LibString.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import {LibBytes} from "./LibBytes.sol";

/// @notice Library for converting numbers into strings and other string operations.
/// @author Solady (https://github.com/vectorized/solady/blob/main/src/utils/LibString.sol)
/// @author Modified from Solmate (https://github.com/transmissions11/solmate/blob/main/src/utils/LibString.sol)
///
/// @dev Note:
/// For performance and bytecode compactness, most of the string operations are restricted to
/// byte strings (7-bit ASCII), except where otherwise specified.
/// Usage of byte string operations on charsets with runes spanning two or more bytes
/// can lead to undefined behavior.
library LibString {
    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                          STRUCTS                           */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Goated string storage struct that totally MOGs, no cap, fr.
    /// Uses less gas and bytecode than Solidity's native string storage. It's meta af.
    /// Packs length with the first 31 bytes if <255 bytes, so it’s mad tight.
    struct StringStorage {
        bytes32 _spacer;
    }

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                        CUSTOM ERRORS                       */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev The length of the output is too small to contain all the hex digits.
    error HexLengthInsufficient();

    /// @dev The length of the string is more than 32 bytes.
    error TooBigForSmallString();

    /// @dev The input string must be a 7-bit ASCII.
    error StringNot7BitASCII();

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                         CONSTANTS                          */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev The constant returned when the `search` is not found in the string.
    uint256 internal constant NOT_FOUND = type(uint256).max;

    /// @dev Lookup for '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.
    uint128 internal constant ALPHANUMERIC_7_BIT_ASCII = 0x7fffffe07fffffe03ff000000000000;

    /// @dev Lookup for 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'.
    uint128 internal constant LETTERS_7_BIT_ASCII = 0x7fffffe07fffffe0000000000000000;

    /// @dev Lookup for 'abcdefghijklmnopqrstuvwxyz'.
    uint128 internal constant LOWERCASE_7_BIT_ASCII = 0x7fffffe000000000000000000000000;

    /// @dev Lookup for 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'.
    uint128 internal constant UPPERCASE_7_BIT_ASCII = 0x7fffffe0000000000000000;

    /// @dev Lookup for '0123456789'.
    uint128 internal constant DIGITS_7_BIT_ASCII = 0x3ff000000000000;

    /// @dev Lookup for '0123456789abcdefABCDEF'.
    uint128 internal constant HEXDIGITS_7_BIT_ASCII = 0x7e0000007e03ff000000000000;

    /// @dev Lookup for '01234567'.
    uint128 internal constant OCTDIGITS_7_BIT_ASCII = 0xff000000000000;

    /// @dev Lookup for '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\x0b\x0c'.
    uint128 internal constant PRINTABLE_7_BIT_ASCII = 0x7fffffffffffffffffffffff00003e00;

    /// @dev Lookup for '!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~'.
    uint128 internal constant PUNCTUATION_7_BIT_ASCII = 0x78000001f8000001fc00fffe00000000;

    /// @dev Lookup for ' \t\n\r\x0b\x0c'.
    uint128 internal constant WHITESPACE_7_BIT_ASCII = 0x100003e00;

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                 STRING STORAGE OPERATIONS                  */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Sets the value of the string storage `$` to `s`.
    function set(StringStorage storage $, string memory s) internal {
        LibBytes.set(bytesStorage($), bytes(s));
    }

    /// @dev Sets the value of the string storage `$` to `s`.
    function setCalldata(StringStorage storage $, string calldata s) internal {
        LibBytes.setCalldata(bytesStorage($), bytes(s));
    }

    /// @dev Sets the value of the string storage `$` to the empty string.
    function clear(StringStorage storage $) internal {
        delete $._spacer;
    }

    /// @dev Returns whether the value stored is `$` is the empty string "".
    function isEmpty(StringStorage storage $) internal view returns (bool) {
        return uint256($._spacer) & 0xff == uint256(0);
    }

    /// @dev Returns the length of the value stored in `$`.
    function length(StringStorage storage $) internal view returns (uint256) {
        return LibBytes.length(bytesStorage($));
    }

    /// @dev Returns the value stored in `$`.
    function get(StringStorage storage $) internal view returns (string memory) {
        return string(LibBytes.get(bytesStorage($)));
    }

    /// @dev Helper to cast `$` to a `BytesStorage`.
    function bytesStorage(StringStorage storage $)
        internal
        pure
        returns (LibBytes.BytesStorage storage casted)
    {
        /// @solidity memory-safe-assembly
        assembly {
            casted.slot := $.slot
        }
    }

