Add python bindings + package (#10)

* wip : python package

* wip : minor fixes

* wip : upload package to main pypi

* wip : initial text encoding

* wip : extending C api

* wip : use map of global instances

* wip : added decode functionality

* update main README

bindings/python/ggwave.pyx

@@ -0,0 +1,65 @@
+cimport cython
+from cpython.mem cimport PyMem_Malloc, PyMem_Free
+
+import re
+import struct
+
+cimport cggwave
+
+def defaultParameters():
+    return cggwave.ggwave_defaultParameters()
+
+def init(parameters = None):
+    if (parameters is None):
+        parameters = defaultParameters()
+
+    return cggwave.ggwave_init(parameters)
+
+def free(instance):
+    return cggwave.ggwave_free(instance)
+
+def encode(payload, txProtocol = 1, volume = 10, instance = None):
+    """ Encode payload into an audio waveform.
+        @param {string} payload, the data to be encoded
+        @return Generated audio waveform bytes representing 16-bit signed integer samples.
+    """
+
+    cdef bytes data_bytes = payload.encode()
+    cdef char* cdata = data_bytes
+
+    cdef bytes output_bytes = bytes(1024*1024)
+    cdef char* coutput = output_bytes
+
+    own = False
+    if (instance is None):
+        own = True
+        instance = init(defaultParameters())
+
+    n = cggwave.ggwave_encode(instance, cdata, len(data_bytes), txProtocol, volume, coutput)
+
+    if (own):
+        free(instance)
+
+    # add short silence at the end
+    n += 16*1024
+
+    return struct.unpack("h"*n, output_bytes[0:2*n])
+
+def decode(instance, waveform):
+    """ Analyze and decode audio waveform to obtain original payload
+        @param {bytes} waveform, the audio waveform to decode
+        @return The decoded payload if successful.
+    """
+
+    cdef bytes data_bytes = waveform
+    cdef char* cdata = data_bytes
+
+    cdef bytes output_bytes = bytes(256)
+    cdef char* coutput = output_bytes
+
+    rxDataLength = cggwave.ggwave_decode(instance, cdata, len(data_bytes), coutput)
+
+    if (rxDataLength > 0):
+        return coutput[0:rxDataLength]
+
+    return None