410 lines
13 KiB
C#
410 lines
13 KiB
C#
namespace Emby.Server.Implementations.TextEncoding
|
|
{
|
|
// Copyright 2015-2016 Jonathan Bennett <jon@autoitscript.com>
|
|
//
|
|
// https://www.autoitscript.com
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
/// <summary>
|
|
/// Credit: https://github.com/AutoIt/text-encoding-detect
|
|
/// </summary>
|
|
public class TextEncodingDetect
|
|
{
|
|
private readonly byte[] _utf16BeBom =
|
|
{
|
|
0xFE,
|
|
0xFF
|
|
};
|
|
|
|
private readonly byte[] _utf16LeBom =
|
|
{
|
|
0xFF,
|
|
0xFE
|
|
};
|
|
|
|
private readonly byte[] _utf8Bom =
|
|
{
|
|
0xEF,
|
|
0xBB,
|
|
0xBF
|
|
};
|
|
|
|
private bool _nullSuggestsBinary = true;
|
|
private double _utf16ExpectedNullPercent = 70;
|
|
private double _utf16UnexpectedNullPercent = 10;
|
|
|
|
public enum CharacterEncoding
|
|
{
|
|
None, // Unknown or binary
|
|
Ansi, // 0-255
|
|
Ascii, // 0-127
|
|
Utf8Bom, // UTF8 with BOM
|
|
Utf8Nobom, // UTF8 without BOM
|
|
Utf16LeBom, // UTF16 LE with BOM
|
|
Utf16LeNoBom, // UTF16 LE without BOM
|
|
Utf16BeBom, // UTF16-BE with BOM
|
|
Utf16BeNoBom // UTF16-BE without BOM
|
|
}
|
|
|
|
/// <summary>
|
|
/// Sets if the presence of nulls in a buffer indicate the buffer is binary data rather than text.
|
|
/// </summary>
|
|
public bool NullSuggestsBinary
|
|
{
|
|
set
|
|
{
|
|
_nullSuggestsBinary = value;
|
|
}
|
|
}
|
|
|
|
public double Utf16ExpectedNullPercent
|
|
{
|
|
set
|
|
{
|
|
if (value > 0 && value < 100)
|
|
{
|
|
_utf16ExpectedNullPercent = value;
|
|
}
|
|
}
|
|
}
|
|
|
|
public double Utf16UnexpectedNullPercent
|
|
{
|
|
set
|
|
{
|
|
if (value > 0 && value < 100)
|
|
{
|
|
_utf16UnexpectedNullPercent = value;
|
|
}
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Gets the BOM length for a given Encoding mode.
|
|
/// </summary>
|
|
/// <param name="encoding"></param>
|
|
/// <returns>The BOM length.</returns>
|
|
public static int GetBomLengthFromEncodingMode(CharacterEncoding encoding)
|
|
{
|
|
int length;
|
|
|
|
switch (encoding)
|
|
{
|
|
case CharacterEncoding.Utf16BeBom:
|
|
case CharacterEncoding.Utf16LeBom:
|
|
length = 2;
|
|
break;
|
|
|
|
case CharacterEncoding.Utf8Bom:
|
|
length = 3;
|
|
break;
|
|
|
|
default:
|
|
length = 0;
|
|
break;
|
|
}
|
|
|
|
return length;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Checks for a BOM sequence in a byte buffer.
|
|
/// </summary>
|
|
/// <param name="buffer"></param>
|
|
/// <param name="size"></param>
|
|
/// <returns>Encoding type or Encoding.None if no BOM.</returns>
|
|
public CharacterEncoding CheckBom(byte[] buffer, int size)
|
|
{
|
|
// Check for BOM
|
|
if (size >= 2 && buffer[0] == _utf16LeBom[0] && buffer[1] == _utf16LeBom[1])
|
|
{
|
|
return CharacterEncoding.Utf16LeBom;
|
|
}
|
|
|
|
if (size >= 2 && buffer[0] == _utf16BeBom[0] && buffer[1] == _utf16BeBom[1])
|
|
{
|
|
return CharacterEncoding.Utf16BeBom;
|
|
}
|
|
|
|
if (size >= 3 && buffer[0] == _utf8Bom[0] && buffer[1] == _utf8Bom[1] && buffer[2] == _utf8Bom[2])
|
|
{
|
|
return CharacterEncoding.Utf8Bom;
|
|
}
|
|
|
|
return CharacterEncoding.None;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Automatically detects the Encoding type of a given byte buffer.
