From a214dbb44bba5cb43d9ca714a69666c096f4953e Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Mon, 25 Nov 2019 18:16:35 +0100
Subject: [PATCH] Reimplement toHex manually.

---
 libdevcore/CommonData.cpp | 46 ++++++++++++++++++++++++++++++---------
 libdevcore/CommonData.h   | 28 +++++++++++-------------
 libdevcore/Exceptions.h   |  1 +
 3 files changed, 50 insertions(+), 25 deletions(-)

diff --git a/libdevcore/CommonData.cpp b/libdevcore/CommonData.cpp
index 1b0e97204..ebdc81a38 100644
--- a/libdevcore/CommonData.cpp
+++ b/libdevcore/CommonData.cpp
@@ -29,26 +29,52 @@
 using namespace std;
 using namespace dev;
 
+namespace
+{
+
+static char const* upperHexChars = "0123456789ABCDEF";
+static char const* lowerHexChars = "0123456789abcdef";
+
+}
+
+string dev::toHex(uint8_t _data, HexCase _case)
+{
+	assertThrow(_case != HexCase::Mixed, BadHexCase, "Mixed case can only be used for byte arrays.");
+
+	char const* chars = _case == HexCase::Upper ? upperHexChars : lowerHexChars;
+
+	return std::string{
+		chars[(unsigned(_data) / 16) & 0xf],
+		chars[unsigned(_data) & 0xf]
+	};
+}
+
 string dev::toHex(bytes const& _data, HexPrefix _prefix, HexCase _case)
 {
-	std::ostringstream ret;
-	if (_prefix == HexPrefix::Add)
-		ret << "0x";
+	std::string ret(_data.size() * 2 + (_prefix == HexPrefix::Add ? 2 : 0), 0);
 
+	size_t i = 0;
+	if (_prefix == HexPrefix::Add)
+	{
+		ret[i++] = '0';
+		ret[i++] = 'x';
+	}
+
+	// Mixed case will be handled inside the loop.
+	char const* chars = _case == HexCase::Upper ? upperHexChars : lowerHexChars;
 	int rix = _data.size() - 1;
 	for (uint8_t c: _data)
 	{
 		// switch hex case every four hexchars
-		auto hexcase = std::nouppercase;
-		if (_case == HexCase::Upper)
-			hexcase = std::uppercase;
-		else if (_case == HexCase::Mixed)
-			hexcase = (rix-- & 2) == 0 ? std::nouppercase : std::uppercase;
+		if (_case == HexCase::Mixed)
+			chars = (rix-- & 2) == 0 ? lowerHexChars : upperHexChars;
 
-		ret << std::hex << hexcase << std::setfill('0') << std::setw(2) << size_t(c);
+		ret[i++] = chars[(unsigned(c) / 16) & 0xf];
+		ret[i++] = chars[unsigned(c) & 0xf];
 	}
+	assertThrow(i == ret.size(), Exception, "");
 
-	return ret.str();
+	return ret;
 }
 
 int dev::fromHex(char _i, WhenError _throw)
diff --git a/libdevcore/CommonData.h b/libdevcore/CommonData.h
index 017a632dc..d6e8f349e 100644
--- a/libdevcore/CommonData.h
+++ b/libdevcore/CommonData.h
@@ -130,9 +130,12 @@ enum class HexCase
 	Mixed = 2,
 };
 
-/// Convert a series of bytes to the corresponding string of hex duplets.
-/// @param _w specifies the width of the first of the elements. Defaults to two - enough to represent a byte.
-/// @example toHex("A\x69") == "4169"
+/// Convert a single byte to a string of hex characters (of length two),
+/// optionally with uppercase hex letters.
+std::string toHex(uint8_t _data, HexCase _case = HexCase::Lower);
+
+/// Convert a series of bytes to the corresponding string of hex duplets,
+/// optionally with "0x" prefix and with uppercase hex letters.
 std::string toHex(bytes const& _data, HexPrefix _prefix = HexPrefix::DontAdd, HexCase _case = HexCase::Lower);
 
 /// Converts a (printable) ASCII hex character into the corresponding integer value.
@@ -207,10 +210,6 @@ inline bytes toCompactBigEndian(T _val, unsigned _min = 0)
 	toBigEndian(_val, ret);
 	return ret;
 }
-inline bytes toCompactBigEndian(uint8_t _val, unsigned _min = 0)
-{
-	return (_min || _val) ? bytes{ _val } : bytes{};
-}
 
 /// Convenience function for conversion of a u256 to hex
 inline std::string toHex(u256 val, HexPrefix prefix = HexPrefix::DontAdd)
@@ -219,13 +218,18 @@ inline std::string toHex(u256 val, HexPrefix prefix = HexPrefix::DontAdd)
 	return (prefix == HexPrefix::Add) ? "0x" + str : str;
 }
 
+inline std::string toCompactHexWithPrefix(u256 const& _value)
+{
+	return toHex(toCompactBigEndian(_value, 1), HexPrefix::Add);
+}
+
 /// Returns decimal representation for small numbers and hex for large numbers.
 inline std::string formatNumber(bigint const& _value)
 {
 	if (_value < 0)
 		return "-" + formatNumber(-_value);
 	if (_value > 0x1000000)
-		return toHex(toCompactBigEndian(_value), HexPrefix::Add);
+		return toHex(toCompactBigEndian(_value, 1), HexPrefix::Add);
 	else
 		return _value.str();
 }
@@ -233,17 +237,11 @@ inline std::string formatNumber(bigint const& _value)
 inline std::string formatNumber(u256 const& _value)
 {
 	if (_value > 0x1000000)
-		return toHex(toCompactBigEndian(_value), HexPrefix::Add);
+		return toCompactHexWithPrefix(_value);
 	else
 		return _value.str();
 }
 
-inline std::string toCompactHexWithPrefix(u256 val)
-{
-	std::ostringstream ret;
-	ret << std::hex << val;
-	return "0x" + ret.str();
-}
 
 // Algorithms for string and string-like collections.
 
diff --git a/libdevcore/Exceptions.h b/libdevcore/Exceptions.h
index 943379d7a..a0ab7c6b5 100644
--- a/libdevcore/Exceptions.h
+++ b/libdevcore/Exceptions.h
@@ -46,6 +46,7 @@ private:
 
 DEV_SIMPLE_EXCEPTION(InvalidAddress);
 DEV_SIMPLE_EXCEPTION(BadHexCharacter);
+DEV_SIMPLE_EXCEPTION(BadHexCase);
 DEV_SIMPLE_EXCEPTION(FileError);
 DEV_SIMPLE_EXCEPTION(DataTooLong);