PATCH: [ 1394247 ] Fix GuessEncoding recognition of codepages

 BUG: [ 1394234 ] GuessEncodings fails to recognize CP-437
  Src: codepage_detect.cpp

diff --git a/Src/Changes.txt b/Src/Changes.txt
index 4d8a41a..c145997 100644 (file)
--- a/Src/Changes.txt
+++ b/Src/Changes.txt
@@ -1,3 +1,8 @@
+2005-12-31 Perry
+ PATCH: [ 1394247 ] Fix GuessEncoding recognition of codepages
+ BUG: [ 1394234 ] GuessEncodings fails to recognize CP-437
+  Src: codepage_detect.cpp
+
 2005-12-30 Perry
  PATCH: [ 1391732 ] Do not offer to unify codepages in UNICODE build
   Also introduces new error IDS_DIFFERENT_UNICODINGS and new

diff --git a/Src/codepage_detect.cpp b/Src/codepage_detect.cpp
index da77ac1..6dc4b57 100644 (file)
--- a/Src/codepage_detect.cpp
+++ b/Src/codepage_detect.cpp
@@ -21,6 +21,85 @@
 static char THIS_FILE[] = __FILE__;
 #endif
 
+/**
+ * @brief Prefixes to handle when searching for codepage names
+ */
+static LPCTSTR f_wincp_prefixes[] =
+{
+       _T("WINDOWS-")
+       , _T("WINDOWS")
+       , _T("CP")
+       , _T("CP-")
+       , _T("MSDOS")
+       , _T("MSDOS-")
+};
+
+/**
+ * @brief Is string non-empty and comprised entirely of numbers?
+ */
+static bool
+isNumeric(const CString & str)
+{
+       if (str.IsEmpty())
+               return false;
+       for (int i=0; i<str.GetLength(); ++i)
+       {
+               TCHAR ch = str[i];
+               if (!_istascii(ch) || !_istdigit(ch))
+                       return false;
+       }
+       return true;
+}
+
+/**
+ * @brief Try to to match codepage name from codepages module, & watch for f_wincp_prefixes aliases
+ */
+static int
+FindEncodingIdFromNameOrAlias(CString encodingName)
+{
+       USES_CONVERSION;
+
+       // Try name as given
+       unsigned encodingId = GetEncodingIdFromName(T2A(encodingName));
+       if (encodingId) return encodingId;
+
+       // Handle purely numeric values (codepages)
+       if (isNumeric(encodingName))
+       {
+               unsigned codepage = _ttoi(encodingName);
+               if (codepage)
+                       encodingId = GetEncodingIdFromCodePage(codepage);
+               return encodingId;
+       }
+
+       for (int i=0; i<sizeof(f_wincp_prefixes)/sizeof(f_wincp_prefixes[0]); ++i)
+       {
+               // prefix is, eg, "WINDOWS-"
+               CString prefix = f_wincp_prefixes[i];
+               prefix.MakeUpper();
+               // check if encodingName starts with prefix
+               if (encodingName.GetLength() > prefix.GetLength())
+               {
+                       CString encpref = encodingName.Left(prefix.GetLength());
+                       encpref.MakeUpper();
+                       if (prefix == encpref)
+                       {
+                               // encoding is, eg, "windows-1251"
+                               CString remainder = encodingName.Mid(prefix.GetLength());
+                               // remainder is, eg, "1251"
+                               if (isNumeric(remainder))
+                               {
+                                       unsigned codepage = _ttoi(remainder);
+                                       if (codepage)
+                                               encodingId = GetEncodingIdFromCodePage(codepage);
+                                       return encodingId;
+                               }
+                       }
+               }
+       }
+
+       return 0; // failed
+}
 
 /**
  * @brief Parser for HTML files to find encoding information
@@ -46,14 +125,7 @@ static unsigned demoGuessEncoding_html(const char *src, size_t len)
                                        {
                                                pchValue[cchValue] = '\0';
                                                // Is it an encoding name known to charsets module ?
-                                               unsigned encodingId = GetEncodingIdFromName(pchValue);
-                                               if (encodingId == 0)
-                                               {
-                                                       if (unsigned codepage = atoi(pchValue))
-                                                       {
-                                                               encodingId = GetEncodingIdFromCodePage(codepage);
-                                                       }
-                                               }
+                                               unsigned encodingId = FindEncodingIdFromNameOrAlias(pchValue);
                                                if (encodingId)
                                                {
                                                        return GetEncodingCodePageFromId(encodingId);
@@ -79,15 +151,8 @@ static unsigned demoGuessEncoding_xml(const char *src, size_t len)
                CMarkdown::String encoding = xml.GetAttribute("encoding");
                if (encoding.A)
                {
-                       // Is it an encoding name known to charsets module ?
-                       unsigned encodingId = GetEncodingIdFromName(encoding.A);
-                       if (encodingId == 0)
-                       {
-                               if (unsigned codepage = atoi(encoding.A))
-                               {
-                                       encodingId = GetEncodingIdFromCodePage(codepage);
-                               }
-                       }
+                       // Is it an encoding name we can find in charsets module ?
+                       unsigned encodingId = FindEncodingIdFromNameOrAlias(encoding.A);
                        if (encodingId)
                        {
                                return GetEncodingCodePageFromId(encodingId);