1 files changed, 71 insertions, 0 deletions
diff --git a/native/jni/src/dictionary/utils/format_utils.cpp b/native/jni/src/dictionary/utils/format_utils.cpp
new file mode 100644
index 000000000..cef3b094c
--- /dev/null
+++ b/native/jni/src/dictionary/utils/format_utils.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "dictionary/utils/format_utils.h"
+
+#include "dictionary/utils/byte_array_utils.h"
+
+namespace latinime {
+
+const uint32_t FormatUtils::MAGIC_NUMBER = 0x9BC13AFE;
+
+// Magic number (4 bytes), version (2 bytes), flags (2 bytes), header size (4 bytes) = 12
+const size_t FormatUtils::DICTIONARY_MINIMUM_SIZE = 12;
+
+/* static */ FormatUtils::FORMAT_VERSION FormatUtils::getFormatVersion(const int formatVersion) {
+    switch (formatVersion) {
+        case VERSION_2:
+        case VERSION_201:
+            AKLOGE("Dictionary versions 2 and 201 are incompatible with this version");
+            return UNKNOWN_VERSION;
+        case VERSION_202:
+            return VERSION_202;
+        case VERSION_4_ONLY_FOR_TESTING:
+            return VERSION_4_ONLY_FOR_TESTING;
+        case VERSION_402:
+            return VERSION_402;
+        case VERSION_403:
+            return VERSION_403;
+        default:
+            return UNKNOWN_VERSION;
+    }
+}
+/* static */ FormatUtils::FORMAT_VERSION FormatUtils::detectFormatVersion(
+        const ReadOnlyByteArrayView dictBuffer) {
+    // The magic number is stored big-endian.
+    // If the dictionary is less than 4 bytes, we can't even read the magic number, so we don't
+    // understand this format.
+    if (dictBuffer.size() < DICTIONARY_MINIMUM_SIZE) {
+        return UNKNOWN_VERSION;
+    }
+    const uint32_t magicNumber = ByteArrayUtils::readUint32(dictBuffer.data(), 0);
+    switch (magicNumber) {
+        case MAGIC_NUMBER:
+            // The layout of the header is as follows:
+            // Magic number (4 bytes) 0x9B 0xC1 0x3A 0xFE
+            // Dictionary format version number (2 bytes)
+            // Options (2 bytes)
+            // Header size (4 bytes) : integer, big endian
+            // Conceptually this converts the hardcoded value of the bytes in the file into
+            // the symbolic value we use in the code. But we want the constants to be the
+            // same so we use them for both here.
+            return getFormatVersion(ByteArrayUtils::readUint16(dictBuffer.data(), 4));
+        default:
+            return UNKNOWN_VERSION;
+    }
+}
+
+} // namespace latinime