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                     DECIMAL OPERATIONS                     */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Returns the base 10 decimal representation of `value`.
    function toString(uint256 value) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            // The maximum value of a uint256 contains 78 digits (1 byte per digit), but
            // we allocate 0xa0 bytes to keep the free memory pointer 32-byte word aligned.
            // We will need 1 word for the trailing zeros padding, 1 word for the length,
            // and 3 words for a maximum of 78 digits.
            result := add(mload(0x40), 0x80)
            mstore(0x40, add(result, 0x20)) // Allocate memory.
            mstore(result, 0) // Zeroize the slot after the string.

            let end := result // Cache the end of the memory to calculate the length later.
            let w := not(0) // Tsk.
            // We write the string from rightmost digit to leftmost digit.
            // The following is essentially a do-while loop that also handles the zero case.
            for { let temp := value } 1 {} {
                result := add(result, w) // `sub(result, 1)`.
                // Store the character to the pointer.
                // The ASCII index of the '0' character is 48.
                mstore8(result, add(48, mod(temp, 10)))
                temp := div(temp, 10) // Keep dividing `temp` until zero.
                if iszero(temp) { break }
            }
            let n := sub(end, result)
            result := sub(result, 0x20) // Move the pointer 32 bytes back to make room for the length.
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the base 10 decimal representation of `value`.
    function toString(int256 value) internal pure returns (string memory result) {
        if (value >= 0) return toString(uint256(value));
        unchecked {
            result = toString(~uint256(value) + 1);
        }
        /// @solidity memory-safe-assembly
        assembly {
            // We still have some spare memory space on the left,
            // as we have allocated 3 words (96 bytes) for up to 78 digits.
            let n := mload(result) // Load the string length.
            mstore(result, 0x2d) // Store the '-' character.
            result := sub(result, 1) // Move back the string pointer by a byte.
            mstore(result, add(n, 1)) // Update the string length.
        }
    }

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                   HEXADECIMAL OPERATIONS                   */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Returns the hexadecimal representation of `value`,
    /// left-padded to an input length of `byteCount` bytes.
    /// The output is prefixed with "0x" encoded using 2 hexadecimal digits per byte,
    /// giving a total length of `byteCount * 2 + 2` bytes.
    /// Reverts if `byteCount` is too small for the output to contain all the digits.
    function toHexString(uint256 value, uint256 byteCount)
        internal
        pure
        returns (string memory result)
    {
        result = toHexStringNoPrefix(value, byteCount);
        /// @solidity memory-safe-assembly
        assembly {
            let n := add(mload(result), 2) // Compute the length.
            mstore(result, 0x3078) // Store the "0x" prefix.
            result := sub(result, 2) // Move the pointer.
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`,
    /// left-padded to an input length of `byteCount` bytes.
    /// The output is not prefixed with "0x" and is encoded using 2 hexadecimal digits per byte,
    /// giving a total length of `byteCount * 2` bytes.
    /// Reverts if `byteCount` is too small for the output to contain all the digits.
    function toHexStringNoPrefix(uint256 value, uint256 byteCount)
        internal
        pure
        returns (string memory result)
    {
        /// @solidity memory-safe-assembly
        assembly {
            // We need 0x20 bytes for the trailing zeros padding, `byteCount * 2` bytes
            // for the digits, 0x02 bytes for the prefix, and 0x20 bytes for the length.
            // We add 0x20 to the total and round down to a multiple of 0x20.
            // (0x20 + 0x20 + 0x02 + 0x20) = 0x62.
            result := add(mload(0x40), and(add(shl(1, byteCount), 0x42), not(0x1f)))
            mstore(0x40, add(result, 0x20)) // Allocate memory.
            mstore(result, 0) // Zeroize the slot after the string.

            let end := result // Cache the end to calculate the length later.
            // Store "0123456789abcdef" in scratch space.
            mstore(0x0f, 0x30313233343536373839616263646566)

