add almost full vfd implementation

board/vfd-frame.c

@@ -0,0 +1,88 @@
+#include <windows.h>
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#define SUPER_VERBOSE 1
+
+#include "board/vfd-frame.h"
+
+#include "hook/iobuf.h"
+
+#include "util/dprintf.h"
+
+static HRESULT vfd_frame_encode_byte(struct iobuf *dest, uint8_t byte);
+
+/* Frame structure:
+
+    REQUEST:
+   [0] Sync byte (0x1A or 0x1B)
+   [1] Packet ID
+   [2...n-1] Data/payload
+
+   --- OR ---
+
+   if no sync byte is given, plain static text in the currently configured encoding is expected.
+
+   RESPONSE:
+   This thing never responds, unless it's VFD_CMD_GET_VERSION
+   */
+
+bool vfd_frame_sync(struct const_iobuf *src) {
+    return src->bytes[src->pos] == VFD_SYNC_BYTE || src->bytes[src->pos] == VFD_SYNC_BYTE2;
+}
+
+HRESULT vfd_frame_encode(
+        struct iobuf *dest,
+        const void *ptr,
+        size_t nbytes) {
+    const uint8_t *src;
+    uint8_t byte;
+    size_t i;
+    HRESULT hr;
+
+    assert(dest != NULL);
+    assert(dest->bytes != NULL || dest->nbytes == 0);
+    assert(dest->pos <= dest->nbytes);
+    assert(ptr != NULL);
+
+    src = ptr;
+
+    if (dest->pos >= dest->nbytes) {
+        return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
+    }
+
+#if SUPER_VERBOSE
+    dprintf("VFD: RX Buffer:\n");
+#endif
+
+    for (i = 1; i < nbytes; i++) {
+        byte = src[i];
+#if SUPER_VERBOSE
+        dprintf("%02x ", byte);
+#endif
+
+        hr = vfd_frame_encode_byte(dest, byte);
+
+        if (FAILED(hr)) {
+            return hr;
+        }
+    }
+#if SUPER_VERBOSE
+    dprintf("\n");
+#endif
+
+    return hr;
+}
+
+static HRESULT vfd_frame_encode_byte(struct iobuf *dest, uint8_t byte) {
+    if (dest->pos + 1 > dest->nbytes) {
+        return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
+    }
+
+    dest->bytes[dest->pos++] = byte;
+
+    return S_OK;
+}