1 '\" te
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  10 .TH T_RCVUDATA 3NSL "May 7, 1998"
  11 .SH NAME
  12 t_rcvudata \- receive a data unit
  13 .SH SYNOPSIS
  14 .LP
  15 .nf
  16 #include <xti.h>
  17 
  18 
  19 
  20 \fBint\fR \fBt_rcvudata\fR(\fBint\fR \fIfd\fR, \fBstruct t_unitdata *\fR\fIunitdata\fR, \fBint *\fR\fIflags\fR);
  21 .fi
  22 
  23 .SH DESCRIPTION
  24 .sp
  25 .LP
  26 This routine is part of the \fBXTI\fR interfaces which evolved from the
  27 \fBTLI\fR interfaces. \fBXTI\fR represents the future evolution of these
  28 interfaces. However, \fBTLI\fR interfaces are supported for compatibility. When
  29 using a \fBTLI\fR routine that has the same name as an \fBXTI\fR routine, the
  30 \fBtiuser.h\fR header file must be used.  Refer to the  \fBTLI\fR
  31 \fBCOMPATIBILITY\fR section for a description of differences between the two
  32 interfaces.
  33 .sp
  34 .LP
  35 This function is used in connectionless-mode to receive a data unit from
  36 another transport user. The argument \fIfd\fR identifies the local transport
  37 endpoint through which data will be received, \fIunitdata\fR holds information
  38 associated with the received data unit, and \fIflags\fR is set on return to
  39 indicate that the complete data unit was not received. The argument
  40 \fIunitdata\fR points to a \fBt_unitdata\fR structure containing the following
  41 members:
  42 .sp
  43 .in +2
  44 .nf
  45 \fBstruct netbuf addr;
  46 struct netbuf opt;
  47 struct netbuf udata;\fR
  48 .fi
  49 .in -2
  50 
  51 .sp
  52 .LP
  53 The \fImaxlen\fR field of \fIaddr\fR, \fIopt\fR and \fIudata\fR must be set
  54 before calling this function to indicate the maximum size of the buffer for
  55 each. If the  \fImaxlen\fR field of  \fIaddr\fR or  \fIopt\fR is set to zero,
  56 no information is returned in the  \fIbuf\fR field of this parameter.
  57 .sp
  58 .LP
  59 On return from this call, \fIaddr\fR specifies the protocol address of the
  60 sending user, \fIopt\fR identifies options that were associated with this data
  61 unit, and \fIudata\fR specifies the user data that was received.
  62 .sp
  63 .LP
  64 By default, \fBt_rcvudata()\fR operates in synchronous mode and will wait for a
  65 data unit to arrive if none is currently available. However, if
  66 \fBO_NONBLOCK\fR is set by means of  \fBt_open\fR(3NSL) or \fBfcntl\fR(2),
  67 \fBt_rcvudata()\fR will execute in asynchronous mode and will fail if no data
  68 units are available.
  69 .sp
  70 .LP
  71 If the buffer defined in the \fIudata\fR field of \fIunitdata\fR is not large
  72 enough to hold the current data unit, the buffer will be filled and
  73 \fBT_MORE\fR will be set in \fIflags\fR on return to indicate that another
  74 \fBt_rcvudata()\fR should be called to retrieve the rest of the data unit.
  75 Subsequent calls to \fBt_rcvudata()\fR will return zero for the length of the
  76 address and options until the full data unit has been received.
  77 .sp
  78 .LP
  79 If the call is interrupted, \fBt_rcvudata()\fR will return \fBEINTR\fR and no
  80 datagrams will have been removed from the endpoint.
  81 .SH RETURN VALUES
  82 .sp
  83 .LP
  84 Upon successful completion, a value of  \fB0\fR is returned.  Otherwise, a
  85 value of  \(mi1 is returned and \fBt_errno\fR is set to indicate an error.
  86 .SH VALID STATES
  87 .sp
  88 .LP
  89 \fBT_IDLE\fR.
  90 .SH ERRORS
  91 .sp
  92 .LP
  93 On failure, \fBt_errno\fR is set to one of the following:
  94 .sp
  95 .ne 2
  96 .na
  97 \fB\fBTBADF\fR\fR
  98 .ad
  99 .RS 15n
 100 The specified file descriptor does not refer to a transport endpoint.
 101 .RE
 102 
 103 .sp
 104 .ne 2
 105 .na
 106 \fB\fBTBUFOVFLW\fR\fR
 107 .ad
 108 .RS 15n
 109 The number of bytes allocated for the incoming protocol address or options
 110 \fI(maxlen)\fR is greater than  \fB0\fR but not sufficient to store the
 111 information. The unit data information to be returned in \fIunitdata\fR will be
 112 discarded.
