Intial ProtoInputStream checkin

Enable proto reading on the Android Framework with a memory efficient
pull parser.

Fixes: 112269636
Test: atest CtsProtoTestCases
Change-Id: If8331edb1ec393acd724ffb5d27d6efad1a42a80

5 files changed, 1353 insertions, 219 deletions

diff --git a/core/java/android/util/proto/ProtoInputStream.java b/core/java/android/util/proto/ProtoInputStream.java
new file mode 100644
index 000000000000..209451bcfe6a
--- /dev/null
+++ b/core/java/android/util/proto/ProtoInputStream.java
@@ -0,0 +1,978 @@
+/*
+ * Copyright (C) 2018 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 android.util.proto;
+
+import android.annotation.TestApi;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+
+/**
+ * Class to read to a protobuf stream.
+ *
+ * Each read method takes an ID code from the protoc generated classes
+ * and return a value of the field. To read a nested object, call #start
+ * and then #end when you are done.
+ *
+ * The ID codes have type information embedded into them, so if you call
+ * the incorrect function you will get an IllegalArgumentException.
+ *
+ * nextField will return the field number of the next field, which can be
+ * matched to the protoc generated ID code and used to determine how to
+ * read the next field.
+ *
+ * It is STRONGLY RECOMMENDED to read from the ProtoInputStream with a switch
+ * statement wrapped in a while loop. Additionally, it is worth logging or
+ * storing unexpected fields or ones that do not match the expected wire type
+ *
+ * ex:
+ * void parseFromProto(ProtoInputStream stream) {
+ *     while(stream.nextField() != ProtoInputStream.NO_MORE_FIELDS) {
+ *         try {
+ *             switch (stream.getFieldNumber()) {
+ *                 case (int) DummyProto.NAME:
+ *                     mName = stream.readString(DummyProto.NAME);
+ *                     break;
+ *                 case (int) DummyProto.VALUE:
+ *                     mValue = stream.readInt(DummyProto.VALUE);
+ *                     break;
+ *                 default:
+ *                     LOG(TAG, "Unhandled field in proto!\n"
+ *                              + ProtoUtils.currentFieldToString(stream));
+ *             }
+ *         } catch (WireTypeMismatchException wtme) {
+ *             LOG(TAG, "Wire Type mismatch in proto!\n" + ProtoUtils.currentFieldToString(stream));
+ *         }
+ *     }
+ * }
+ *
+ * @hide
+ */
+@TestApi
+public final class ProtoInputStream extends ProtoStream {
+
+    public static final int NO_MORE_FIELDS = -1;
+
+    /**
+     * Our stream.  If there is one.
+     */
+    private InputStream mStream;
+
+    /**
+     * The field number of the current field. Will be equal to NO_MORE_FIELDS if end of message is
+     * reached
+     */
+    private int mFieldNumber;
+
+    /**
+     * The wire type of the current field
+     */
+    private int mWireType;
+
+    private static final byte STATE_STARTED_FIELD_READ = 1 << 0;
+    private static final byte STATE_READING_PACKED = 1 << 1;
+    private static final byte STATE_FIELD_MISS = 2 << 1;
+
+    /**
+     * Tracks some boolean states for the proto input stream
+     * bit 0: Started Field Read, true - tag has been read, ready to read field data.
+     * false - field data has been read, reading to start next field.
+     * bit 1: Reading Packed Field, true - currently reading values from a packed field
+     * false - not reading from packed field.
+     */
+    private byte mState = 0;
+
+    /**
+     * Keeps track of the currently read nested Objects, for end object sanity checking and debug
+     */
+    private ArrayList<Long> mExpectedObjectTokenStack = null;
+
+    /**
+     * Current nesting depth of start calls.
+     */
+    private int mDepth = -1;
+
+    /**
+     * Buffer for the to be read data. If mStream is not null, it will be constantly refilled from
+     * the stream.
+     */
+    private byte[] mBuffer;
+
+    private static final int DEFAULT_BUFFER_SIZE = 8192;
+
+    /**
+     * Size of the buffer if reading from a stream.
+     */
+    private final int mBufferSize;
+
+    /**
+     * The number of bytes that have been skipped or dropped from the buffer.
+     */
+    private int mDiscardedBytes = 0;
+
+    /**
+     * Current offset in the buffer
+     * mOffset + mDiscardedBytes = current offset in proto binary
+     */
+    private int mOffset = 0;
+
+    /**
+     * Note the offset of the last byte in the buffer. Usually will equal the size of the buffer.
+     * mEnd + mDiscardedBytes = the last known byte offset + 1
+     */
+    private int mEnd = 0;
+
+    /**
+     * Packed repeated fields are not read in one go. mPackedEnd keeps track of where the packed
+     * field ends in the proto binary if current field is packed.
+     */
+    private int mPackedEnd = 0;
+
+    /**
+     * Construct a ProtoInputStream on top of an InputStream to read a proto. Also specify the
+     * number of bytes the ProtoInputStream will buffer from the input stream
+     *
+     * @param stream from which the proto is read
+     */
+    public ProtoInputStream(InputStream stream, int bufferSize) {
+        mStream = stream;
+        if (bufferSize > 0) {
+            mBufferSize = bufferSize;
+        } else {
+            mBufferSize = DEFAULT_BUFFER_SIZE;
+        }
+        mBuffer = new byte[mBufferSize];
+    }
+
+    /**
+     * Construct a ProtoInputStream on top of an InputStream to read a proto
+     *
+     * @param stream from which the proto is read
+     */
+    public ProtoInputStream(InputStream stream) {
+        this(stream, DEFAULT_BUFFER_SIZE);
+    }
+
+    /**
+     * Construct a ProtoInputStream to read a proto directly from a byte array
+     *
+     * @param buffer - the byte array to be parsed
+     */
+    public ProtoInputStream(byte[] buffer) {
+        mBufferSize = buffer.length;
+        mEnd = buffer.length;
+        mBuffer = buffer;
+        mStream = null;
+    }
+
+    /**
+     * Get the field number of the current field.
+     */
+    public int getFieldNumber() {
+        return mFieldNumber;
+    }
+
+    /**
+     * Get the wire type of the current field.
+     *
+     * @return an int that matches one of the ProtoStream WIRE_TYPE_ constants
+     */
+    public int getWireType() {
+        if ((mState & STATE_READING_PACKED) == STATE_READING_PACKED) {
+            // mWireType got overwritten when STATE_READING_PACKED was set. Send length delimited
+            // constant instead
+            return WIRE_TYPE_LENGTH_DELIMITED;
+        }
+        return mWireType;
+    }
+
+    /**
+     * Get the current offset in the proto binary.
+     */
+    public int getOffset() {
+        return mOffset + mDiscardedBytes;
+    }
+
+    /**
+     * Reads the tag of the next field from the stream. If previous field value was not read, its
+     * data will be skipped over.
