[NOTEPAD] Encoding detection (#1852)

CORE-15548
In notepad, if there is no BOM in the input file, then judge the text encoding.

base/applications/notepad/text.c

@@ -4,6 +4,7 @@
  *  Copyright 1998,99 Marcel Baur <[email protected]>
  *  Copyright 2002 Sylvain Petreolle <[email protected]>
  *  Copyright 2002 Andriy Palamarchuk
+ *  Copyright 2019 Katayama Hirofumi MZ <[email protected]>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -47,6 +48,32 @@ static BOOL Append(LPWSTR *ppszText, DWORD *pdwTextLen, LPCWSTR pszAppendText, D
     return TRUE;
 }
 
+ENCODING AnalyzeEncoding(const char *pBytes, DWORD dwSize)
+{
+    INT flags = IS_TEXT_UNICODE_STATISTICS;
+
+    if (dwSize <= 1)
+        return ENCODING_ANSI;
+
+    if (IsTextUnicode(pBytes, dwSize, &flags))
+    {
+        return ENCODING_UTF16LE;
+    }
+
+    if ((flags & IS_TEXT_UNICODE_REVERSE_MASK) && !(flags & IS_TEXT_UNICODE_ILLEGAL_CHARS))
+    {
+        return ENCODING_UTF16BE;
+    }
+
+    /* is it UTF-8? */
+    if (MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, pBytes, dwSize, NULL, 0))
+    {
+        return ENCODING_UTF8;
+    }
+
+    return ENCODING_ANSI;
+}
+
 BOOL
 ReadText(HANDLE hFile, LPWSTR *ppszText, DWORD *pdwTextLen, ENCODING *pencFile, int *piEoln)
 {
@@ -98,6 +125,10 @@ ReadText(HANDLE hFile, LPWSTR *ppszText, DWORD *pdwTextLen, ENCODING *pencFile,
         encFile = ENCODING_UTF8;
         dwPos += 3;
     }
+    else
+    {
+        encFile = AnalyzeEncoding((const char *)pBytes, dwSize);
+    }
 
     switch(encFile)
     {