private static IEnumerable <ExtractedString> Extract(Stream data, long base_offset, int minimum_length, ExtractedStringType type, string source)
{
if (data is null)
{
throw new ArgumentNullException(nameof(data));
}
if (minimum_length <= 0)
{
throw new ArgumentException("Must specify a minimum length of at least 1.");
}
StringBuilder ascii = new StringBuilder();
StringBuilder unicode = new StringBuilder();
StringBuilder unicode_unaligned = new StringBuilder();
bool parse_ascii = type.HasFlagSet(ExtractedStringType.Ascii);
bool parse_unicode = type.HasFlagSet(ExtractedStringType.Unicode);
byte[] unicode_char = new byte[2];
int b = data.ReadByte();
long i = 0;
while (b >= 0)
{
if (parse_ascii)
{
char c = (char)b;
if (IsPrintable(c))
{
ascii.Append(c);
}
else
{
if (ascii.Length >= minimum_length)
{
yield return(ascii.CreateResult(base_offset, i, ExtractedStringType.Ascii, source));
}
ascii.Clear();
}
}
if (parse_unicode)
{
unicode_char[0] = unicode_char[1];
unicode_char[1] = (byte)b;
char c = BitConverter.ToChar(unicode_char, 0);
if ((i & 1) == 1)
{
if (IsPrintable(c))
{
unicode.Append(c);
}
else
{
if (unicode.Length >= minimum_length)
{
yield return(unicode.CreateResult(base_offset, i, ExtractedStringType.Unicode, source));
}
unicode.Clear();
}
}
else if (i > 1)
{
if (IsPrintable(c))
{
unicode_unaligned.Append(c);
}
else
{
if (unicode_unaligned.Length >= minimum_length)
{
yield return(unicode_unaligned.CreateResult(base_offset, i, ExtractedStringType.Unicode, source));
}
unicode_unaligned.Clear();
}
}
}
i++;
b = data.ReadByte();
}
if (ascii.Length >= minimum_length)
{
yield return(ascii.CreateResult(base_offset, i, ExtractedStringType.Ascii, source));
}
if (unicode.Length >= minimum_length)
{
yield return(unicode.CreateResult(base_offset, i, ExtractedStringType.Unicode, source));
}
if (unicode_unaligned.Length >= minimum_length)
{
yield return(unicode_unaligned.CreateResult(base_offset, i, ExtractedStringType.Unicode, source));
}
}
private static ExtractedString CreateResult(this StringBuilder builder, long base_offset, long i, ExtractedStringType type, string source)
{
int str_length = type.HasFlagSet(ExtractedStringType.Unicode) ? (builder.Length * 2 + 1) : builder.Length;
return(new ExtractedString(builder.ToString(), base_offset + i - str_length, type, source));
}