            let start := sub(result, add(byteCount, byteCount))
            let w := not(1) // Tsk.
            let temp := value
            // We write the string from rightmost digit to leftmost digit.
            // The following is essentially a do-while loop that also handles the zero case.
            for {} 1 {} {
                result := add(result, w) // `sub(result, 2)`.
                mstore8(add(result, 1), mload(and(temp, 15)))
                mstore8(result, mload(and(shr(4, temp), 15)))
                temp := shr(8, temp)
                if iszero(xor(result, start)) { break }
            }
            if temp {
                mstore(0x00, 0x2194895a) // `HexLengthInsufficient()`.
                revert(0x1c, 0x04)
            }
            let n := sub(end, result)
            result := sub(result, 0x20)
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output is prefixed with "0x" and encoded using 2 hexadecimal digits per byte.
    /// As address are 20 bytes long, the output will left-padded to have
    /// a length of `20 * 2 + 2` bytes.
    function toHexString(uint256 value) internal pure returns (string memory result) {
        result = toHexStringNoPrefix(value);
        /// @solidity memory-safe-assembly
        assembly {
            let n := add(mload(result), 2) // Compute the length.
            mstore(result, 0x3078) // Store the "0x" prefix.
            result := sub(result, 2) // Move the pointer.
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output is prefixed with "0x".
    /// The output excludes leading "0" from the `toHexString` output.
    /// `0x00: "0x0", 0x01: "0x1", 0x12: "0x12", 0x123: "0x123"`.
    function toMinimalHexString(uint256 value) internal pure returns (string memory result) {
        result = toHexStringNoPrefix(value);
        /// @solidity memory-safe-assembly
        assembly {
            let o := eq(byte(0, mload(add(result, 0x20))), 0x30) // Whether leading zero is present.
            let n := add(mload(result), 2) // Compute the length.
            mstore(add(result, o), 0x3078) // Store the "0x" prefix, accounting for leading zero.
            result := sub(add(result, o), 2) // Move the pointer, accounting for leading zero.
            mstore(result, sub(n, o)) // Store the length, accounting for leading zero.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output excludes leading "0" from the `toHexStringNoPrefix` output.
    /// `0x00: "0", 0x01: "1", 0x12: "12", 0x123: "123"`.
    function toMinimalHexStringNoPrefix(uint256 value)
        internal
        pure
        returns (string memory result)
    {
        result = toHexStringNoPrefix(value);
        /// @solidity memory-safe-assembly
        assembly {
            let o := eq(byte(0, mload(add(result, 0x20))), 0x30) // Whether leading zero is present.
            let n := mload(result) // Get the length.
            result := add(result, o) // Move the pointer, accounting for leading zero.
            mstore(result, sub(n, o)) // Store the length, accounting for leading zero.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output is encoded using 2 hexadecimal digits per byte.
    /// As address are 20 bytes long, the output will left-padded to have
    /// a length of `20 * 2` bytes.
    function toHexStringNoPrefix(uint256 value) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            // We need 0x20 bytes for the trailing zeros padding, 0x20 bytes for the length,
            // 0x02 bytes for the prefix, and 0x40 bytes for the digits.
            // The next multiple of 0x20 above (0x20 + 0x20 + 0x02 + 0x40) is 0xa0.
            result := add(mload(0x40), 0x80)
            mstore(0x40, add(result, 0x20)) // Allocate memory.
            mstore(result, 0) // Zeroize the slot after the string.

            let end := result // Cache the end to calculate the length later.
            mstore(0x0f, 0x30313233343536373839616263646566) // Store the "0123456789abcdef" lookup.

            let w := not(1) // Tsk.
            // We write the string from rightmost digit to leftmost digit.
            // The following is essentially a do-while loop that also handles the zero case.
            for { let temp := value } 1 {} {
                result := add(result, w) // `sub(result, 2)`.
                mstore8(add(result, 1), mload(and(temp, 15)))
                mstore8(result, mload(and(shr(4, temp), 15)))
                temp := shr(8, temp)
                if iszero(temp) { break }
            }
            let n := sub(end, result)
            result := sub(result, 0x20)
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output is prefixed with "0x", encoded using 2 hexadecimal digits per byte,
    /// and the alphabets are capitalized conditionally according to
    /// https://eips.ethereum.org/EIPS/eip-55
    function toHexStringChecksummed(address value) internal pure returns (string memory result) {
        result = toHexString(value);
        /// @solidity memory-safe-assembly
        assembly {
            let mask := shl(6, div(not(0), 255)) // `0b010000000100000000 ...`
            let o := add(result, 0x22)
            let hashed := and(keccak256(o, 40), mul(34, mask)) // `0b10001000 ... `
            let t := shl(240, 136) // `0b10001000 << 240`
            for { let i := 0 } 1 {} {
                mstore(add(i, i), mul(t, byte(i, hashed)))
                i := add(i, 1)
                if eq(i, 20) { break }
            }
            mstore(o, xor(mload(o), shr(1, and(mload(0x00), and(mload(o), mask)))))
            o := add(o, 0x20)
            mstore(o, xor(mload(o), shr(1, and(mload(0x20), and(mload(o), mask)))))
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output is prefixed with "0x" and encoded using 2 hexadecimal digits per byte.
    function toHexString(address value) internal pure returns (string memory result) {
        result = toHexStringNoPrefix(value);
        /// @solidity memory-safe-assembly
        assembly {
            let n := add(mload(result), 2) // Compute the length.
            mstore(result, 0x3078) // Store the "0x" prefix.
            result := sub(result, 2) // Move the pointer.
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the hexadecimal representation of `value`.
    /// The output is encoded using 2 hexadecimal digits per byte.
    function toHexStringNoPrefix(address value) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(0x40)
            // Allocate memory.
            // We need 0x20 bytes for the trailing zeros padding, 0x20 bytes for the length,
            // 0x02 bytes for the prefix, and 0x28 bytes for the digits.
            // The next multiple of 0x20 above (0x20 + 0x20 + 0x02 + 0x28) is 0x80.
            mstore(0x40, add(result, 0x80))
            mstore(0x0f, 0x30313233343536373839616263646566) // Store the "0123456789abcdef" lookup.

