/// <summary>
/// Parses a <see cref="BencodeStream"/> into an <see cref="IBObject"/>.
/// </summary>
/// <param name="stream">The stream to parse.</param>
/// <returns>The parsed object.</returns>
public IBObject Parse(BencodeStream stream)
{
if (stream == null)
{
throw new ArgumentNullException("stream");
}
switch (stream.PeekChar())
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9': return(Parse <BString>(stream));
case 'i': return(Parse <BNumber>(stream));
case 'l': return(Parse <BList>(stream));
case 'd': return(Parse <BDictionary>(stream));
}
throw InvalidBencodeException <IBObject> .InvalidBeginningChar(stream.PeekChar(), stream.Position);
}
/// <summary>
/// Parses the next <see cref="BString"/> from the stream.
/// </summary>
/// <param name="stream">The stream to parse from.</param>
/// <returns>The parsed <see cref="BString"/>.</returns>
/// <exception cref="InvalidBencodeException{BString}">Invalid bencode</exception>
/// <exception cref="UnsupportedBencodeException{BString}">The bencode is unsupported by this library</exception>
protected BString ParseStr(BencodeStream stream)
{
if (stream == null)
{
throw new ArgumentNullException("stream");
}
// Minimum valid bencode string is '0:' meaning an empty string
if (stream.Length < MinimumStrLength)
{
throw InvalidBencodeException <BString> .BelowMinimumLength(MinimumStrLength, stream.Length, stream.Position);
}
var startPosition = stream.Position;
var lengthString = new StringBuilder();
for (var c = stream.ReadChar(); c != ':' && c != default(char); c = stream.ReadChar())
{
// Because of memory limitations (~1-2 GB) we know for certain we cannot handle more than 10 digits (10GB)
if (lengthString.Length >= BString.LengthMaxDigits)
{
throw UnsupportedStrException(
string.Format("Length of string is more than {0} digits (>10GB) and is not supported (max is ~1-2GB).", BString.LengthMaxDigits),
startPosition);
}
lengthString.Append(c);
}
long stringLength;
if (!TryParseLongFast(lengthString.ToString(), out stringLength))
{
throw InvalidStrException(string.Format("Invalid length '{0}' of string.", lengthString), startPosition);
}
// Int32.MaxValue is ~2GB and is the absolute maximum that can be handled in memory
if (stringLength > int.MaxValue)
{
throw UnsupportedStrException(
string.Format("Length of string is {0:N0} but maximum supported length is {1:N0}.", stringLength, int.MaxValue),
startPosition);
}
var bytes = stream.Read((int)stringLength);
// If the two don't match we've reached the end of the stream before reading the expected number of chars
if (bytes.Length != stringLength)
{
throw InvalidStrException(
string.Format("Expected string to be {0:N0} bytes long but could only read {1:N0} bytes.", stringLength, bytes.Length),
startPosition);
}
return(new BString(bytes, Encoding));
}
/// <summary>
/// Parses the next <see cref="BList"/> from the stream.
/// </summary>
/// <param name="stream">The stream to parse from.</param>
/// <returns>The parsed <see cref="BList"/>.</returns>
/// <exception cref="InvalidBencodeException{BList}">Invalid bencode</exception>
protected BList ParseList(BencodeStream stream)
{
if (stream == null)
{
throw new ArgumentNullException("stream");
}
if (stream.Length < MinimumListLength)
{
throw InvalidBencodeException <BList> .BelowMinimumLength(MinimumListLength, stream.Length, stream.Position);
}
// Lists must start with 'l'
char c = stream.ReadChar();
if (c != 'l')
{
throw InvalidBencodeException <BList> .UnexpectedChar('l', c, stream.Position);
}
var list = new BList();
// Loop until next character is the end character 'e' or end of stream
while (stream.Peek() != 'e' && stream.Peek() != -1)
{
// Decode next object in stream
var bObject = Parse(stream);
list.Add(bObject);
}
c = stream.ReadChar();
if (c != 'e')
{
if (stream.EndOfStream)
{
throw InvalidBencodeException <BList> .MissingEndChar();
}
throw InvalidBencodeException <BList> .InvalidEndChar(c, stream.Position);
}
return(list);
}
/// <summary>
/// Parses the next <see cref="BNumber"/> from the stream.
