1 files changed, 145 insertions, 0 deletions
diff --git a/quantum/serial_link/protocol/byte_stuffer.c b/quantum/serial_link/protocol/byte_stuffer.c
new file mode 100644
index 0000000000..fb4c45a8dc
--- /dev/null
+++ b/quantum/serial_link/protocol/byte_stuffer.c
@@ -0,0 +1,145 @@
+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 Fred Sundvik
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "serial_link/protocol/byte_stuffer.h"
+#include "serial_link/protocol/frame_validator.h"
+#include "serial_link/protocol/physical.h"
+#include <stdbool.h>
+
+// This implements the "Consistent overhead byte stuffing protocol"
+// https://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing
+// http://www.stuartcheshire.org/papers/COBSforToN.pdf
+
+#define MAX_FRAME_SIZE 1024
+#define NUM_LINKS 2
+
+typedef struct byte_stuffer_state {
+    uint16_t next_zero;
+    uint16_t data_pos;
+    bool long_frame;
+    uint8_t data[MAX_FRAME_SIZE];
+}byte_stuffer_state_t;
+
+static byte_stuffer_state_t states[NUM_LINKS];
+
+void init_byte_stuffer_state(byte_stuffer_state_t* state) {
+    state->next_zero = 0;
+    state->data_pos = 0;
+    state->long_frame = false;
+}
+
+void init_byte_stuffer(void) {
+    int i;
+    for (i=0;i<NUM_LINKS;i++) {
+        init_byte_stuffer_state(&states[i]);
+    }
+}
+
+void byte_stuffer_recv_byte(uint8_t link, uint8_t data) {
+    byte_stuffer_state_t* state = &states[link];
+    // Start of a new frame
+    if (state->next_zero == 0) {
+        state->next_zero = data;
+        state->long_frame = data == 0xFF;
+        state->data_pos = 0;
+        return;
+    }
+
+    state->next_zero--;
+    if (data == 0) {
+        if (state->next_zero == 0) {
+            // The frame is completed
+            if (state->data_pos > 0) {
+                validator_recv_frame(link, state->data, state->data_pos);
+            }
+        }
+        else {
+            // The frame is invalid, so reset
+            init_byte_stuffer_state(state);
+        }
+    }
+    else {
+        if (state->data_pos == MAX_FRAME_SIZE) {
+            // We exceeded our maximum frame size
+            // therefore there's nothing else to do than reset to a new frame
+            state->next_zero = data;
+            state->long_frame = data == 0xFF;
+            state->data_pos = 0;
+        }
+        else if (state->next_zero == 0) {
+            if (state->long_frame) {
+                // This is part of a long frame, so continue
+                state->next_zero = data;
+                state->long_frame = data == 0xFF;
+            }
+            else {
+                // Special case for zeroes
+                state->next_zero = data;
+                state->data[state->data_pos++] = 0;
+            }
+        }
+        else {
+            state->data[state->data_pos++] = data;
+        }
+    }
+}
+
+static void send_block(uint8_t link, uint8_t* start, uint8_t* end, uint8_t num_non_zero) {
+    send_data(link, &num_non_zero, 1);
+    if (end > start) {
+        send_data(link, start, end-start);
+    }
+}
+
+void byte_stuffer_send_frame(uint8_t link, uint8_t* data, uint16_t size) {
+    const uint8_t zero = 0;
+    if (size > 0) {
+        uint16_t num_non_zero = 1;
+        uint8_t* end = data + size;
+        uint8_t* start = data;
+        while (data < end) {
+            if (num_non_zero == 0xFF) {
+                // There's more data after big non-zero block
+                // So send it, and start a new block
+                send_block(link, start, data, num_non_zero);
+                start = data;
+                num_non_zero = 1;
+            }
+            else {
+                if (*data == 0) {
+                    // A zero encountered, so send the block
+                    send_block(link, start, data, num_non_zero);
+                    start = data + 1;
+                    num_non_zero = 1;
+                }
+                else {
+                    num_non_zero++;
+                }
+                ++data;
+            }
+        }
+        send_block(link, start, data, num_non_zero);
+        send_data(link, &zero, 1);
+    }
+}