docs: add project description and server setup instructions to README

esp/microcoapy/coap_writer.py

@@ -0,0 +1,67 @@
+from .coap_macros import _BUF_MAX_SIZE
+from .coap_macros import COAP_VERSION
+
+
+def CoapOptionDelta(v):
+    if v < 13:
+        return (0xFF & v)
+    elif v <= 0xFF + 13:
+        return 13
+    else:
+        return 14
+
+
+def writePacketHeaderInfo(buffer, packet):
+    buffer.append(COAP_VERSION.COAP_VERSION_1 << 6)
+    buffer[0] |= (packet.type & 0x03) << 4
+    tokenLength = 0
+    if (packet.token is not None) and (len(packet.token) <= 0x0F):
+        tokenLength = len(packet.token)
+
+    buffer[0] |= (tokenLength & 0x0F)
+    buffer.append(packet.method)
+    buffer.append(packet.messageid >> 8)
+    buffer.append(packet.messageid & 0xFF)
+
+    if tokenLength > 0:
+        buffer.extend(packet.token)
+
+
+def writePacketOptions(buffer, packet):
+    runningDelta = 0
+    for opt in sorted(packet.options, key=lambda x: x.number):
+        if (opt is None) or (opt.buffer is None) or (len(opt.buffer) == 0):
+            continue
+
+        optBufferLen = len(opt.buffer)
+
+        if (len(buffer) + 5 + optBufferLen) >= _BUF_MAX_SIZE:
+            return 0
+
+        optdelta = opt.number - runningDelta
+        delta = CoapOptionDelta(optdelta)
+        length = CoapOptionDelta(optBufferLen)
+
+        buffer.append(0xFF & (delta << 4 | length))
+        if delta == 13:
+            buffer.append(optdelta - 13)
+        elif delta == 14:
+            buffer.append((optdelta - 269) >> 8)
+            buffer.append(0xFF & (optdelta - 269))
+
+        if length == 13:
+            buffer.append(optBufferLen - 13)
+        elif length == 14:
+            buffer.append(optBufferLen >> 8)
+            buffer.append(0xFF & (optBufferLen - 269))
+
+        buffer.extend(opt.buffer)
+        runningDelta = opt.number
+
+
+def writePacketPayload(buffer, packet):
+    if (packet.payload is not None) and (len(packet.payload)):
+        if (len(buffer) + 1 + len(packet.payload)) >= _BUF_MAX_SIZE:
+            return 0
+        buffer.append(0xFF)
+        buffer.extend(packet.payload)