Add CPP lexer (#813)

lexers/cpp.go

@@ -0,0 +1,36 @@
+package lexers
+
+import (
+	"regexp"
+
+	. "github.com/alecthomas/chroma/v2" // nolint
+)
+
+var (
+	cppAnalyserIncludeRe   = regexp.MustCompile(`#include <[a-z_]+>`)
+	cppAnalyserNamespaceRe = regexp.MustCompile(`using namespace `)
+)
+
+var CPP = Register(MustNewXMLLexer(
+	embedded,
+	"embedded/c++.xml",
+).SetConfig(
+	&Config{
+		Name:      "C++",
+		Aliases:   []string{"cpp", "c++"},
+		Filenames: []string{"*.cpp", "*.hpp", "*.c++", "*.h++", "*.cc", "*.hh", "*.cxx", "*.hxx", "*.C", "*.H", "*.cp", "*.CPP", "*.cppm", "*.ixx"},
+		MimeTypes: []string{"text/x-c++hdr", "text/x-c++src"},
+		Priority:  0.1,
+		EnsureNL:  true,
+	},
+)).SetAnalyser(func(text string) float32 {
+	if cppAnalyserIncludeRe.MatchString(text) {
+		return 0.2
+	}
+
+	if cppAnalyserNamespaceRe.MatchString(text) {
+		return 0.4
+	}
+
+	return 0
+})