QMimeDatabase: introduce QMimeMagicResult to accumulate magic results

Better than two pointer parameters. However it can't be a return
value as we initially thought, it's an in/out parameter, in order to
compare the results in the current directory with those found in earlier
directories.

Change-Id: Ic6137f2627703f8d6930c3f7dd1a1102187eef30
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 29 insertions, 18 deletions

diff --git a/src/corelib/mimetypes/qmimedatabase.cpp b/src/corelib/mimetypes/qmimedatabase.cpp
index 01712a0c26..96bcb24902 100644
--- a/src/corelib/mimetypes/qmimedatabase.cpp
+++ b/src/corelib/mimetypes/qmimedatabase.cpp
@@ -337,13 +337,14 @@ QMimeType QMimeDatabasePrivate::findByData(const QByteArray &data, int *accuracy
         return mimeTypeForName(QStringLiteral("application/x-zerosize"));
     }
 
-    *accuracyPtr = 0;
-    QString candidate;
+    QMimeMagicResult result;
     for (const auto &provider : providers())
-        provider->findByMagic(data, accuracyPtr, &candidate);
+        provider->findByMagic(data, result);
 
-    if (!candidate.isEmpty())
-        return QMimeType(QMimeTypePrivate(candidate));
+    if (result.isValid()) {
+        *accuracyPtr = result.accuracy;
+        return QMimeType(QMimeTypePrivate(result.candidate));
+    }
 
     if (isTextFile(data)) {
         *accuracyPtr = 5;
diff --git a/src/corelib/mimetypes/qmimeprovider.cpp b/src/corelib/mimetypes/qmimeprovider.cpp
index 4d2e7c7efb..64046dad60 100644
--- a/src/corelib/mimetypes/qmimeprovider.cpp
+++ b/src/corelib/mimetypes/qmimeprovider.cpp
@@ -348,7 +348,7 @@ bool QMimeBinaryProvider::matchMagicRule(QMimeBinaryProvider::CacheFile *cacheFi
     return false;
 }
 
-void QMimeBinaryProvider::findByMagic(const QByteArray &data, int *accuracyPtr, QString *candidate)
+void QMimeBinaryProvider::findByMagic(const QByteArray &data, QMimeMagicResult &result)
 {
     const int magicListOffset = m_cacheFile->getUint32(PosMagicListOffset);
     const int numMatches = m_cacheFile->getUint32(magicListOffset);
@@ -362,11 +362,13 @@ void QMimeBinaryProvider::findByMagic(const QByteArray &data, int *accuracyPtr,
         if (matchMagicRule(m_cacheFile.get(), numMatchlets, firstMatchletOffset, data)) {
             const int mimeTypeOffset = m_cacheFile->getUint32(off + 4);
             const char *mimeType = m_cacheFile->getCharStar(mimeTypeOffset);
-            *accuracyPtr = m_cacheFile->getUint32(off);
-            // Return the first match. We have no rules for conflicting magic data...
-            // (mime.cache itself is sorted, but what about local overrides with a lower prio?)
-            *candidate = QString::fromLatin1(mimeType);
-            return;
+            const int accuracy = static_cast<int>(m_cacheFile->getUint32(off));
+            if (accuracy > result.accuracy) {
+                result.accuracy = accuracy;
+                result.candidate = QString::fromLatin1(mimeType);
+                // Return the first match, mime.cache is sorted
+                return;
+            }
         }
     }
 }
@@ -718,14 +720,14 @@ void QMimeXMLProvider::addFileNameMatches(const QString &fileName, QMimeGlobMatc
     m_mimeTypeGlobs.matchingGlobs(fileName, result, filterFunc);
 }
 
-void QMimeXMLProvider::findByMagic(const QByteArray &data, int *accuracyPtr, QString *candidate)
+void QMimeXMLProvider::findByMagic(const QByteArray &data, QMimeMagicResult &result)
 {
     for (const QMimeMagicRuleMatcher &matcher : std::as_const(m_magicMatchers)) {
         if (matcher.matches(data)) {
             const int priority = matcher.priority();
-            if (priority > *accuracyPtr) {
-                *accuracyPtr = priority;
-                *candidate = matcher.mimetype();
+            if (priority > result.accuracy) {
+                result.accuracy = priority;
+                result.candidate = matcher.mimetype();
             }
         }
     }
diff --git a/src/corelib/mimetypes/qmimeprovider_p.h b/src/corelib/mimetypes/qmimeprovider_p.h
index 4fbd63af92..c61744772e 100644
--- a/src/corelib/mimetypes/qmimeprovider_p.h
+++ b/src/corelib/mimetypes/qmimeprovider_p.h
@@ -31,6 +31,14 @@ class QMimeMagicRuleMatcher;
 class QMimeTypeXMLData;
 class QMimeProviderBase;
 
+struct QMimeMagicResult
+{
+    bool isValid() const { return !candidate.isEmpty(); }
+
+    QString candidate;
+    int accuracy = 0;
+};
+
 class QMimeProviderBase
 {
     Q_DISABLE_COPY(QMimeProviderBase)
@@ -46,7 +54,7 @@ public:
     virtual void addParents(const QString &mime, QStringList &result) = 0;
     virtual QString resolveAlias(const QString &name) = 0;
     virtual void addAliases(const QString &name, QStringList &result) = 0;
-    virtual void findByMagic(const QByteArray &data, int *accuracyPtr, QString *candidate) = 0;
+    virtual void findByMagic(const QByteArray &data, QMimeMagicResult &result) = 0;
     virtual void addAllMimeTypes(QList<QMimeType> &result) = 0;
     virtual QMimeTypePrivate::LocaleHash localeComments(const QString &name) = 0;
     virtual bool hasGlobDeleteAll(const QString &name) = 0;
@@ -82,7 +90,7 @@ public:
     void addParents(const QString &mime, QStringList &result) override;
     QString resolveAlias(const QString &name) override;
     void addAliases(const QString &name, QStringList &result) override;
-    void findByMagic(const QByteArray &data, int *accuracyPtr, QString *candidate) override;
+    void findByMagic(const QByteArray &data, QMimeMagicResult &result) override;
     void addAllMimeTypes(QList<QMimeType> &result) override;
     QMimeTypePrivate::LocaleHash localeComments(const QString &name) override;
     bool hasGlobDeleteAll(const QString &name) override;
@@ -144,7 +152,7 @@ public:
     void addParents(const QString &mime, QStringList &result) override;
     QString resolveAlias(const QString &name) override;
     void addAliases(const QString &name, QStringList &result) override;
-    void findByMagic(const QByteArray &data, int *accuracyPtr, QString *candidate) override;
+    void findByMagic(const QByteArray &data, QMimeMagicResult &result) override;
     void addAllMimeTypes(QList<QMimeType> &result) override;
     void ensureLoaded() override;
     QMimeTypePrivate::LocaleHash localeComments(const QString &name) override;