Require length in sk_wchar_to_string.

This information is already available at all call sites and allows
the call to WideCharToMultiByte to not overwrite the '\0' in the
writable_str() which isn't really writable.

BUG=skia:1989
R=reed@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/500113002

3 files changed, 39 insertions, 45 deletions

diff --git a/src/ports/SkTypeface_win_dw.cpp b/src/ports/SkTypeface_win_dw.cpp
index 566f3d166b..7b6b522cea 100644
--- a/src/ports/SkTypeface_win_dw.cpp
+++ b/src/ports/SkTypeface_win_dw.cpp
@@ -27,17 +27,17 @@
 void DWriteFontTypeface::onGetFontDescriptor(SkFontDescriptor* desc,
                                              bool* isLocalStream) const {
     // Get the family name.
-    SkTScopedComPtr<IDWriteLocalizedStrings> dwFamilyNames;
-    HRV(fDWriteFontFamily->GetFamilyNames(&dwFamilyNames));
+    SkTScopedComPtr<IDWriteLocalizedStrings> familyNames;
+    HRV(fDWriteFontFamily->GetFamilyNames(&familyNames));
 
-    UINT32 dwFamilyNamesLength;
-    HRV(dwFamilyNames->GetStringLength(0, &dwFamilyNamesLength));
+    UINT32 familyNamesLen;
+    HRV(familyNames->GetStringLength(0, &familyNamesLen));
 
-    SkSMallocWCHAR dwFamilyNameChar(dwFamilyNamesLength+1);
-    HRV(dwFamilyNames->GetString(0, dwFamilyNameChar.get(), dwFamilyNamesLength+1));
+    SkSMallocWCHAR familyName(familyNamesLen+1);
+    HRV(familyNames->GetString(0, familyName.get(), familyNamesLen+1));
 
     SkString utf8FamilyName;
-    HRV(sk_wchar_to_skstring(dwFamilyNameChar.get(), &utf8FamilyName));
+    HRV(sk_wchar_to_skstring(familyName.get(), familyNamesLen, &utf8FamilyName));
 
     desc->setFamilyName(utf8FamilyName.c_str());
     *isLocalStream = SkToBool(fDWriteFontFileLoader.get());
@@ -140,24 +140,22 @@ public:
         }
 
         // String
-        UINT32 stringLength;
-        HRBM(fStrings->GetStringLength(fIndex, &stringLength), "Could not get string length.");
-        stringLength += 1;
+        UINT32 stringLen;
+        HRBM(fStrings->GetStringLength(fIndex, &stringLen), "Could not get string length.");
 
-        SkSMallocWCHAR wString(stringLength);
-        HRBM(fStrings->GetString(fIndex, wString.get(), stringLength), "Could not get string.");
+        SkSMallocWCHAR wString(stringLen+1);
+        HRBM(fStrings->GetString(fIndex, wString.get(), stringLen+1), "Could not get string.");
 
-        HRB(sk_wchar_to_skstring(wString.get(), &localizedString->fString));
+        HRB(sk_wchar_to_skstring(wString.get(), stringLen, &localizedString->fString));
 
         // Locale
-        UINT32 localeLength;
-        HRBM(fStrings->GetLocaleNameLength(fIndex, &localeLength), "Could not get locale length.");
-        localeLength += 1;
+        UINT32 localeLen;
+        HRBM(fStrings->GetLocaleNameLength(fIndex, &localeLen), "Could not get locale length.");
 
-        SkSMallocWCHAR wLocale(localeLength);
-        HRBM(fStrings->GetLocaleName(fIndex, wLocale.get(), localeLength), "Could not get locale.");
+        SkSMallocWCHAR wLocale(localeLen+1);
+        HRBM(fStrings->GetLocaleName(fIndex, wLocale.get(), localeLen+1), "Could not get locale.");
 
-        HRB(sk_wchar_to_skstring(wLocale.get(), &localizedString->fLanguage));
+        HRB(sk_wchar_to_skstring(wLocale.get(), localeLen, &localizedString->fLanguage));
 
         ++fIndex;
         return true;
@@ -349,14 +347,13 @@ SkAdvancedTypefaceMetrics* DWriteFontTypeface::onGetAdvancedTypefaceMetrics(
     SkTScopedComPtr<IDWriteLocalizedStrings> familyNames;
     hr = fDWriteFontFamily->GetFamilyNames(&familyNames);
 
-    UINT32 familyNameLength;
-    hr = familyNames->GetStringLength(0, &familyNameLength);
+    UINT32 familyNameLen;
+    hr = familyNames->GetStringLength(0, &familyNameLen);
 
