new

diff --git a/measure_energy_iot/buffer.py b/measure_energy_iot/buffer.py
new file mode 100644 (file)
index 0000000..373a777
--- /dev/null
+++ b/measure_energy_iot/buffer.py
@@ -0,0 +1,42 @@
+class Buffer:
+    def __init__(self,s):
+        '''Buffer a pre-created socket.
+        '''
+        self.sock = s
+        self.buffer = b''
+
+    def get_bytes(self,n):
+        '''Read exactly n bytes from the buffered socket.
+           Return remaining buffer if <n bytes remain and socket closes.
+        '''
+        while len(self.buffer) < n:
+            data = self.sock.recv(1024)
+            if not data:
+                data = self.buffer
+                self.buffer = b''
+                return data
+            self.buffer += data
+        # split off the message bytes from the buffer.
+        data,self.buffer = self.buffer[:n],self.buffer[n:]
+        return data
+
+    def put_bytes(self,data):
+        self.sock.sendall(data)
+
+    def get_utf8(self):
+        '''Read a null-terminated UTF8 data string and decode it.
+           Return an empty string if the socket closes before receiving a null.
+        '''
+        while b'\x00' not in self.buffer:
+            data = self.sock.recv(1024)
+            if not data:
+                return ''
+            self.buffer += data
+        # split off the string from the buffer.
+        data,_,self.buffer = self.buffer.partition(b'\x00')
+        return data.decode()
+
+    def put_utf8(self,s):
+        if '\x00' in s:
+            raise ValueError('string contains delimiter(null)')
+        self.sock.sendall(s.encode() + b'\x00')