 113 .RE
 114 
 115 .sp
 116 .ne 2
 117 .na
 118 \fB\fBTLOOK\fR\fR
 119 .ad
 120 .RS 15n
 121 An asynchronous event has occurred on this transport endpoint and requires
 122 immediate attention.
 123 .RE
 124 
 125 .sp
 126 .ne 2
 127 .na
 128 \fB\fBTNODATA\fR\fR
 129 .ad
 130 .RS 15n
 131 \fBO_NONBLOCK\fR was set, but no data units are currently available from the
 132 transport provider.
 133 .RE
 134 
 135 .sp
 136 .ne 2
 137 .na
 138 \fB\fBTNOTSUPPORT\fR\fR
 139 .ad
 140 .RS 15n
 141 This function is not supported by the underlying transport provider.
 142 .RE
 143 
 144 .sp
 145 .ne 2
 146 .na
 147 \fB\fBTOUTSTATE\fR\fR
 148 .ad
 149 .RS 15n
 150 The communications endpoint referenced by  \fIfd\fR is not in one of the states
 151 in which a call to this function is valid.
 152 .RE
 153 
 154 .sp
 155 .ne 2
 156 .na
 157 \fB\fBTPROTO\fR\fR
 158 .ad
 159 .RS 15n
 160 This error indicates that a communication problem has been detected between XTI
 161 and the transport provider for which there is no other suitable XTI error
 162 \fB(t_errno)\fR.
 163 .RE
 164 
 165 .sp
 166 .ne 2
 167 .na
 168 \fB\fBTSYSERR\fR\fR
 169 .ad
 170 .RS 15n
 171 A system error has occurred during execution of this function.
 172 .RE
 173 
 174 .SH TLI COMPATIBILITY
 175 .sp
 176 .LP
 177 The \fBXTI\fR and \fBTLI\fR interface definitions have common names but use
 178 different header files. This, and other semantic differences between the two
 179 interfaces are described in the subsections below.
 180 .SS "Interface Header"
 181 .sp
 182 .LP
 183 The \fBXTI\fR interfaces use the header file, \fBxti.h\fR. \fBTLI\fR interfaces
 184 should \fInot\fR use this header.  They should use the header:
 185 .br
 186 .in +2
 187 #include <tiuser.h>
 188 .in -2
 189 .SS "Error Description Values"
 190 .sp
 191 .LP
 192 The \fBt_errno\fR values that can be set by the \fBXTI\fR interface and cannot
 193 be set by the \fBTLI\fR interface are:
 194 .br
 195 .in +2
 196 \fBTPROTO\fR
 197 .in -2
 198 .br
 199 .in +2
 200 \fBTOUTSTATE\fR
 201 .in -2
 202 .sp
 203 .LP
 204 A \fBt_errno\fR value that this routine can return under different
 205 circumstances than its \fBXTI\fR counterpart is \fBTBUFOVFLW.\fR It can be
 206 returned even when the \fBmaxlen\fR field of the corresponding buffer has been
 207 set to zero.
 208 .SS "Option Buffers"
 209 .sp
 210 .LP
 211 The format of the options in an \fBopt\fR buffer is dictated by the transport
 212 provider. Unlike the \fBXTI\fR interface, the \fBTLI\fR interface does not fix
 213 the buffer format.
 214 .SH ATTRIBUTES
 215 .sp
 216 .LP
 217 See \fBattributes\fR(5)  for descriptions of the following attributes:
 218 .sp
 219 
 220 .sp
 221 .TS
 222 box;
 223 c | c
 224 l | l .
 225 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 226 _
 227 MT Level        Safe
 228 .TE
 229 
 230 .SH SEE ALSO
 231 .sp
 232 .LP
 233 \fBfcntl\fR(2), \fBt_alloc\fR(3NSL), \fBt_open\fR(3NSL),
 234 \fBt_rcvuderr\fR(3NSL), \fBt_sndudata\fR(3NSL), \fBattributes\fR(5)