/// <summary>
/// Replaces all instances of %XX in the input string with the character represented
/// by the hexadecimal number XX.
/// </summary>
/// <param name="escapedString">The string to unescape.</param>
/// <param name="escapingWasNecessary">Whether any replacements were made.</param>
/// <returns>unescaped string</returns>
internal static string UnescapeAll
(
string escapedString,
out bool escapingWasNecessary
)
{
escapingWasNecessary = false;
// If the string doesn't contain anything, then by definition it doesn't
// need unescaping.
if (String.IsNullOrEmpty(escapedString))
{
return(escapedString);
}
// If there are no percent signs, just return the original string immediately.
// Don't even instantiate the StringBuilder.
int indexOfPercent = escapedString.IndexOf('%');
if (indexOfPercent == -1)
{
return(escapedString);
}
// This is where we're going to build up the final string to return to the caller.
StringBuilder unescapedString = StringBuilderCache.Acquire(escapedString.Length);
int currentPosition = 0;
// Loop until there are no more percent signs in the input string.
while (indexOfPercent != -1)
{
// There must be two hex characters following the percent sign
// for us to even consider doing anything with this.
if (
(indexOfPercent <= (escapedString.Length - 3)) &&
IsHexDigit(escapedString[indexOfPercent + 1]) &&
IsHexDigit(escapedString[indexOfPercent + 2])
)
{
// First copy all the characters up to the current percent sign into
// the destination.
unescapedString.Append(escapedString, currentPosition, indexOfPercent - currentPosition);
// Convert the %XX to an actual real character.
string hexString = escapedString.Substring(indexOfPercent + 1, 2);
char unescapedCharacter = (char)int.Parse(hexString, System.Globalization.NumberStyles.HexNumber,
CultureInfo.InvariantCulture);
// if the unescaped character is not on the exception list, append it
unescapedString.Append(unescapedCharacter);
// Advance the current pointer to reflect the fact that the destination string
// is up to date with everything up to and including this escape code we just found.
currentPosition = indexOfPercent + 3;
escapingWasNecessary = true;
}
// Find the next percent sign.
indexOfPercent = escapedString.IndexOf('%', indexOfPercent + 1);
}
// Okay, there are no more percent signs in the input string, so just copy the remaining
// characters into the destination.
unescapedString.Append(escapedString, currentPosition, escapedString.Length - currentPosition);
return(StringBuilderCache.GetStringAndRelease(unescapedString));
}
/// <summary>
/// Replaces all instances of %XX in the input string with the character represented
/// by the hexadecimal number XX.
/// </summary>
/// <param name="escapedString">The string to unescape.</param>
/// <param name="trim">If the string should be trimmed before being unescaped.</param>
/// <returns>unescaped string</returns>
internal static string UnescapeAll(string escapedString, bool trim = false)
{
// If the string doesn't contain anything, then by definition it doesn't
// need unescaping.
if (String.IsNullOrEmpty(escapedString))
{
return(escapedString);
}
// If there are no percent signs, just return the original string immediately.
// Don't even instantiate the StringBuilder.
int indexOfPercent = escapedString.IndexOf('%');
if (indexOfPercent == -1)
{
return(trim ? escapedString.Trim() : escapedString);
}
// This is where we're going to build up the final string to return to the caller.
StringBuilder unescapedString = StringBuilderCache.Acquire(escapedString.Length);
int currentPosition = 0;
int escapedStringLength = escapedString.Length;
if (trim)
{
while (currentPosition < escapedString.Length && Char.IsWhiteSpace(escapedString[currentPosition]))
{
currentPosition++;
}
if (currentPosition == escapedString.Length)
{
return(String.Empty);
}
while (Char.IsWhiteSpace(escapedString[escapedStringLength - 1]))
{
escapedStringLength--;
}
}
// Loop until there are no more percent signs in the input string.
while (indexOfPercent != -1)
{
// There must be two hex characters following the percent sign
// for us to even consider doing anything with this.
if (
(indexOfPercent <= (escapedStringLength - 3)) &&
TryDecodeHexDigit(escapedString[indexOfPercent + 1], out int digit1) &&
TryDecodeHexDigit(escapedString[indexOfPercent + 2], out int digit2)
)
{
// First copy all the characters up to the current percent sign into
// the destination.
unescapedString.Append(escapedString, currentPosition, indexOfPercent - currentPosition);
// Convert the %XX to an actual real character.
char unescapedCharacter = (char)((digit1 << 4) + digit2);
// if the unescaped character is not on the exception list, append it
unescapedString.Append(unescapedCharacter);
// Advance the current pointer to reflect the fact that the destination string
// is up to date with everything up to and including this escape code we just found.
currentPosition = indexOfPercent + 3;
}
// Find the next percent sign.
indexOfPercent = escapedString.IndexOf('%', indexOfPercent + 1);
}
// Okay, there are no more percent signs in the input string, so just copy the remaining
// characters into the destination.
unescapedString.Append(escapedString, currentPosition, escapedStringLength - currentPosition);
return(StringBuilderCache.GetStringAndRelease(unescapedString));
}
