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Initial commit of OpenSPARC T2 architecture model.
[OpenSPARC-T2-SAM] / sam-t2 / devtools / amd64 / html / python / ext / pure-embedding.html
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16<title>5.3 Pure Embedding </title>
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52
53<H1><A NAME="SECTION007300000000000000000"></A><A NAME="pure-embedding"></A>
54<BR>
555.3 Pure Embedding
56
57</H1>
58
59<P>
60The first program aims to execute a function in a Python
61script. Like in the section about the very high level interface,
62the Python interpreter does not directly interact with the
63application (but that will change in the next section).
64
65<P>
66The code to run a function defined in a Python script is:
67
68<P>
69<div class="verbatim">
70<pre>#include &lt;Python.h&gt;
71
72int
73main(int argc, char *argv[])
74{
75 PyObject *pName, *pModule, *pDict, *pFunc;
76 PyObject *pArgs, *pValue;
77 int i;
78
79 if (argc &lt; 3) {
80 fprintf(stderr,"Usage: call pythonfile funcname [args]&#92;n");
81 return 1;
82 }
83
84 Py_Initialize();
85 pName = PyString_FromString(argv[1]);
86 /* Error checking of pName left out */
87
88 pModule = PyImport_Import(pName);
89 Py_DECREF(pName);
90
91 if (pModule != NULL) {
92 pFunc = PyDict_GetAttrString(pModule, argv[2]);
93 /* pFunc is a new reference */
94
95 if (pFunc &amp;&amp; PyCallable_Check(pFunc)) {
96 pArgs = PyTuple_New(argc - 3);
97 for (i = 0; i &lt; argc - 3; ++i) {
98 pValue = PyInt_FromLong(atoi(argv[i + 3]));
99 if (!pValue) {
100 Py_DECREF(pArgs);
101 Py_DECREF(pModule);
102 fprintf(stderr, "Cannot convert argument&#92;n");
103 return 1;
104 }
105 /* pValue reference stolen here: */
106 PyTuple_SetItem(pArgs, i, pValue);
107 }
108 pValue = PyObject_CallObject(pFunc, pArgs);
109 Py_DECREF(pArgs);
110 if (pValue != NULL) {
111 printf("Result of call: %ld&#92;n", PyInt_AsLong(pValue));
112 Py_DECREF(pValue);
113 }
114 else {
115 Py_DECREF(pFunc);
116 Py_DECREF(pModule);
117 PyErr_Print();
118 fprintf(stderr,"Call failed&#92;n");
119 return 1;
120 }
121 }
122 else {
123 if (PyErr_Occurred())
124 PyErr_Print();
125 fprintf(stderr, "Cannot find function &#92;"%s&#92;"&#92;n", argv[2]);
126 }
127 Py_XDECREF(pFunc);
128 Py_DECREF(pModule);
129 }
130 else {
131 PyErr_Print();
132 fprintf(stderr, "Failed to load &#92;"%s&#92;"&#92;n", argv[1]);
133 return 1;
134 }
135 Py_Finalize();
136 return 0;
137}
138</pre>
139<div class="footer">
140<a href="run-func.txt" type="text/plain">Download as text (original file name: <span class="file">run-func.c</span>).</a>
141</div></div>
142
143<P>
144This code loads a Python script using <code>argv[1]</code>, and calls the
145function named in <code>argv[2]</code>. Its integer arguments are the other
146values of the <code>argv</code> array. If you compile and link this
147program (let's call the finished executable <b class="program">call</b>), and use
148it to execute a Python script, such as:
149
150<P>
151<div class="verbatim"><pre>
152def multiply(a,b):
153 print "Will compute", a, "times", b
154 c = 0
155 for i in range(0, a):
156 c = c + b
157 return c
158</pre></div>
159
160<P>
161then the result should be:
162
163<P>
164<div class="verbatim"><pre>
165$ call multiply multiply 3 2
166Will compute 3 times 2
167Result of call: 6
168</pre></div>
169<P>
170Although the program is quite large for its functionality, most of the
171code is for data conversion between Python and C, and for error
172reporting. The interesting part with respect to embedding Python
173starts with
174
175<P>
176<div class="verbatim"><pre>
177 Py_Initialize();
178 pName = PyString_FromString(argv[1]);
179 /* Error checking of pName left out */
180 pModule = PyImport_Import(pName);
181</pre></div>
182
183<P>
184After initializing the interpreter, the script is loaded using
185<tt class="cfunction">PyImport_Import()</tt>. This routine needs a Python string
186as its argument, which is constructed using the
187<tt class="cfunction">PyString_FromString()</tt> data conversion routine.
188
189<P>
190<div class="verbatim"><pre>
191 pFunc = PyObject_GetAttrString(pModule, argv[2]);
192 /* pFunc is a new reference */
193
194 if (pFunc &amp;&amp; PyCallable_Check(pFunc)) {
195 ...
196 }
197 Py_XDECREF(pFunc);
198</pre></div>
199
200<P>
201Once the script is loaded, the name we're looking for is retrieved
202using <tt class="cfunction">PyObject_GetAttrString()</tt>. If the name exists, and
203the object returned is callable, you can safely assume that it is a
204function. The program then proceeds by constructing a tuple of
205arguments as normal. The call to the Python function is then made
206with:
207
208<P>
209<div class="verbatim"><pre>
210 pValue = PyObject_CallObject(pFunc, pArgs);
211</pre></div>
212
213<P>
214Upon return of the function, <code>pValue</code> is either <tt class="constant">NULL</tt> or it
215contains a reference to the return value of the function. Be sure to
216release the reference after examining the value.
217
218<P>
219
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234<td align="center" width="100%">Extending and Embedding the Python Interpreter</td>
235<td class='online-navigation'><a rel="contents" title="Table of Contents"
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237 border='0' height='32' alt='Contents' width='32' /></A></td>
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250</div>
251</div>
252<hr />
253<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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Full OpenSPARC architecture tarball including simulator, hypervisor, and OBP.