            result := add(result, 2)
            mstore(result, 40) // Store the length.
            let o := add(result, 0x20)
            mstore(add(o, 40), 0) // Zeroize the slot after the string.
            value := shl(96, value)
            // We write the string from rightmost digit to leftmost digit.
            // The following is essentially a do-while loop that also handles the zero case.
            for { let i := 0 } 1 {} {
                let p := add(o, add(i, i))
                let temp := byte(i, value)
                mstore8(add(p, 1), mload(and(temp, 15)))
                mstore8(p, mload(shr(4, temp)))
                i := add(i, 1)
                if eq(i, 20) { break }
            }
        }
    }

    /// @dev Returns the hex encoded string from the raw bytes.
    /// The output is encoded using 2 hexadecimal digits per byte.
    function toHexString(bytes memory raw) internal pure returns (string memory result) {
        result = toHexStringNoPrefix(raw);
        /// @solidity memory-safe-assembly
        assembly {
            let n := add(mload(result), 2) // Compute the length.
            mstore(result, 0x3078) // Store the "0x" prefix.
            result := sub(result, 2) // Move the pointer.
            mstore(result, n) // Store the length.
        }
    }

    /// @dev Returns the hex encoded string from the raw bytes.
    /// The output is encoded using 2 hexadecimal digits per byte.
    function toHexStringNoPrefix(bytes memory raw) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            let n := mload(raw)
            result := add(mload(0x40), 2) // Skip 2 bytes for the optional prefix.
            mstore(result, add(n, n)) // Store the length of the output.

            mstore(0x0f, 0x30313233343536373839616263646566) // Store the "0123456789abcdef" lookup.
            let o := add(result, 0x20)
            let end := add(raw, n)
            for {} iszero(eq(raw, end)) {} {
                raw := add(raw, 1)
                mstore8(add(o, 1), mload(and(mload(raw), 15)))
                mstore8(o, mload(and(shr(4, mload(raw)), 15)))
                o := add(o, 2)
            }
            mstore(o, 0) // Zeroize the slot after the string.
            mstore(0x40, add(o, 0x20)) // Allocate memory.
        }
    }

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                   RUNE STRING OPERATIONS                   */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Returns the number of UTF characters in the string.
    function runeCount(string memory s) internal pure returns (uint256 result) {
        /// @solidity memory-safe-assembly
        assembly {
            if mload(s) {
                mstore(0x00, div(not(0), 255))
                mstore(0x20, 0x0202020202020202020202020202020202020202020202020303030304040506)
                let o := add(s, 0x20)
                let end := add(o, mload(s))
                for { result := 1 } 1 { result := add(result, 1) } {
                    o := add(o, byte(0, mload(shr(250, mload(o)))))
                    if iszero(lt(o, end)) { break }
                }
            }
        }
    }

    /// @dev Returns if this string is a 7-bit ASCII string.
    /// (i.e. all characters codes are in [0..127])
    function is7BitASCII(string memory s) internal pure returns (bool result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := 1
            let mask := shl(7, div(not(0), 255))
            let n := mload(s)
            if n {
                let o := add(s, 0x20)
                let end := add(o, n)
                let last := mload(end)
                mstore(end, 0)
                for {} 1 {} {
                    if and(mask, mload(o)) {
                        result := 0
                        break
                    }
                    o := add(o, 0x20)
                    if iszero(lt(o, end)) { break }
                }
                mstore(end, last)
            }
        }
    }

    /// @dev Returns if this string is a 7-bit ASCII string,
    /// AND all characters are in the `allowed` lookup.
    /// Note: If `s` is empty, returns true regardless of `allowed`.
    function is7BitASCII(string memory s, uint128 allowed) internal pure returns (bool result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := 1
            if mload(s) {
                let allowed_ := shr(128, shl(128, allowed))
                let o := add(s, 0x20)
                for { let end := add(o, mload(s)) } 1 {} {
                    result := and(result, shr(byte(0, mload(o)), allowed_))
                    o := add(o, 1)
                    if iszero(and(result, lt(o, end))) { break }
                }
            }
        }
    }

