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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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<head><title>15 Data Flow Management: Bulk IO</title>
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<h2 class="chapterHead"><span class="titlemark">Chapter 15</span><br /><a
id="x17-20700015"></a>Data Flow Management: Bulk IO</h2>
<h3 class="sectionHead"><span class="titlemark">15.1 </span> <a
id="x17-20800015.1"></a>Introduction</h3>
<!--l. 6--><p class="noindent" >Data flow through REDHAWK <a
href="mainli2.html#glo:component">Components</a> is managed through a module of interfaces called
<a
href="mainap3.html#bulkio">BulkIO</a>. The <a
href="mainap3.html#bulkio">BulkIO</a> module is designed to provide a standardized methodology for transferring
data between <a
href="mainli2.html#glo:component">Components</a>/<a
href="mainli2.html#glo:device">Devices</a>. As the name implies, <a
href="mainap3.html#bulkio">BulkIO</a> is designed for bulk data
transfers. The code generators are constructed to provide <a
href="mainli2.html#glo:port">Port</a> implementations that maximize the
efficiency of data throughput while providing network-accessible data ingest/egress and minimizing
the complexity of the implementation.
<!--l. 11--><p class="noindent" >Data is transferred either in-band (through the <a
href="mainli2.html#glo:port">Port</a> object directly) or out-of-band
(i.e., User Datagram Protocol (<a
href="mainap3.html#udp">UDP</a>) multicast). In the case of out-of-band transfers,
the <a
href="mainli2.html#glo:port">Port</a> provides only metadata regarding connections, such as multicast address in a
Virtual Local Area Network (<a
href="mainap3.html#vlan">VLAN</a>). Data transferred in-band is embedded with some
fixed-field metadata, like a birth date timestamp, and variable-field metadata in key/value
pairs.
<!--l. 1--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">15.2 </span> <a
id="x17-20900015.2"></a>SRI</h3>
<!--l. 3--><p class="noindent" ><a
href="mainap3.html#sri">SRI</a> is delivered with the data (when in-band) that describes the data payload.
<!--l. 5--><p class="noindent" >The <a
href="mainap3.html#sri">SRI</a> data structure contains the following 12 fields:
<div class="table">
<!--l. 12--><p class="noindent" ><a
id="x17-209001r1"></a><hr class="float"><div class="float"
><table class="float"><tr class="float"><td class="float"
>
<table class="caption"
><tr style="vertical-align:baseline;" class="caption"><td class="id">Table 15.1: </td><td
class="content"><a
href="mainap3.html#sri">SRI</a> fields</td></tr></table><!--tex4ht:label?: x17-209001r1 -->
<div class="tabular"> <table id="TBL-1" class="tabular"
cellspacing="0" cellpadding="0" rules="groups"
><colgroup id="TBL-1-1g"><col
id="TBL-1-1"></colgroup><colgroup id="TBL-1-2g"><col
id="TBL-1-2"></colgroup><colgroup id="TBL-1-3g"><col
id="TBL-1-3"></colgroup><tr
style="vertical-align:baseline;" id="TBL-1-1-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-1-1"
class="td11"> <span
class="cmbx-12">Name </span></td><td style="white-space:wrap; text-align:left;" id="TBL-1-1-2"
class="td11"> <!--l. 15--><p class="noindent" ><span
class="cmbx-12">Type</span> </td><td style="white-space:wrap; text-align:left;" id="TBL-1-1-3"
class="td11"> <!--l. 15--><p class="noindent" ><span
class="cmbx-12">Description</span> </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-2-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-2-1"
class="td11"> hversion </td><td style="white-space:wrap; text-align:left;" id="TBL-1-2-2"
class="td11"> <!--l. 16--><p class="noindent" >long </td><td style="white-space:wrap; text-align:left;" id="TBL-1-2-3"
class="td11"> <!--l. 16--><p class="noindent" >Version of the Stream <a
href="mainap3.html#sri">SRI</a> header. This field
is ignored by the code generators, so a default
1.0 is adequate. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-3-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-3-1"
class="td11"> xstart </td><td style="white-space:wrap; text-align:left;" id="TBL-1-3-2"
class="td11"> <!--l. 17--><p class="noindent" >double </td><td style="white-space:wrap; text-align:left;" id="TBL-1-3-3"
class="td11"> <!--l. 17--><p class="noindent" >Start time of the stream. This is epoch time
from January 1, 1970 in seconds. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-4-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-4-1"
class="td11"> xdelta </td><td style="white-space:wrap; text-align:left;" id="TBL-1-4-2"
class="td11"> <!--l. 18--><p class="noindent" >double </td><td style="white-space:wrap; text-align:left;" id="TBL-1-4-3"
class="td11"> <!--l. 18--><p class="noindent" >Delta between two values in the payload
vector. in the case of time data, this is the
sampling period. In the case of spectral data,
this is the frequency difference between two
adjacent Fast Fourier Transform (<a
href="mainap3.html#fft">FFT</a>) bins. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-5-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-5-1"
class="td11"> xunits </td><td style="white-space:wrap; text-align:left;" id="TBL-1-5-2"
class="td11"> <!--l. 19--><p class="noindent" >short </td><td style="white-space:wrap; text-align:left;" id="TBL-1-5-3"
class="td11"> <!--l. 19--><p class="noindent" >Unit types;
common codes defined in <a
href="mainap3.html#idl">IDL</a> (i.e: 0=None,
1=time, 2=delay, 3=frequency) </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-6-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-6-1"
class="td11"> subsize </td><td style="white-space:wrap; text-align:left;" id="TBL-1-6-2"
