Add a controller shell.

This adds a mini shell to the tcp server that allows the user
to modify the current state.

Commands are in the form:

  set [int_attribute] (=|+=|-=) [number]
  set [bool_attribute] (on|off|toggle)
  print
  end

for example:

  set brightness += 5
  set power on
  print
  end

2 files changed, 40 insertions, 1 deletions

diff --git a/include/sockbuf.h b/include/sockbuf.h
new file mode 100644
index 0000000..664e134
--- /dev/null
+++ b/include/sockbuf.h
@@ -0,0 +1,39 @@
+#pragma once
+#ifndef SOCKBUF_H_
+#define SOCKBUF_H_
+
+#include <inttypes.h>
+
+#define SOCKBUF_BUFLEN 128
+#define SOCKBUF_CLOSED 1
+
+typedef struct {
+  uint8_t buf[SOCKBUF_BUFLEN];
+
+  uint8_t next;
+  uint8_t last;
+
+  int socket;
+  uint8_t flags;
+} sockbuf_t;
+
+/* Initialize a sockbuf from the provided file descriptor. */
+sockbuf_t* init_sockbuf(sockbuf_t* sockbuf, int socket);
+
+/* Writes a null-terminated string to the socket. */
+void sockbuf_write(sockbuf_t* sockbuf, const char* value);
+
+/*
+ * Return the next character of the sockbuf or -1 if EOF was reached.
+ *
+ * This does not advance the pointer.
+ */
+int peek_char(sockbuf_t* sockbuf);
+
+/*
+ * Return and consume the next character of the sockbuf or -1 if EOF was
+ * reached.
+ */
+int get_char(sockbuf_t* sockbuf);
+
+#endif /* SOCKBUF_H_ */
diff --git a/include/ws2812b_writer.h b/include/ws2812b_writer.h
index 2252230..9da9345 100644
--- a/include/ws2812b_writer.h
+++ b/include/ws2812b_writer.h
@@ -11,7 +11,7 @@ typedef struct {
 
   struct {
     uint32_t time;
-    int32_t timetick;
+    int timetick;
     uint8_t brightness;
     uint8_t off;
     uint8_t n_snow;