|
|
/// </summary>
|
|
/// <param name="buffer">The byte buffer.</param>
|
|
/// <param name="size">The size of the byte buffer.</param>
|
|
/// <returns>The Encoding type or Encoding.None if unknown.</returns>
|
|
public CharacterEncoding DetectEncoding(byte[] buffer, int size)
|
|
{
|
|
// First check if we have a BOM and return that if so
|
|
CharacterEncoding encoding = CheckBom(buffer, size);
|
|
if (encoding != CharacterEncoding.None)
|
|
{
|
|
return encoding;
|
|
}
|
|
|
|
// Now check for valid UTF8
|
|
encoding = CheckUtf8(buffer, size);
|
|
if (encoding != CharacterEncoding.None)
|
|
{
|
|
return encoding;
|
|
}
|
|
|
|
// Now try UTF16
|
|
encoding = CheckUtf16NewlineChars(buffer, size);
|
|
if (encoding != CharacterEncoding.None)
|
|
{
|
|
return encoding;
|
|
}
|
|
|
|
encoding = CheckUtf16Ascii(buffer, size);
|
|
if (encoding != CharacterEncoding.None)
|
|
{
|
|
return encoding;
|
|
}
|
|
|
|
// ANSI or None (binary) then
|
|
if (!DoesContainNulls(buffer, size))
|
|
{
|
|
return CharacterEncoding.Ansi;
|
|
}
|
|
|
|
// Found a null, return based on the preference in null_suggests_binary_
|
|
return _nullSuggestsBinary ? CharacterEncoding.None : CharacterEncoding.Ansi;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Checks if a buffer contains text that looks like utf16 by scanning for
|
|
/// newline chars that would be present even in non-english text.
|
|
/// </summary>
|
|
/// <param name="buffer">The byte buffer.</param>
|
|
/// <param name="size">The size of the byte buffer.</param>
|
|
/// <returns>Encoding.none, Encoding.Utf16LeNoBom or Encoding.Utf16BeNoBom.</returns>
|
|
private static CharacterEncoding CheckUtf16NewlineChars(byte[] buffer, int size)
|
|
{
|
|
if (size < 2)
|
|
{
|
|
return CharacterEncoding.None;
|
|
}
|
|
|
|
// Reduce size by 1 so we don't need to worry about bounds checking for pairs of bytes
|
|
size--;
|
|
|
|
var leControlChars = 0;
|
|
var beControlChars = 0;
|
|
|
|
uint pos = 0;
|
|
while (pos < size)
|
|
{
|
|
byte ch1 = buffer[pos++];
|
|
byte ch2 = buffer[pos++];
|
|
|
|
if (ch1 == 0)
|
|
{
|
|
if (ch2 == 0x0a || ch2 == 0x0d)
|
|
{
|
|
++beControlChars;
|
|
}
|
|
}
|
|
else if (ch2 == 0)
|
|
{
|
|
if (ch1 == 0x0a || ch1 == 0x0d)
|
|
{
|
|
++leControlChars;
|
|
}
|
|
}
|
|
|
|
// If we are getting both LE and BE control chars then this file is not utf16
|
|
if (leControlChars > 0 && beControlChars > 0)
|
|
{
|
|
return CharacterEncoding.None;
|
|
}
|
|
}
|
|
|
|
if (leControlChars > 0)
|
|
{
|
|
return CharacterEncoding.Utf16LeNoBom;
|
|
}
|
|
|
|
return beControlChars > 0 ? CharacterEncoding.Utf16BeNoBom : CharacterEncoding.None;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Checks if a buffer contains any nulls. Used to check for binary vs text data.
|
|
/// </summary>
|
|
/// <param name="buffer">The byte buffer.</param>
|
|
/// <param name="size">The size of the byte buffer.</param>
|
|
private static bool DoesContainNulls(byte[] buffer, int size)
|
|
{
|
|
uint pos = 0;
|
|
while (pos < size)
|
|
{
|
|
if (buffer[pos++] == 0)
|
|
{
|
|
return true;
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Checks if a buffer contains text that looks like utf16. This is done based
|
|
/// on the use of nulls which in ASCII/script like text can be useful to identify.