class="td11"> <!--l. 20--><p class="noindent" >long </td><td style="white-space:wrap; text-align:left;" id="TBL-1-6-3"
class="td11"> <!--l. 20--><p class="noindent" >0 if the data is one dimensional; <span
class="cmmi-12">></span>0 if two
dimensional. This applies to framed data;
ydelta describes the frame length. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-7-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-7-1"
class="td11"> ystart </td><td style="white-space:wrap; text-align:left;" id="TBL-1-7-2"
class="td11"> <!--l. 21--><p class="noindent" >double </td><td style="white-space:wrap; text-align:left;" id="TBL-1-7-3"
class="td11"> <!--l. 21--><p class="noindent" >Start of second dimension </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-8-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-8-1"
class="td11"> ydelta </td><td style="white-space:wrap; text-align:left;" id="TBL-1-8-2"
class="td11"> <!--l. 22--><p class="noindent" >double </td><td style="white-space:wrap; text-align:left;" id="TBL-1-8-3"
class="td11"> <!--l. 22--><p class="noindent" >Delta between two samples of second
dimension (e.g., frame length in framed data) </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-9-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-9-1"
class="td11"> yunits </td><td style="white-space:wrap; text-align:left;" id="TBL-1-9-2"
class="td11"> <!--l. 23--><p class="noindent" >short </td><td style="white-space:wrap; text-align:left;" id="TBL-1-9-3"
class="td11"> <!--l. 23--><p class="noindent" >Unit types;
common codes defined in <a
href="mainap3.html#idl">IDL</a> (i.e: 0=None,
1=time, 2=delay, 3=frequency) </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-10-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-10-1"
class="td11"> mode </td><td style="white-space:wrap; text-align:left;" id="TBL-1-10-2"
class="td11"> <!--l. 24--><p class="noindent" >short </td><td style="white-space:wrap; text-align:left;" id="TBL-1-10-3"
class="td11"> <!--l. 24--><p class="noindent" >0-Scalar, 1-Complex. Complex data is passed
as interleaved I/Q values in the sequence.
The type for the sequence remains the same
for both real and complex data. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-11-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-11-1"
class="td11"> streamID </td><td style="white-space:wrap; text-align:left;" id="TBL-1-11-2"
class="td11"> <!--l. 25--><p class="noindent" >string </td><td style="white-space:wrap; text-align:left;" id="TBL-1-11-3"
class="td11"> <!--l. 25--><p class="noindent" >Stream <a
href="mainap3.html#id">ID</a>. Unique streams can be delivered
over the same <a
href="mainli2.html#glo:port">Port</a>, where each stream
is identified by a unique string (generated
or passed along by the provides side).
The generation of this stream <a
href="mainap3.html#id">ID</a> is
<a
href="mainli2.html#glo:application">Application</a>-specific and not controlled by
the REDHAWK Core Framework. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-12-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-12-1"
class="td11"> blocking </td><td style="white-space:wrap; text-align:left;" id="TBL-1-12-2"
class="td11"> <!--l. 26--><p class="noindent" >boolean </td><td style="white-space:wrap; text-align:left;" id="TBL-1-12-3"
class="td11"> <!--l. 26--><p class="noindent" >Flag to determine whether the receiving <a
href="mainli2.html#glo:port">Port</a>
should exhibit back pressure. If this is false
and the provides-side queue is full, the data is
dumped. If this is true and the provides-side
queue is full, the <span
class="cmtt-12">pushPacket() </span>call blocks. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-1-13-"><td style="white-space:nowrap; text-align:left;" id="TBL-1-13-1"
class="td11"> keywords </td><td style="white-space:wrap; text-align:left;" id="TBL-1-13-2"
class="td11"> <!--l. 27--><p class="noindent" >sequence
<span
class="cmmi-12"><</span>CF::DataType<span
class="cmmi-12">></span> </td><td style="white-space:wrap; text-align:left;" id="TBL-1-13-3"
class="td11"> <!--l. 27--><p class="noindent" >User defined keywords. This is a sequence
of structures that contain an <a
href="mainap3.html#id">ID</a> of type
string and a value of type <a
href="mainap3.html#corba">CORBA</a> Any. The
content of the <a
href="mainap3.html#corba">CORBA</a> Any can be any type. </td>
</tr></table></div>
</td></tr></table></div><hr class="endfloat" />
</div>
<!--l. 35--><p class="noindent" ><a
href="mainap3.html#sri">SRI</a> is transferred over a connection by the uses-side invoking the providesside function
<span
class="cmtt-12">pushSRI()</span>. The <span
class="cmtt-12">pushSRI() </span>function contains a single argument, an instance of an <a
href="mainap3.html#sri">SRI</a>
object.
<!--l. 38--><p class="noindent" >Each provides-side <a
href="mainli2.html#glo:port">Port</a> that implements a <a
href="mainap3.html#bulkio">BulkIO</a> interface expects that <a
href="mainap3.html#sri">SRI</a> regarding data being
received become available before any data is transferred. When using the code generators and base
classes in the REDHAWK development tools, this behavior is hard-coded into the uses-side <a
href="mainap3.html#bulkio">BulkIO</a>
<a
href="mainli2.html#glo:port">Ports</a>. If the user code on the uses-side of a <a
href="mainap3.html#bulkio">BulkIO</a> connection does not explicitly invoke a
<span
class="cmtt-12">pushSRI() </span>call before any data is sent out, the auto-generated code will create a trivial <a
href="mainap3.html#sri">SRI</a>
message with normalized values.
