adding message head and message skip head blocks

grc/CMakeLists.txt

@@ -30,5 +30,7 @@ install(FILES
     text_input.xml
     text_output.xml
     meta_text_output.xml
+    skip_head.xml
+    head.xml
     DESTINATION share/gnuradio/grc/blocks
 )

grc/head.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0"?>
+<block>
+  <name>Message Head</name>
+  <key>pyqt_head</key>
+  <category>pyqt</category>
+  <import>import pyqt</import>
+  <make>pyqt.head($n)</make>
+
+  <param>
+    <name>N</name>
+    <key>n</key>
+    <value>10</value>
+    <type>int</type>
+  </param>
+
+  <sink>
+    <name>pdus</name>
+    <type>message</type>
+    <optional>1</optional>
+  </sink>
+
+  <source>
+    <name>pdus</name>
+    <type>message</type>
+    <optional>1</optional>
+  </source>
+</block>

grc/skip_head.xml

@@ -0,0 +1,27 @@
+<?xml version="1.0"?>
+<block>
+  <name>Message Skip Head</name>
+  <key>pyqt_skip_head</key>
+  <category>pyqt</category>
+  <import>import pyqt</import>
+  <make>pyqt.skip_head($n)</make>
+
+  <param>
+    <name>N</name>
+    <key>n</key>
+    <value>10</value>
+    <type>int</type>
+  </param>
+
+  <sink>
+    <name>pdus</name>
+    <type>message</type>
+    <optional>1</optional>
+  </sink>
+
+  <source>
+    <name>pdus</name>
+    <type>message</type>
+    <optional>1</optional>
+  </source>
+</block>

python/CMakeLists.txt

@@ -44,6 +44,8 @@ GR_PYTHON_INSTALL(
     text_input.py
     text_output.py
     meta_text_output.py
+    head.py
+    skip_head.py
     DESTINATION ${GR_PYTHON_DIR}/pyqt
 )
 

python/__init__.py

@@ -60,6 +60,8 @@
 from text_input import *;
 from text_output import *;
 from meta_text_output import *;
+from skip_head import *
+from head import *
 
 # ----------------------------------------------------------------
 # Tail of workaround

python/head.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python
+#
+# Copyright 2014 Tim O'Shea
+#
+# This file is part of GNU Radio
+#
+# GNU Radio is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GNU Radio is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+import numpy
+from gnuradio import gr;
+import pmt
+
+class head(gr.sync_block):
+    def __init__(self, nitems):
+        self.nitems = nitems
+        gr.sync_block.__init__(self,"message_head",[],[])
+        self.message_port_register_in(pmt.intern("pdus"))
+        self.message_port_register_out(pmt.intern("pdus"))
+        self.set_msg_handler(pmt.intern("pdus"), self.handler)   
+
+    def handler(self, pdu):
+        meta = pmt.car(pdu)
+        vec = pmt.to_python(pmt.cdr(pdu))
+        vec = vec[0:self.nitems]
+        self.message_port_pub(pmt.intern("pdus"), pmt.cons( meta, pmt.to_pmt(vec) ) );
+
+    def work(self, input_items, output_items):
+        pass
+
+
+
+

python/skip_head.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python
+#
+# Copyright 2014 Tim O'Shea
+#
+# This file is part of GNU Radio
+#
+# GNU Radio is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GNU Radio is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNU Radio; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+import numpy
+from gnuradio import gr;
+import pmt
+
+class skip_head(gr.sync_block):
+    def __init__(self, nitems):
+        self.nitems = nitems
+        gr.sync_block.__init__(self,"message_skip_head",[],[])
+        self.message_port_register_in(pmt.intern("pdus"))
+        self.message_port_register_out(pmt.intern("pdus"))
+        self.set_msg_handler(pmt.intern("pdus"), self.handler)   
+
+    def handler(self, pdu):
+        meta = pmt.car(pdu)
+        vec = pmt.to_python(pmt.cdr(pdu))
+        vec = vec[self.nitems:]
+        self.message_port_pub(pmt.intern("pdus"), pmt.cons( meta, pmt.to_pmt(vec) ) );
+
+    def work(self, input_items, output_items):
+        pass
+
+
+
+