+     *
+     * @return the field number of the next field
+     * @throws IOException if an I/O error occurs
+     */
+    public int nextField() throws IOException {
+
+        if ((mState & STATE_FIELD_MISS) == STATE_FIELD_MISS) {
+            // Data from the last nextField was not used, reuse the info
+            mState &= ~STATE_FIELD_MISS;
+            return mFieldNumber;
+        }
+        if ((mState & STATE_STARTED_FIELD_READ) == STATE_STARTED_FIELD_READ) {
+            // Field data was not read, skip to the next field
+            skip();
+            mState &= ~STATE_STARTED_FIELD_READ;
+        }
+        if ((mState & STATE_READING_PACKED) == STATE_READING_PACKED) {
+            if (getOffset() < mPackedEnd) {
+                // In the middle of a packed field, return the same tag until last packed value
+                // has been read
+                mState |= STATE_STARTED_FIELD_READ;
+                return mFieldNumber;
+            } else if (getOffset() == mPackedEnd) {
+                // Reached the end of the packed field
+                mState &= ~STATE_READING_PACKED;
+            } else {
+                throw new ProtoParseException(
+                        "Unexpectedly reached end of packed field at offset 0x"
+                                + Integer.toHexString(mPackedEnd)
+                                + dumpDebugData());
+            }
+        }
+
+        if ((mDepth >= 0) && (getOffset() == getOffsetFromToken(
+                mExpectedObjectTokenStack.get(mDepth)))) {
+            // reached end of a embedded message
+            mFieldNumber = NO_MORE_FIELDS;
+        } else {
+            readTag();
+        }
+        return mFieldNumber;
+    }
+
+    /**
+     * Attempt to guess the next field. If there is a match, the field data will be ready to read.
+     * If there is no match, nextField will need to be called to get the field number
+     *
+     * @return true if fieldId matches the next field, false if not
+     */
+    public boolean isNextField(long fieldId) throws IOException {
+        if (nextField() == (int) fieldId) {
+            return true;
+        }
+        // Note to reuse the info from the nextField call in the next call.
+        mState |= STATE_FIELD_MISS;
+        return false;
+    }
+
+    /**
+     * Read a single double.
+     * Will throw if the current wire type is not fixed64
+     *
+     * @param fieldId - must match the current field number and field type
+     */
+    public double readDouble(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+        checkPacked(fieldId);
+
+        double value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK)
+                >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_DOUBLE >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_FIXED64);
+                value = Double.longBitsToDouble(readFixed64());
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field id (" + getFieldIdString(fieldId)
+                                + ") cannot be read as a double"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Read a single float.
+     * Will throw if the current wire type is not fixed32
+     *
+     * @param fieldId - must match the current field number and field type
+     */
+    public float readFloat(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+        checkPacked(fieldId);
+
+        float value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK)
+                >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_FLOAT >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_FIXED32);
+                value = Float.intBitsToFloat(readFixed32());
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field id (" + getFieldIdString(fieldId) + ") is not a float"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Read a single 32bit or varint proto type field as an int.
+     * Will throw if the current wire type is not varint or fixed32
+     *
+     * @param fieldId - must match the current field number and field type
+     */
+    public int readInt(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+        checkPacked(fieldId);
+
+        int value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK)
+                >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_FIXED32 >>> FIELD_TYPE_SHIFT):
+            case (int) (FIELD_TYPE_SFIXED32 >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_FIXED32);
+                value = readFixed32();
+                break;
+            case (int) (FIELD_TYPE_SINT32 >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_VARINT);
+                value = decodeZigZag32((int) readVarint());
+                break;
+            case (int) (FIELD_TYPE_INT32 >>> FIELD_TYPE_SHIFT):
+            case (int) (FIELD_TYPE_UINT32 >>> FIELD_TYPE_SHIFT):
+            case (int) (FIELD_TYPE_ENUM >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_VARINT);
+                value = (int) readVarint();
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field id (" + getFieldIdString(fieldId) + ") is not an int"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Read a single 64bit or varint proto type field as an long.
+     *
+     * @param fieldId - must match the current field number
+     */
+    public long readLong(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+        checkPacked(fieldId);
+
+        long value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK)
+                >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_FIXED64 >>> FIELD_TYPE_SHIFT):
+            case (int) (FIELD_TYPE_SFIXED64 >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_FIXED64);
+                value = readFixed64();
+                break;
+            case (int) (FIELD_TYPE_SINT64 >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_VARINT);
+                value = decodeZigZag64(readVarint());
+                break;
+            case (int) (FIELD_TYPE_INT64 >>> FIELD_TYPE_SHIFT):
+            case (int) (FIELD_TYPE_UINT64 >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_VARINT);
+                value = readVarint();
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field id (" + getFieldIdString(fieldId) + ") is not an long"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Read a single 32bit or varint proto type field as an boolean.
+     *
+     * @param fieldId - must match the current field number
+     */
+    public boolean readBoolean(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+        checkPacked(fieldId);
+
+        boolean value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK)
+                >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_BOOL >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_VARINT);
+                value = readVarint() != 0;
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field id (" + getFieldIdString(fieldId) + ") is not an boolean"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Read a string field
+     *
+     * @param fieldId - must match the current field number
+     */
+    public String readString(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+
+        String value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK) >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_STRING >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_LENGTH_DELIMITED);
+                int len = (int) readVarint();
+                value = readRawString(len);
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field id(" + getFieldIdString(fieldId)
+                                + ") is not an string"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Read a bytes field
+     *
+     * @param fieldId - must match the current field number
+     */
+    public byte[] readBytes(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+
+        byte[] value;
+        switch ((int) ((fieldId & FIELD_TYPE_MASK) >>> FIELD_TYPE_SHIFT)) {
+            case (int) (FIELD_TYPE_MESSAGE >>> FIELD_TYPE_SHIFT):
+            case (int) (FIELD_TYPE_BYTES >>> FIELD_TYPE_SHIFT):
+                assertWireType(WIRE_TYPE_LENGTH_DELIMITED);
+                int len = (int) readVarint();
+                value = readRawBytes(len);
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "Requested field type (" + getFieldIdString(fieldId)
+                                + ") cannot be read as raw bytes"
+                                + dumpDebugData());
+        }
+        // Successfully read the field
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return value;
+    }
+
+    /**
+     * Start the read of an embedded Object
+     *
+     * @param fieldId - must match the current field number
+     * @return a token. The token must be handed back when finished reading embedded Object
+     */
+    public long start(long fieldId) throws IOException {
+        assertFreshData();
+        assertFieldNumber(fieldId);
+        assertWireType(WIRE_TYPE_LENGTH_DELIMITED);
+
+        int messageSize = (int) readVarint();
+
+        if (mExpectedObjectTokenStack == null) {
+            mExpectedObjectTokenStack = new ArrayList<>();
+        }
+        if (++mDepth == mExpectedObjectTokenStack.size()) {
+            // Create a token to keep track of nested Object and extend the object stack
+            mExpectedObjectTokenStack.add(makeToken(0,
+                    (fieldId & FIELD_COUNT_REPEATED) == FIELD_COUNT_REPEATED, mDepth,
+                    (int) fieldId, getOffset() + messageSize));
+
+        } else {
+            // Create a token to keep track of nested Object
+            mExpectedObjectTokenStack.set(mDepth, makeToken(0,
+                    (fieldId & FIELD_COUNT_REPEATED) == FIELD_COUNT_REPEATED, mDepth,
+                    (int) fieldId, getOffset() + messageSize));
+        }
+
+        // Sanity check
+        if (mDepth > 0
+                && getOffsetFromToken(mExpectedObjectTokenStack.get(mDepth))
+                > getOffsetFromToken(mExpectedObjectTokenStack.get(mDepth - 1))) {
+            throw new ProtoParseException("Embedded Object ("
+                    + token2String(mExpectedObjectTokenStack.get(mDepth))
+                    + ") ends after of parent Objects's ("
+                    + token2String(mExpectedObjectTokenStack.get(mDepth - 1))
+                    + ") end"
+                    + dumpDebugData());
+        }
+        mState &= ~STATE_STARTED_FIELD_READ;
+        return mExpectedObjectTokenStack.get(mDepth);
+    }
+
+    /**
+     * Note the end of a nested object. Must be called to continue streaming the rest of the proto.
