Bootloader: Add API to create GUID from string

bootloader/installer/GUID.cpp

@@ -3,6 +3,54 @@
 #include <iomanip>
 #include <cstring>
 
+std::optional<uint64_t> parse_hex(std::string_view hex_string)
+{
+	uint64_t result = 0;
+	for (char c : hex_string)
+	{
+		if (!isxdigit(c))
+			return {};
+
+		uint8_t nibble = 0;
+		if ('0' <= c && c <= '9')
+			nibble = c - '0';
+		else if ('a' <= c && c <= 'f')
+			nibble = c - 'a' + 10;
+		else
+			nibble = c - 'A' + 10;
+		result = (result << 4) | nibble;
+	}
+	return result;
+}
+
+std::optional<GUID> GUID::from_string(std::string_view guid_string)
+{
+	if (guid_string.size() != 36)
+		return {};
+
+	if (guid_string[8] != '-' || guid_string[13] != '-' || guid_string[18] != '-' || guid_string[23] != '-')
+		return {};
+
+	auto comp1 = parse_hex(guid_string.substr(0, 8));
+	auto comp2 = parse_hex(guid_string.substr(9, 4));
+	auto comp3 = parse_hex(guid_string.substr(14, 4));
+	auto comp4 = parse_hex(guid_string.substr(19, 4));
+	auto comp5 = parse_hex(guid_string.substr(24, 12));
+
+	if (!comp1.has_value() || !comp2.has_value() || !comp3.has_value() || !comp4.has_value() || !comp5.has_value())
+		return {};
+
+	GUID result;
+	result.component1 = *comp1;
+	result.component2 = *comp2;
+	result.component3 = *comp3;
+	for (int i = 0; i < 2; i++)
+		result.component45[i + 0] = *comp4 >> ((2-1) * 8 - i * 8);
+	for (int i = 0; i < 6; i++)
+		result.component45[i + 2] = *comp5 >> ((6-1) * 8 - i * 8);
+	return result;
+}
+
 bool GUID::operator==(const GUID& other) const
 {
 	return std::memcmp(this, &other, sizeof(GUID)) == 0;
@@ -19,7 +67,7 @@ std::ostream& operator<<(std::ostream& out, const GUID& guid)
 	out << std::setw(2);
 	for (int i = 0; i < 2; i++) out << +guid.component45[i];
 	out << '-';
-	for (int i = 2; i < 6; i++) out << +guid.component45[i];
+	for (int i = 2; i < 8; i++) out << +guid.component45[i];
 
 	out.flags(flags);
 	return out;

bootloader/installer/GUID.h

@@ -1,10 +1,14 @@
 #pragma once
 
 #include <cstdint>
+#include <optional>
 #include <ostream>
+#include <string_view>
 
 struct GUID
 {
+	static std::optional<GUID> from_string(std::string_view);
+
 	uint32_t component1;
 	uint16_t component2;
 	uint16_t component3;