_IPv4Address.cs source code in C# .NET

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Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Net / System / _IPv4Address.cs / 1 / _IPv4Address.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System { 
 
    // The class designed as to keep minimal the working set of Uri class.
    // The idea is to stay with static helper methods and strings 
    internal class IPv4AddressHelper {

    // fields
        private IPv4AddressHelper() { 
        }
 
        private const int NumberOfLabels = 4; 

        // methods 

        internal static string ParseCanonicalName(string str, int start, int end, ref bool isLoopback) {
            unsafe {
                byte* numbers = stackalloc byte[NumberOfLabels]; 
                isLoopback = Parse(str, numbers, start, end);
                return numbers[0] + "." + numbers[1] + "." + numbers[2] + "." + numbers[3]; 
            } 
        }
 
        internal static int ParseHostNumber(string str, int start, int end) {
            unsafe {
                byte* numbers = stackalloc byte[NumberOfLabels];
                Parse(str, numbers, start, end); 
                return (numbers[0] << 24) + (numbers[1] << 16) + (numbers[2] << 8) + numbers[3];
            } 
        } 

        // 
        // IsValid
        //
        //  Performs IsValid on a substring. Updates the index to where we
        //  believe the IPv4 address ends 
        //
        // Inputs: 
        //    name 
        //      string containing possible IPv4 address
        // 
        //    start
        //      offset in  to start checking for IPv4 address
        //
        //    end 
        //      offset in  of the last character we can touch in the check
        // 
        // Outputs: 
        //    end
        //      index of last character in  we checked 
        //
        // Assumes:
        // The address string is terminated by either
        // end of the string, characters ':' '/' '\' '?' 
        //
        // 
        // Returns: 
        //  bool
        // 
        // Throws:
        //  Nothing
        //
 
        //internal unsafe static bool IsValid(char* name, int start, ref int end) {
        //    return IsValid(name, start, ref end, false); 
        //} 

        //Remark: MUST NOT be used unless all input indexes are are verified and trusted. 
        internal unsafe static bool IsValid(char* name, int start, ref int end, bool allowIPv6, bool notImplicitFile) {

            int dots = 0;
            int number = 0; 
            bool haveNumber = false;
 
            while (start < end) { 
                char ch = name[start];
                if (allowIPv6) { 
                    // for ipv4 inside ipv6 the terminator is either ScopeId, prefix or ipv6 terminator
                    if(ch == ']' || ch == '/' || ch == '%') break;
                }
                else if (ch == '/' || ch == '\\' || (notImplicitFile && (ch == ':' || ch == '?' || ch == '#'))) { 
                    break;
                } 
 
                if (ch <= '9' && ch >= '0') {
                    haveNumber = true; 
                    number = number * 10 + (name[start] - '0');
                    if (number > 255) {
                        return false;
                    } 
                } else if (ch == '.') {
                    if (!haveNumber) { 
                        return false; 
                    }
                    ++dots; 
                    haveNumber = false;
                    number = 0;
                } else {
                    return false; 
                }
                ++start; 
            } 
            bool res = (dots == 3) && haveNumber;
            if (res) { 
                end = start;
            }
            return res;
        } 

        // 
        // Parse 
        //
        //  Convert this IPv4 address into a sequence of 4 8-bit numbers 
        //
        // Assumes:
        //   has been validated and contains only decimal digits in groups
        //  of 8-bit numbers and the characters '.' 
        //  Address may terminate with ':' or with the end of the string
        // 
        unsafe private static bool Parse(string name, byte* numbers, int start, int end) { 
            for (int i = 0; i < NumberOfLabels; ++i) {
 
                byte b = 0;
                char ch;
                for (; (start < end) && (ch = name[start]) != '.' && ch != ':'; ++start) {
                    b = (byte)(b * 10 + (byte)(ch - '0')); 
                }
                numbers[i] = b; 
                ++start; 
            }
            return numbers[0] == 127; 
        }
    }
}

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