From d38a52f0650b6d213f0a72eb66c722acd8f6312b Mon Sep 17 00:00:00 2001
From: David Wehr <wehrdo@users.noreply.github.com>
Date: Fri, 6 Jan 2017 17:59:14 -0600
Subject: [PATCH] Added circular buffer for async UART
---
quad/sw/comm_dev/src/circ_buffer.c | 76 ++++++++++++++++++++++++++++++
quad/sw/comm_dev/src/circ_buffer.h | 42 +++++++++++++++++
2 files changed, 118 insertions(+)
create mode 100644 quad/sw/comm_dev/src/circ_buffer.c
create mode 100644 quad/sw/comm_dev/src/circ_buffer.h
diff --git a/quad/sw/comm_dev/src/circ_buffer.c b/quad/sw/comm_dev/src/circ_buffer.c
new file mode 100644
index 000000000..ef90c1acf
--- /dev/null
+++ b/quad/sw/comm_dev/src/circ_buffer.c
@@ -0,0 +1,76 @@
+//
+// Created by dawehr on 10/24/2016.
+//
+
+#include "circ_buffer.h"
+
+#define circ_buf_min(a,b) \
+ ({ __typeof__ (a) _a = (a); \
+ __typeof__ (b) _b = (b); \
+ _a < _b ? _a : _b; })
+
+
+unsigned char buffer[CIRC_BUFFER_SIZE];
+size_t buf_start = 0;
+size_t buf_end = 0;
+size_t size = 0;
+
+
+struct data_chunk getChunk() {
+ size_t chunk_end = buf_end;
+ if (buf_end < buf_start) {
+ chunk_end = CIRC_BUFFER_SIZE;
+ }
+ size_t ret_size = chunk_end - buf_start;
+ struct data_chunk c = {
+ ret_size,
+ &buffer[buf_start]
+ };
+ return c;
+}
+
+
+void markConsumed(size_t n_consumed) {
+ size_t chunk_end = buf_start + n_consumed;
+ buf_start = chunk_end;
+ size -= n_consumed;
+ if (buf_start == CIRC_BUFFER_SIZE) {
+ buf_start = 0;
+ }
+
+}
+
+size_t putChunk(struct data_chunk c) {
+ // The amount that will be placed into the buffer
+ size_t will_place = circ_buf_min(CIRC_BUFFER_SIZE - size, c.length);
+ // Actual amount placed so far
+ size_t placed = 0;
+ while (placed < will_place) {
+ // Available room without wrapping
+ size_t to_copy;
+ if (buf_end >= buf_start) {
+ // If buffer is not wrapped, we can copy until the end of the buffer
+ to_copy = circ_buf_min(will_place, CIRC_BUFFER_SIZE - buf_end);
+ } else {
+ // Otherwise, remaining space in buffer is contiguous
+ to_copy = will_place - placed;
+ }
+ memcpy(buffer + buf_end, c.data + placed, to_copy);
+ // Update buffer endpoint
+ buf_end += to_copy;
+ if (buf_end > CIRC_BUFFER_SIZE) {
+ printf("Error: buf_end: %d\n", buf_end);
+ }
+ // If we copied to the end
+ if (buf_end == CIRC_BUFFER_SIZE) {
+ buf_end = 0;
+ }
+ placed += to_copy;
+ }
+ size += placed;
+ return placed;
+}
+
+size_t get_buffer_size() {
+ return size;
+}
diff --git a/quad/sw/comm_dev/src/circ_buffer.h b/quad/sw/comm_dev/src/circ_buffer.h
new file mode 100644
index 000000000..493543112
--- /dev/null
+++ b/quad/sw/comm_dev/src/circ_buffer.h
@@ -0,0 +1,42 @@
+//
+// Created by dawehr on 10/24/2016.
+//
+
+#ifndef CIRC_BUFFER_H
+#define CIRC_BUFFER_H
+
+#define CIRC_BUFFER_SIZE 2048
+#include <unistd.h>
+#include <memory.h>
+#include <stdio.h>
+
+struct data_chunk {
+ size_t length;
+ unsigned char* data;
+};
+
+/*
+ * Returns the largest contiguous chunk from the buffer
+ * Does not move the buffer forward. You must call markConsumed to
+ * mark the area as free.
+ */
+struct data_chunk getChunk();
+
+/*
+ * Marks the n_consumed bytes as used, and that
+ * area of the buffer can be used for new data now
+ */
+void markConsumed(size_t n_consumed);
+
+/*
+ * Places data into the circular buffer. Returns the number of bytes stored.
+ * Will store the entire chunk, unless there is not enough remaining size in the buffer
+ */
+size_t putChunk(struct data_chunk);
+
+/*
+ * Returns the remaining size in the buffer
+ */
+size_t get_buffer_size();
+
+#endif //CIRC_BUFFER_H
--
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