/// </summary>
/// <param name="stream">The stream to parse from.</param>
/// <returns>The parsed <see cref="BNumber"/>.</returns>
/// <exception cref="InvalidBencodeException{BNumber}">Invalid bencode</exception>
/// <exception cref="UnsupportedBencodeException{BNumber}">The bencode is unsupported by this library</exception>
protected BNumber ParseNumber(BencodeStream stream)
{
if (stream == null)
{
throw new ArgumentNullException("stream");
}
if (stream.Length < MinimumNumberLength)
{
throw InvalidBencodeException <BNumber> .BelowMinimumLength(MinimumNumberLength, stream.Length, stream.Position);
}
var startPosition = stream.Position;
// Numbers must start with 'i'
char c = stream.ReadChar();
if (c != 'i')
{
throw InvalidBencodeException <BNumber> .UnexpectedChar('i', c, stream.Position);
}
var digits = new StringBuilder();
for (c = stream.ReadChar(); c != 'e' && c != default(char); c = stream.ReadChar())
{
digits.Append(c);
}
// Last read character should be 'e'
if (c != 'e')
{
if (stream.EndOfStream)
{
throw InvalidBencodeException <BNumber> .MissingEndChar();
}
throw InvalidBencodeException <BNumber> .InvalidEndChar(c, stream.Position);
}
var isNegative = digits[0] == '-';
var numberOfDigits = isNegative ? digits.Length - 1 : digits.Length;
// We do not support numbers that cannot be stored as a long (Int64)
if (numberOfDigits > BNumber.MaxDigits)
{
throw UnsupportedNumException(
string.Format("The number '{0}' has more than 19 digits and cannot be stored as a long (Int64) and therefore is not supported.", digits),
startPosition);
}
// We need at least one digit
if (numberOfDigits < 1)
{
throw InvalidNumException("It contains no digits.", startPosition);
}
var firstDigit = isNegative ? digits[1] : digits[0];
// Leading zeros are not valid
if (firstDigit == '0' && numberOfDigits > 1)
{
throw InvalidNumException(string.Format("Leading '0's are not valid. Found value '{0}'.", digits), startPosition);
}
// '-0' is not valid either
if (firstDigit == '0' && numberOfDigits == 1 && isNegative)
{
throw InvalidNumException("'-0' is not a valid number.", startPosition);
}
long number;
if (!TryParseLongFast(digits.ToString(), out number))
{
var nonSignChars = isNegative ? digits.ToString(1, digits.Length - 1) : digits.ToString();
if (nonSignChars.Any(x => !x.IsDigit()))
{
throw InvalidNumException(string.Format("The value '{0}' is not a valid number.", digits), startPosition);
}
throw UnsupportedNumException(
string.Format("The value '{0}' is not a valid long (Int64). Supported values range from '{1:N0}' to '{2:N0}'.", digits, long.MinValue, long.MaxValue),
startPosition);
}
return(new BNumber(number));
}
/// <summary>
/// Parses the next <see cref="BDictionary"/> from the stream and its contained keys and values.
/// </summary>
/// <param name="stream">The stream to parse from.</param>
/// <returns>The parsed <see cref="BDictionary"/>.</returns>
/// <exception cref="InvalidBencodeException{BDictionary}">Invalid bencode</exception>
protected BDictionary ParseDict(BencodeStream stream)
{
if (stream == null)
{
throw new ArgumentNullException("stream");
}
var startPosition = stream.Position;
if (stream.Length < MinimumDictLength)
{
throw InvalidBencodeException <BDictionary> .BelowMinimumLength(MinimumDictLength, stream.Length, startPosition);
}
// Dictionaries must start with 'd'
char c = stream.ReadChar();
if (c != 'd')
{
throw InvalidBencodeException <BDictionary> .UnexpectedChar('d', c, startPosition);
}
var dictionary = new BDictionary();
// Loop until next character is the end character 'e' or end of stream
while (stream.Peek() != 'e' && stream.Peek() != -1)
{
BString key;
try {
// Decode next string in stream as the key
key = ParseStr(stream);
} catch (BencodeException <BString> ex) {
throw InvalidDictException("Could not parse dictionary key. Keys must be strings.", ex, startPosition);
}
IBObject value;
try {
// Decode next object in stream as the value
value = Parse(stream);
} catch (BencodeException ex) {
throw InvalidDictException(
string.Format("Could not parse dictionary value for the key '{0}'. There needs to be a value for each key.", key),
ex, startPosition);
}
if (dictionary.ContainsKey(key))
{
throw InvalidDictException(
string.Format("The dictionary already contains the key '{0}'. Duplicate keys are not supported.", key), startPosition);
}
dictionary.Add(key, value);
}
c = stream.ReadChar();
if (c != 'e')
{
if (stream.EndOfStream)
{
throw InvalidBencodeException <BDictionary> .MissingEndChar();
}
throw InvalidBencodeException <BDictionary> .InvalidEndChar(c, stream.Position);
}
return(dictionary);
}