<!--l. 42--><p class="noindent" >Part of the hard-coded behavior on the uses-side <a
href="mainap3.html#bulkio">BulkIO</a> <a
href="mainli2.html#glo:port">Port</a> is to issue a <span
class="cmtt-12">pushSRI() </span>when a new
connection is made to the newly-connected object. For example, a system is created in which data
is flowing between <a
href="mainli2.html#glo:component">Components</a> A and B. As data is flowing between these <a
href="mainli2.html#glo:component">Components</a>, a new
connection is established between <a
href="mainli2.html#glo:component">Components</a> A and C. When this connection is established, a
<span
class="cmtt-12">pushSRI() </span>method call will automatically be made from <a
href="mainli2.html#glo:component">Component</a> A to <a
href="mainli2.html#glo:component">Component</a>
C.
<h3 class="sectionHead"><span class="titlemark">15.3 </span> <a
id="x17-21000015.3"></a><span
class="cmtt-12">BULKIO::PrecisionUTCTime </span>Timestamp</h3>
<!--l. 4--><p class="noindent" >The following code segment provides an example of how to construct a <span
class="cmtt-12">BULKIO::PrecisionUTCTime</span>
time stamp to be sent in the <a
href="mainap3.html#sri">SRI</a>:
<script type="syntaxhighlighter" class="brush: cpp"><![CDATA[
//To create a PrecisionUTCTime object, use the following
//code:
struct timeval tmp_time;
struct timezone tmp_tz;
gettimeofday(&tmp_time, &tmp_tz);
double wsec = tmp_time.tv_sec;
double fsec = tmp_time.tv_usec / 1e6;;
BULKIO::PrecisionUTCTime tstamp =
BULKIO::PrecisionUTCTime();
tstamp.tcmode = BULKIO::TCM_CPU;
tstamp.tcstatus = (short)1;
tstamp.toff = 0.0;
tstamp.twsec = wsec;
tstamp.tfsec = fsec;
]]></script>
<!--l. 1--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">15.4 </span> <a
id="x17-21100015.4"></a>Data Transfers</h3>
<!--l. 3--><p class="noindent" >The <a
href="mainap3.html#bulkio">BulkIO</a> data transfers happen with the <span
class="cmtt-12">pushPacket() </span>call. As mentioned earlier, the
provides-side <a
href="mainli2.html#glo:port">Port</a> expects a <span
class="cmtt-12">pushSRI() </span>call before the first <span
class="cmtt-12">pushPacket()</span>. The auto-generated
code in <a
href="mainli2.html#glo:component">Components</a> guarantees this behavior. Zero or more <span
class="cmtt-12">pushPacket() </span>calls may happen after
a <span
class="cmtt-12">pushSRI()</span>.
<!--l. 8--><p class="noindent" >In the case of in-band data, the <span
class="cmtt-12">pushPacket() </span>arguments are shown in <a
href="#x17-21100015.4">Table 15.4</a>.
<div class="table">
<!--l. 11--><p class="noindent" ><a
id="x17-211001r2"></a><hr class="float"><div class="float"
><table class="float"><tr class="float"><td class="float"
>
<div class="tabular"> <table id="TBL-2" class="tabular"
cellspacing="0" cellpadding="0" rules="groups"
><colgroup id="TBL-2-1g"><col
id="TBL-2-1"></colgroup><colgroup id="TBL-2-2g"><col
id="TBL-2-2"></colgroup><colgroup id="TBL-2-3g"><col
id="TBL-2-3"></colgroup><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-2-1-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-1-1"
class="td11"> <span
class="cmbx-12">Name </span></td><td style="white-space:nowrap; text-align:left;" id="TBL-2-1-2"
class="td11"> <span
class="cmbx-12">Type </span></td><td style="white-space:wrap; text-align:left;" id="TBL-2-1-3"
class="td11"> <!--l. 15--><p class="noindent" ><span
class="cmbx-12">Description</span> </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-2-2-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-2-1"
class="td11"> data </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-2-2"
class="td11"> sequence<span
class="cmmi-12"><</span>TYPE<span
class="cmmi-12">> </span></td><td style="white-space:wrap; text-align:left;" id="TBL-2-2-3"
class="td11"> <!--l. 16--><p class="noindent" >A sequence of a particular type,
where TYPE is some native
<a
href="mainap3.html#corba">CORBA</a> type (e.g., float, short).