    /// @dev Converts the bytes in the 7-bit ASCII string `s` to
    /// an allowed lookup for use in `is7BitASCII(s, allowed)`.
    /// To save runtime gas, you can cache the result in an immutable variable.
    function to7BitASCIIAllowedLookup(string memory s) internal pure returns (uint128 result) {
        /// @solidity memory-safe-assembly
        assembly {
            if mload(s) {
                let o := add(s, 0x20)
                for { let end := add(o, mload(s)) } 1 {} {
                    result := or(result, shl(byte(0, mload(o)), 1))
                    o := add(o, 1)
                    if iszero(lt(o, end)) { break }
                }
                if shr(128, result) {
                    mstore(0x00, 0xc9807e0d) // `StringNot7BitASCII()`.
                    revert(0x1c, 0x04)
                }
            }
        }
    }

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                   BYTE STRING OPERATIONS                   */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    // For performance and bytecode compactness, byte string operations are restricted
    // to 7-bit ASCII strings. All offsets are byte offsets, not UTF character offsets.
    // Usage of byte string operations on charsets with runes spanning two or more bytes
    // can lead to undefined behavior.

    /// @dev Returns `subject` all occurrences of `needle` replaced with `replacement`.
    function replace(string memory subject, string memory needle, string memory replacement)
        internal
        pure
        returns (string memory)
    {
        return string(LibBytes.replace(bytes(subject), bytes(needle), bytes(replacement)));
    }

    /// @dev Returns the byte index of the first location of `needle` in `subject`,
    /// needleing from left to right, starting from `from`.
    /// Returns `NOT_FOUND` (i.e. `type(uint256).max`) if the `needle` is not found.
    function indexOf(string memory subject, string memory needle, uint256 from)
        internal
        pure
        returns (uint256)
    {
        return LibBytes.indexOf(bytes(subject), bytes(needle), from);
    }

    /// @dev Returns the byte index of the first location of `needle` in `subject`,
    /// needleing from left to right.
    /// Returns `NOT_FOUND` (i.e. `type(uint256).max`) if the `needle` is not found.
    function indexOf(string memory subject, string memory needle) internal pure returns (uint256) {
        return LibBytes.indexOf(bytes(subject), bytes(needle), 0);
    }

    /// @dev Returns the byte index of the first location of `needle` in `subject`,
    /// needleing from right to left, starting from `from`.
    /// Returns `NOT_FOUND` (i.e. `type(uint256).max`) if the `needle` is not found.
    function lastIndexOf(string memory subject, string memory needle, uint256 from)
        internal
        pure
        returns (uint256)
    {
        return LibBytes.lastIndexOf(bytes(subject), bytes(needle), from);
    }

    /// @dev Returns the byte index of the first location of `needle` in `subject`,
    /// needleing from right to left.
    /// Returns `NOT_FOUND` (i.e. `type(uint256).max`) if the `needle` is not found.
    function lastIndexOf(string memory subject, string memory needle)
        internal
        pure
        returns (uint256)
    {
        return LibBytes.lastIndexOf(bytes(subject), bytes(needle), type(uint256).max);
    }

    /// @dev Returns true if `needle` is found in `subject`, false otherwise.
    function contains(string memory subject, string memory needle) internal pure returns (bool) {
        return LibBytes.contains(bytes(subject), bytes(needle));
    }

    /// @dev Returns whether `subject` starts with `needle`.
    function startsWith(string memory subject, string memory needle) internal pure returns (bool) {
        return LibBytes.startsWith(bytes(subject), bytes(needle));
    }

    /// @dev Returns whether `subject` ends with `needle`.
    function endsWith(string memory subject, string memory needle) internal pure returns (bool) {
        return LibBytes.endsWith(bytes(subject), bytes(needle));
    }

    /// @dev Returns `subject` repeated `times`.
    function repeat(string memory subject, uint256 times) internal pure returns (string memory) {
        return string(LibBytes.repeat(bytes(subject), times));
    }

    /// @dev Returns a copy of `subject` sliced from `start` to `end` (exclusive).
    /// `start` and `end` are byte offsets.
    function slice(string memory subject, uint256 start, uint256 end)
        internal
        pure
        returns (string memory)
    {
        return string(LibBytes.slice(bytes(subject), start, end));
    }

    /// @dev Returns a copy of `subject` sliced from `start` to the end of the string.
    /// `start` is a byte offset.
    function slice(string memory subject, uint256 start) internal pure returns (string memory) {
        return string(LibBytes.slice(bytes(subject), start, type(uint256).max));
    }

    /// @dev Returns all the indices of `needle` in `subject`.
    /// The indices are byte offsets.
    function indicesOf(string memory subject, string memory needle)
        internal
        pure
        returns (uint256[] memory)
    {
        return LibBytes.indicesOf(bytes(subject), bytes(needle));
    }

