_read : count;
+        buf = xmalloc(max_read);
+
+        do {
+                r = off ? pread(filefd, buf, max_read, *off) :
+                          read(filefd, buf, max_read);
+        } while (r < 0 && errno == EINTR);
+
+        if (r <= 0) {
+                int err = errno;
+                xfree(buf);
+                errno = err;
+                return r;
+        }
+        w = write(sockfd, buf, r);
+        if (w > 0 && off)
+                *off += w;
+        xfree(buf);
+        return w;
+}
+#    define linux_sendfile(out_fd, in_fd, offset, count) \
+            pread_sendfile((out_fd),(in_fd),(offset),(count))
+#endif
+
+struct sf_args {
+        int dst_fd;
+        int src_fd;
+        off_t *off;
+        size_t count;
+};
+
+static VALUE sym_wait_writable;
+
+static VALUE nogvl_sf(void *ptr)
+{
+        struct sf_args *a = ptr;
+
+        return (VALUE)linux_sendfile(a->dst_fd, a->src_fd, a->off, a->count);
+}
+
+static VALUE lsf(VALUE mod, VALUE dst, VALUE src, VALUE src_off, VALUE count)
+{
+        off_t off = 0;
+        struct sf_args a;
+        ssize_t bytes;
+        int retried = 0;
+
+        a.off = NIL_P(src_off) ? NULL : (off = NUM2OFFT(src_off), &off);
+        a.count = NUM2SIZET(count);
+again:
+        a.src_fd = rb_sp_fileno(src);
+        a.dst_fd = rb_sp_fileno(dst);
+        bytes = (ssize_t)rb_sp_fd_region(nogvl_sf, &a, a.dst_fd);
+        if (bytes < 0) {
+                switch (errno) {
+                case EAGAIN:
+                        return sym_wait_writable;
+                case ENOMEM:
+                case ENOBUFS:
+                        if (!retried) {
+                                rb_gc();
+                                retried = 1;
+                                goto again;
+                        }
+                }
+                rb_sys_fail("sendfile");
+        }
+        return SSIZET2NUM(bytes);
+}
+
+void sleepy_penguin_init_sendfile(void)
+{
+        VALUE m = rb_define_module("SleepyPenguin");
+        rb_define_singleton_method(m, "__lsf", lsf, 4);
+        sym_wait_writable = ID2SYM(rb_intern("wait_writable"));
+}
diff --git a/lib/sleepy_penguin.rb b/lib/sleepy_penguin.rb
index 07c431b..5722f2a 100644
--- a/lib/sleepy_penguin.rb
+++ b/lib/sleepy_penguin.rb
@@ -19,4 +19,23 @@ end
 module SleepyPenguin
   require_relative 'sleepy_penguin/splice' if respond_to?(:__splice)
   require_relative 'sleepy_penguin/cfr' if respond_to?(:__cfr)
+
+  # Copies +len+ bytes from +src+ to +dst+, where +src+ refers to
+  # an open, mmap(2)-able File and +dst+ refers to a Socket.
+  # An optional +offset+ keyword may be specified for the +src+ File.
+  # Using +offset+ will not adjust the offset of the underlying file
+  # handle itself; in other words: this allows concurrent threads to
+  # use linux_sendfile to write data from one open file to multiple
+  # sockets.
+  #
+  # Returns the number of bytes written on success, or :wait_writable
+  # if the +dst+ Socket is non-blocking and the operation would block.
+  # A return value of zero bytes indicates EOF is reached on the +src+
+  # file.
+  #
+  # Newer OSes may be more flexible in whether or not +dst+ or +src+
+  # is a regular file or socket, respectively.
+  def self.linux_sendfile(dst, src, len, offset: nil)
+    __lsf(dst, src, offset, len)
+  end
 end
diff --git a/test/test_sendfile.rb b/test/test_sendfile.rb
new file mode 100644
index 0000000..a25b711
--- /dev/null
+++ b/test/test_sendfile.rb
@@ -0,0 +1,28 @@
+# -*- encoding: binary -*-
+require 'test/unit'
+require 'tempfile'
+require 'socket'
+$-w = true
+require 'sleepy_penguin'
+
+class TestSendfile < Test::Unit::TestCase
+  def test_linux_sendfile
+    rd, wr = UNIXSocket.pair
+    size = 5
+    src = Tempfile.new('ruby_sf_src')
+    assert_equal 0, SleepyPenguin.linux_sendfile(wr, src, size)
+    str = 'abcde'.freeze
+    assert_equal str.bytesize, src.syswrite(str)
+    assert_equal 0, SleepyPenguin.linux_sendfile(wr, src, size)
+    src.sysseek(0, IO::SEEK_SET)
+    assert_equal str.bytesize,
+                 SleepyPenguin.linux_sendfile(wr, src, size, offset: 0)
+    assert_equal str, rd.read(size)
+    assert_equal 0, src.sysseek(0, IO::SEEK_CUR), 'handle offset not changed'
+    assert_equal 3, SleepyPenguin.linux_sendfile(wr, src, 3)
+    assert_equal 3, src.sysseek(0, IO::SEEK_CUR), 'handle offset changed'
+  ensure
+    [ rd, wr ].compact.each(&:close)
+    src.close! if src
+  end
+end