From 01e48c29ad46a03be54af4e8806b493e84091214 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Tue, 27 Aug 2024 14:53:18 +0300
Subject: [PATCH] Write strings containing binary data as base64

---
 source/textwriter.cpp | 55 +++++++++++++++++++++++++++++++++++++++++--
 source/textwriter.h   |  4 ++++
 2 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/source/textwriter.cpp b/source/textwriter.cpp
index 04fccff..460bfb3 100644
--- a/source/textwriter.cpp
+++ b/source/textwriter.cpp
@@ -1,4 +1,5 @@
 #include <msp/io/print.h>
+#include <msp/stringcodec/utf8.h>
 #include <msp/strings/utils.h>
 #include "output.h"
 #include "statement.h"
@@ -10,7 +11,8 @@ namespace Msp {
 namespace DataFile {
 
 TextWriter::TextWriter(Output &o):
-	WriterMode(o)
+	WriterMode(o),
+	codec(make_unique<StringCodec::Utf8>())
 {
 	float_format.showpoint().precision(7);
 }
@@ -34,7 +36,13 @@ void TextWriter::write_(const Statement &st, unsigned level)
 	{
 		out.put(' ');
 		if(v.get_signature()==StringType::signature)
-			out.write(format("\"%s\"", c_escape(v.get<StringType::Store>(), false)));
+		{
+			StringType::Store str = v.get<StringType::Store>();
+			if(codec->detect(str))
+				out.write(format("\"%s\"", c_escape(str, false)));
+			else
+				out.write(format("=%s=", base64_encode(str)));
+		}
 		else if(v.get_signature()==BoolType::signature)
 			out.write(v.get<BoolType::Store>() ? "true" : "false");
 		else if(v.get_signature()==IntType::signature)
@@ -60,5 +68,48 @@ void TextWriter::write_(const Statement &st, unsigned level)
 	out.write(";\n");
 }
 
+string TextWriter::base64_encode(const string &str)
+{
+	string b64;
+	b64.reserve(str.size()*4/3+3);
+	unsigned accum = 0;
+	unsigned a_bits = 0;
+	for(auto i=str.begin(); i!=str.end(); )
+	{
+		accum = (accum<<8)|static_cast<unsigned char>(*i);
+		a_bits += 8;
+
+		++i;
+		if(i==str.end() && a_bits%6)
+		{
+			accum <<= 4;
+			a_bits += 4;
+		}
+
+		while(a_bits>=6)
+		{
+			unsigned d = (accum>>(a_bits-6))&63;
+			a_bits -= 6;
+			accum &= (1<<a_bits)-1;
+
+			if(d<26)
+				b64 += 'A'+d;
+			else if(d<52)
+				b64 += 'a'+(d-26);
+			else if(d<62)
+				b64 += '0'+(d-52);
+			else if(d==62)
+				b64 += '+';
+			else if(d==63)
+				b64 += '/';
+		}
+	}
+
+	for(unsigned i=(str.size()+2)%3; i<2; ++i)
+		b64 += '=';
+
+	return b64;
+}
+
 } // namespace DataFile
 } // namespace Msp
diff --git a/source/textwriter.h b/source/textwriter.h
index 641fc2e..6753639 100644
--- a/source/textwriter.h
+++ b/source/textwriter.h
@@ -1,6 +1,8 @@
 #ifndef MSP_DATAFILE_TEXTWRITER_H_
 #define MSP_DATAFILE_TEXTWRITER_H_
 
+#include <memory>
+#include <msp/stringcodec/codec.h>
 #include <msp/strings/fmt.h>
 #include "writermode.h"
 
@@ -11,6 +13,7 @@ class TextWriter: public WriterMode
 {
 private:
 	Fmt float_format;
+	std::unique_ptr<StringCodec::Codec> codec;
 
 public:
 	TextWriter(Output &o);
@@ -19,6 +22,7 @@ public:
 	void write(const Statement &st) override;
 private:
 	void write_(const Statement &st, unsigned);
+	std::string base64_encode(const std::string &);
 };
 
 } // namespace DataFile
-- 
2.45.2