1 files changed, 93 insertions, 0 deletions
diff --git a/src/openvic/utility/StringUtils.hpp b/src/openvic/utility/StringUtils.hpp
new file mode 100644
index 0000000..72f4038
--- /dev/null
+++ b/src/openvic/utility/StringUtils.hpp
@@ -0,0 +1,93 @@
+#include <cstdint>
+#include <limits>
+
+namespace OpenVic::StringUtils {
+	/* The constexpr function 'string_to_int64' will convert a string into a int64 integer value.
+		* The function takes four parameters: the input string (as a pair of pointers marking the start and
+		* end of the string), a bool pointer for reporting success, and the base for numerical conversion.
+		* The base parameter defaults to 10 (decimal), but it can be any value between 2 and 36. If the base
+		* given is 0, it will be set to 16 if the string starts with "0x" or "0X", otherwise 8 if the string
+		* still starts with "0", otherwise 10. The success bool pointer parameter is used to report whether
+		* or not conversion was successful. It can be nullptr if this information is not needed.
+		*/
+	constexpr int64_t string_to_int64(char const* str, const char* end, bool* successful, int base = 10) {
+		if (successful != nullptr) *successful = false;
+
+		// Base value should be between 2 and 36. If it's not, return 0 as an invalid case.
+		if (str == nullptr || end <= str || base < 0 || base == 1 || base > 36)
+			return 0;
+
+		// The result of the conversion will be stored in this variable.
+		int64_t result = 0;
+		// This flag will be set if the number is negative.
+		bool is_negative = false;
+
+		// Check if there is a sign character.
+		if (*str == '+' || *str == '-') {
+			if (*str == '-')
+				is_negative = true;
+			++str;
+			if (str == end) return 0;
+		}
+
+		// If base is zero, base is determined by the string prefix.
+		if (base == 0) {
+			if (*str == '0') {
+				if (str + 1 != end && (str[1] == 'x' || str[1] == 'X')) {
+					base = 16; // Hexadecimal.
+					str += 2;  // Skip '0x' or '0X'
+					if (str == end) return 0;
+				} else {
+					base = 8; // Octal.
+				}
+			} else {
+				base = 10; // Decimal.
+			}
+		} else if (base == 16) {
+			// If base is 16 and string starts with '0x' or '0X', skip these characters.
+			if (*str == '0' && str + 1 != end && (str[1] == 'x' || str[1] == 'X')) {
+				str += 2;
+				if (str == end) return 0;
+			}
+		}
+
+		// Convert the number in the string.
+		for (; str != end; ++str) {
+			int digit;
+			if (*str >= '0' && *str <= '9') {
+				digit = *str - '0'; // Calculate digit value for '0'-'9'.
+			} else if (*str >= 'a' && *str <= 'z') {
+				digit = *str - 'a' + 10; // Calculate digit value for 'a'-'z'.
+			} else if (*str >= 'A' && *str <= 'Z') {
+				digit = *str - 'A' + 10; // Calculate digit value for 'A'-'Z'.
+			} else {
+				break; // Stop conversion if current character is not a digit.
+			}
+
+			if (digit >= base) {
+				break; // Stop conversion if current digit is greater than or equal to the base.
+			}
+
+			// Check for overflow on multiplication
+			if (result > std::numeric_limits<int64_t>::max() / base) {
+				return is_negative ? std::numeric_limits<int64_t>::min() : std::numeric_limits<int64_t>::max();
+			}
+
+			result *= base;
+
+			// Check for overflow on addition
+			if (result > std::numeric_limits<int64_t>::max() - digit) {
+				return is_negative ? std::numeric_limits<int64_t>::min() : std::numeric_limits<int64_t>::max();
+			}
+
+			result += digit;
+		}
+
+		// If successful is not null and the entire string was parsed,
+		// set *successful to true (if not it is already false).
+		if (successful != nullptr && str == end) *successful = true;
+
+		// Return the result. If the number was negative, the result is negated.
+		return is_negative ? -result : result;
+	}
+}