Don't read unecessary font files on Android.

src/ports/SkFontConfigParser_android.cpp

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkFontConfigParser_android.h"
 #include "SkTDArray.h"
 #include "SkTSearch.h"
 #include "SkTypeface.h"
 
 #include <expat.h>
 #include <dirent.h>
 #include <stdio.h>
 
 #include <limits>
 
-
-
 // From Android version LMP onwards, all font files collapse into
 // /system/etc/fonts.xml. Instead of trying to detect which version
 // we're on, try to open fonts.xml; if that fails, fall back to the
 // older filename.
 #define LMP_SYSTEM_FONTS_FILE "/system/etc/fonts.xml"
 #define OLD_SYSTEM_FONTS_FILE "/system/etc/system_fonts.xml"
 #define FALLBACK_FONTS_FILE "/system/etc/fallback_fonts.xml"
 #define VENDOR_FONTS_FILE "/vendor/etc/fallback_fonts.xml"
 
 #define LOCALE_FALLBACK_FONTS_SYSTEM_DIR "/system/etc"
@@ skipping 13 matching lines @@
 // for now.
 #define NO_TAG 0
 #define NAMESET_TAG 1
 #define FILESET_TAG 2
 
 /**
  * The FamilyData structure is passed around by the parser so that each handler
  * can read these variables that are relevant to the current parsing.
  */
 struct FamilyData {
-    FamilyData(XML_Parser parser, SkTDArray<FontFamily*> &families)
+    FamilyData(XML_Parser parser, SkTDArray<FontFamily*>& families)
         : fParser(parser)
         , fFamilies(families)
         , fCurrentFamily(NULL)
         , fCurrentFontInfo(NULL)
         , fCurrentTag(NO_TAG)
-    { };
+        , fVersion(0)
+    { }
 
     XML_Parser fParser;                       // The expat parser doing the work, owned by caller
     SkTDArray<FontFamily*>& fFamilies;        // The array to append families, owned by caller
     SkAutoTDelete<FontFamily> fCurrentFamily; // The family being created, owned by this
     FontFileInfo* fCurrentFontInfo;           // The fontInfo being created, owned by currentFamily
     int fCurrentTag;                          // Flag to indicate when we're in nameset/fileset tags
+    int fVersion;                             // The version of the file parsed.
 };
 
 /** http://www.w3.org/TR/html-markup/datatypes.html#common.data.integer.non-negative-def */
-template <typename T> static bool parseNonNegativeInteger(const char* s, T* value) {
+template <typename T> static bool parse_non_negative_integer(const char* s, T* value) {
     SK_COMPILE_ASSERT(std::numeric_limits<T>::is_integer, T_must_be_integer);
     const T nMax = std::numeric_limits<T>::max() / 10;
     const T dMax = std::numeric_limits<T>::max() - (nMax * 10);
     T n = 0;
     for (; *s; ++s) {
         // Check if digit
         if (*s < '0' || '9' < *s) {
             return false;
         }
         int d = *s - '0';
@@ skipping 45 matching lines @@
 void fontElementHandler(XML_Parser parser, FontFileInfo* file, const char** attributes) {
     // A <font> should have weight (integer) and style (normal, italic) attributes.
     // NOTE: we ignore the style.
     // The element should contain a filename.
     for (size_t i = 0; attributes[i] != NULL &&
                        attributes[i+1] != NULL; i += 2) {
         const char* name = attributes[i];
         const char* value = attributes[i+1];
         size_t nameLen = strlen(name);
         if (nameLen == 6 && !strncmp("weight", name, nameLen)) {
-            if (!parseNonNegativeInteger(value, &file->fWeight)) {
+            if (!parse_non_negative_integer(value, &file->fWeight)) {
                 SkDebugf("---- Font weight %s (INVALID)", value);
                 file->fWeight = 0;
             }
         }
     }
     XML_SetCharacterDataHandler(parser, fontFileNameHandler);
 }
 
 FontFamily* findFamily(FamilyData* familyData, const char* familyName) {
     size_t nameLen = strlen(familyName);
@@ skipping 24 matching lines @@
                        attributes[i+1] != NULL; i += 2) {
         const char* name = attributes[i];
         const char* value = attributes[i+1];
         size_t nameLen = strlen(name);
         if (nameLen == 4 && !strncmp("name", name, nameLen)) {
             SkAutoAsciiToLC tolc(value);
             aliasName.set(tolc.lc());
         } else if (nameLen == 2 && !strncmp("to", name, nameLen)) {
             to.set(value);
         } else if (nameLen == 6 && !strncmp("weight", name, nameLen)) {
-            parseNonNegativeInteger(value, &weight);
+            parse_non_negative_integer(value, &weight);
         }
     }
 