+     * end can be called mid object parse. The offset will be moved to the next field outside the
+     * object.
+     *
+     * @param token - token
+     */
+    public void end(long token) {
+        // Sanity check to make sure user is keeping track of their embedded messages
+        if (mExpectedObjectTokenStack.get(mDepth) != token) {
+            throw new ProtoParseException(
+                    "end token " + token + " does not match current message token "
+                            + mExpectedObjectTokenStack.get(mDepth)
+                            + dumpDebugData());
+        }
+        if (getOffsetFromToken(mExpectedObjectTokenStack.get(mDepth)) > getOffset()) {
+            // Did not read all of the message, skip to the end
+            incOffset(getOffsetFromToken(mExpectedObjectTokenStack.get(mDepth)) - getOffset());
+        }
+        mDepth--;
+        mState &= ~STATE_STARTED_FIELD_READ;
+    }
+
+    /**
+     * Read the tag at the start of the next field and collect field number and wire type.
+     * Will set mFieldNumber to NO_MORE_FIELDS if end of buffer/stream reached.
+     */
+    private void readTag() throws IOException {
+        fillBuffer();
+        if (mOffset >= mEnd) {
+            // reached end of the stream
+            mFieldNumber = NO_MORE_FIELDS;
+            return;
+        }
+        int tag = (int) readVarint();
+        mFieldNumber = tag >>> FIELD_ID_SHIFT;
+        mWireType = tag & WIRE_TYPE_MASK;
+        mState |= STATE_STARTED_FIELD_READ;
+    }
+
+    /**
+     * Decode a 32 bit ZigZag encoded signed int.
+     *
+     * @param n - int to decode
+     * @return the decoded signed int
+     */
+    public int decodeZigZag32(final int n) {
+        return (n >>> 1) ^ -(n & 1);
+    }
+
+    /**
+     * Decode a 64 bit ZigZag encoded signed long.
+     *
+     * @param n - long to decode
+     * @return the decoded signed long
+     */
+    public long decodeZigZag64(final long n) {
+        return (n >>> 1) ^ -(n & 1);
+    }
+
+    /**
+     * Read a varint from the buffer
+     *
+     * @return the varint as a long
+     */
+    private long readVarint() throws IOException {
+        long value = 0;
+        int shift = 0;
+        while (true) {
+            fillBuffer();
+            // Limit how much bookkeeping is done by checking how far away the end of the buffer is
+            // and directly accessing buffer up until the end.
+            final int fragment = mEnd - mOffset;
+            for (int i = 0; i < fragment; i++) {
+                byte b = mBuffer[(mOffset + i)];
+                value |= (b & 0x7FL) << shift;
+                if ((b & 0x80) == 0) {
+                    incOffset(i + 1);
+                    return value;
+                }
+                shift += 7;
+                if (shift > 63) {
+                    throw new ProtoParseException(
+                            "Varint is too large at offset 0x"
+                                    + Integer.toHexString(getOffset() + i)
+                                    + dumpDebugData());
+                }
+            }
+            // Hit the end of the buffer, do some incrementing and checking, then continue
+            incOffset(fragment);
+        }
+    }
+
+    /**
+     * Read a fixed 32 bit int from the buffer
+     *
+     * @return the fixed32 as a int
+     */
+    private int readFixed32() throws IOException {
+        // check for fast path, which is likely with a reasonable buffer size
+        if (mOffset + 4 <= mEnd) {
+            // don't bother filling buffer since we know the end is plenty far away
+            incOffset(4);
+            return (mBuffer[mOffset - 4] & 0xFF)
+                    | ((mBuffer[mOffset - 3] & 0xFF) << 8)
+                    | ((mBuffer[mOffset - 2] & 0xFF) << 16)
+                    | ((mBuffer[mOffset - 1] & 0xFF) << 24);
+        }
+
+        // the Fixed32 crosses the edge of a chunk, read the Fixed32 in multiple fragments.
+        // There will be two fragment reads except when the chunk size is 2 or less.
+        int value = 0;
+        int shift = 0;
+        int bytesLeft = 4;
+        while (bytesLeft > 0) {
+            fillBuffer();
+            // Find the number of bytes available until the end of the chunk or Fixed32
+            int fragment = (mEnd - mOffset) < bytesLeft ? (mEnd - mOffset) : bytesLeft;
+            incOffset(fragment);
+            bytesLeft -= fragment;
+            while (fragment > 0) {
+                value |= ((mBuffer[mOffset - fragment] & 0xFF) << shift);
+                fragment--;
+                shift += 8;
+            }
+        }
+        return value;
+    }
+
+    /**
+     * Read a fixed 64 bit long from the buffer
+     *
+     * @return the fixed64 as a long
+     */
+    private long readFixed64() throws IOException {
+        // check for fast path, which is likely with a reasonable buffer size
+        if (mOffset + 8 <= mEnd) {
+            // don't bother filling buffer since we know the end is plenty far away
+            incOffset(8);
+            return (mBuffer[mOffset - 8] & 0xFFL)
+                    | ((mBuffer[mOffset - 7] & 0xFFL) << 8)
+                    | ((mBuffer[mOffset - 6] & 0xFFL) << 16)
+                    | ((mBuffer[mOffset - 5] & 0xFFL) << 24)
+                    | ((mBuffer[mOffset - 4] & 0xFFL) << 32)
+                    | ((mBuffer[mOffset - 3] & 0xFFL) << 40)
+                    | ((mBuffer[mOffset - 2] & 0xFFL) << 48)
+                    | ((mBuffer[mOffset - 1] & 0xFFL) << 56);
+        }
+
+        // the Fixed64 crosses the edge of a chunk, read the Fixed64 in multiple fragments.
