1 files changed, 83 insertions, 0 deletions
diff --git a/deimos/core/format.cpp b/deimos/core/format.cpp
new file mode 100644
index 0000000..f4f4e83
--- /dev/null
+++ b/deimos/core/format.cpp
@@ -0,0 +1,83 @@
+#include "deimos/core/format.h"
+#include "deimos/core/io.h"
+
+#include <stdio.h> // NOLINT
+#include <inttypes.h> // NOLINT
+
+namespace deimos
+{
+
+class FormatContext
+{
+    IWriter*    m_writer;
+
+public:
+    explicit FormatContext(IWriter* writer) : m_writer{writer} {}
+
+    void PushChar(char c)
+    {
+        m_writer->Write(AsBytes(Span<char>(&c, 1)));
+    }
+
+    void PushString(Span<const char> str)
+    {
+        m_writer->Write(AsBytes(str));
+    }
+
+    void PushUnsignedInteger(int64_t value)
+    {
+        char buffer[64];
+        const int size = snprintf(&buffer[0], 64, "%" PRIu64, value);
+        PushString({ &buffer[0], size });
+    }
+
+    void PushInteger(int64_t value)
+    {
+        char buffer[64];
+        const int size = snprintf(&buffer[0], 64, "%" PRIi64, value);
+        PushString({ &buffer[0], size });
+    }
+
+    void PushArg(const FormatArg& arg)
+    {
+        switch (arg.type)
+        {
+            case FormatArg::kString:
+                PushString(arg.string);
+                break;
+            case FormatArg::kInteger:
+                PushInteger(arg.integer);
+                break;
+            case FormatArg::kUnsignedInteger:
+                PushUnsignedInteger(arg.integer);
+                break;
+        }
+    }
+};
+
+void FormatVa(IWriter* writer, gsl::czstring fmt, Span<const FormatArg> args)
+{
+    if (fmt == nullptr) { return; }
+
+    const FormatArg* arg = args.begin();
+    const FormatArg* const end_arg = args.end();
+
+    FormatContext ctx(writer);
+
+    while (*fmt != '\0')
+    {
+        if (*fmt == '$' && arg < end_arg)
+        {
+            ctx.PushArg(*arg++); // NOLINT
+        }
+        else
+        {
+            ctx.PushChar(*fmt);
+        }
+
+        fmt += 1;
+    }
+}
+
+} // namespace deimos
+