     // Assumes that the named family is already declared
     FontFamily* targetFamily = findFamily(familyData, to.c_str());
     if (!targetFamily) {
         SkDebugf("---- Font alias target %s (NOT FOUND)", to.c_str());
         return;
     }
 
@@ skipping 38 matching lines @@
 }
 
 } // lmpParser
 
 namespace jbParser {
 
 /**
  * Handler for arbitrary text. This is used to parse the text inside each name
  * or file tag. The resulting strings are put into the fNames or FontFileInfo arrays.
  */
-static void textHandler(void* data, const char* s, int len) {
+static void text_handler(void* data, const char* s, int len) {
     FamilyData* familyData = (FamilyData*) data;
     // Make sure we're in the right state to store this name information
     if (familyData->fCurrentFamily.get() &&
             (familyData->fCurrentTag == NAMESET_TAG || familyData->fCurrentTag == FILESET_TAG)) {
         switch (familyData->fCurrentTag) {
         case NAMESET_TAG: {
             SkAutoAsciiToLC tolc(s, len);
             familyData->fCurrentFamily->fNames.push_back().set(tolc.lc(), len);
             break;
         }
         case FILESET_TAG:
             if (familyData->fCurrentFontInfo) {
                 familyData->fCurrentFontInfo->fFileName.set(s, len);
             }
             break;
         default:
             // Noop - don't care about any text that's not in the Fonts or Names list
             break;
         }
     }
 }
 
 /**
  * Handler for font files. This processes the attributes for language and
  * variants then lets textHandler handle the actual file name
  */
-static void fontFileElementHandler(FamilyData* familyData, const char** attributes) {
+static void font_file_element_handler(FamilyData* familyData, const char** attributes) {
     FontFileInfo& newFileInfo = familyData->fCurrentFamily->fFonts.push_back();
     if (attributes) {
         size_t currentAttributeIndex = 0;
         while (attributes[currentAttributeIndex] &&
                attributes[currentAttributeIndex + 1]) {
             const char* attributeName = attributes[currentAttributeIndex];
             const char* attributeValue = attributes[currentAttributeIndex+1];
             size_t nameLength = strlen(attributeName);
             size_t valueLength = strlen(attributeValue);
             if (nameLength == 7 && strncmp(attributeName, "variant", nameLength) == 0) {
@@ skipping 13 matching lines @@
             } else if (nameLength == 4 && strncmp(attributeName, "lang", nameLength) == 0) {
                 SkLanguage prevLang = familyData->fCurrentFamily->fLanguage;
                 familyData->fCurrentFamily->fLanguage = SkLanguage(attributeValue);
                 if (familyData->fCurrentFamily->fFonts.count() > 1 &&
                         familyData->fCurrentFamily->fLanguage != prevLang) {
                     SkDebugf("Every font file within a family must have identical languages");
                     sk_throw();
                 }
             } else if (nameLength == 5 && strncmp(attributeName, "index", nameLength) == 0) {
                 int value;
-                if (parseNonNegativeInteger(attributeValue, &value)) {
+                if (parse_non_negative_integer(attributeValue, &value)) {
                     newFileInfo.fIndex = value;
                 } else {
                     SkDebugf("---- SystemFonts index=%s (INVALID)", attributeValue);
                 }
             }
             //each element is a pair of attributeName/attributeValue string pairs
             currentAttributeIndex += 2;
         }
     }
     familyData->fCurrentFontInfo = &newFileInfo;
-    XML_SetCharacterDataHandler(familyData->fParser, textHandler);
+    XML_SetCharacterDataHandler(familyData->fParser, text_handler);
 }
 
