1 files changed, 154 insertions, 0 deletions
diff --git a/s2storage/src/readonly/java/com/android/storage/block/read/BlockData.java b/s2storage/src/readonly/java/com/android/storage/block/read/BlockData.java
new file mode 100644
index 0000000..f9ce802
--- /dev/null
+++ b/s2storage/src/readonly/java/com/android/storage/block/read/BlockData.java
@@ -0,0 +1,154 @@
+/*
+ * Copyright (C) 2020 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.storage.block.read;
+
+import com.android.storage.io.read.TypedInputStream;
+import com.android.storage.util.BitwiseUtils;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Objects;
+
+/**
+ * Provides typed, absolute position, random access to a block's data.
+ *
+ * <p>See also {@link TypedInputStream} for a streamed
+ * equivalent.
+ */
+public final class BlockData {
+
+    private final ByteBuffer mDataBytes;
+
+    /** Wraps a read-only, big-endian {@link ByteBuffer}. */
+    public BlockData(ByteBuffer dataBytes) {
+        if (!dataBytes.isReadOnly()) {
+            throw new IllegalArgumentException("dataBytes must be readonly");
+        }
+        if (dataBytes.order() != ByteOrder.BIG_ENDIAN) {
+            throw new IllegalArgumentException("dataBytes must be big-endian");
+        }
+        mDataBytes = Objects.requireNonNull(dataBytes);
+    }
+
+    /** Returns a copy of the underlying {@link ByteBuffer}. */
+    public ByteBuffer getByteBuffer() {
+        return mDataBytes.duplicate();
+    }
+
+    /** Returns the value of the byte at the specified position. */
+    public byte getByte(int byteOffset) {
+        return mDataBytes.get(byteOffset);
+    }
+
+    /** Returns the value of the byte at the specified position as an unsigned value. */
+    public int getUnsignedByte(int byteOffset) {
+        return mDataBytes.get(byteOffset) & 0xFF;
+    }
+
+    /** Returns the value of the 16-bit char at the specified position as an unsigned value. */
+    public char getChar(int byteOffset) {
+        return mDataBytes.getChar(byteOffset);
+    }
+
+    /** Returns the value of the 32-bit int at the specified position as an signed value. */
+    public int getInt(int byteOffset) {
+        return mDataBytes.getInt(byteOffset);
+    }
+
+    /** Returns the value of the 64-bit long at the specified position as an signed value. */
+    public long getLong(int byteOffset) {
+        return mDataBytes.getLong(byteOffset);
+    }
+
+    /**
+     * Returns a tiny (<= 255 entries) array of signed bytes starting at the specified position,
+     * where the length is encoded in the data.
+     */
+    public byte[] getTinyByteArray(int byteOffset) {
+        int size = getUnsignedByte(byteOffset);
+        return getBytes(byteOffset + 1, size);
+    }
+
+    /**
+     * Returns an array of signed bytes starting at the specified position.
+     */
+    public byte[] getBytes(int byteOffset, int byteCount) {
+        byte[] bytes = new byte[byteCount];
+        for (int i = 0; i < byteCount; i++) {
+            bytes[i] = mDataBytes.get(byteOffset + i);
+        }
+        return bytes;
+    }
+
+    /**
+     * Returns a tiny (<= 255 entries) array of chars starting at the specified position, where the
+     * length is encoded in the data.
+     */
+    public char[] getTinyCharArray(int byteOffset) {
+        int size = getUnsignedByte(byteOffset);
+        return getChars(byteOffset + 1, size);
+    }
+
+    /**
+     * Returns an array of chars starting at the specified position.
+     */
+    public char[] getChars(int byteOffset, int charCount) {
+        char[] array = new char[charCount];
+        for (int i = 0; i < charCount; i++) {
+            array[i] = getChar(byteOffset);
+            byteOffset += Character.BYTES;
+        }
+        return array;
+    }
+
+    /**
+     * Returns 1-8 bytes ({@code valueSizeBytes}) starting as the specified position as a
+     * {@code long}. The value can be interpreted as signed or unsigned depending on
+     * {@code signExtend}.
+     */
+    public long getValueAsLong(int valueSizeBytes, int byteOffset, boolean signExtend) {
+        if (valueSizeBytes < 0 || valueSizeBytes > Long.BYTES) {
+            throw new IllegalArgumentException("valueSizeBytes must be <= 8 bytes");
+        }
+        return getValueInternal(valueSizeBytes, byteOffset, signExtend);
+    }
+
+    /** Returns the size of the block data. */
+    public int getSize() {
+        return mDataBytes.limit();
+    }
+
+    private long getValueInternal(int valueSizeBytes, int byteOffset, boolean signExtend) {
+        if (byteOffset < 0) {
+            throw new IllegalArgumentException(
+                    "byteOffset=" + byteOffset + " must not be negative");
+        }
+
+        // High bytes read first.
+        long value = 0;
+        int bytesRead = 0;
+        while (bytesRead++ < valueSizeBytes) {
+            value <<= 8;
+            value |= (mDataBytes.get(byteOffset++) & 0xFF);
+        }
+        if (valueSizeBytes < 8 && signExtend) {
+            int entrySizeBits = valueSizeBytes * Byte.SIZE;
+            value = BitwiseUtils.signExtendToLong(entrySizeBits, value);
+        }
+        return value;
+    }
+}