    /// @dev Returns a arrays of strings based on the `delimiter` inside of the `subject` string.
    function split(string memory subject, string memory delimiter)
        internal
        pure
        returns (string[] memory result)
    {
        bytes[] memory a = LibBytes.split(bytes(subject), bytes(delimiter));
        /// @solidity memory-safe-assembly
        assembly {
            result := a
        }
    }

    /// @dev Returns a concatenated string of `a` and `b`.
    /// Cheaper than `string.concat()` and does not de-align the free memory pointer.
    function concat(string memory a, string memory b) internal pure returns (string memory) {
        return string(LibBytes.concat(bytes(a), bytes(b)));
    }

    /// @dev Returns a copy of the string in either lowercase or UPPERCASE.
    /// WARNING! This function is only compatible with 7-bit ASCII strings.
    function toCase(string memory subject, bool toUpper)
        internal
        pure
        returns (string memory result)
    {
        /// @solidity memory-safe-assembly
        assembly {
            let n := mload(subject)
            if n {
                result := mload(0x40)
                let o := add(result, 0x20)
                let d := sub(subject, result)
                let flags := shl(add(70, shl(5, toUpper)), 0x3ffffff)
                for { let end := add(o, n) } 1 {} {
                    let b := byte(0, mload(add(d, o)))
                    mstore8(o, xor(and(shr(b, flags), 0x20), b))
                    o := add(o, 1)
                    if eq(o, end) { break }
                }
                mstore(result, n) // Store the length.
                mstore(o, 0) // Zeroize the slot after the string.
                mstore(0x40, add(o, 0x20)) // Allocate memory.
            }
        }
    }

    /// @dev Returns a string from a small bytes32 string.
    /// `s` must be null-terminated, or behavior will be undefined.
    function fromSmallString(bytes32 s) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(0x40)
            let n := 0
            for {} byte(n, s) { n := add(n, 1) } {} // Scan for '\0'.
            mstore(result, n) // Store the length.
            let o := add(result, 0x20)
            mstore(o, s) // Store the bytes of the string.
            mstore(add(o, n), 0) // Zeroize the slot after the string.
            mstore(0x40, add(result, 0x40)) // Allocate memory.
        }
    }

    /// @dev Returns the small string, with all bytes after the first null byte zeroized.
    function normalizeSmallString(bytes32 s) internal pure returns (bytes32 result) {
        /// @solidity memory-safe-assembly
        assembly {
            for {} byte(result, s) { result := add(result, 1) } {} // Scan for '\0'.
            mstore(0x00, s)
            mstore(result, 0x00)
            result := mload(0x00)
        }
    }

    /// @dev Returns the string as a normalized null-terminated small string.
    function toSmallString(string memory s) internal pure returns (bytes32 result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(s)
            if iszero(lt(result, 33)) {
                mstore(0x00, 0xec92f9a3) // `TooBigForSmallString()`.
                revert(0x1c, 0x04)
            }
            result := shl(shl(3, sub(32, result)), mload(add(s, result)))
        }
    }

    /// @dev Returns a lowercased copy of the string.
    /// WARNING! This function is only compatible with 7-bit ASCII strings.
    function lower(string memory subject) internal pure returns (string memory result) {
        result = toCase(subject, false);
    }

    /// @dev Returns an UPPERCASED copy of the string.
    /// WARNING! This function is only compatible with 7-bit ASCII strings.
    function upper(string memory subject) internal pure returns (string memory result) {
        result = toCase(subject, true);
    }

    /// @dev Escapes the string to be used within HTML tags.
    function escapeHTML(string memory s) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(0x40)
            let end := add(s, mload(s))
            let o := add(result, 0x20)
            // Store the bytes of the packed offsets and strides into the scratch space.
            // `packed = (stride << 5) | offset`. Max offset is 20. Max stride is 6.
            mstore(0x1f, 0x900094)
            mstore(0x08, 0xc0000000a6ab)
            // Store "&quot;&amp;&#39;&lt;&gt;" into the scratch space.
            mstore(0x00, shl(64, 0x2671756f743b26616d703b262333393b266c743b2667743b))
            for {} iszero(eq(s, end)) {} {
                s := add(s, 1)
                let c := and(mload(s), 0xff)
                // Not in `["\"","'","&","<",">"]`.
                if iszero(and(shl(c, 1), 0x500000c400000000)) {
                    mstore8(o, c)
                    o := add(o, 1)
                    continue
                }
                let t := shr(248, mload(c))
                mstore(o, mload(and(t, 0x1f)))
                o := add(o, shr(5, t))
            }
            mstore(o, 0) // Zeroize the slot after the string.
            mstore(result, sub(o, add(result, 0x20))) // Store the length.
            mstore(0x40, add(o, 0x20)) // Allocate memory.
        }
    }