+        // There will be two fragment reads except when the chunk size is 6 or less.
+        long value = 0;
+        int shift = 0;
+        int bytesLeft = 8;
+        while (bytesLeft > 0) {
+            fillBuffer();
+            // Find the number of bytes available until the end of the chunk or Fixed64
+            int fragment = (mEnd - mOffset) < bytesLeft ? (mEnd - mOffset) : bytesLeft;
+            incOffset(fragment);
+            bytesLeft -= fragment;
+            while (fragment > 0) {
+                value |= ((mBuffer[(mOffset - fragment)] & 0xFFL) << shift);
+                fragment--;
+                shift += 8;
+            }
+        }
+        return value;
+    }
+
+    /**
+     * Read raw bytes from the buffer
+     *
+     * @param n - number of bytes to read
+     * @return a byte array with raw bytes
+     */
+    private byte[] readRawBytes(int n) throws IOException {
+        byte[] buffer = new byte[n];
+        int pos = 0;
+        while (mOffset + n - pos > mEnd) {
+            int fragment = mEnd - mOffset;
+            if (fragment > 0) {
+                System.arraycopy(mBuffer, mOffset, buffer, pos, fragment);
+                incOffset(fragment);
+                pos += fragment;
+            }
+            fillBuffer();
+            if (mOffset >= mEnd) {
+                throw new ProtoParseException(
+                        "Unexpectedly reached end of the InputStream at offset 0x"
+                                + Integer.toHexString(mEnd)
+                                + dumpDebugData());
+            }
+        }
+        System.arraycopy(mBuffer, mOffset, buffer, pos, n - pos);
+        incOffset(n - pos);
+        return buffer;
+    }
+
+    /**
+     * Read raw string from the buffer
+     *
+     * @param n - number of bytes to read
+     * @return a string
+     */
+    private String readRawString(int n) throws IOException {
+        fillBuffer();
+        if (mOffset + n <= mEnd) {
+            // fast path read. String is well within the current buffer
+            String value = StringFactory.newStringFromBytes(mBuffer, mOffset, n,
+                    StandardCharsets.UTF_8);
+            incOffset(n);
+            return value;
+        } else if (n <= mBufferSize) {
+            // String extends past buffer, but can be encapsulated in a buffer. Copy the first chunk
+            // of the string to the start of the buffer and then fill the rest of the buffer from
+            // the stream.
+            final int stringHead = mEnd - mOffset;
+            System.arraycopy(mBuffer, mOffset, mBuffer, 0, stringHead);
+            mEnd = stringHead + mStream.read(mBuffer, stringHead, n - stringHead);
+
+            mDiscardedBytes += mOffset;
+            mOffset = 0;
+
+            String value = StringFactory.newStringFromBytes(mBuffer, mOffset, n,
+                    StandardCharsets.UTF_8);
+            incOffset(n);
+            return value;
+        }
+        // Otherwise, the string is too large to use the buffer. Create the string from a
+        // separate byte array.
+        return StringFactory.newStringFromBytes(readRawBytes(n), 0, n, StandardCharsets.UTF_8);
+    }
+
+    /**
+     * Fill the buffer with a chunk from the stream if need be.
+     * Will skip chunks until mOffset is reached
+     */
+    private void fillBuffer() throws IOException {
+        if (mOffset >= mEnd && mStream != null) {
+            mOffset -= mEnd;
+            mDiscardedBytes += mEnd;
+            if (mOffset >= mBufferSize) {
+                int skipped = (int) mStream.skip((mOffset / mBufferSize) * mBufferSize);
+                mDiscardedBytes += skipped;
+                mOffset -= skipped;
+            }
+            mEnd = mStream.read(mBuffer);
+        }
+    }
+
+    /**
+     * Skips the rest of current field and moves to the start of the next field. This should only be
+     * called while state is STATE_STARTED_FIELD_READ
+     */
+    public void skip() throws IOException {
+        if ((mState & STATE_READING_PACKED) == STATE_READING_PACKED) {
+            incOffset(mPackedEnd - getOffset());
+        } else {
+            switch (mWireType) {
+                case WIRE_TYPE_VARINT:
+                    byte b;
+                    do {
+                        fillBuffer();
+                        b = mBuffer[mOffset];
+                        incOffset(1);
+                    } while ((b & 0x80) != 0);
+                    break;
+                case WIRE_TYPE_FIXED64:
+                    incOffset(8);
+                    break;
+                case WIRE_TYPE_LENGTH_DELIMITED:
+                    fillBuffer();
+                    int length = (int) readVarint();
+                    incOffset(length);
+                    break;
+                /*
+            case WIRE_TYPE_START_GROUP:
+                // Not implemented
+                break;
+            case WIRE_TYPE_END_GROUP:
+                // Not implemented
+                break;
+                */
+                case WIRE_TYPE_FIXED32:
+                    incOffset(4);
+                    break;
+                default:
+                    throw new ProtoParseException(
+                            "Unexpected wire type: " + mWireType + " at offset 0x"
+                                    + Integer.toHexString(mOffset)
+                                    + dumpDebugData());
+            }
+        }
+        mState &= ~STATE_STARTED_FIELD_READ;
+    }
+
+    /**
+     * Increment the offset and handle all the relevant bookkeeping
+     * Refilling the buffer when its end is reached will be handled elsewhere (ideally just before
+     * a read, to avoid unnecessary reads from stream)
+     *
+     * @param n - number of bytes to increment
+     */
+    private void incOffset(int n) {
+        mOffset += n;
+
+        if (mDepth >= 0 && getOffset() > getOffsetFromToken(
+                mExpectedObjectTokenStack.get(mDepth))) {
+            throw new ProtoParseException("Unexpectedly reached end of embedded object.  "
+                    + token2String(mExpectedObjectTokenStack.get(mDepth))
+                    + dumpDebugData());
+        }
+    }
+
+    /**
+     * Check the current wire type to determine if current numeric field is packed. If it is packed,
+     * set up to deal with the field
+     * This should only be called for primitive numeric field types.
+     *
+     * @param fieldId - used to determine what the packed wire type is.
+     */
+    private void checkPacked(long fieldId) throws IOException {
+        if (mWireType == WIRE_TYPE_LENGTH_DELIMITED) {
+            // Primitive Field is length delimited, must be a packed field.