The sequence may be zero-length. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-2-3-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-3-1"
class="td11"> T </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-3-2"
class="td11"> PrecisionUTCTime </td><td style="white-space:wrap; text-align:left;" id="TBL-2-3-3"
class="td11"> <!--l. 17--><p class="noindent" >The epoch birth date of the first
sample of the sequence passed in
this call. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-2-4-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-4-1"
class="td11"> <a
href="mainap3.html#eos">EOS</a> </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-4-2"
class="td11"> boolean </td><td style="white-space:wrap; text-align:left;" id="TBL-2-4-3"
class="td11"> <!--l. 18--><p class="noindent" >Flag describing whether this
particular stream ends with this
<span
class="cmtt-12">pushPacket() </span>call. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-2-5-"><td style="white-space:nowrap; text-align:left;" id="TBL-2-5-1"
class="td11"> streamID </td><td style="white-space:nowrap; text-align:left;" id="TBL-2-5-2"
class="td11"> string </td><td style="white-space:wrap; text-align:left;" id="TBL-2-5-3"
class="td11"> <!--l. 19--><p class="noindent" >Stream ID for this particular
payload. This string is used to
reconcile this sequence of data
with a particular Stream <a
href="mainap3.html#sri">SRI</a>
data structure. </td>
</tr></table></div>
<br /> <table class="caption"
><tr style="vertical-align:baseline;" class="caption"><td class="id">Table 15.2: </td><td
class="content">In-band data fields for <span
class="cmtt-12">pushPacket() </span>call</td></tr></table><!--tex4ht:label?: x17-211001r2 -->
</td></tr></table></div><hr class="endfloat" />
</div>
<!--l. 24--><p class="noindent" >In the case of file transfers, the arguments are shown in <a
href="#x17-21100015.4">Table 15.4</a>.
<div class="table">
<!--l. 27--><p class="noindent" ><a
id="x17-211002r3"></a><hr class="float"><div class="float"
><table class="float"><tr class="float"><td class="float"
>
<div class="tabular"> <table id="TBL-3" class="tabular"
cellspacing="0" cellpadding="0" rules="groups"
><colgroup id="TBL-3-1g"><col
id="TBL-3-1"></colgroup><colgroup id="TBL-3-2g"><col
id="TBL-3-2"></colgroup><colgroup id="TBL-3-3g"><col
id="TBL-3-3"></colgroup><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-3-1-"><td style="white-space:wrap; text-align:left;" id="TBL-3-1-1"
class="td11"> <!--l. 31--><p class="noindent" ><span
class="cmbx-12">Name</span> </td><td style="white-space:nowrap; text-align:left;" id="TBL-3-1-2"
class="td11"> <span
class="cmbx-12">Type </span></td><td style="white-space:wrap; text-align:left;" id="TBL-3-1-3"
class="td11"> <!--l. 31--><p class="noindent" ><span
class="cmbx-12">Description</span> </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-3-2-"><td style="white-space:wrap; text-align:left;" id="TBL-3-2-1"
class="td11"> <!--l. 33--><p class="noindent" >Uniform
Resource
Locator (<a
href="mainap3.html#url">URL</a>) </td><td style="white-space:nowrap; text-align:left;" id="TBL-3-2-2"
class="td11"> string </td><td style="white-space:wrap; text-align:left;" id="TBL-3-2-3"
class="td11"> <!--l. 33--><p class="noindent" >The <a
href="mainap3.html#url">URL</a> describing the file.
Appropriate schemes for the
<a
href="mainap3.html#url">URL</a>s are file:// and <a
href="mainap3.html#sca">SCA</a>://. The
file scheme applies to the local
file system, while the <a
href="mainap3.html#sca">SCA</a> scheme
applies to the <a
href="mainap3.html#sca">SCA</a> <a
href="mainli2.html#glo:filemanager">File Manager</a>. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-3-3-"><td style="white-space:wrap; text-align:left;" id="TBL-3-3-1"
class="td11"> <!--l. 35--><p class="noindent" >T </td><td style="white-space:nowrap; text-align:left;" id="TBL-3-3-2"
class="td11"> PrecisionUTCTime </td><td style="white-space:wrap; text-align:left;" id="TBL-3-3-3"
class="td11"> <!--l. 35--><p class="noindent" >The epoch birth date of the first
sample of the sequence passed in
this call. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-3-4-"><td style="white-space:wrap; text-align:left;" id="TBL-3-4-1"
class="td11"> <!--l. 37--><p class="noindent" ><a
href="mainap3.html#eos">EOS</a> </td><td style="white-space:nowrap; text-align:left;" id="TBL-3-4-2"
class="td11"> boolean </td><td style="white-space:wrap; text-align:left;" id="TBL-3-4-3"
class="td11"> <!--l. 37--><p class="noindent" >Flag describing whether this
particular stream ends with this
<span
class="cmtt-12">pushPacket() </span>call. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-3-5-"><td style="white-space:wrap; text-align:left;" id="TBL-3-5-1"
class="td11"> <!--l. 39--><p class="noindent" >streamID </td><td style="white-space:nowrap; text-align:left;" id="TBL-3-5-2"
class="td11"> string </td><td style="white-space:wrap; text-align:left;" id="TBL-3-5-3"
class="td11"> <!--l. 39--><p class="noindent" >Stream ID for this particular
payload. This string is used to
reconcile this sequence of data
with a particular Stream <a
href="mainap3.html#sri">SRI</a>
data structure. </td>
</tr></table></div>
<br /> <table class="caption"
><tr style="vertical-align:baseline;" class="caption"><td class="id">Table 15.3: </td><td
class="content">Data fields for <span
class="cmtt-12">pushPacket() </span>call in file transfers</td></tr></table><!--tex4ht:label?: x17-211002r3 -->
</td></tr></table></div><hr class="endfloat" />
</div>
<!--l. 44--><p class="noindent" >As many <span
class="cmtt-12">pushPacket() </span>calls can happen as are needed to transfer data from a uses side to a
provides side. If using omniORB (this is the REDHAWK default), there is maximum
transfer size, which can be is set in the <span
class="cmtt-12">/etc/omniORB.cfg </span>file by changing the defined
value for <span
class="cmtt-12">giopMaxMsgSize</span>. The default maximum transfer size is set to <span
class="cmtt-12">2097152 </span>(2
Megabyte (<a
href="mainap3.html#mb">MB</a>)). For every <span
class="cmtt-12">pushPacket()</span>, the data+headers must be less than this
value, otherwise a <span
class="cmtt-12">MARSHAL </span>exception will be raise by the middleware. The maximum
value can be found during run time by using the <span
class="cmtt-12">omniORB::giopMaxMsgSize() </span>function
call.