 /**
  * Handler for the start of a tag. The only tags we expect are familyset, family,
  * nameset, fileset, name, and file.
  */
-static void startElementHandler(void* data, const char* tag, const char** atts) {
+static void start_element_handler(void* data, const char* tag, const char** atts) {
     FamilyData* familyData = (FamilyData*) data;
     size_t len = strlen(tag);
     if (len == 9 && strncmp(tag, "familyset", len) == 0) {
         // The familyset tag has an optional "version" attribute with an integer value >= 0
         for (size_t i = 0; atts[i] != NULL &&
                            atts[i+1] != NULL; i += 2) {
             size_t nameLen = strlen(atts[i]);
             if (nameLen == 7 && strncmp(atts[i], "version", nameLen)) continue;
             const char* valueString = atts[i+1];
             int version;
-            if (parseNonNegativeInteger(valueString, &version) && (version >= 21)) {
+            if (parse_non_negative_integer(valueString, &version) && (version >= 21)) {
                 XML_SetElementHandler(familyData->fParser,
                                       lmpParser::startElementHandler,
                                       lmpParser::endElementHandler);
+                familyData->fVersion = version;
             }
         }
     } else if (len == 6 && strncmp(tag, "family", len) == 0) {
         familyData->fCurrentFamily.reset(new FontFamily());
         // The Family tag has an optional "order" attribute with an integer value >= 0
         // If this attribute does not exist, the default value is -1
         for (size_t i = 0; atts[i] != NULL &&
                            atts[i+1] != NULL; i += 2) {
             const char* valueString = atts[i+1];
             int value;
-            if (parseNonNegativeInteger(valueString, &value)) {
+            if (parse_non_negative_integer(valueString, &value)) {
                 familyData->fCurrentFamily->fOrder = value;
             }
         }
     } else if (len == 7 && strncmp(tag, "nameset", len) == 0) {
         familyData->fCurrentTag = NAMESET_TAG;
     } else if (len == 7 && strncmp(tag, "fileset", len) == 0) {
         familyData->fCurrentTag = FILESET_TAG;
     } else if (len == 4 && strncmp(tag, "name", len) == 0 && familyData->fCurrentTag == NAMESET_TAG) {
         // If it's a Name, parse the text inside
-        XML_SetCharacterDataHandler(familyData->fParser, textHandler);
+        XML_SetCharacterDataHandler(familyData->fParser, text_handler);
     } else if (len == 4 && strncmp(tag, "file", len) == 0 && familyData->fCurrentTag == FILESET_TAG) {
         // If it's a file, parse the attributes, then parse the text inside
-        fontFileElementHandler(familyData, atts);
+        font_file_element_handler(familyData, atts);
     }
 }
 
 /**
  * Handler for the end of tags. We only care about family, nameset, fileset,
  * name, and file.
  */
-static void endElementHandler(void* data, const char* tag) {
+static void end_element_handler(void* data, const char* tag) {
     FamilyData* familyData = (FamilyData*) data;
     size_t len = strlen(tag);
     if (len == 6 && strncmp(tag, "family", len)== 0) {
         // Done parsing a Family - store the created currentFamily in the families array
         *familyData->fFamilies.append() = familyData->fCurrentFamily.detach();
     } else if (len == 7 && strncmp(tag, "nameset", len) == 0) {
         familyData->fCurrentTag = NO_TAG;
     } else if (len == 7 && strncmp(tag, "fileset", len) == 0) {
         familyData->fCurrentTag = NO_TAG;
     } else if ((len == 4 &&
                 strncmp(tag, "name", len) == 0 &&
                 familyData->fCurrentTag == NAMESET_TAG) ||
                (len == 4 &&
                 strncmp(tag, "file", len) == 0 &&
                 familyData->fCurrentTag == FILESET_TAG)) {
         // Disable the arbitrary text handler installed to load Name data
         XML_SetCharacterDataHandler(familyData->fParser, NULL);
     }
 }
 
 } // namespace jbParser
 
 /**
  * This function parses the given filename and stores the results in the given
- * families array.
+ * families array. Returns the version of the file, negative if the file does not exist.
  */
-static void parseConfigFile(const char* filename, SkTDArray<FontFamily*> &families) {
+static int parse_config_file(const char* filename, SkTDArray<FontFamily*>& families) {
 
     FILE* file = fopen(filename, "r");
 
     // Some of the files we attempt to parse (in particular, /vendor/etc/fallback_fonts.xml)
     // are optional - failure here is okay because one of these optional files may not exist.
     if (NULL == file) {
-        return;
+        return -1;
     }
 