    /// @dev Escapes the string to be used within double-quotes in a JSON.
    /// If `addDoubleQuotes` is true, the result will be enclosed in double-quotes.
    function escapeJSON(string memory s, bool addDoubleQuotes)
        internal
        pure
        returns (string memory result)
    {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(0x40)
            let o := add(result, 0x20)
            if addDoubleQuotes {
                mstore8(o, 34)
                o := add(1, o)
            }
            // Store "\\u0000" in scratch space.
            // Store "0123456789abcdef" in scratch space.
            // Also, store `{0x08:"b", 0x09:"t", 0x0a:"n", 0x0c:"f", 0x0d:"r"}`.
            // into the scratch space.
            mstore(0x15, 0x5c75303030303031323334353637383961626364656662746e006672)
            // Bitmask for detecting `["\"","\\"]`.
            let e := or(shl(0x22, 1), shl(0x5c, 1))
            for { let end := add(s, mload(s)) } iszero(eq(s, end)) {} {
                s := add(s, 1)
                let c := and(mload(s), 0xff)
                if iszero(lt(c, 0x20)) {
                    if iszero(and(shl(c, 1), e)) {
                        // Not in `["\"","\\"]`.
                        mstore8(o, c)
                        o := add(o, 1)
                        continue
                    }
                    mstore8(o, 0x5c) // "\\".
                    mstore8(add(o, 1), c)
                    o := add(o, 2)
                    continue
                }
                if iszero(and(shl(c, 1), 0x3700)) {
                    // Not in `["\b","\t","\n","\f","\d"]`.
                    mstore8(0x1d, mload(shr(4, c))) // Hex value.
                    mstore8(0x1e, mload(and(c, 15))) // Hex value.
                    mstore(o, mload(0x19)) // "\\u00XX".
                    o := add(o, 6)
                    continue
                }
                mstore8(o, 0x5c) // "\\".
                mstore8(add(o, 1), mload(add(c, 8)))
                o := add(o, 2)
            }
            if addDoubleQuotes {
                mstore8(o, 34)
                o := add(1, o)
            }
            mstore(o, 0) // Zeroize the slot after the string.
            mstore(result, sub(o, add(result, 0x20))) // Store the length.
            mstore(0x40, add(o, 0x20)) // Allocate memory.
        }
    }

    /// @dev Escapes the string to be used within double-quotes in a JSON.
    function escapeJSON(string memory s) internal pure returns (string memory result) {
        result = escapeJSON(s, false);
    }

    /// @dev Encodes `s` so that it can be safely used in a URI,
    /// just like `encodeURIComponent` in JavaScript.
    /// See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent
    /// See: https://datatracker.ietf.org/doc/html/rfc2396
    /// See: https://datatracker.ietf.org/doc/html/rfc3986
    function encodeURIComponent(string memory s) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(0x40)
            // Store "0123456789ABCDEF" in scratch space.
            // Uppercased to be consistent with JavaScript's implementation.
            mstore(0x0f, 0x30313233343536373839414243444546)
            let o := add(result, 0x20)
            for { let end := add(s, mload(s)) } iszero(eq(s, end)) {} {
                s := add(s, 1)
                let c := and(mload(s), 0xff)
                // If not in `[0-9A-Z-a-z-_.!~*'()]`.
                if iszero(and(1, shr(c, 0x47fffffe87fffffe03ff678200000000))) {
                    mstore8(o, 0x25) // '%'.
                    mstore8(add(o, 1), mload(and(shr(4, c), 15)))
                    mstore8(add(o, 2), mload(and(c, 15)))
                    o := add(o, 3)
                    continue
                }
                mstore8(o, c)
                o := add(o, 1)
            }
            mstore(result, sub(o, add(result, 0x20))) // Store the length.
            mstore(o, 0) // Zeroize the slot after the string.
            mstore(0x40, add(o, 0x20)) // Allocate memory.
        }
    }

    /// @dev Returns whether `a` equals `b`.
    function eq(string memory a, string memory b) internal pure returns (bool result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := eq(keccak256(add(a, 0x20), mload(a)), keccak256(add(b, 0x20), mload(b)))
        }
    }

    /// @dev Returns whether `a` equals `b`, where `b` is a null-terminated small string.
    function eqs(string memory a, bytes32 b) internal pure returns (bool result) {
        /// @solidity memory-safe-assembly
        assembly {
            // These should be evaluated on compile time, as far as possible.
            let m := not(shl(7, div(not(iszero(b)), 255))) // `0x7f7f ...`.
            let x := not(or(m, or(b, add(m, and(b, m)))))
            let r := shl(7, iszero(iszero(shr(128, x))))
            r := or(r, shl(6, iszero(iszero(shr(64, shr(r, x))))))
            r := or(r, shl(5, lt(0xffffffff, shr(r, x))))
            r := or(r, shl(4, lt(0xffff, shr(r, x))))
            r := or(r, shl(3, lt(0xff, shr(r, x))))
            // forgefmt: disable-next-item
            result := gt(eq(mload(a), add(iszero(x), xor(31, shr(3, r)))),
                xor(shr(add(8, r), b), shr(add(8, r), mload(add(a, 0x20)))))
        }
    }