<h3 class="sectionHead"><span class="titlemark">15.5 </span> <a
id="x17-21200015.5"></a>Data File Guidance</h3>
<!--l. 3--><p class="noindent" >Data files may be sent via the <a
href="mainap3.html#bulkio">BulkIO</a> <span
class="cmtt-12">dataFile </span>type. When using the <a
href="mainap3.html#bulkio">BulkIO</a> <span
class="cmtt-12">dataFile </span>type, a
filename is passed to the <span
class="cmtt-12">pushPacket() </span>method. The location of the file is specified by a Uniform
Resource Identifier (<a
href="mainap3.html#uri">URI</a>) that either points to the local file system or the <a
href="mainap3.html#sdr">SDR</a> file system. In
order to support portability, use of the <a
href="mainap3.html#sdr">SDR</a> file system is recommended.
<!--l. 9--><p class="noindent" >The following table describes in greater detail the <a
href="mainap3.html#uri">URI</a> options.
<table id="TBL-6" class="tabular"
cellspacing="0" cellpadding="0" rules="groups"
><colgroup id="TBL-6-1g"><col
id="TBL-6-1"></colgroup><colgroup id="TBL-6-2g"><col
id="TBL-6-2"></colgroup><colgroup id="TBL-6-3g"><col
id="TBL-6-3"></colgroup><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-6-1-"><td style="white-space:nowrap; text-align:left;" id="TBL-6-1-1"
class="td11"> <span
class="cmbx-12">Protocol </span></td><td style="white-space:wrap; text-align:left;" id="TBL-6-1-2"
class="td11"> <!--l. 20--><p class="noindent" ><span
class="cmbx-12">Format</span> </td><td style="white-space:wrap; text-align:left;" id="TBL-6-1-3"
class="td11"> <!--l. 20--><p class="noindent" ><span
class="cmbx-12">Description</span> </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-6-2-"><td style="white-space:nowrap; text-align:left;" id="TBL-6-2-1"
class="td11"> file </td><td style="white-space:wrap; text-align:left;" id="TBL-6-2-2"
class="td11"> <!--l. 20--><p class="noindent" ><span
class="cmtt-12">file://[localhost]/</span><span
class="cmmi-12"><</span><span
class="cmtt-12">path</span><span
class="cmmi-12">></span> </td><td style="white-space:wrap; text-align:left;" id="TBL-6-2-3"
class="td11"> <!--l. 20--><p class="noindent" >A host specific absolute path of
the deployed
<a
href="mainli2.html#glo:component">Component</a>/<a
href="mainli2.html#glo:device">Device</a>/<a
href="mainli2.html#glo:service">Service</a>. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-6-3-"><td style="white-space:nowrap; text-align:left;" id="TBL-6-3-1"
class="td11"> sdr </td><td style="white-space:wrap; text-align:left;" id="TBL-6-3-2"
class="td11"> <!--l. 20--><p class="noindent" ><span
class="cmtt-12">sdr://[</span><a
href="mainap3.html#ior"><span
class="cmtt-12">IOR</span></a><span
class="cmtt-12">]/</span><span
class="cmmi-12"><</span><span
class="cmtt-12">path</span><span
class="cmmi-12">></span> </td><td style="white-space:wrap; text-align:left;" id="TBL-6-3-3"
class="td11"> <!--l. 20--><p class="noindent" >A path on the <a
href="mainli2.html#glo:domainmanager">Domain Manager</a>’s
file system. If the optional <a
href="mainap3.html#ior">IOR</a> is
provided, this path provides the
reference to the <a
href="mainli2.html#glo:domainmanager">Domain Manager</a>.
If not
provided, the <a
href="mainli2.html#glo:domainmanager">Domain Manager</a>
should be default used by the
<a
href="mainli2.html#glo:component">Component</a>/<a
href="mainli2.html#glo:device">Device</a>/<a
href="mainli2.html#glo:service">Service</a> </td>
</tr></table>
<!--l. 1--><p class="noindent" >
<h3 class="sectionHead"><span class="titlemark">15.6 </span> <a
id="x17-21300015.6"></a>Link Statistics</h3>
<!--l. 3--><p class="noindent" >All <a
href="mainap3.html#bulkio">BulkIO</a> <a
href="mainli2.html#glo:port">Ports</a> contain a read only attribute called statistics. The statistics attribute is of type
<span
class="cmtt-12">BULKIO::PortStatistics</span>, and it contains information regarding the performance of the <a
href="mainli2.html#glo:port">Port</a>.
