Rewrite core of the XTLDR boot loader

Reviewed-on: xt-sys/exectos#7
Reviewed-by: Piotr Likoski <likoski@noreply.codingworkshop.git>
Co-authored-by: Rafal Kupiec <belliash@codingworkshop.eu.org>
Co-committed-by: Rafal Kupiec <belliash@codingworkshop.eu.org>

xtldr/shell.c

@@ -0,0 +1,50 @@
+/**
+ * PROJECT:         ExectOS
+ * COPYRIGHT:       See COPYING.md in the top level directory
+ * FILE:            xtldr/shell.c
+ * DESCRIPTION:     XT Boot Loader shell
+ * DEVELOPERS:      Rafal Kupiec <belliash@codingworkshop.eu.org>
+ */
+
+#include <xtldr.h>
+
+
+/**
+ * Starts XTLDR shell.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+VOID
+BlStartLoaderShell()
+{
+    /* Initialize console */
+    BlInitializeConsole();
+
+    /* Print prompt */
+    BlpPrintShellPrompt();
+    for(;;);
+}
+
+/**
+ * Prints XTLDR shell prompt.
+ *
+ * @return This routine does not return any value.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+VOID
+BlpPrintShellPrompt()
+{
+    /* Set prompt color */
+    BlSetConsoleAttributes(EFI_TEXT_BGCOLOR_BLACK | EFI_TEXT_FGCOLOR_YELLOW);
+
+    /* Print prompt */
+    BlConsolePrint(L"XTLDR> ");
+
+    /* Reset standard shell colors */
+    BlSetConsoleAttributes(EFI_TEXT_BGCOLOR_BLACK | EFI_TEXT_FGCOLOR_LIGHTGRAY);
+}