    /// @dev Returns 0 if `a == b`, -1 if `a < b`, +1 if `a > b`.
    /// If `a` == b[:a.length]`, and `a.length < b.length`, returns -1.
    function cmp(string memory a, string memory b) internal pure returns (int256) {
        return LibBytes.cmp(bytes(a), bytes(b));
    }

    /// @dev Packs a single string with its length into a single word.
    /// Returns `bytes32(0)` if the length is zero or greater than 31.
    function packOne(string memory a) internal pure returns (bytes32 result) {
        /// @solidity memory-safe-assembly
        assembly {
            // We don't need to zero right pad the string,
            // since this is our own custom non-standard packing scheme.
            result :=
                mul(
                    // Load the length and the bytes.
                    mload(add(a, 0x1f)),
                    // `length != 0 && length < 32`. Abuses underflow.
                    // Assumes that the length is valid and within the block gas limit.
                    lt(sub(mload(a), 1), 0x1f)
                )
        }
    }

    /// @dev Unpacks a string packed using {packOne}.
    /// Returns the empty string if `packed` is `bytes32(0)`.
    /// If `packed` is not an output of {packOne}, the output behavior is undefined.
    function unpackOne(bytes32 packed) internal pure returns (string memory result) {
        /// @solidity memory-safe-assembly
        assembly {
            result := mload(0x40) // Grab the free memory pointer.
            mstore(0x40, add(result, 0x40)) // Allocate 2 words (1 for the length, 1 for the bytes).
            mstore(result, 0) // Zeroize the length slot.
            mstore(add(result, 0x1f), packed) // Store the length and bytes.
            mstore(add(add(result, 0x20), mload(result)), 0) // Right pad with zeroes.
        }
    }

    /// @dev Packs two strings with their lengths into a single word.
    /// Returns `bytes32(0)` if combined length is zero or greater than 30.
    function packTwo(string memory a, string memory b) internal pure returns (bytes32 result) {
        /// @solidity memory-safe-assembly
        assembly {
            let aLen := mload(a)
            // We don't need to zero right pad the strings,
            // since this is our own custom non-standard packing scheme.
            result :=
                mul(
                    or( // Load the length and the bytes of `a` and `b`.
                    shl(shl(3, sub(0x1f, aLen)), mload(add(a, aLen))), mload(sub(add(b, 0x1e), aLen))),
                    // `totalLen != 0 && totalLen < 31`. Abuses underflow.
                    // Assumes that the lengths are valid and within the block gas limit.
                    lt(sub(add(aLen, mload(b)), 1), 0x1e)
                )
        }
    }

    /// @dev Unpacks strings packed using {packTwo}.
    /// Returns the empty strings if `packed` is `bytes32(0)`.
    /// If `packed` is not an output of {packTwo}, the output behavior is undefined.
    function unpackTwo(bytes32 packed)
        internal
        pure
        returns (string memory resultA, string memory resultB)
    {
        /// @solidity memory-safe-assembly
        assembly {
            resultA := mload(0x40) // Grab the free memory pointer.
            resultB := add(resultA, 0x40)
            // Allocate 2 words for each string (1 for the length, 1 for the byte). Total 4 words.
            mstore(0x40, add(resultB, 0x40))
            // Zeroize the length slots.
            mstore(resultA, 0)
            mstore(resultB, 0)
            // Store the lengths and bytes.
            mstore(add(resultA, 0x1f), packed)
            mstore(add(resultB, 0x1f), mload(add(add(resultA, 0x20), mload(resultA))))
            // Right pad with zeroes.
            mstore(add(add(resultA, 0x20), mload(resultA)), 0)
            mstore(add(add(resultB, 0x20), mload(resultB)), 0)
        }
    }

    /// @dev Directly returns `a` without copying.
    function directReturn(string memory a) internal pure {
        /// @solidity memory-safe-assembly
        assembly {
            // Assumes that the string does not start from the scratch space.
            let retStart := sub(a, 0x20)
            let retUnpaddedSize := add(mload(a), 0x40)
            // Right pad with zeroes. Just in case the string is produced
            // by a method that doesn't zero right pad.
            mstore(add(retStart, retUnpaddedSize), 0)
            mstore(retStart, 0x20) // Store the return offset.
            // End the transaction, returning the string.
            return(retStart, and(not(0x1f), add(0x1f, retUnpaddedSize)))
        }
    }
}