<a
href="#x17-213001r4">Table 15.4</a> contains a description of a statistics structure
<div class="table">
<!--l. 8--><p class="noindent" ><a
id="x17-213001r4"></a><hr class="float"><div class="float"
><table class="float"><tr class="float"><td class="float"
>
<div class="tabular"> <table id="TBL-7" class="tabular"
cellspacing="0" cellpadding="0" rules="groups"
><colgroup id="TBL-7-1g"><col
id="TBL-7-1"></colgroup><colgroup id="TBL-7-2g"><col
id="TBL-7-2"></colgroup><colgroup id="TBL-7-3g"><col
id="TBL-7-3"></colgroup><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-1-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-1-1"
class="td11"> <span
class="cmbx-12">Name </span></td><td style="white-space:wrap; text-align:left;" id="TBL-7-1-2"
class="td11"> <!--l. 11--><p class="noindent" ><span
class="cmbx-12">Type</span> </td><td style="white-space:wrap; text-align:left;" id="TBL-7-1-3"
class="td11"> <!--l. 11--><p class="noindent" ><span
class="cmbx-12">Description</span> </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-2-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-2-1"
class="td11"> portName </td><td style="white-space:wrap; text-align:left;" id="TBL-7-2-2"
class="td11"> <!--l. 12--><p class="noindent" >string </td><td style="white-space:wrap; text-align:left;" id="TBL-7-2-3"
class="td11"> <!--l. 12--><p class="noindent" >Name of this <a
href="mainli2.html#glo:port">Port</a> </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-3-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-3-1"
class="td11"> elementsPerSecond </td><td style="white-space:wrap; text-align:left;" id="TBL-7-3-2"
class="td11"> <!--l. 13--><p class="noindent" >float </td><td style="white-space:wrap; text-align:left;" id="TBL-7-3-3"
class="td11"> <!--l. 13--><p class="noindent" >A moving average describing
the rate at which elements are
arriving. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-4-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-4-1"
class="td11"> bitsPerSecond </td><td style="white-space:wrap; text-align:left;" id="TBL-7-4-2"
class="td11"> <!--l. 14--><p class="noindent" >float </td><td style="white-space:wrap; text-align:left;" id="TBL-7-4-3"
class="td11"> <!--l. 14--><p class="noindent" >This should be the same as
elementsPerSecond * bits per
elements. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-5-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-5-1"
class="td11"> callsPerSecond </td><td style="white-space:wrap; text-align:left;" id="TBL-7-5-2"
class="td11"> <!--l. 15--><p class="noindent" >float </td><td style="white-space:wrap; text-align:left;" id="TBL-7-5-3"
class="td11"> <!--l. 15--><p class="noindent" >Number of <span
class="cmtt-12">pushPacket() </span>calls
per second. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-6-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-6-1"
class="td11"> streamIDs </td><td style="white-space:wrap; text-align:left;" id="TBL-7-6-2"
class="td11"> <!--l. 16--><p class="noindent" >CF::StringSequence </td><td style="white-space:wrap; text-align:left;" id="TBL-7-6-3"
class="td11"> <!--l. 16--><p class="noindent" >List of all stream ids where a
<span
class="cmtt-12">pushSRI() </span>has occurred but no
<a
href="mainap3.html#eos">EOS</a> has been received. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-7-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-7-1"
class="td11"> averageQueueDepth </td><td style="white-space:wrap; text-align:left;" id="TBL-7-7-2"
class="td11"> <!--l. 17--><p class="noindent" >float </td><td style="white-space:wrap; text-align:left;" id="TBL-7-7-3"
class="td11"> <!--l. 17--><p class="noindent" >Moving average calculation of the
percentage queue depth. </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-8-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-8-1"
class="td11"> timeSinceLastCall </td><td style="white-space:wrap; text-align:left;" id="TBL-7-8-2"
class="td11"> <!--l. 18--><p class="noindent" >float </td><td style="white-space:wrap; text-align:left;" id="TBL-7-8-3"
class="td11"> <!--l. 18--><p class="noindent" >The
elapsed time, in seconds, since the
last packet was transferred via a
<span
class="cmtt-12">pushPacket() </span>call </td>
</tr><tr
class="hline"><td><hr></td><td><hr></td><td><hr></td></tr><tr
style="vertical-align:baseline;" id="TBL-7-9-"><td style="white-space:nowrap; text-align:left;" id="TBL-7-9-1"
class="td11"> keywords </td><td style="white-space:wrap; text-align:left;" id="TBL-7-9-2"
class="td11"> <!--l. 19--><p class="noindent" >sequence
<span
class="cmmi-12"><</span>CF::DataType<span
class="cmmi-12">></span> </td><td style="white-space:wrap; text-align:left;" id="TBL-7-9-3"
class="td11"> <!--l. 19--><p class="noindent" >Additional statistics information
provided by the <a
href="mainli2.html#glo:port">Port</a>. </td>
</tr></table></div>
<br /> <table class="caption"
><tr style="vertical-align:baseline;" class="caption"><td class="id">Table 15.4: </td><td
class="content">Fields in returned link statistics</td></tr></table><!--tex4ht:label?: x17-213001r4 -->
</td></tr></table></div><hr class="endfloat" />
</div>
<!--l. 25--><p class="noindent" >The provides-side <a
href="mainli2.html#glo:port">Port</a> contains a single <span
class="cmtt-12">PortStatistics </span>structure. The uses-side <a
href="mainli2.html#glo:port">Port</a>
contains a sequence of <span
class="cmtt-12">PortStatistics </span>structures; each one associated with a single
connection.
