Diff: c_api/framing.c

Revision:

5:cd94bb58e096

Parent:

3:37d2d127bc83

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/c_api/framing.c	Wed Mar 09 12:15:13 2016 +0000
@@ -0,0 +1,183 @@
+#include "framing.h"
+
+typedef enum _state
+{
+  IDLE, // No incoming frame is in process
+  ESCAPING, // incoming frame in process, next character to be escaped
+  ACTIVE // frame in process
+} _state ;
+
+typedef struct storage storage;
+struct storage
+{
+   uint8_t * ptr;
+   uint32_t size;
+   uint32_t cursor;
+
+};
+
+static storage incomingStorage;
+static storage outgoingStorage;
+
+int8_t safe_append(storage * s, uint8_t byte);
+
+static uint8_t SOF_;
+static uint8_t EOF_;
+static uint8_t ESC_;
+
+static _state incoming_state;
+
+void (*on_incoming_frame_cb)(uint8_t * storage, uint32_t occupiedSize);
+void (*on_error_cb)(int32_t errCode);
+
+void initialize_framing()
+{
+  incomingStorage.ptr = NULL;
+  outgoingStorage.ptr = NULL;
+
+  incomingStorage.size = 0;
+  outgoingStorage.size = 0;
+
+  incomingStorage.cursor = 0;
+  incomingStorage.cursor = 0;
+
+  SOF_ = 0xF7;
+  EOF_ = 0x7F;
+  ESC_ = 0x7D;
+
+  incoming_state = IDLE;
+}
+
+void outgoing_storage(uint8_t * buf, uint32_t bufSize)
+{
+  outgoingStorage.ptr = buf;
+  outgoingStorage.size = bufSize;
+}
+
+void begin()
+{
+  if(outgoingStorage.size == 0 || outgoingStorage.ptr == NULL)
+    return;
+
+  outgoingStorage.cursor = 0;
+
+  // Should not fail
+  safe_append(&outgoingStorage,SOF_);
+}
+
+void append(uint8_t byte)
+{
+  if(outgoingStorage.size == 0 || outgoingStorage.ptr == NULL)
+    return;
+
+  // byte == to flag, need to escape it
+  if(byte == SOF_ || byte == EOF_ || byte == ESC_)
+  {
+    if(!safe_append(&outgoingStorage,ESC_))
+      return;
+  }
+
+  if(!safe_append(&outgoingStorage,byte))
+    return;
+}
+
+void append2(uint16_t twobytes)
+{
+  uint8_t * ptr = (uint8_t*)(&twobytes);
+  append(ptr[0]);
+  append(ptr[1]);
+}
+
+void append4(uint32_t fourbytes)
+{
+  uint8_t * ptr = (uint8_t*)(&fourbytes);
+  append(ptr[0]);
+  append(ptr[1]);
+  append(ptr[2]);
+  append(ptr[3]);
+}
+
+uint32_t end()
+{
+  if(outgoingStorage.size == 0 || outgoingStorage.ptr == NULL)
+    return 0;
+
+  if(!safe_append(&outgoingStorage,EOF_))
+    return 0;
+
+  return outgoingStorage.cursor;
+}
+
+void incoming_storage(uint8_t * buf, uint32_t bufSize)
+{
+  incomingStorage.ptr = buf;
+  incomingStorage.size = bufSize;
+}
+
+void set_on_incoming_frame(void (*callback)(uint8_t * storage, uint32_t occupiedSize))
+{
+  on_incoming_frame_cb = callback;
+}
+
+void set_on_incoming_error(void (*callback)(int32_t errCode))
+{
+  on_error_cb = callback;
+}
+
+void feed(uint8_t byte)
+{
+  if(incomingStorage.size == 0 || incomingStorage.ptr == NULL)
+    return;
+
+  if(incoming_state == ESCAPING)
+  {
+    if(!safe_append(&incomingStorage,byte))
+    {
+      incoming_state = IDLE;
+      return;
+    }
+    incoming_state = ACTIVE;
+    return;
+  }
+
+  if(byte == SOF_)
+  {
+      incoming_state = ACTIVE;
+      incomingStorage.cursor = 0;
+      return;
+  }
+
+  if(incoming_state == ACTIVE)
+  {
+    if(byte == EOF_)
+    {
+        incoming_state = IDLE;
+        on_incoming_frame_cb(incomingStorage.ptr, incomingStorage.cursor);
+    }
+    // Escape next character
+    else if(byte == ESC_)
+    {
+        incoming_state = ESCAPING;
+    }
+    else
+    {
+      if(!safe_append(&incomingStorage,byte))
+      {
+        incoming_state = IDLE;
+        return;
+      }
+      incoming_state = ACTIVE;
+    }
+  }
+}
+
+int8_t safe_append(storage * s, uint8_t byte)
+{
+  // Not enough space for 1 more character
+  if(s->cursor + 1 >= s->size)
+    return 0;
+
+  s->ptr[s->cursor++] = byte;
+
+  return 1;
+}