FastPrenormCompare.swift

extension String {
    public func _compareStringLinux(_ rhs: String) -> Int {
        // Fast lexigraphic comparison of (composed) pre-normalized prefixes
        var lhsCore = self._core
        var rhsCore = rhs._core
        let minCount = Swift.min(lhsCore.count, rhsCore.count)
        for idx in 0..<minCount {
            // Detect when pre-normalization ends: Quick check if next code unit might be combining
            if idx+1 < minCount && (lhsCore[idx+1] >= 0x300 || rhsCore[idx+1] >= 0x300) {
                lhsCore = lhsCore[idx...]
                rhsCore = rhsCore[idx...]
                break
            }
            let lhsCU = lhsCore[idx]
            let rhsCU = rhsCore[idx]
            if lhsCU < rhsCU {
                return -1
            }
            if rhsCU < lhsCU {
                return 1
            }
            
            // Check for equality
            if idx == minCount - 1 {
                if lhsCore.count == rhsCore.count {
                    return 0
                }
                return lhsCore.count < rhsCore.count ? -1 : 1
            }
        }
        
        // Fall back to UCA
        return String(lhsCore)._compareDeterministicUnicodeCollation(String(rhsCore))
    }
}