dep/ACE_wrappers/ace/OS_NS_sys_uio.cpp

   1 // $Id: OS_NS_sys_uio.cpp 81756 2008-05-22 09:47:33Z johnnyw $
   2
   3 #include "ace/OS_NS_sys_uio.h"
   4
   5 ACE_RCSID(ace, OS_NS_sys_uio, "$Id: OS_NS_sys_uio.cpp 81756 2008-05-22 09:47:33Z johnnyw $")
   6
   7 #if !defined (ACE_HAS_INLINED_OSCALLS)
   8 # include "ace/OS_NS_sys_uio.inl"
   9 #endif /* ACE_HAS_INLINED_OSCALLS */
  10
  11 #include "ace/OS_Memory.h"
  12 #include "ace/OS_NS_string.h"
  13 #include "ace/OS_NS_unistd.h"
  14
  15 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  16
  17 # if defined (ACE_LACKS_READV)
  18
  19 // "Fake" readv for operating systems without it.  Note that this is
  20 // thread-safe.
  21
  22 ssize_t
  23 ACE_OS::readv_emulation (ACE_HANDLE handle,
  24                          const iovec *iov,
  25                          int n)
  26 {
  27   ACE_OS_TRACE ("ACE_OS::readv_emulation");
  28
  29   // In case there's a single element, skip the memcpy.
  30   if (1 == n)
  31     return ACE_OS::read (handle, iov[0].iov_base, iov[0].iov_len);
  32
  33   ssize_t length = 0;
  34   int i;
  35
  36   for (i = 0; i < n; ++i)
  37     if (static_cast<int> (iov[i].iov_len) < 0)
  38       return -1;
  39     else
  40       length += iov[i].iov_len;
  41
  42   char *buf;
  43 #   if defined (ACE_HAS_ALLOCA)
  44   buf = (char *) alloca (length);
  45 #   else
  46   ACE_NEW_RETURN (buf,
  47                   char[length],
  48                   -1);
  49 #   endif /* !defined (ACE_HAS_ALLOCA) */
  50
  51   length = ACE_OS::read (handle, buf, length);
  52
  53   if (length != -1)
  54     {
  55       char *ptr = buf;
  56       ssize_t copyn = length;
  57
  58       for (i = 0;
  59            i < n && copyn > 0;
  60            ++i)
  61         {
  62           ACE_OS::memcpy (iov[i].iov_base, ptr,
  63                           // iov_len is int on some platforms, size_t on others
  64                           copyn > (int) iov[i].iov_len
  65                             ? (size_t) iov[i].iov_len
  66                             : (size_t) copyn);
  67           ptr += iov[i].iov_len;
  68           copyn -= iov[i].iov_len;
  69         }
  70     }
  71
  72 #   if !defined (ACE_HAS_ALLOCA)
  73   delete [] buf;
  74 #   endif /* !defined (ACE_HAS_ALLOCA) */
  75   return length;
  76 }
  77 # endif /* ACE_LACKS_READV */
  78
  79 # if defined (ACE_LACKS_WRITEV)
  80
  81 // "Fake" writev for operating systems without it.  Note that this is
  82 // thread-safe.
  83
  84 ssize_t
  85 ACE_OS::writev_emulation (ACE_HANDLE handle, const iovec *iov, int n)
  86 {
  87   ACE_OS_TRACE ("ACE_OS::writev_emulation");
  88
  89   // To avoid having to allocate a temporary buffer to which all of
  90   // the data will be copied and then written, this implementation
  91   // performs incremental writes.
  92
  93   ssize_t bytes_sent = 0;
  94
  95   for (int i = 0; i < n; ++i)
  96     {
  97       ssize_t const result =
  98         ACE_OS::write (handle, iov[i].iov_base, iov[i].iov_len);
  99
 100       if (result == -1)
 101         {
 102           // There is a subtle difference in behaviour depending on
 103           // whether or not any data was sent.  If no data was sent,
 104           // then always return -1.  Otherwise return bytes_sent.
 105           // This gives the caller an opportunity to keep track of
 106           // bytes that have already been sent.
 107           if (bytes_sent > 0)
 108             break;
 109           else
 110             return -1;
 111         }
 112       else
 113         {
 114           bytes_sent += result;
 115
 116           // Do not continue on to the next loop iteration if the
 117           // amount of data sent was less than the amount data given.
 118           // This avoids a subtle problem where "holes" in the data
 119           // stream would occur if partial sends of a given buffer in
 120           // the iovec array occured.
 121           if (static_cast<size_t> (result) < iov[i].iov_len)
 122             break;
 123         }
 124     }
 125
 126   return bytes_sent;
 127 }
 128 # endif /* ACE_LACKS_WRITEV */
 129
 130 ACE_END_VERSIONED_NAMESPACE_DECL