Provide user friendly messages for OTS parsing of fonts

Source/platform/fonts/opentype/OpenTypeSanitizer.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 40 matching lines @@
         else if (data[0] == 'w' && data[1] == 'O' && data[2] == 'F' && data[3] == '2')
             histogramName = "WebFont.DecodeSpeed.WOFF2";
     }
 
     double kbPerSecond = decodedSize / (1000 * decodeTime);
     Platform::current()->histogramCustomCounts(histogramName, kbPerSecond, 1000, 300000, 50);
 }
 
 PassRefPtr<SharedBuffer> OpenTypeSanitizer::sanitize()
 {
+    // OTS parsing is not called yet, setting parsing error for OTS as false
+    setParsingError(false);

[jungshik at Google, 2015/06/01 23:22:19]

You don't need to call an accessor. Why don't you just set it directly? 

[h.joshi, 2015/06/04 15:19:16]

Done.

     if (!m_buffer)

[jungshik at Google, 2015/06/01 23:22:19]

Set the error message to 'Empty Buffer' or something like that. 

Otherwise, otsParseError in callers would be uninitialized. (or fix the caller
to initialize it)

[h.joshi, 2015/06/04 15:19:16]

Done.

         return nullptr;
 
     // This is the largest web font size which we'll try to transcode.
     static const size_t maxWebFontSize = 30 * 1024 * 1024; // 30 MB
     if (m_buffer->size() > maxWebFontSize)
         return nullptr;

[jungshik at Google, 2015/06/01 23:22:19]

IMHO, you'd better set a custom error string here, too. (e.g. 'Web font is
larger than 30MB'). 

[h.joshi, 2015/06/04 15:19:16]

Done.

 
     // A transcoded font is usually smaller than an original font.
     // However, it can be slightly bigger than the original one due to
     // name table replacement and/or padding for glyf table.
     //
     // With WOFF fonts, however, we'll be decompressing, so the result can be
     // much larger than the original.
 
     ots::ExpandingMemoryStream output(m_buffer->size(), maxWebFontSize);
     double start = currentTime();
     BlinkOTSContext otsContext;
 
-    if (!otsContext.Process(&output, reinterpret_cast<const uint8_t*>(m_buffer->data()), m_buffer->size()))
+    if (!otsContext.Process(&output, reinterpret_cast<const uint8_t*>(m_buffer->data()), m_buffer->size())) {
+        setParsingError(true);
+        setErrorString(otsContext.getErrorString());

[jungshik at Google, 2015/06/01 23:22:19]

again, you don't need accessors to set member variables here. 

[h.joshi, 2015/06/04 15:19:16]

Done.

         return nullptr;
+    }
 
     const size_t transcodeLen = output.Tell();
     recordDecodeSpeedHistogram(m_buffer, currentTime() - start, transcodeLen);
     return SharedBuffer::create(static_cast<unsigned char*>(output.get()), transcodeLen);
 }
 
 bool OpenTypeSanitizer::supportsFormat(const String& format)
 {
     return equalIgnoringCase(format, "woff") || equalIgnoringCase(format, "woff2");
 }
 
+void BlinkOTSContext::Message(int level, const char *format, ...)
+{
+    va_list args;
+    va_start(args, format);
+
+#if COMPILER(MSVC)
+    int result = _vscprintf(format, args);
+#else
+    char ch;
+    int result = vsnprintf(&ch, 1, format, args);
+#endif
+    va_end(args);
+
+    if (result <= 0) {
+        m_errorString = String("OTS Error");
+    } else {
+        Vector<char, 256> buffer;
+        unsigned len = result;
+        buffer.grow(len + 1);
+
+        va_start(args, format);
+        vsnprintf(buffer.data(), buffer.size(), format, args);
+        va_end(args);
+        m_errorString = StringImpl::create(reinterpret_cast<const LChar*>(buffer.data()), len);
+    }
+}
+
+ots::TableAction BlinkOTSContext::GetTableAction(uint32_t tag)
+{
+#define TABLE_TAG(c1, c2, c3, c4) ((uint32_t)((((uint8_t)(c1)) << 24) | (((uint8_t)(c2)) << 16) | (((uint8_t)(c3)) << 8) | ((uint8_t)(c4))))
+
+    const uint32_t cbdtTag = TABLE_TAG('C', 'B', 'D', 'T');
+    const uint32_t cblcTag = TABLE_TAG('C', 'B', 'L', 'C');
+    const uint32_t colrTag = TABLE_TAG('C', 'O', 'L', 'R');
+    const uint32_t cpalTag = TABLE_TAG('C', 'P', 'A', 'L');
+
+    switch (tag) {
+    // Google Color Emoji Tables
+    case cbdtTag:
+    case cblcTag:
+    // Windows Color Emoji Tables
+    case colrTag:
+    case cpalTag:
+        return ots::TABLE_ACTION_PASSTHRU;
+    default:
+        return ots::TABLE_ACTION_DEFAULT;
+    }
+#undef TABLE_TAG
+}
+
 } // namespace blink