<!--l. 28--><p class="noindent" >An interesting exercise is to create <a
href="mainli2.html#glo:component">Components</a> that generate and consume data in the three
languages supported by REDHAWK. The data generator and consumer should generate/consume
data as fast as possible. The statistics data structure can provide metrics regarding data transfer
rates, average latency, and other relevant data. Shifting the transfer length (by changing the size of
the sequence in the <span
class="cmtt-12">pushPacket() </span>call) and seeing its effects on the performance of the connection
is also instructive.
<h3 class="sectionHead"><span class="titlemark">15.7 </span> <a
id="x17-21400015.7"></a>Examples</h3>
<!--l. 3--><p class="noindent" >These two examples illustrate high-speed data exchange between two C++ <a
href="mainli2.html#glo:component">Components</a> and basic
data manipulation through the Sandbox
<!--l. 5--><p class="noindent" >
<h4 class="subsectionHead"><span class="titlemark">15.7.1 </span> <a
id="x17-21500015.7.1"></a>High-speed data</h4>
<!--l. 7--><p class="noindent" >In this example, two C++ <a
href="mainli2.html#glo:component">Components</a> are created: a source and a sink. We will then deploy these
<a
href="mainli2.html#glo:component">Components</a> through the Sandbox and evaluate the statistics of the data transfer between
them.
<!--l. 10--><p class="noindent" >
<ol class="enumerate1" >
<li
class="enumerate" id="x17-215002x1">Create a C++ <a
href="mainli2.html#glo:component">Component</a> called <span
class="cmti-12">source </span>with a uses <a
href="mainli2.html#glo:port">Port</a> called <span
class="cmti-12">output </span>of type
<span
class="cmti-12">dataShort</span>. Add a simple <a
href="mainli2.html#glo:property">Property</a> with <a
href="mainap3.html#id">ID</a> <span
class="cmti-12">xfer</span><span
class="cmti-12">_length</span>, type <span
class="cmti-12">ulong</span>, and default value
of <span
class="cmti-12">100000</span>. Generate the <a
href="mainli2.html#glo:component">Component</a> code.
</li>
<li
class="enumerate" id="x17-215004x2">Open the file <span
class="cmtt-12">source.h </span>and add the following member to the <span
class="cmtt-12">source</span><span
class="cmtt-12">_i </span>class: <script type="syntaxhighlighter" class="brush: cpp"><![CDATA[
std::vector<short> data;
]]></script>
</li>
<li
class="enumerate" id="x17-215006x3">Open the file <span
class="cmtt-12">source.cpp </span>and edit it in the following ways:
<ul class="itemize1">
<li class="itemize">In the <span
class="cmtt-12">source</span><span
class="cmtt-12">_i </span>constructor:</li></ul>
<script type="syntaxhighlighter" class="brush: cpp"><![CDATA[
data.resize(0);
<!--l. 22--><p class="noindent" >]]></script>
</li>
<li
class="enumerate" id="x17-215008x4">In <span
class="cmtt-12">serviceFunction() </span>comment-out the <span
class="cmtt-12">LOG</span><span
class="cmtt-12">_DEBUG </span>statement and add the following lines: <script type="syntaxhighlighter" class="brush: cpp"><![CDATA[
if (data.size() != this->xfer_length) {
data.resize(xfer_length);
BULKIO::StreamSRI sri = BULKIO::StreamSRI();
sri.hversion = 1;
sri.xstart = 0.0;
sri.xdelta = 0.0;
sri.xunits = BULKIO::UNITS_TIME;
sri.subsize = 0;
sri.ystart = 0.0;
sri.ydelta = 0.0;
sri.yunits = BULKIO::UNITS_NONE;
sri.mode = 0;
sri.streamID = "sample";
this->output->pushSRI(sri);
}
BULKIO::PrecisionUTCTime tstamp =
BULKIO::PrecisionUTCTime();
tstamp.tcmode = BULKIO::TCM_CPU;
tstamp.tcstatus = (short)1;
tstamp.toff = 0.0;
tstamp.twsec = 0.0;
tstamp.tfsec = 0.0;
this->output->pushPacket(data,tstamp,false,"sample");
return NORMAL;
]]></script>
</li>
<li
class="enumerate" id="x17-215010x5">Compile the <a
href="mainli2.html#glo:component">Component</a> <span
class="cmtt-12">source </span>and install it on Target SDR.
</li>
<li
class="enumerate" id="x17-215012x6">Create a C++ <a
href="mainli2.html#glo:component">Component</a> called <span
class="cmti-12">sink </span>with a provides <a
href="mainli2.html#glo:port">Port</a> called <span
class="cmti-12">input </span>of type <span
class="cmti-12">dataShort</span>.
Generate the <a
href="mainli2.html#glo:component">Component</a> code.