+            final int length = (int) readVarint();
+            mPackedEnd = getOffset() + length;
+            mState |= STATE_READING_PACKED;
+
+            // Fake the wire type, based on the field type
+            switch ((int) ((fieldId & FIELD_TYPE_MASK)
+                    >>> FIELD_TYPE_SHIFT)) {
+                case (int) (FIELD_TYPE_FLOAT >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_FIXED32 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_SFIXED32 >>> FIELD_TYPE_SHIFT):
+                    if (length % 4 != 0) {
+                        throw new IllegalArgumentException(
+                                "Requested field id (" + getFieldIdString(fieldId)
+                                        + ") packed length " + length
+                                        + " is not aligned for fixed32"
+                                        + dumpDebugData());
+                    }
+                    mWireType = WIRE_TYPE_FIXED32;
+                    break;
+                case (int) (FIELD_TYPE_DOUBLE >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_FIXED64 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_SFIXED64 >>> FIELD_TYPE_SHIFT):
+                    if (length % 8 != 0) {
+                        throw new IllegalArgumentException(
+                                "Requested field id (" + getFieldIdString(fieldId)
+                                        + ") packed length " + length
+                                        + " is not aligned for fixed64"
+                                        + dumpDebugData());
+                    }
+                    mWireType = WIRE_TYPE_FIXED64;
+                    break;
+                case (int) (FIELD_TYPE_SINT32 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_INT32 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_UINT32 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_SINT64 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_INT64 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_UINT64 >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_ENUM >>> FIELD_TYPE_SHIFT):
+                case (int) (FIELD_TYPE_BOOL >>> FIELD_TYPE_SHIFT):
+                    mWireType = WIRE_TYPE_VARINT;
+                    break;
+                default:
+                    throw new IllegalArgumentException(
+                            "Requested field id (" + getFieldIdString(fieldId)
+                                    + ") is not a packable field"
+                                    + dumpDebugData());
+            }
+        }
+    }
+
+
+    /**
+     * Check a field id constant against current field number
+     *
+     * @param fieldId - throws if fieldId does not match mFieldNumber
+     */
+    private void assertFieldNumber(long fieldId) {
+        if ((int) fieldId != mFieldNumber) {
+            throw new IllegalArgumentException("Requested field id (" + getFieldIdString(fieldId)
+                    + ") does not match current field number (0x" + Integer.toHexString(
+                    mFieldNumber)
+                    + ") at offset 0x" + Integer.toHexString(getOffset())
+                    + dumpDebugData());
+        }
+    }
+
+
+    /**
+     * Check a wire type against current wire type.
+     *
+     * @param wireType - throws if wireType does not match mWireType.
+     */
+    private void assertWireType(int wireType) {
+        if (wireType != mWireType) {
+            throw new WireTypeMismatchException(
+                    "Current wire type " + getWireTypeString(mWireType)
+                            + " does not match expected wire type " + getWireTypeString(wireType)
+                            + " at offset 0x" + Integer.toHexString(getOffset())
+                            + dumpDebugData());
+        }
+    }
+
+    /**
+     * Check if there is data ready to be read.
+     */
+    private void assertFreshData() {
+        if ((mState & STATE_STARTED_FIELD_READ) != STATE_STARTED_FIELD_READ) {
+            throw new ProtoParseException(
+                    "Attempting to read already read field at offset 0x" + Integer.toHexString(
+                            getOffset()) + dumpDebugData());
+        }
+    }
+
+    /**
+     * Dump debugging data about the buffer.
+     */
+    public String dumpDebugData() {
+        StringBuilder sb = new StringBuilder();
+
+        sb.append("\nmFieldNumber : 0x" + Integer.toHexString(mFieldNumber));
+        sb.append("\nmWireType : 0x" + Integer.toHexString(mWireType));
+        sb.append("\nmState : 0x" + Integer.toHexString(mState));
+        sb.append("\nmDiscardedBytes : 0x" + Integer.toHexString(mDiscardedBytes));
+        sb.append("\nmOffset : 0x" + Integer.toHexString(mOffset));
+        sb.append("\nmExpectedObjectTokenStack : ");
+        if (mExpectedObjectTokenStack == null) {
+            sb.append("null");
+        } else {
+            sb.append(mExpectedObjectTokenStack);
+        }
+        sb.append("\nmDepth : 0x" + Integer.toHexString(mDepth));
+        sb.append("\nmBuffer : ");
+        if (mBuffer == null) {
+            sb.append("null");
+        } else {
+            sb.append(mBuffer);
+        }
+        sb.append("\nmBufferSize : 0x" + Integer.toHexString(mBufferSize));
+        sb.append("\nmEnd : 0x" + Integer.toHexString(mEnd));
+
+        return sb.toString();
+    }
+}
diff --git a/core/java/android/util/proto/ProtoOutputStream.java b/core/java/android/util/proto/ProtoOutputStream.java
index a94806a02fbb..a1ee61c15f24 100644
--- a/core/java/android/util/proto/ProtoOutputStream.java
+++ b/core/java/android/util/proto/ProtoOutputStream.java
@@ -100,88 +100,12 @@ import java.io.UnsupportedEncodingException;
  * errors if they are not matched.
  */
 @TestApi
-public final class ProtoOutputStream {
+public final class ProtoOutputStream extends ProtoStream {
+    /**
+     * @hide
+     */
     public static final String TAG = "ProtoOutputStream";
 
-    public static final int FIELD_ID_SHIFT = 3;
-    public static final int WIRE_TYPE_MASK = (1<<FIELD_ID_SHIFT)-1;
-    public static final int FIELD_ID_MASK = ~WIRE_TYPE_MASK;
-
-    public static final int WIRE_TYPE_VARINT = 0;
-    public static final int WIRE_TYPE_FIXED64 = 1;
-    public static final int WIRE_TYPE_LENGTH_DELIMITED = 2;
-    public static final int WIRE_TYPE_START_GROUP = 3;
-    public static final int WIRE_TYPE_END_GROUP = 4;
-    public static final int WIRE_TYPE_FIXED32 = 5;
-
-    /**
-     * Position of the field type in a (long) fieldId.
-     */
-    public static final int FIELD_TYPE_SHIFT = 32;
-
-    /**
-     * Mask for the field types stored in a fieldId.  Leaves a whole
-     * byte for future expansion, even though there are currently only 17 types.
-     */
-    public static final long FIELD_TYPE_MASK = 0x0ffL << FIELD_TYPE_SHIFT;
-
-    public static final long FIELD_TYPE_UNKNOWN = 0;
-
-    /**
-     * The types are copied from external/protobuf/src/google/protobuf/descriptor.h directly,
-     * so no extra mapping needs to be maintained in this case.
-     */
-    public static final long FIELD_TYPE_DOUBLE = 1L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_FLOAT = 2L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_INT64 = 3L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_UINT64 = 4L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_INT32 = 5L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_FIXED64 = 6L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_FIXED32 = 7L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_BOOL = 8L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_STRING = 9L << FIELD_TYPE_SHIFT;
-//  public static final long FIELD_TYPE_GROUP = 10L << FIELD_TYPE_SHIFT; // Deprecated.
