From 9bd28f39a50cdf4d4cbf4a5cab5150fde66658c2 Mon Sep 17 00:00:00 2001
From: Jean-Baptiste Boric <jblbeurope@gmail.com>
Date: Thu, 10 Dec 2020 22:42:04 +0100
Subject: [PATCH] StringUtil: Add base support and hexadecimal functions

---
 src/common/string_util.cpp | 28 +++++++++++++++++++++++
 src/common/string_util.h   | 47 +++++++++++++++++++++++---------------
 2 files changed, 57 insertions(+), 18 deletions(-)

diff --git a/src/common/string_util.cpp b/src/common/string_util.cpp
index 420830d25..fcbf44435 100644
--- a/src/common/string_util.cpp
+++ b/src/common/string_util.cpp
@@ -2,6 +2,7 @@
 #include <cctype>
 #include <codecvt>
 #include <cstdio>
+#include <sstream>
 
 #ifdef WIN32
 #include "windows_headers.h"
@@ -163,6 +164,33 @@ std::size_t Strlcpy(char* dst, const std::string_view& src, std::size_t size)
   return len;
 }
 
+std::optional<std::vector<u8>> DecodeHex(const std::string_view& in)
+{
+  std::vector<u8> data;
+  data.reserve(in.size()/2);
+
+  for (int i = 0; i < in.size()/2; i++) {
+    auto byte = StringUtil::FromChars<u8>(in.substr(i*2, 2), 16);
+    if (byte) {
+      data.push_back(*byte);
+    }
+    else {
+      return std::nullopt;
+    }
+  }
+
+  return { data };
+}
+
+std::string EncodeHex(const u8* data, int length)
+{
+  std::stringstream ss;
+  for (int i = 0; i < length; i++) {
+    ss << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(data[i]);
+  }
+  return ss.str();
+}
+
 #ifdef WIN32
 
 std::wstring UTF8StringToWideString(const std::string_view& str)
diff --git a/src/common/string_util.h b/src/common/string_util.h
index f1a43111c..50aa31572 100644
--- a/src/common/string_util.h
+++ b/src/common/string_util.h
@@ -3,9 +3,11 @@
 #include <cstdarg>
 #include <cstddef>
 #include <cstring>
+#include <iomanip>
 #include <optional>
 #include <string>
 #include <string_view>
+#include <vector>
 
 #if defined(__has_include) && __has_include(<charconv>)
 #include <charconv>
@@ -52,16 +54,37 @@ static inline int Strncasecmp(const char* s1, const char* s2, std::size_t n)
 }
 
 /// Wrapper arond std::from_chars
-template<typename T>
-inline std::optional<T> FromChars(const std::string_view& str)
+template<typename T, std::enable_if_t<std::is_integral<T>::value, bool> = true>
+inline std::optional<T> FromChars(const std::string_view& str, int base = 10)
 {
   T value;
 
 #if defined(__has_include) && __has_include(<charconv>)
+  const std::from_chars_result result = std::from_chars(str.data(), str.data() + str.length(), value, base);
+  if (result.ec != std::errc())
+    return std::nullopt;
+#else
+  std::string temp(str);
+  std::istringstream ss(temp);
+  ss >> std::setbase(base) >> value;
+  if (ss.fail())
+    return std::nullopt;
+#endif
+
+  return value;
+}
+
+template<typename T, std::enable_if_t<std::is_floating_point<T>::value, bool> = true>
+inline std::optional<T> FromChars(const std::string_view& str)
+{
+  T value;
+
+#if defined(__has_include) && __has_include(<charconv>) && defined(_MSC_VER)
   const std::from_chars_result result = std::from_chars(str.data(), str.data() + str.length(), value);
   if (result.ec != std::errc())
     return std::nullopt;
 #else
+  /// libstdc++ does not support from_chars with floats yet
   std::string temp(str);
   std::istringstream ss(temp);
   ss >> value;
@@ -74,7 +97,7 @@ inline std::optional<T> FromChars(const std::string_view& str)
 
 /// Explicit override for booleans
 template<>
-inline std::optional<bool> FromChars(const std::string_view& str)
+inline std::optional<bool> FromChars(const std::string_view& str, int base)
 {
   if (Strncasecmp("true", str.data(), str.length()) == 0 || Strncasecmp("yes", str.data(), str.length()) == 0 ||
       Strncasecmp("on", str.data(), str.length()) == 0 || Strncasecmp("1", str.data(), str.length()) == 0)
@@ -91,21 +114,9 @@ inline std::optional<bool> FromChars(const std::string_view& str)
   return std::nullopt;
 }
 
-#ifndef _MSC_VER
-/// from_chars doesn't seem to work with floats on gcc
-template<>
-inline std::optional<float> FromChars(const std::string_view& str)
-{
-  float value;
-  std::string temp(str);
-  std::istringstream ss(temp);
-  ss >> value;
-  if (ss.fail())
-    return std::nullopt;
-  else
-    return value;
-}
-#endif
+/// Encode/decode hexadecimal byte buffers
+std::optional<std::vector<u8>> DecodeHex(const std::string_view& str);
+std::string EncodeHex(const u8* data, int length);
 
 /// starts_with from C++20
 ALWAYS_INLINE static bool StartsWith(const std::string_view& str, const char* prefix)