1 files changed, 69 insertions, 0 deletions
diff --git a/src/main/java/com/android/apkzlib/sign/v2/ZFileDigestSource.java b/src/main/java/com/android/apkzlib/sign/v2/ZFileDigestSource.java
new file mode 100644
index 0000000..7513987
--- /dev/null
+++ b/src/main/java/com/android/apkzlib/sign/v2/ZFileDigestSource.java
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+package com.android.apkzlib.sign.v2;
+
+import java.io.IOException;
+import java.security.MessageDigest;
+
+import com.android.annotations.NonNull;
+import com.android.apkzlib.zip.ZFile;
+import com.google.common.base.Preconditions;
+
+/**
+ * Contiguous section of {@link ZFile} which is fed into {@link MessageDigest} instances.
+ */
+public class ZFileDigestSource implements DigestSource {
+    private final ZFile mFile;
+    private final long mOffset;
+    private final long mSize;
+
+    /**
+     * Constructs a new {@code ZFileDigestSource} representing the section of the file starting
+     * at the provided {@code offset} and extending for the provided {@code size} number of bytes.
+     */
+    public ZFileDigestSource(@NonNull ZFile file, long offset, long size) {
+        Preconditions.checkArgument(offset >= 0, "offset: %s", offset);
+        Preconditions.checkArgument(size >= 0, "size: %s", size);
+        mFile = file;
+        mOffset = offset;
+        mSize = size;
+    }
+
+
+    @Override
+    public long size() {
+        return mSize;
+    }
+
+    @Override
+    public void feedDigests(long offset, int size, @NonNull MessageDigest[] digests)
+            throws IOException {
+        Preconditions.checkArgument(offset >= 0, "offset: %s", offset);
+        Preconditions.checkArgument(size >= 0, "size: %s", size);
+        Preconditions.checkArgument(offset <= mSize, "offset: %s, file size: %s", offset, mSize);
+        long chunkStartOffset = mOffset + offset;
+        long availableSize = mSize - offset;
+        Preconditions.checkArgument(
+                size <= availableSize, "offset: %s, size: %s, file size: %s", offset, size, mSize);
+
+        byte[] chunk = new byte[size];
+        mFile.directFullyRead(chunkStartOffset, chunk);
+        for (MessageDigest md : digests) {
+            md.update(chunk);
+        }
+    }
+}