internal static int GetRangeItemLength(StringSegment input, int startIndex, out RangeItemHeaderValue parsedValue)
{
Contract.Requires(startIndex >= 0);
// This parser parses number ranges: e.g. '1-2', '1-', '-2'.
parsedValue = null;
if (StringSegment.IsNullOrEmpty(input) || (startIndex >= input.Length))
{
return(0);
}
// Caller must remove leading whitespaces. If not, we'll return 0.
var current = startIndex;
// Try parse the first value of a value pair.
var fromStartIndex = current;
var fromLength = HttpRuleParser.GetNumberLength(input, current, false);
if (fromLength > HttpRuleParser.MaxInt64Digits)
{
return(0);
}
current = current + fromLength;
current = current + HttpRuleParser.GetWhitespaceLength(input, current);
// After the first value, the '-' character must follow.
if ((current == input.Length) || (input[current] != '-'))
{
// We need a '-' character otherwise this can't be a valid range.
return(0);
}
current++; // skip the '-' character
current = current + HttpRuleParser.GetWhitespaceLength(input, current);
var toStartIndex = current;
var toLength = 0;
// If we didn't reach the end of the string, try parse the second value of the range.
if (current < input.Length)
{
toLength = HttpRuleParser.GetNumberLength(input, current, false);
if (toLength > HttpRuleParser.MaxInt64Digits)
{
return(0);
}
current = current + toLength;
current = current + HttpRuleParser.GetWhitespaceLength(input, current);
}
if ((fromLength == 0) && (toLength == 0))
{
return(0); // At least one value must be provided in order to be a valid range.
}
// Try convert first value to int64
long from = 0;
if ((fromLength > 0) && !HeaderUtilities.TryParseNonNegativeInt64(input.Subsegment(fromStartIndex, fromLength), out from))
{
return(0);
}
// Try convert second value to int64
long to = 0;
if ((toLength > 0) && !HeaderUtilities.TryParseNonNegativeInt64(input.Subsegment(toStartIndex, toLength), out to))
{
return(0);
}
// 'from' must not be greater than 'to'
if ((fromLength > 0) && (toLength > 0) && (from > to))
{
return(0);
}
parsedValue = new RangeItemHeaderValue((fromLength == 0 ? (long?)null : (long?)from),
(toLength == 0 ? (long?)null : (long?)to));
return(current - startIndex);
}