-    public static final long FIELD_TYPE_MESSAGE = 11L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_BYTES = 12L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_UINT32 = 13L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_ENUM = 14L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_SFIXED32 = 15L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_SFIXED64 = 16L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_SINT32 = 17L << FIELD_TYPE_SHIFT;
-    public static final long FIELD_TYPE_SINT64 = 18L << FIELD_TYPE_SHIFT;
-
-    private static final String[] FIELD_TYPE_NAMES = new String[] {
-        "Double",
-        "Float",
-        "Int64",
-        "UInt64",
-        "Int32",
-        "Fixed64",
-        "Fixed32",
-        "Bool",
-        "String",
-        "Group",  // This field is deprecated but reserved here for indexing.
-        "Message",
-        "Bytes",
-        "UInt32",
-        "Enum",
-        "SFixed32",
-        "SFixed64",
-        "SInt32",
-        "SInt64",
-    };
-
-    //
-    // FieldId flags for whether the field is single, repeated or packed.
-    //
-    public static final int FIELD_COUNT_SHIFT = 40;
-    public static final long FIELD_COUNT_MASK = 0x0fL << FIELD_COUNT_SHIFT;
-
-    public static final long FIELD_COUNT_UNKNOWN = 0;
-    public static final long FIELD_COUNT_SINGLE = 1L << FIELD_COUNT_SHIFT;
-    public static final long FIELD_COUNT_REPEATED = 2L << FIELD_COUNT_SHIFT;
-    public static final long FIELD_COUNT_PACKED = 5L << FIELD_COUNT_SHIFT;
-
     /**
      * Our buffer.
      */
@@ -1997,94 +1921,6 @@ public final class ProtoOutputStream {
         }
     }
 
-    //
-    // Child objects
-    //
-
-    /**
-     * Make a token.
-     *  Bits 61-63 - tag size (So we can go backwards later if the object had not data)
-     *                - 3 bits, max value 7, max value needed 5
-     *  Bit  60    - true if the object is repeated (lets us require endObject or endRepeatedObject)
-     *  Bits 59-51 - depth (For error checking)
-     *                - 9 bits, max value 512, when checking, value is masked (if we really
-     *                  are more than 512 levels deep)
-     *  Bits 32-50 - objectId (For error checking)
-     *                - 19 bits, max value 524,288. that's a lot of objects. IDs will wrap
-     *                  because of the overflow, and only the tokens are compared.
-     *  Bits  0-31 - offset of the first size field in the buffer.
-     */
-    // VisibleForTesting
-    public static long makeToken(int tagSize, boolean repeated, int depth, int objectId,
-            int sizePos) {
-        return ((0x07L & (long)tagSize) << 61)
-                | (repeated ? (1L << 60) : 0)
-                | (0x01ffL & (long)depth) << 51
-                | (0x07ffffL & (long)objectId) << 32
-                | (0x0ffffffffL & (long)sizePos);
-    }
-
-    /**
-     * Get the encoded tag size from the token.
-     */
-    public static int getTagSizeFromToken(long token) {
-        return (int)(0x7 & (token >> 61));
-    }
-
-    /**
-     * Get whether this is a call to startObject (false) or startRepeatedObject (true).
-     */
-    public static boolean getRepeatedFromToken(long token) {
-        return (0x1 & (token >> 60)) != 0;
-    }
-
-    /**
-     * Get the nesting depth of startObject calls from the token.
-     */
-    public static int getDepthFromToken(long token) {
-        return (int)(0x01ff & (token >> 51));
-    }
-
-    /**
-     * Get the object ID from the token. The object ID is a serial number for the
-     * startObject calls that have happened on this object.  The values are truncated
-     * to 9 bits, but that is sufficient for error checking.
-     */
-    public static int getObjectIdFromToken(long token) {
-        return (int)(0x07ffff & (token >> 32));
-    }
-
-    /**
-     * Get the location of the childRawSize (the first 32 bit size field) in this object.
-     */
-    public static int getSizePosFromToken(long token) {
-        return (int)token;
-    }
-
-    /**
-     * Convert the object ID to the ordinal value -- the n-th call to startObject.
-     * The object IDs start at -1 and count backwards, so that the value is unlikely
-     * to alias with an actual size field that had been written.
-     */
-    public static int convertObjectIdToOrdinal(int objectId) {
-        return (-1 & 0x07ffff) - objectId;
-    }
-
-    /**
-     * Return a debugging string of a token.
-     */
-    public static String token2String(long token) {
-        if (token == 0L) {
-            return "Token(0)";
-        } else {
-            return "Token(val=0x" + Long.toHexString(token)
-                    + " depth=" + getDepthFromToken(token)
-                    + " object=" + convertObjectIdToOrdinal(getObjectIdFromToken(token))
-                    + " tagSize=" + getTagSizeFromToken(token)
-                    + " sizePos=" + getSizePosFromToken(token)
-                    + ')';
-        }
-    }
 
     /**
      * Start a child object.
@@ -2175,7 +2011,7 @@ public final class ProtoOutputStream {
         // at which to write the size.
         final int depth = getDepthFromToken(token);
         final boolean expectedRepeated = getRepeatedFromToken(token);
-        final int sizePos = getSizePosFromToken(token);
+        final int sizePos = getOffsetFromToken(token);
         final int childRawSize = mBuffer.getWritePos() - sizePos - 8;
 
         if (repeated != expectedRepeated) {
@@ -2346,56 +2182,6 @@ public final class ProtoOutputStream {
     }
 
     /**
-     * Get the developer-usable name of a field type.
-     */
-    private static String getFieldTypeString(long fieldType) {
-        int index = ((int)((fieldType & FIELD_TYPE_MASK) >>> FIELD_TYPE_SHIFT)) - 1;
-        if (index >= 0 && index < FIELD_TYPE_NAMES.length) {
-            return FIELD_TYPE_NAMES[index];
-        } else {
-            return null;
-        }
-    }
-
-    /**
-     * Get the developer-usable name of a field count.
-     */
-    private static String getFieldCountString(long fieldCount) {
-        if (fieldCount == FIELD_COUNT_SINGLE) {
-            return "";
-        } else if (fieldCount == FIELD_COUNT_REPEATED) {
-            return "Repeated";
-        } else if (fieldCount == FIELD_COUNT_PACKED) {
-            return "Packed";
-        } else {
-            return null;
-        }
-    }
-
-    /**
-     * Get a debug string for a fieldId.
-     */
-    private String getFieldIdString(long fieldId) {
-        final long fieldCount = fieldId & FIELD_COUNT_MASK;
-        String countString = getFieldCountString(fieldCount);
-        if (countString == null) {
-            countString = "fieldCount=" + fieldCount;
-        }
-        if (countString.length() > 0) {
-            countString += " ";
-        }
-
-        final long fieldType = fieldId & FIELD_TYPE_MASK;
-        String typeString = getFieldTypeString(fieldType);
-        if (typeString == null) {
-            typeString = "fieldType=" + fieldType;
-        }
-
-        return countString + typeString + " tag=" + ((int) fieldId)
-                + " fieldId=0x" + Long.toHexString(fieldId);
-    }
-
-    /**
      * Return how many bytes an encoded field tag will require.