     XML_Parser parser = XML_ParserCreate(NULL);
     FamilyData familyData(parser, families);
     XML_SetUserData(parser, &familyData);
     // Start parsing oldschool; switch these in flight if we detect a newer version of the file.
-    XML_SetElementHandler(parser, jbParser::startElementHandler, jbParser::endElementHandler);
+    XML_SetElementHandler(parser, jbParser::start_element_handler, jbParser::end_element_handler);
 
     char buffer[512];
     bool done = false;
     while (!done) {
         fgets(buffer, sizeof(buffer), file);
         size_t len = strlen(buffer);
         if (feof(file) != 0) {
             done = true;
         }
         XML_Parse(parser, buffer, len, done);
     }
     XML_ParserFree(parser);
     fclose(file);
+    return familyData.fVersion;
 }
 
-static void getSystemFontFamilies(SkTDArray<FontFamily*> &fontFamilies) {
+/** Returns the version of the system font file actually found, negative if none. */
+static int append_system_font_families(SkTDArray<FontFamily*>& fontFamilies) {
     int initialCount = fontFamilies.count();
-    parseConfigFile(LMP_SYSTEM_FONTS_FILE, fontFamilies);
-
-    if (initialCount == fontFamilies.count()) {
-        parseConfigFile(OLD_SYSTEM_FONTS_FILE, fontFamilies);
+    int version = parse_config_file(LMP_SYSTEM_FONTS_FILE, fontFamilies);
+    if (version < 0 || fontFamilies.count() == initialCount) {
+        version = parse_config_file(OLD_SYSTEM_FONTS_FILE, fontFamilies);
     }
+    return version;
 }
 
 /**
  * In some versions of Android prior to Android 4.2 (JellyBean MR1 at API
  * Level 17) the fallback fonts for certain locales were encoded in their own
  * XML files with a suffix that identified the locale.  We search the provided
  * directory for those files,add all of their entries to the fallback chain, and
  * include the locale as part of each entry.
  */
-static void getFallbackFontFamiliesForLocale(SkTDArray<FontFamily*> &fallbackFonts, const char* dir) {
+static void append_fallback_font_families_for_locale(SkTDArray<FontFamily*>& fallbackFonts,
+                                                     const char* dir)
+{
 #if defined(SK_BUILD_FOR_ANDROID_FRAMEWORK)
     // The framework is beyond Android 4.2 and can therefore skip this function
     return;
 #endif
 
     DIR* fontDirectory = opendir(dir);
     if (fontDirectory != NULL){
         struct dirent* dirEntry = readdir(fontDirectory);
         while (dirEntry) {
 
             // The size of both the prefix, suffix, and a minimum valid language code
             static const size_t minSize = strlen(LOCALE_FALLBACK_FONTS_PREFIX) +
                                           strlen(LOCALE_FALLBACK_FONTS_SUFFIX) + 2;
 
             SkString fileName(dirEntry->d_name);
             if (fileName.size() >= minSize &&
                     fileName.startsWith(LOCALE_FALLBACK_FONTS_PREFIX) &&
                     fileName.endsWith(LOCALE_FALLBACK_FONTS_SUFFIX)) {
 
                 static const size_t fixedLen = strlen(LOCALE_FALLBACK_FONTS_PREFIX) -
                                                strlen(LOCALE_FALLBACK_FONTS_SUFFIX);
 
                 SkString locale(fileName.c_str() - strlen(LOCALE_FALLBACK_FONTS_PREFIX),
                                 fileName.size() - fixedLen);
 
                 SkString absoluteFilename;
                 absoluteFilename.printf("%s/%s", dir, fileName.c_str());
 
                 SkTDArray<FontFamily*> langSpecificFonts;
-                parseConfigFile(absoluteFilename.c_str(), langSpecificFonts);
+                parse_config_file(absoluteFilename.c_str(), langSpecificFonts);
 
                 for (int i = 0; i < langSpecificFonts.count(); ++i) {
                     FontFamily* family = langSpecificFonts[i];
                     family->fLanguage = SkLanguage(locale);
                     *fallbackFonts.append() = family;
                 }
             }
 
             // proceed to the next entry in the directory
             dirEntry = readdir(fontDirectory);
         }
         // cleanup the directory reference
         closedir(fontDirectory);
     }
 }
 
