From 7f0f37fca781a578c7736f59cf70c859fdde271a Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Mon, 3 Aug 2020 13:18:43 -0400
Subject: partition_data_manager: Make data arrays constexpr

Previously the constructor for all of these would run at program
startup, consuming time before the application can enter main().

This is also particularly dangerous, given the logging system wouldn't
have been initialized properly yet, yet the program would use the logs
to signify an error.

To rectify this, we can replace the literals with constexpr functions
that perform the conversion at compile-time, completely eliminating the
runtime cost of initializing these arrays.
---
 src/common/hex_util.h | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

(limited to 'src/common/hex_util.h')

diff --git a/src/common/hex_util.h b/src/common/hex_util.h
index bb4736f96..a0a0e78a4 100644
--- a/src/common/hex_util.h
+++ b/src/common/hex_util.h
@@ -14,19 +14,31 @@
 
 namespace Common {
 
-u8 ToHexNibble(char c1);
+constexpr u8 ToHexNibble(char c) {
+    if (c >= 65 && c <= 70) {
+        return c - 55;
+    }
+
+    if (c >= 97 && c <= 102) {
+        return c - 87;
+    }
+
+    return c - 48;
+}
 
 std::vector<u8> HexStringToVector(std::string_view str, bool little_endian);
 
 template <std::size_t Size, bool le = false>
-std::array<u8, Size> HexStringToArray(std::string_view str) {
+constexpr std::array<u8, Size> HexStringToArray(std::string_view str) {
     std::array<u8, Size> out{};
     if constexpr (le) {
-        for (std::size_t i = 2 * Size - 2; i <= 2 * Size; i -= 2)
+        for (std::size_t i = 2 * Size - 2; i <= 2 * Size; i -= 2) {
             out[i / 2] = (ToHexNibble(str[i]) << 4) | ToHexNibble(str[i + 1]);
+        }
     } else {
-        for (std::size_t i = 0; i < 2 * Size; i += 2)
+        for (std::size_t i = 0; i < 2 * Size; i += 2) {
             out[i / 2] = (ToHexNibble(str[i]) << 4) | ToHexNibble(str[i + 1]);
+        }
     }
     return out;
 }
@@ -48,7 +60,12 @@ std::string HexToString(const ContiguousContainer& data, bool upper = true) {
     return out;
 }
 
-std::array<u8, 0x10> operator"" _array16(const char* str, std::size_t len);
-std::array<u8, 0x20> operator"" _array32(const char* str, std::size_t len);
+constexpr std::array<u8, 16> AsArray(const char (&data)[17]) {
+    return HexStringToArray<16>(data);
+}
+
+constexpr std::array<u8, 32> AsArray(const char (&data)[65]) {
+    return HexStringToArray<32>(data);
+}
 
 } // namespace Common
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