      */
     private static int getTagSize(int id) {
diff --git a/core/java/android/util/proto/ProtoStream.java b/core/java/android/util/proto/ProtoStream.java
new file mode 100644
index 000000000000..9e2e95a5923d
--- /dev/null
+++ b/core/java/android/util/proto/ProtoStream.java
@@ -0,0 +1,280 @@
+/*
+ * Copyright (C) 2018 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 android.util.proto;
+
+import android.annotation.TestApi;
+
+/**
+ * Abstract base class for both protobuf streams.
+ *
+ * Contains a set of useful constants and methods used by both
+ * ProtoOutputStream and ProtoInputStream
+ *
+ * @hide
+ */
+@TestApi
+public abstract class ProtoStream {
+
+    public static final int FIELD_ID_SHIFT = 3;
+    public static final int WIRE_TYPE_MASK = (1 << FIELD_ID_SHIFT) - 1;
+    public static final int FIELD_ID_MASK = ~WIRE_TYPE_MASK;
+
+    public static final int WIRE_TYPE_VARINT = 0;
+    public static final int WIRE_TYPE_FIXED64 = 1;
+    public static final int WIRE_TYPE_LENGTH_DELIMITED = 2;
+    public static final int WIRE_TYPE_START_GROUP = 3;
+    public static final int WIRE_TYPE_END_GROUP = 4;
+    public static final int WIRE_TYPE_FIXED32 = 5;
+
+    /**
+     * Position of the field type in a (long) fieldId.
+     */
+    public static final int FIELD_TYPE_SHIFT = 32;
+
+    /**
+     * Mask for the field types stored in a fieldId.  Leaves a whole
+     * byte for future expansion, even though there are currently only 17 types.
+     */
+    public static final long FIELD_TYPE_MASK = 0x0ffL << FIELD_TYPE_SHIFT;
+
+    public static final long FIELD_TYPE_UNKNOWN = 0;
+
+    /**
+     * The types are copied from external/protobuf/src/google/protobuf/descriptor.h directly,
+     * so no extra mapping needs to be maintained in this case.
+     */
+    public static final long FIELD_TYPE_DOUBLE = 1L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_FLOAT = 2L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_INT64 = 3L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_UINT64 = 4L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_INT32 = 5L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_FIXED64 = 6L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_FIXED32 = 7L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_BOOL = 8L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_STRING = 9L << FIELD_TYPE_SHIFT;
+    //  public static final long FIELD_TYPE_GROUP = 10L << FIELD_TYPE_SHIFT; // Deprecated.
+    public static final long FIELD_TYPE_MESSAGE = 11L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_BYTES = 12L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_UINT32 = 13L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_ENUM = 14L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_SFIXED32 = 15L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_SFIXED64 = 16L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_SINT32 = 17L << FIELD_TYPE_SHIFT;
+    public static final long FIELD_TYPE_SINT64 = 18L << FIELD_TYPE_SHIFT;
+
+    protected static final String[] FIELD_TYPE_NAMES = new String[]{
+            "Double",
+            "Float",
+            "Int64",
+            "UInt64",
+            "Int32",
+            "Fixed64",
+            "Fixed32",
+            "Bool",
+            "String",
+            "Group",  // This field is deprecated but reserved here for indexing.
+            "Message",
+            "Bytes",
+            "UInt32",
+            "Enum",
+            "SFixed32",
+            "SFixed64",
+            "SInt32",
+            "SInt64",
+    };
+
+    //
+    // FieldId flags for whether the field is single, repeated or packed.
+    //
+    public static final int FIELD_COUNT_SHIFT = 40;
+    public static final long FIELD_COUNT_MASK = 0x0fL << FIELD_COUNT_SHIFT;
+
+    public static final long FIELD_COUNT_UNKNOWN = 0;
+    public static final long FIELD_COUNT_SINGLE = 1L << FIELD_COUNT_SHIFT;
+    public static final long FIELD_COUNT_REPEATED = 2L << FIELD_COUNT_SHIFT;
+    public static final long FIELD_COUNT_PACKED = 5L << FIELD_COUNT_SHIFT;
+
+
+    /**
+     * Get the developer-usable name of a field type.
+     */
+    public static String getFieldTypeString(long fieldType) {
+        int index = ((int) ((fieldType & FIELD_TYPE_MASK) >>> FIELD_TYPE_SHIFT)) - 1;
+        if (index >= 0 && index < FIELD_TYPE_NAMES.length) {
+            return FIELD_TYPE_NAMES[index];
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Get the developer-usable name of a field count.
+     */
+    public static String getFieldCountString(long fieldCount) {
+        if (fieldCount == FIELD_COUNT_SINGLE) {
+            return "";
+        } else if (fieldCount == FIELD_COUNT_REPEATED) {
+            return "Repeated";
+        } else if (fieldCount == FIELD_COUNT_PACKED) {
+            return "Packed";
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Get the developer-usable name of a wire type.
+     */
+    public static String getWireTypeString(int wireType) {
+        switch (wireType) {
+            case WIRE_TYPE_VARINT:
+                return "Varint";
+            case WIRE_TYPE_FIXED64:
+                return "Fixed64";
+            case WIRE_TYPE_LENGTH_DELIMITED:
+                return "Length Delimited";
+            case WIRE_TYPE_START_GROUP:
+                return "Start Group";
+            case WIRE_TYPE_END_GROUP:
+                return "End Group";
+            case WIRE_TYPE_FIXED32:
+                return "Fixed32";
+            default:
+                return null;
+        }
+    }
+
+    /**
+     * Get a debug string for a fieldId.
+     */
+    public static String getFieldIdString(long fieldId) {
+        final long fieldCount = fieldId & FIELD_COUNT_MASK;
+        String countString = getFieldCountString(fieldCount);
+        if (countString == null) {
+            countString = "fieldCount=" + fieldCount;
+        }
+        if (countString.length() > 0) {
+            countString += " ";
+        }
+
+        final long fieldType = fieldId & FIELD_TYPE_MASK;
+        String typeString = getFieldTypeString(fieldType);
+        if (typeString == null) {
+            typeString = "fieldType=" + fieldType;
+        }
+
+        return countString + typeString + " tag=" + ((int) fieldId)
+                + " fieldId=0x" + Long.toHexString(fieldId);
+    }
+
+    /**
+     * Combine a fieldId (the field keys in the proto file) and the field flags.
+     * Mostly useful for testing because the generated code contains the fieldId
+     * constants.
+     */
+    public static long makeFieldId(int id, long fieldFlags) {
+        return fieldFlags | (((long) id) & 0x0ffffffffL);
+    }
+
+    //
+    // Child objects
+    //
+
+    /**
+     * Make a token.
