nestlog: + terminal colors for entry/exit/code location

include/nestlog/color.hpp

@@ -0,0 +1,123 @@
+/* color.hpp */
+
+#pragma once
+
+#include <ostream>
+//#include <utility>  // for std::move
+#include <cstdint>
+
+namespace xo {
+    enum color_encoding {
+        CE_None,
+        CE_Ansi,
+        CE_Xterm,
+    };
+
+    enum color_flags {
+        CF_None = 0x0,
+        CF_ColorOn = 0x01,
+        CF_Contents = 0x02,
+        CF_ColorOff = 0x04,
+        CF_All = 0x07
+    };
+
+    template <typename Contents>
+    class color_impl {
+    public:
+        color_impl(color_flags flags, color_encoding encoding, std::uint32_t color, Contents && contents)
+            : flags_{flags}, encoding_{encoding}, color_{color}, contents_{std::move(contents)} {}
+
+        std::uint32_t color() const { return color_; }
+        Contents const & contents() const { return contents_; }
+
+        void print(std::ostream & os) const {
+            if ((flags_ & CF_ColorOn) && (color_ > 0)) {
+                switch(encoding_) {
+                case CE_Ansi:
+                    os << "\033[" << color_ << "m";
+                    break;
+                case CE_Xterm:
+                    os << "\033[38;5;" << color_ << "m";
+                    break;
+                }
+            }
+
+            if (flags_ & CF_Contents)
+                os << contents_;
+
+            if ((flags_ & CF_ColorOff) && (color_ > 0))
+                os << "\033[0m";
+        } /*print*/
+
+    private:
+        color_flags flags_ = CF_None;
+
+        color_encoding encoding_ = CE_Ansi;
+        /* .encoding = CE_Ansi:
+         *   0 = no color
+         *  30 = black
+         *  31 = red
+         *  32 = green
+         *  33 = yellow
+         *  34 = blue
+         *  35 = magenta
+         *  36 = cyan
+         *
+         * .encoding = CE_Xterm:
+         *   see [[https://i.stack.imgur.com/KTSQa.png]]
+         *  0..7               standard colors (muted: grey, red, green, yellow, blue, pink, cyan, white)
+         *  8..15              high-intensity colors (grey, red, green, yellow, blue, pink, cyan, white)
+         *  16..51             chooses hue
+         *  16..51 + (0..5)x36 increases whiteness
+         */
+        std::uint32_t color_ = 0;
+
+        Contents contents_;
+    }; /*color_impl*/
+
+    template <typename Contents>
+    color_impl<Contents> with_ansi_color(std::uint32_t color, Contents && contents) {
+        return color_impl<Contents>(CF_All, CE_Ansi, color, std::move(contents));
+    } /*with_ansi_color*/
+
+    template <typename Contents>
+    color_impl<Contents> with_xterm_color(std::uint32_t color, Contents && contents) {
+        return color_impl<Contents>(CF_All, CE_Xterm, color, std::move(contents));
+    } /*with_ansi_color*/
+
+    template <typename Contents>
+    color_impl<Contents> with_color(color_encoding encoding, std::uint32_t color, Contents && contents) {
+        return color_impl<Contents>(CF_All, encoding, color, std::move(contents));
+    } /*with_color*/
+
+    inline color_impl<int>
+    color_on_ansi(std::uint32_t color) {
+        return color_impl<int>(CF_ColorOn, CE_Ansi, color, 0);
+    } /*color_on_ansi*/
+
+    inline color_impl<int>
+    color_on_xterm(std::uint32_t color) {
+        return color_impl<int>(CF_ColorOn, CE_Xterm, color, 0);
+    } /*color_on_xterm*/
+
+    inline color_impl<int>
+    color_on(color_encoding encoding, std::uint32_t color) {
+        return color_impl<int>(CF_ColorOn, encoding, color, 0);
+    } /*color_on*/
+
+    inline color_impl<int>
+    color_off() {
+        /* any non-zero value works here for color */
+        return color_impl<int>(CF_ColorOff, CE_None, 1 /*color*/, 0);
+    } /*color_off*/
+
+    template <typename Contents>
+    inline std::ostream &
+    operator<<(std::ostream & os, color_impl<Contents> const & x) {
+        x.print(os);
+        return os;
+    } /*operator<<*/
+
+} /*namespace xo*/
+
+/* end color.hpp */