/WCFWebApi/src/System.Net.Http/System/Net/Http/Headers/ByteArrayHeaderParser.cs

using System.Diagnostics.Contracts;



namespace System.Net.Http.Headers

{

    // Don't derive from BaseHeaderParser since parsing the Base64 string is delegated to Convert.FromBase64String() 

    // which will remove leading, trailing, and whitespaces in the middle of the string.

    internal class ByteArrayHeaderParser : HttpHeaderParser

    {

        internal static readonly ByteArrayHeaderParser Parser = new ByteArrayHeaderParser();



        private ByteArrayHeaderParser()

            : base(false)

        {

        }



        public override string ToString(object value)

        {

            Contract.Assert(value is byte[]);



            return Convert.ToBase64String((byte[])value);

        }



        public override bool TryParseValue(string value, object storeValue, ref int index, out object parsedValue)

        {

            parsedValue = null;



            // Some headers support empty/null values. This one doesn't.

            if (string.IsNullOrEmpty(value) || (index == value.Length))

            {

                return false;

            }

            

            string base64String = value;

            if (index > 0)

            {

                base64String = value.Substring(index);

            }



            // Try convert the string (we assume it's a valid Base64 string) to byte[].

            try

            {

                // The RFC specifies that the MD5 should be a 128 bit digest. However, we don't validate the length and

                // let the user decide whether or not the byte[] is a valid Content-MD5 value or not.

                parsedValue = Convert.FromBase64String(base64String);

                index = value.Length;

                return true;

            }

            catch (FormatException e)

            {

                if (Logging.On) Logging.PrintError(Logging.Http, string.Format(System.Globalization.CultureInfo.InvariantCulture, SR.net_http_parser_invalid_base64_string, base64String, e.Message));

            }



            return false;

        }

    }

}