+     * Bits 61-63 - tag size (So we can go backwards later if the object had not data)
+     *            - 3 bits, max value 7, max value needed 5
+     * Bit  60    - true if the object is repeated (lets us require endObject or endRepeatedObject)
+     * Bits 59-51 - depth (For error checking)
+     *            - 9 bits, max value 512, when checking, value is masked (if we really
+     *              are more than 512 levels deep)
+     * Bits 32-50 - objectId (For error checking)
+     *            - 19 bits, max value 524,288. that's a lot of objects. IDs will wrap
+     *              because of the overflow, and only the tokens are compared.
+     * Bits  0-31 - offset of interest for the object.
+     */
+    public static long makeToken(int tagSize, boolean repeated, int depth, int objectId,
+            int offset) {
+        return ((0x07L & (long) tagSize) << 61)
+                | (repeated ? (1L << 60) : 0)
+                | (0x01ffL & (long) depth) << 51
+                | (0x07ffffL & (long) objectId) << 32
+                | (0x0ffffffffL & (long) offset);
+    }
+
+    /**
+     * Get the encoded tag size from the token.
+     */
+    public static int getTagSizeFromToken(long token) {
+        return (int) (0x7 & (token >> 61));
+    }
+
+    /**
+     * Get whether this is a call to startObject (false) or startRepeatedObject (true).
+     */
+    public static boolean getRepeatedFromToken(long token) {
+        return (0x1 & (token >> 60)) != 0;
+    }
+
+    /**
+     * Get the nesting depth of startObject calls from the token.
+     */
+    public static int getDepthFromToken(long token) {
+        return (int) (0x01ff & (token >> 51));
+    }
+
+    /**
+     * Get the object ID from the token. The object ID is a serial number for the
+     * startObject calls that have happened on this object.  The values are truncated
+     * to 9 bits, but that is sufficient for error checking.
+     */
+    public static int getObjectIdFromToken(long token) {
+        return (int) (0x07ffff & (token >> 32));
+    }
+
+    /**
+     * Get the location of the offset recorded in the token.
+     */
+    public static int getOffsetFromToken(long token) {
+        return (int) token;
+    }
+
+    /**
+     * Convert the object ID to the ordinal value -- the n-th call to startObject.
+     * The object IDs start at -1 and count backwards, so that the value is unlikely
+     * to alias with an actual size field that had been written.
+     */
+    public static int convertObjectIdToOrdinal(int objectId) {
+        return (-1 & 0x07ffff) - objectId;
+    }
+
+    /**
+     * Return a debugging string of a token.
+     */
+    public static String token2String(long token) {
+        if (token == 0L) {
+            return "Token(0)";
+        } else {
+            return "Token(val=0x" + Long.toHexString(token)
+                    + " depth=" + getDepthFromToken(token)
+                    + " object=" + convertObjectIdToOrdinal(getObjectIdFromToken(token))
+                    + " tagSize=" + getTagSizeFromToken(token)
+                    + " offset=" + getOffsetFromToken(token)
+                    + ')';
+        }
+    }
+}
diff --git a/core/java/android/util/proto/ProtoUtils.java b/core/java/android/util/proto/ProtoUtils.java
index c7bbb9f2a044..03bf590902c0 100644
--- a/core/java/android/util/proto/ProtoUtils.java
+++ b/core/java/android/util/proto/ProtoUtils.java
@@ -19,6 +19,8 @@ package android.util.proto;
 import android.util.AggStats;
 import android.util.Duration;
 
+import java.io.IOException;
+
 /**
  * This class contains a list of helper functions to write common proto in
  * //frameworks/base/core/proto/android/base directory
@@ -70,4 +72,54 @@ public class ProtoUtils {
             }
         }
     }
+
+    /**
+     * Provide debug data about the current field as a string
+     */
+    public static String currentFieldToString(ProtoInputStream proto) throws IOException {
+        StringBuilder sb = new StringBuilder();
+
+        final int fieldNumber = proto.getFieldNumber();
+        final int wireType = proto.getWireType();
+        long fieldConstant;
+
+        sb.append("Offset : 0x" + Integer.toHexString(proto.getOffset()));
+        sb.append("\nField Number : 0x" + Integer.toHexString(proto.getFieldNumber()));
+        sb.append("\nWire Type : ");
+        switch (wireType) {
+            case ProtoStream.WIRE_TYPE_VARINT:
+                sb.append("varint");
+                fieldConstant = ProtoStream.makeFieldId(fieldNumber,
+                        ProtoStream.FIELD_COUNT_SINGLE | ProtoStream.FIELD_TYPE_INT64);
+                sb.append("\nField Value : 0x" + Long.toHexString(proto.readLong(fieldConstant)));
+                break;
+            case ProtoStream.WIRE_TYPE_FIXED64:
+                sb.append("fixed64");
+                fieldConstant = ProtoStream.makeFieldId(fieldNumber,
+                        ProtoStream.FIELD_COUNT_SINGLE | ProtoStream.FIELD_TYPE_FIXED64);
+                sb.append("\nField Value : 0x" + Long.toHexString(proto.readLong(fieldConstant)));
+                break;
+            case ProtoStream.WIRE_TYPE_LENGTH_DELIMITED:
+                sb.append("length delimited");
+                fieldConstant = ProtoStream.makeFieldId(fieldNumber,
+                        ProtoStream.FIELD_COUNT_SINGLE | ProtoStream.FIELD_TYPE_BYTES);
+                sb.append("\nField Bytes : " + proto.readBytes(fieldConstant));
+                break;
+            case ProtoStream.WIRE_TYPE_START_GROUP:
+                sb.append("start group");
+                break;
+            case ProtoStream.WIRE_TYPE_END_GROUP:
+                sb.append("end group");
+                break;
+            case ProtoStream.WIRE_TYPE_FIXED32:
+                sb.append("fixed32");
+                fieldConstant = ProtoStream.makeFieldId(fieldNumber,
+                        ProtoStream.FIELD_COUNT_SINGLE | ProtoStream.FIELD_TYPE_FIXED32);
+                sb.append("\nField Value : 0x" + Integer.toHexString(proto.readInt(fieldConstant)));
+                break;
+            default:
+                sb.append("unknown(" + proto.getWireType() + ")");
+        }
+        return sb.toString();
+    }
 }
diff --git a/core/java/android/util/proto/WireTypeMismatchException.java b/core/java/android/util/proto/WireTypeMismatchException.java
new file mode 100644
index 000000000000..d90b4f8df8ae
--- /dev/null
+++ b/core/java/android/util/proto/WireTypeMismatchException.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2018 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 android.util.proto;
+
+import android.annotation.TestApi;
+
+/**
+ * Thrown when there is an error parsing protobuf data.
+ *
+ * @hide
+ */
+@TestApi
+public class WireTypeMismatchException extends ProtoParseException {
+
+    /**
+     * Construct a WireTypeMismatchException.
+     *
+     * @param msg The message.
+     */
+    public WireTypeMismatchException(String msg) {
+        super(msg);
+    }
+}
+