-static void getFallbackFontFamilies(SkTDArray<FontFamily*> &fallbackFonts) {
+static void append_system_fallback_font_families(SkTDArray<FontFamily*>& fallbackFonts) {
+    parse_config_file(FALLBACK_FONTS_FILE, fallbackFonts);
+    append_fallback_font_families_for_locale(fallbackFonts, LOCALE_FALLBACK_FONTS_SYSTEM_DIR);
+}
+
+static void mixin_vendor_fallback_font_families(SkTDArray<FontFamily*>& fallbackFonts) {
     SkTDArray<FontFamily*> vendorFonts;
-    parseConfigFile(FALLBACK_FONTS_FILE, fallbackFonts);
-    parseConfigFile(VENDOR_FONTS_FILE, vendorFonts);
-
-    getFallbackFontFamiliesForLocale(fallbackFonts, LOCALE_FALLBACK_FONTS_SYSTEM_DIR);
-    getFallbackFontFamiliesForLocale(vendorFonts, LOCALE_FALLBACK_FONTS_VENDOR_DIR);
+    parse_config_file(VENDOR_FONTS_FILE, vendorFonts);
+    append_fallback_font_families_for_locale(vendorFonts, LOCALE_FALLBACK_FONTS_VENDOR_DIR);
 
     // This loop inserts the vendor fallback fonts in the correct order in the
     // overall fallbacks list.
     int currentOrder = -1;
     for (int i = 0; i < vendorFonts.count(); ++i) {
         FontFamily* family = vendorFonts[i];
         int order = family->fOrder;
         if (order < 0) {
             if (currentOrder < 0) {
                 // Default case - just add it to the end of the fallback list
                 *fallbackFonts.append() = family;
             } else {
                 // no order specified on this font, but we're incrementing the order
                 // based on an earlier order insertion request
                 *fallbackFonts.insert(currentOrder++) = family;
             }
         } else {
             // Add the font into the fallback list in the specified order. Set
             // currentOrder for correct placement of other fonts in the vendor list.
             *fallbackFonts.insert(order) = family;
             currentOrder = order + 1;
         }
     }
 }
 
 /**
  * Loads data on font families from various expected configuration files. The
  * resulting data is returned in the given fontFamilies array.
  */
-void SkFontConfigParser::GetFontFamilies(SkTDArray<FontFamily*> &fontFamilies) {
-
-    getSystemFontFamilies(fontFamilies);
+void SkFontConfigParser::GetFontFamilies(SkTDArray<FontFamily*>& fontFamilies) {
+    // Version 21 of the system font configuration does not need any fallback configuration files.
+    if (append_system_font_families(fontFamilies) >= 21) {
+        return;
+    }
 
     // Append all the fallback fonts to system fonts
     SkTDArray<FontFamily*> fallbackFonts;
-    getFallbackFontFamilies(fallbackFonts);
+    append_system_fallback_font_families(fallbackFonts);
+    mixin_vendor_fallback_font_families(fallbackFonts);
     for (int i = 0; i < fallbackFonts.count(); ++i) {
         fallbackFonts[i]->fIsFallbackFont = true;
         *fontFamilies.append() = fallbackFonts[i];
     }
 }
 
-void SkFontConfigParser::GetTestFontFamilies(SkTDArray<FontFamily*> &fontFamilies,
+void SkFontConfigParser::GetTestFontFamilies(SkTDArray<FontFamily*>& fontFamilies,
                                              const char* testMainConfigFile,
                                              const char* testFallbackConfigFile) {
-    parseConfigFile(testMainConfigFile, fontFamilies);
+    parse_config_file(testMainConfigFile, fontFamilies);
 
     SkTDArray<FontFamily*> fallbackFonts;
     if (testFallbackConfigFile) {
-        parseConfigFile(testFallbackConfigFile, fallbackFonts);
+        parse_config_file(testFallbackConfigFile, fallbackFonts);
     }
 
     // Append all fallback fonts to system fonts
     for (int i = 0; i < fallbackFonts.count(); ++i) {
         fallbackFonts[i]->fIsFallbackFont = true;
         *fontFamilies.append() = fallbackFonts[i];
     }
 }
 
 SkLanguage SkLanguage::getParent() const {
     SkASSERT(!fTag.isEmpty());
     const char* tag = fTag.c_str();
 
     // strip off the rightmost "-.*"
     const char* parentTagEnd = strrchr(tag, '-');
     if (parentTagEnd == NULL) {
         return SkLanguage();
     }
     size_t parentTagLen = parentTagEnd - tag;
     return SkLanguage(tag, parentTagLen);
 }