/// <summary>
/// Try to find a target header value among the set of given header values and parse it as a
/// <see cref="TimeSpan"/>.
/// </summary>
/// <param name="headerValues">
/// The <see cref="StringValues"/> containing the set of header values to search.
/// </param>
/// <param name="targetValue">
/// The target header value to look for.
/// </param>
/// <param name="value">
/// When this method returns, contains the parsed <see cref="TimeSpan"/>, if the parsing succeeded, or
/// null if the parsing failed. The conversion fails if the <paramref name="targetValue"/> was not
/// found or could not be parsed as a <see cref="TimeSpan"/>. This parameter is passed uninitialized;
/// any value originally supplied in result will be overwritten.
/// </param>
/// <returns>
/// <code>true</code> if <paramref name="targetValue"/> is found and successfully parsed; otherwise,
/// <code>false</code>.
/// </returns>
// e.g. { "headerValue=10, targetHeaderValue=30" }
public static bool TryParseSeconds(StringValues headerValues, string targetValue, out TimeSpan?value)
{
if (StringValues.IsNullOrEmpty(headerValues) || string.IsNullOrEmpty(targetValue))
{
value = null;
return(false);
}
for (var i = 0; i < headerValues.Count; i++)
{
// Trim leading white space
var current = HttpRuleParser.GetWhitespaceLength(headerValues[i], 0);
while (current < headerValues[i].Length)
{
long seconds;
var initial = current;
var tokenLength = HttpRuleParser.GetTokenLength(headerValues[i], current);
if (tokenLength == targetValue.Length &&
string.Compare(headerValues[i], current, targetValue, 0, tokenLength, StringComparison.OrdinalIgnoreCase) == 0 &&
TryParseNonNegativeInt64FromHeaderValue(current + tokenLength, headerValues[i], out seconds))
{
// Token matches target value and seconds were parsed
value = TimeSpan.FromSeconds(seconds);
return(true);
}
current = AdvanceCacheDirectiveIndex(current + tokenLength, headerValues[i]);
// Ensure index was advanced
if (current <= initial)
{
Debug.Assert(false, $"Index '{nameof(current)}' not advanced, this is a bug.");
value = null;
return(false);
}
}
}
value = null;
return(false);
}
internal static int GetValueLength(StringSegment input, int startIndex)
{
Contract.Requires(input != null);
if (startIndex >= input.Length)
{
return(0);
}
var valueLength = HttpRuleParser.GetTokenLength(input, startIndex);
if (valueLength == 0)
{
// A value can either be a token or a quoted string. Check if it is a quoted string.
if (HttpRuleParser.GetQuotedStringLength(input, startIndex, out valueLength) != HttpParseResult.Parsed)
{
// We have an invalid value. Reset the name and return.
return(0);
}
}
return(valueLength);
}
/// <summary>
/// Check if a target directive exists among the set of given cache control directives.
/// </summary>
/// <param name="cacheControlDirectives">
/// The <see cref="StringValues"/> containing the set of cache control directives.
/// </param>
/// <param name="targetDirectives">
/// The target cache control directives to look for.
/// </param>
/// <returns>
/// <code>true</code> if <paramref name="targetDirectives"/> is contained in <paramref name="cacheControlDirectives"/>;
/// otherwise, <code>false</code>.
/// </returns>
public static bool ContainsCacheDirective(StringValues cacheControlDirectives, string targetDirectives)
{
if (StringValues.IsNullOrEmpty(cacheControlDirectives) || string.IsNullOrEmpty(targetDirectives))
{
return(false);
}
for (var i = 0; i < cacheControlDirectives.Count; i++)
{
// Trim leading white space
var current = HttpRuleParser.GetWhitespaceLength(cacheControlDirectives[i], 0);
while (current < cacheControlDirectives[i].Length)
{
var initial = current;
var tokenLength = HttpRuleParser.GetTokenLength(cacheControlDirectives[i], current);
if (tokenLength == targetDirectives.Length &&
string.Compare(cacheControlDirectives[i], current, targetDirectives, 0, tokenLength, StringComparison.OrdinalIgnoreCase) == 0)
{
// Token matches target value
return(true);
}
current = AdvanceCacheDirectiveIndex(current + tokenLength, cacheControlDirectives[i]);
// Ensure index was advanced
if (current <= initial)
{
Debug.Assert(false, $"Index '{nameof(current)}' not advanced, this is a bug.");
return(false);
}
}
}
return(false);
}