-    UINT32 size = familyNameLength+1;
-    SkSMallocWCHAR wFamilyName(size);
-    hr = familyNames->GetString(0, wFamilyName.get(), size);
+    SkSMallocWCHAR familyName(familyNameLen+1);
+    hr = familyNames->GetString(0, familyName.get(), familyNameLen+1);
 
-    hr = sk_wchar_to_skstring(wFamilyName.get(), &info->fFontName);
+    hr = sk_wchar_to_skstring(familyName.get(), familyNameLen, &info->fFontName);
 
     if (perGlyphInfo & SkAdvancedTypefaceMetrics::kToUnicode_PerGlyphInfo) {
         populate_glyph_to_unicode(fDWriteFontFace.get(), glyphCount, &(info->fGlyphToUnicode));
diff --git a/src/utils/win/SkDWrite.cpp b/src/utils/win/SkDWrite.cpp
index 87826b5194..7801059187 100644
--- a/src/utils/win/SkDWrite.cpp
+++ b/src/utils/win/SkDWrite.cpp
@@ -67,23 +67,19 @@ HRESULT sk_cstring_to_wchar(const char* skname, SkSMallocWCHAR* name) {
 }
 
 /** Converts a WCHAR string to a utf8 string. */
-HRESULT sk_wchar_to_skstring(WCHAR* name, SkString* skname) {
-    int len = WideCharToMultiByte(CP_UTF8, 0, name, -1, NULL, 0, NULL, NULL);
+HRESULT sk_wchar_to_skstring(WCHAR* name, int nameLen, SkString* skname) {
+    int len = WideCharToMultiByte(CP_UTF8, 0, name, nameLen, NULL, 0, NULL, NULL);
     if (0 == len) {
+        if (nameLen <= 0) {
+            skname->reset();
+            return S_OK;
+        }
         HRM(HRESULT_FROM_WIN32(GetLastError()),
             "Could not get length for utf-8 to wchar conversion.");
     }
-    skname->resize(len - 1);
-
-    // TODO: remove after https://code.google.com/p/skia/issues/detail?id=1989 is fixed.
-    // If we resize to 0 then the skname points to gEmptyRec (the unique empty SkString::Rec).
-    // gEmptyRec is static const and on Windows this means the value is in a read only page.
-    // Writing to it in the following call to WideCharToMultiByte will cause an access violation.
-    if (1 == len) {
-        return S_OK;
-    }
+    skname->resize(len);
 
-    len = WideCharToMultiByte(CP_UTF8, 0, name, -1, skname->writable_str(), len, NULL, NULL);
+    len = WideCharToMultiByte(CP_UTF8, 0, name, nameLen, skname->writable_str(), len, NULL, NULL);
     if (0 == len) {
         HRM(HRESULT_FROM_WIN32(GetLastError()), "Could not convert utf-8 to wchar.");
     }
@@ -105,14 +101,13 @@ void sk_get_locale_string(IDWriteLocalizedStrings* names, const WCHAR* preferedL
         }
     }
 
-    UINT32 nameLength;
-    HRVM(names->GetStringLength(nameIndex, &nameLength), "Could not get name length.");
-    nameLength += 1;
+    UINT32 nameLen;
+    HRVM(names->GetStringLength(nameIndex, &nameLen), "Could not get name length.");
 
-    SkSMallocWCHAR name(nameLength);
-    HRVM(names->GetString(nameIndex, name.get(), nameLength), "Could not get string.");
+    SkSMallocWCHAR name(nameLen+1);
+    HRVM(names->GetString(nameIndex, name.get(), nameLen+1), "Could not get string.");
 
-    HRV(sk_wchar_to_skstring(name.get(), skname));
+    HRV(sk_wchar_to_skstring(name.get(), nameLen, skname));
 }
 
 HRESULT SkGetGetUserDefaultLocaleNameProc(SkGetUserDefaultLocaleNameProc* proc) {
diff --git a/src/utils/win/SkDWrite.h b/src/utils/win/SkDWrite.h
index e763b4a097..a7799921d2 100644
--- a/src/utils/win/SkDWrite.h
+++ b/src/utils/win/SkDWrite.h
@@ -28,8 +28,10 @@ typedef SkAutoSTMalloc<16, WCHAR> SkSMallocWCHAR;
 /** Converts a utf8 string to a WCHAR string. */
 HRESULT sk_cstring_to_wchar(const char* skname, SkSMallocWCHAR* name);
 
-/** Converts a WCHAR string to a utf8 string. */
-HRESULT sk_wchar_to_skstring(WCHAR* name, SkString* skname);
+/** Converts a WCHAR string to a utf8 string.
+ *  @param nameLen the number of WCHARs in the name.
+ */
+HRESULT sk_wchar_to_skstring(WCHAR* name, int nameLen, SkString* skname);
 
 ////////////////////////////////////////////////////////////////////////////////
 // Locale