Started implementing a C++ stdlib. And improved the print function by adding newline support and scrolling.

SConstruct

@@ -26,6 +26,8 @@ os_sources = Split('''
     src/kernel/startup.cpp
 
     src/os/tty.cpp
+
+    src/stdlib/string.cpp
 ''')
 env['LINKCOM'] = env['LINKCOM'].replace('$_LIBFLAGS', f'{crti_o[0]} {crtbegin_o} $_LIBFLAGS {crtend_o} {crtn_o[0]}')
 

include/cstring

@@ -0,0 +1,14 @@
+
+#pragma once
+
+#if !defined(BAD_APPLE_OS_CSTRING_HPP_INCLUDED)
+#define BAD_APPLE_OS_CSTRING_HPP_INCLUDED
+
+#include <string.h>
+
+namespace std
+{
+using ::strlen;
+}
+
+#endif // !defined(BAD_APPLE_OS_CSTRING_HPP_INCLUDED)

include/detail/attributes.h

@@ -0,0 +1,15 @@
+
+#pragma once
+
+#if !defined(BAD_APPLE_OS_DETAIL_ATTRIBUTES_H_INCLUDED)
+#define BAD_APPLE_OS_DETAIL_ATTRIBUTES_H_INCLUDED
+
+#if defined(__cplusplus)
+#define BA_CXX_NODISCARD [[nodiscard]]
+#define BA_CXX_NOEXCEPT noexcept
+#else
+#define BA_CXX_NODISCARD
+#define BA_CXX_NOEXCEPT
+#endif
+
+#endif // !defined(BAD_APPLE_OS_DETAIL_ATTRIBUTES_H_INCLUDED)

include/os/tty.hpp

@@ -35,17 +35,12 @@ struct VgaDoubleColor
     VgaColor background : 4 = VgaColor::BLACK;
 };
 
-[[nodiscard]] size_t strlen(const char* str); // TODO: move to standard lib
 void initialize();
 void setColor(VgaDoubleColor color);
 void putEntryAt(char chr, VgaDoubleColor color, size_t posX, size_t posY);
 void putChar(char chr);
 void write(const char* data, size_t size);
-
+void write(const char* data);
-inline void write(const char* data)
-{
-    write(data, strlen(data));
-}
 } // namespace tty
 
 #endif // OS_TTY_HPP_INCLUDED

include/string.h

@@ -0,0 +1,19 @@
+
+#pragma once
+
+#if !defined(BAD_APPLE_OS_STRING_H_INCLUDED)
+#define BAD_APPLE_OS_STRING_H_INCLUDED
+
+#include <stddef.h>
+
+#include "./detail/attributes.h"
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+BA_CXX_NODISCARD size_t strlen(const char* str) BA_CXX_NOEXCEPT;
+#if defined(__cplusplus)
+}
+#endif
+
+#endif // !defined(BAD_APPLE_OS_STRING_H_INCLUDED)

src/kernel/startup.cpp

@@ -1,5 +1,3 @@
-#include <stddef.h>
-#include <stdint.h>
 
 #include "os/tty.hpp"
 
@@ -17,7 +15,15 @@ extern "C" void kernel_main(void)
 {
 	/* Initialize terminal interface */
 	tty::initialize();
- 
+
-	/* Newline support is left as an exercise. */
 	tty::write("Hello, kernel World!\n");
+
+    while (true)
+    {
+        for (char chr = 'A'; chr <= 'Z'; ++chr)
+        {
+            char buf[2] = {chr, '\n'};
+            tty::write(buf, 2);
+        }
+    }
 }

src/os/tty.cpp

@@ -1,6 +1,8 @@
 
 #include "os/tty.hpp"
 
+#include <cstring>
+
 namespace tty
 {
 namespace
@@ -8,6 +10,11 @@ namespace
 inline const size_t VGA_WIDTH = 80;
 inline const size_t VGA_HEIGHT = 25;
 
+size_t gTerminalRow = 0;
+size_t gTerminalColumn = 0;
+VgaDoubleColor gTerminalColor = VgaDoubleColor();
+uint16_t* gTerminalBuffer = reinterpret_cast<uint16_t*>(0xB8000);
+
 constexpr uint8_t vgaEntryColor(VgaDoubleColor color)
 {
     return static_cast<uint8_t>(color.foreground) | static_cast<uint8_t>(color.background) << 4;
@@ -18,19 +25,28 @@ constexpr uint16_t vgaEntry(const unsigned char chr, const VgaDoubleColor color)
     return static_cast<uint16_t>(chr) | static_cast<uint16_t>(vgaEntryColor(color) << 8);
 }
 
-size_t gTerminalRow = 0;
+void newline()
-size_t gTerminalColumn = 0;
-VgaDoubleColor gTerminalColor = VgaDoubleColor();
-uint16_t* gTerminalBuffer = reinterpret_cast<uint16_t*>(0xB8000);
-}
-
-size_t strlen(const char* str) // TODO: move to standard lib
 {
-    size_t len = 0;
+    gTerminalColumn = 0;
-    while (str[len] != '\0') {
+    if (gTerminalRow < VGA_HEIGHT - 1)
-        ++len;
+    {
+        ++gTerminalRow;
     }
-    return len;
+    else
+    {
+        // scrolling up
+        for (size_t y = 0; y < VGA_HEIGHT - 1; ++y)
+        {
+            // TODO: this is where I'd put my memcpy. If I had one.
+            for (size_t x = 0; x < VGA_WIDTH; ++x)
+            {
+                const size_t indexTo = y * VGA_WIDTH + x;
+                const size_t indexFrom = (y + 1) * VGA_WIDTH + x;
+                gTerminalBuffer[indexTo] = gTerminalBuffer[indexFrom];
+            }
+        }
+    }
+}
 }
 
 void initialize()
@@ -61,11 +77,7 @@ void putChar(char chr)
     putEntryAt(chr, gTerminalColor, gTerminalColumn, gTerminalRow);
     if (++gTerminalColumn == VGA_WIDTH)
     {
-        gTerminalColumn = 0;
+        newline();
-        if (++gTerminalRow == VGA_HEIGHT)
-        {
-            gTerminalRow = 0;
-        }
     }
 }
 
@@ -73,7 +85,19 @@ void write(const char* data, size_t size)
 {
     for (size_t idx = 0; idx < size; idx++)
     {
-        putChar(data[idx]);
+        if (data[idx] == '\n')
+        {
+            newline();
+        }
+        else
+        {
+            putChar(data[idx]);
+        }
     }
 }
+
+void write(const char* data)
+{
+    write(data, std::strlen(data));
+}
 }

src/stdlib/string.cpp

@@ -0,0 +1,14 @@
+
+#include <string.h>
+
+extern "C"
+{
+size_t strlen(const char* str) noexcept
+{
+    size_t len = 0;
+    while (str[len] != '\0') {
+        ++len;
+    }
+    return len;
+}
+}