// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.IO;
using System.Text;
namespace Unity.CodeEditor.Utils
{
/// <summary>
/// Class that can open text files with auto-detection of the encoding.
/// </summary>
internal static class FileReader
{
/// <summary>
/// Gets if the given encoding is a Unicode encoding (UTF).
/// </summary>
/// <remarks>
/// Returns true for UTF-7, UTF-8, UTF-16 LE, UTF-16 BE, UTF-32 LE and UTF-32 BE.
/// Returns false for all other encodings.
/// </remarks>
internal static bool IsUnicode(Encoding encoding)
{
if (encoding == null)
throw new ArgumentNullException(nameof(encoding));
switch (encoding)
{
case UnicodeEncoding _:
case UTF8Encoding _:
return true;
default:
return false;
}
//switch (encoding) {
// case 65000: // UTF-7
// case 65001: // UTF-8
// case 1200: // UTF-16 LE
// case 1201: // UTF-16 BE
// case 12000: // UTF-32 LE
// case 12001: // UTF-32 BE
// return true;
// default:
// return false;
//}
}
private static bool IsAsciiCompatible(Encoding encoding)
{
var bytes = encoding.GetBytes("Az");
return bytes.Length == 2 && bytes[0] == 'A' && bytes[1] == 'z';
}
private static Encoding RemoveBom(Encoding encoding)
{
if (encoding is UTF8Encoding)
{
return UTF8NoBOM;
}
return encoding;
//switch (encoding.CodePage) {
// case 65001: // UTF-8
// return UTF8NoBOM;
// default:
// return encoding;
//}
}
/// <summary>
/// Reads the content of the given stream.
/// </summary>
/// <param name="stream">The stream to read.
/// The stream must support seeking and must be positioned at its beginning.</param>
/// <param name="defaultEncoding">The encoding to use if the encoding cannot be auto-detected.</param>
/// <returns>The file content as string.</returns>
internal static string ReadFileContent(Stream stream, Encoding defaultEncoding)
{
using (var reader = OpenStream(stream, defaultEncoding))
{
return reader.ReadToEnd();
}
}
/// <summary>
/// Reads the content of the file.
/// </summary>
/// <param name="fileName">The file name.</param>
/// <param name="defaultEncoding">The encoding to use if the encoding cannot be auto-detected.</param>
/// <returns>The file content as string.</returns>
internal static string ReadFileContent(string fileName, Encoding defaultEncoding)
{
throw new NotImplementedException();
//using (FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read)) {
// return ReadFileContent(fs, defaultEncoding);
//}
}
/// <summary>
/// Opens the specified file for reading.
/// </summary>
/// <param name="fileName">The file to open.</param>
/// <param name="defaultEncoding">The encoding to use if the encoding cannot be auto-detected.</param>
/// <returns>Returns a StreamReader that reads from the stream. Use
/// <see cref="StreamReader.CurrentEncoding"/> to get the encoding that was used.</returns>
internal static StreamReader OpenFile(string fileName, Encoding defaultEncoding)
{
throw new NotImplementedException();
//if (fileName == null)
// throw new ArgumentNullException("fileName");
//FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
//try {
// return OpenStream(fs, defaultEncoding);
// // don't use finally: the stream must be kept open until the StreamReader closes it
//} catch {
// fs.Dispose();
// throw;
//}
}
/// <summary>
/// Opens the specified stream for reading.
/// </summary>
/// <param name="stream">The stream to open.</param>
/// <param name="defaultEncoding">The encoding to use if the encoding cannot be auto-detected.</param>
/// <returns>Returns a StreamReader that reads from the stream. Use
/// <see cref="StreamReader.CurrentEncoding"/> to get the encoding that was used.</returns>
internal static StreamReader OpenStream(Stream stream, Encoding defaultEncoding)
{
if (stream == null)
throw new ArgumentNullException(nameof(stream));
if (stream.Position != 0)
throw new ArgumentException("stream is not positioned at beginning.", nameof(stream));
if (defaultEncoding == null)
throw new ArgumentNullException(nameof(defaultEncoding));
if (stream.Length >= 2)
{
// the autodetection of StreamReader is not capable of detecting the difference
// between ISO-8859-1 and UTF-8 without BOM.
var firstByte = stream.ReadByte();
var secondByte = stream.ReadByte();
switch ((firstByte << 8) | secondByte)
{
case 0x0000: // either UTF-32 Big Endian or a binary file; use StreamReader
case 0xfffe: // Unicode BOM (UTF-16 LE or UTF-32 LE)
case 0xfeff: // UTF-16 BE BOM
case 0xefbb: // start of UTF-8 BOM
// StreamReader autodetection works
stream.Position = 0;
return new StreamReader(stream);
default:
return AutoDetect(stream, (byte) firstByte, (byte) secondByte, defaultEncoding);
}
}
return new StreamReader(stream, defaultEncoding);
}
// ReSharper disable once InconsistentNaming
private static readonly Encoding UTF8NoBOM = new UTF8Encoding(false);
private static StreamReader AutoDetect(Stream fs, byte firstByte, byte secondByte, Encoding defaultEncoding)
{
var max = (int)Math.Min(fs.Length, 500000); // look at max. 500 KB
// ReSharper disable InconsistentNaming
const int ASCII = 0;
const int Error = 1;
const int UTF8 = 2;
const int UTF8Sequence = 3;
// ReSharper restore InconsistentNaming
var state = ASCII;
var sequenceLength = 0;
for (var i = 0; i < max; i++)
{
byte b;
if (i == 0)
{
b = firstByte;
}
else if (i == 1)
{
b = secondByte;
}
else
{
b = (byte)fs.ReadByte();
}
if (b < 0x80)
{
// normal ASCII character
if (state == UTF8Sequence)
{
state = Error;
break;
}
}
else if (b < 0xc0)
{
// 10xxxxxx : continues UTF8 byte sequence
if (state == UTF8Sequence)
{
--sequenceLength;
if (sequenceLength < 0)
{
state = Error;
break;
}
else if (sequenceLength == 0)
{
state = UTF8;
}
}
else
{
state = Error;
break;
}
}
else if (b >= 0xc2 && b < 0xf5)
{
// beginning of byte sequence
if (state == UTF8 || state == ASCII)
{
state = UTF8Sequence;
if (b < 0xe0)
{
sequenceLength = 1; // one more byte following
}
else if (b < 0xf0)
{
sequenceLength = 2; // two more bytes following
}
else
{
sequenceLength = 3; // three more bytes following
}
}
else
{
state = Error;
break;
}
}
else
{
// 0xc0, 0xc1, 0xf5 to 0xff are invalid in UTF-8 (see RFC 3629)
state = Error;
break;
}
}
fs.Position = 0;
switch (state)
{
case ASCII:
// TODO: Encoding.ASCII
return new StreamReader(fs, IsAsciiCompatible(defaultEncoding) ? RemoveBom(defaultEncoding) : Encoding.UTF8);
case Error:
// When the file seems to be non-UTF8,
// we read it using the user-specified encoding so it is saved again
// using that encoding.
if (IsUnicode(defaultEncoding))
{
// the file is not Unicode, so don't read it using Unicode even if the
// user has choosen Unicode as the default encoding.
defaultEncoding = Encoding.UTF8; // use system encoding instead
}
return new StreamReader(fs, RemoveBom(defaultEncoding));
default:
return new StreamReader(fs, UTF8NoBOM);
}
}
}
}