|
|
/// </summary>
|
|
/// <param name="buffer">The byte buffer.</param>
|
|
/// <param name="size">The size of the byte buffer.</param>
|
|
/// <returns>Encoding.none, Encoding.Utf16LeNoBom or Encoding.Utf16BeNoBom.</returns>
|
|
private CharacterEncoding CheckUtf16Ascii(byte[] buffer, int size)
|
|
{
|
|
var numOddNulls = 0;
|
|
var numEvenNulls = 0;
|
|
|
|
// Get even nulls
|
|
uint pos = 0;
|
|
while (pos < size)
|
|
{
|
|
if (buffer[pos] == 0)
|
|
{
|
|
numEvenNulls++;
|
|
}
|
|
|
|
pos += 2;
|
|
}
|
|
|
|
// Get odd nulls
|
|
pos = 1;
|
|
while (pos < size)
|
|
{
|
|
if (buffer[pos] == 0)
|
|
{
|
|
numOddNulls++;
|
|
}
|
|
|
|
pos += 2;
|
|
}
|
|
|
|
double evenNullThreshold = numEvenNulls * 2.0 / size;
|
|
double oddNullThreshold = numOddNulls * 2.0 / size;
|
|
double expectedNullThreshold = _utf16ExpectedNullPercent / 100.0;
|
|
double unexpectedNullThreshold = _utf16UnexpectedNullPercent / 100.0;
|
|
|
|
// Lots of odd nulls, low number of even nulls
|
|
if (evenNullThreshold < unexpectedNullThreshold && oddNullThreshold > expectedNullThreshold)
|
|
{
|
|
return CharacterEncoding.Utf16LeNoBom;
|
|
}
|
|
|
|
// Lots of even nulls, low number of odd nulls
|
|
if (oddNullThreshold < unexpectedNullThreshold && evenNullThreshold > expectedNullThreshold)
|
|
{
|
|
return CharacterEncoding.Utf16BeNoBom;
|
|
}
|
|
|
|
// Don't know
|
|
return CharacterEncoding.None;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Checks if a buffer contains valid utf8.
|
|
/// </summary>
|
|
/// <param name="buffer">The byte buffer.</param>
|
|
/// <param name="size">The size of the byte buffer.</param>
|
|
/// <returns>
|
|
/// Encoding type of Encoding.None (invalid UTF8), Encoding.Utf8NoBom (valid utf8 multibyte strings) or
|
|
/// Encoding.ASCII (data in 0.127 range).
|
|
/// </returns>
|
|
/// <returns>2</returns>
|
|
private CharacterEncoding CheckUtf8(byte[] buffer, int size)
|
|
{
|
|
// UTF8 Valid sequences
|
|
// 0xxxxxxx ASCII
|
|
// 110xxxxx 10xxxxxx 2-byte
|
|
// 1110xxxx 10xxxxxx 10xxxxxx 3-byte
|
|
// 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx 4-byte
|
|
//
|
|
// Width in UTF8
|
|
// Decimal Width
|
|
// 0-127 1 byte
|
|
// 194-223 2 bytes
|
|
// 224-239 3 bytes
|
|
// 240-244 4 bytes
|
|
//
|
|
// Subsequent chars are in the range 128-191
|
|
var onlySawAsciiRange = true;
|
|
uint pos = 0;
|
|
|
|
while (pos < size)
|
|
{
|
|
byte ch = buffer[pos++];
|
|
|
|
if (ch == 0 && _nullSuggestsBinary)
|
|
{
|
|
return CharacterEncoding.None;
|
|
}
|
|
|
|
int moreChars;
|
|
if (ch <= 127)
|
|
{
|
|
// 1 byte
|
|
moreChars = 0;
|
|
}
|
|
else if (ch >= 194 && ch <= 223)
|
|
{
|
|
// 2 Byte
|
|
moreChars = 1;
|
|
}
|
|
else if (ch >= 224 && ch <= 239)
|
|
{
|
|
// 3 Byte
|
|
moreChars = 2;
|
|
}
|
|
else if (ch >= 240 && ch <= 244)
|
|
{
|
|
// 4 Byte
|
|
moreChars = 3;
|
|
}
|
|
else
|
|
{
|
|
return CharacterEncoding.None; // Not utf8
|
|
}
|
|
|
|
// Check secondary chars are in range if we are expecting any
|
|
while (moreChars > 0 && pos < size)
|
|
{
|
|
onlySawAsciiRange = false; // Seen non-ascii chars now
|
|
|
|
ch = buffer[pos++];
|
|
if (ch < 128 || ch > 191)
|
|
{
|
|
return CharacterEncoding.None; // Not utf8
|
|
}
|
|
|
|
--moreChars;
|
|
}
|
|
}
|
|
|
|
// If we get to here then only valid UTF-8 sequences have been processed
|
|
|
|
// If we only saw chars in the range 0-127 then we can't assume UTF8 (the caller will need to decide)
|
|
return onlySawAsciiRange ? CharacterEncoding.Ascii : CharacterEncoding.Utf8Nobom;
|
|
}
|
|
}
|
|
}
|