From d13c10c6047a02d695c9fb03f7912b7d17844bbd Mon Sep 17 00:00:00 2001
From: Tomasz Sowa <t.sowa@ttmath.org>
Date: Tue, 26 Jul 2022 05:14:35 +0200
Subject: [PATCH] add methods for converting from hex string to bytes

add to convert/text.h:
template<typename HexStringPointerType, typename BytesStringType>
bool hex_string_pointer_to_bytes(const HexStringPointerType * hex_string, BytesStringType & bytes, bool clear_bytes = true);

template<typename HexStringType, typename BytesStringType>
bool hex_string_to_bytes(const HexStringType & hex_string, BytesStringType & bytes, bool clear_bytes = true);
---
 src/convert/text.h | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/convert/text.h b/src/convert/text.h
index 1962d5a..0f73650 100644
--- a/src/convert/text.h
+++ b/src/convert/text.h
@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (c) 2017-2021, Tomasz Sowa
+ * Copyright (c) 2017-2022, Tomasz Sowa
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -44,6 +44,49 @@ namespace pt
 bool is_white(wchar_t c, bool check_additional_chars = true, bool treat_new_line_as_white = true);
 bool is_digit(wchar_t c, int base = 10, int * digit = 0);
 
+
+// IMPROVEME add tests
+template<typename HexStringPointerType, typename BytesStringType>
+bool hex_string_pointer_to_bytes(const HexStringPointerType * hex_string, BytesStringType & bytes, bool clear_bytes = true)
+{
+	bool converted_correctly = true;
+	size_t i = 0;
+
+	if( clear_bytes )
+		bytes.clear();
+
+	for( ; converted_correctly && hex_string[i] != 0 && hex_string[i+1] != 0 ; i += 2)
+	{
+		int c1, c2;
+
+		converted_correctly = converted_correctly && is_digit(hex_string[i],   16, &c1);
+		converted_correctly = converted_correctly && is_digit(hex_string[i+1], 16, &c2);
+
+		if( converted_correctly )
+		{
+			bytes += (char)(unsigned char)(((c1 << 4) | c2));
+		}
+	}
+
+	if( hex_string[i] != 0 )
+	{
+		// one digit has left
+		converted_correctly = false;
+	}
+
+	return converted_correctly;
+}
+
+
+// IMPROVEME add tests
+template<typename HexStringType, typename BytesStringType>
+bool hex_string_to_bytes(const HexStringType & hex_string, BytesStringType & bytes, bool clear_bytes = true)
+{
+	return hex_string_pointer_to_bytes(hex_string.c_str(), bytes, clear_bytes);
+}
+
+
+
 const char *    skip_white(const char * str,    bool check_additional_chars = true, bool treat_new_line_as_white = true);
 const wchar_t * skip_white(const wchar_t * str, bool check_additional_chars = true, bool treat_new_line_as_white = true);