</li>
<li
class="enumerate" id="x17-215014x7">Open the file <span
class="cmtt-12">sink.cpp </span>and edit it in the following ways:
<ol class="enumerate2" >
<li
class="enumerate" id="x17-215016x1">In <span
class="cmtt-12">serviceFunction()</span>, comment-out the <span
class="cmtt-12">LOG</span><span
class="cmtt-12">_DEBUG </span>statement
</li>
<li
class="enumerate" id="x17-215018x2">Add the following lines: <script type="syntaxhighlighter" class="brush: cpp"><![CDATA[
::BULKIO_dataShort_In_i::dataTransfer *tmp =
this->input->getPacket(-1);
if (tmp == NULL) {
return NOOP;
} else {
delete tmp;
return NORMAL;
}
]]></script>
</li></ol>
</li>
<li
class="enumerate" id="x17-215020x8">Compile the <a
href="mainli2.html#glo:component">Component</a> <span
class="cmtt-12">sink </span>and install it on Target SDR.
<!--l. 72--><p class="noindent" >Start a Python session in a command line terminal and run the following commands:</li></ol>
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
>>> from ossie.utils import sb
>>> source = sb.Component("source")
>>> sink = sb.Component("sink")
>>> source.connect(sink)
>>> sb.start()
>>> print source._ports[0]._get_statistics()[0].statistics
]]></script>
<!--l. 84--><p class="noindent" >The output of the print statement is an instance of the <span
class="cmtt-12">PortStatistics </span>structure in <a
href="mainap3.html#bulkio">BulkIO</a>. This
structure contains the statistics gathered from this connection. A measure of data rate is bits per
second.
<!--l. 88--><p class="noindent" >To display the number of Gigabits per second, run the following command:
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
>>> print source._ports[0]._get_statistics()[0].\
... statistics.bitsPerSecond/1e9
]]></script>
<!--l. 95--><p class="noindent" >The resulting value is the measured data transfer rate between the two <a
href="mainli2.html#glo:component">Components</a>. The current
<span
class="cmtt-12">xfer</span><span
class="cmtt-12">_length </span><a
href="mainli2.html#glo:property">Property</a> can be viewed by typing the following:
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
>>> source.xfer_length
]]></script>
<!--l. 102--><p class="noindent" >The default value is <span
class="cmtt-12">100000</span>. Update the <a
href="mainli2.html#glo:property">Property</a> to <span
class="cmtt-12">200000 </span>by running the following
command:
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
>>> source.xfer_length = 200000
]]></script>
<!--l. 108--><p class="noindent" >Check the new data rate by repeating the call to <span
class="cmtt-12">_get</span><span
class="cmtt-12">_statistics()</span>. The resulting data rate
should now be different.
<!--l. 111--><p class="noindent" >
<h4 class="subsectionHead"><span class="titlemark">15.7.2 </span> <a
id="x17-21600015.7.2"></a>Data manipulation</h4>
<!--l. 113--><p class="noindent" >In this example, a Python <a
href="mainli2.html#glo:component">Component</a> is created that takes vectors of floats as inputs, multiplies
the vector by some arbitrary number, and then outputs the resulting vector. This example
demonstrates some basic data manipulation as well as the interaction between the Python
environment and the running <a
href="mainli2.html#glo:component">Component</a>.
<!--l. 115--><p class="noindent" >
<ol class="enumerate1" >
<li
class="enumerate" id="x17-216002x1">Create a Python <a
href="mainli2.html#glo:component">Component</a> called <span
class="cmti-12">mult </span>with a provides <a
href="mainli2.html#glo:port">Port</a> called <span
class="cmti-12">input </span>of type
<span
class="cmti-12">dataFloat </span>and a uses <a
href="mainli2.html#glo:port">Port</a> called <span
class="cmti-12">output </span>of type <span
class="cmti-12">dataFloat</span>. Add a simple <a
href="mainli2.html#glo:property">Property</a> with
<a
href="mainap3.html#id">ID</a> <span
class="cmti-12">factor</span>, type <span
class="cmti-12">float</span>, and default value of <span
class="cmti-12">1</span>. Generate the <a
href="mainli2.html#glo:component">Component</a> code.
</li>
<li
class="enumerate" id="x17-216004x2">Open the file <span
class="cmtt-12">mult.py </span>and add the following lines:
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
data, T, EOS, streamID, sri, sriChanged, inputQueueFlushed =
self.port_input.getPacket()
if data == None:
return NOOP
outData = []
for value in data:
outData.append(value*self.factor)
if sriChanged:
self.port_output.pushSRI(sri)
self.port_output.pushPacket(outData, T, EOS, streamID)
return NORMAL
]]></script>
</li>
<li
class="enumerate" id="x17-216006x3">Save the project and drag the <span
class="cmtt-12">mult </span>project to SCA Explorer<span
class="cmmi-12">> </span>Target SDR.
</li>
<li
class="enumerate" id="x17-216008x4">Start a Python session in a command line terminal and run the following commands:
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
>>> from ossie.utils import sb
>>> mult = sb.Component("mult")
>>> source = sb.DataSource(dataFormat="float")
>>> sink = sb.DataSink()
>>> source.connect(mult)
>>> mult.connect(sink)
>>> sb.start()
>>> source.push([1,2,3,4,5])
>>> sink.getData()
[1.0, 2.0, 3.0, 4.0, 5.0]
]]></script>
</li>
<li
class="enumerate" id="x17-216010x5">The multiplication factor can be changed while the Sandbox is up.
<script type="syntaxhighlighter" class="brush: python"><![CDATA[
>>> mult.factor = 2
>>> source.push([1,2,3,4,5])
>>> sink.getData()
[2.0, 4.0, 6.0, 8.0, 10.0]
]]></script>
</li></ol>
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