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[Java][FlexBuffers] Deprecate typed vector strings due to design flaw (#5722)

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* [Java][FlexBuffers] Deprecate typed vector strings due to design flaw

It will still be possible to read buffers with this type, but the
elements will be treated as FBT_KEY and will be read as null-terminated
string.

Trying to build a vector of strings as typed will throw an exception.

More information on https://github.com/google/flatbuffers/issues/5627

Also, fix another bug on strings, where long strings were not properly
aligned.

* [Java][FlexBuffers] Make FBT_VECTOR_STRING_DEPRECATED considered typed.

The logic for FlexBuffers.isVectorType() was changed
to not consider FBT_VECTOR_STRING_DEPRECATED a typed
vector, but that can lead to missinterpretation for
existing serialized data. So we are reverting.
This commit is contained in:
Paulo Pinheiro
2020-01-24 18:58:15 +01:00
committed by Wouter van Oortmerssen
parent a593a11e59
commit 3f677f2414
3 changed files with 106 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
java/com/google/flatbuffers/FlexBuffers.java
View File

@@ -77,7 +77,9 @@ public class FlexBuffers {
/** Represent a vector of keys type */
public static final int FBT_VECTOR_KEY = 14;
/** Represent a vector of strings type */
public static final int FBT_VECTOR_STRING = 15;
// DEPRECATED, use FBT_VECTOR or FBT_VECTOR_KEY instead.
// more info on thttps://github.com/google/flatbuffers/issues/5627.
public static final int FBT_VECTOR_STRING_DEPRECATED = 15;
/// @cond FLATBUFFERS_INTERNAL
public static final int FBT_VECTOR_INT2 = 16; // Typed tuple = no type table; no size field).
@@ -107,7 +109,7 @@ public class FlexBuffers {
* @return true if typed vector
*/
static boolean isTypedVector(int type) {
return (type >= FBT_VECTOR_INT && type <= FBT_VECTOR_STRING) || type == FBT_VECTOR_BOOL;
return (type >= FBT_VECTOR_INT && type <= FBT_VECTOR_STRING_DEPRECATED) || type == FBT_VECTOR_BOOL;
}
/**
@@ -145,7 +147,7 @@ public class FlexBuffers {
}
static boolean isTypedVectorElementType(int type) {
return (type >= FBT_INT && type <= FBT_STRING) || type == FBT_BOOL;
return (type >= FBT_INT && type <= FBT_KEY) || type == FBT_BOOL;
}
// return position of the element that the offset is pointing to
@@ -322,8 +324,7 @@ public class FlexBuffers {
* @return true if a typed vector type
*/
public boolean isTypedVector() {
return (type >= FBT_VECTOR_INT && type <= FBT_VECTOR_STRING) ||
type == FBT_VECTOR_BOOL;
return FlexBuffers.isTypedVector(type);
}
/**
@@ -482,7 +483,7 @@ public class FlexBuffers {
public String asString() {
if (isString()) {
int start = indirect(bb, end, parentWidth);
int size = readInt(bb, start - byteWidth, byteWidth);
int size = (int) readUInt(bb, start - byteWidth, byteWidth);
return Utf8.getDefault().decodeUtf8(bb, start, size);
}
else if (isKey()){
@@ -516,6 +517,9 @@ public class FlexBuffers {
public Vector asVector() {
if (isVector()) {
return new Vector(bb, indirect(bb, end, parentWidth), byteWidth);
} else if(type == FlexBuffers.FBT_VECTOR_STRING_DEPRECATED) {
// deprecated. Should be treated as key vector
return new TypedVector(bb, indirect(bb, end, parentWidth), byteWidth, FlexBuffers.FBT_KEY);
} else if (FlexBuffers.isTypedVector(type)) {
return new TypedVector(bb, indirect(bb, end, parentWidth), byteWidth, FlexBuffers.toTypedVectorElementType(type));
} else {
@@ -590,7 +594,7 @@ public class FlexBuffers {
case FBT_VECTOR_UINT:
case FBT_VECTOR_FLOAT:
case FBT_VECTOR_KEY:
case FBT_VECTOR_STRING:
case FBT_VECTOR_STRING_DEPRECATED:
case FBT_VECTOR_BOOL:
return sb.append(asVector());
case FBT_VECTOR_INT2:

17
java/com/google/flatbuffers/FlexBuffersBuilder.java
View File

@@ -358,24 +358,24 @@ public class FlexBuffersBuilder {
}
private Value writeString(int key, String s) {
return writeBlob(key, s.getBytes(StandardCharsets.UTF_8), FBT_STRING);
return writeBlob(key, s.getBytes(StandardCharsets.UTF_8), FBT_STRING, true);
}
// in bits to fit a unsigned int
private static int widthUInBits(long len) {
static int widthUInBits(long len) {
if (len <= byteToUnsignedInt((byte)0xff)) return WIDTH_8;
if (len <= shortToUnsignedInt((short)0xffff)) return WIDTH_16;
if (len <= intToUnsignedLong(0xffff_ffff)) return WIDTH_32;
return WIDTH_64;
}
private Value writeBlob(int key, byte[] blob, int type) {
private Value writeBlob(int key, byte[] blob, int type, boolean trailing) {
int bitWidth = widthUInBits(blob.length);
int byteWidth = align(bitWidth);
writeInt(blob.length, byteWidth);
int sloc = bb.position();
bb.put(blob);
if (type == FBT_STRING) {
if (trailing) {
bb.put((byte) 0);
}
return Value.blob(key, sloc, type, bitWidth);
@@ -384,7 +384,7 @@ public class FlexBuffersBuilder {
// Align to prepare for writing a scalar with a certain size.
private int align(int alignment) {
int byteWidth = 1 << alignment;
int padBytes = Value.paddingBytes(bb.capacity(), byteWidth);
int padBytes = Value.paddingBytes(bb.position(), byteWidth);
while (padBytes-- != 0) {
bb.put((byte) 0);
}
@@ -417,7 +417,7 @@ public class FlexBuffersBuilder {
*/
public int putBlob(String key, byte[] val) {
int iKey = putKey(key);
Value value = writeBlob(iKey, val, FBT_BLOB);
Value value = writeBlob(iKey, val, FBT_BLOB, false);
stack.add(value);
return (int) value.iValue;
}
@@ -504,6 +504,9 @@ public class FlexBuffersBuilder {
if (typed) {
if (i == start) {
vectorType = stack.get(i).type;
if (!FlexBuffers.isTypedVectorElementType(vectorType)) {
throw new FlexBufferException("TypedVector does not support this element type");
}
} else {
// If you get this assert, you are writing a typed vector with
// elements that are not all the same type.
@@ -659,7 +662,7 @@ public class FlexBuffersBuilder {
}
static Value blob(int key, int position, int type, int bitWidth) {
return new Value(key, type, WIDTH_8, position);
return new Value(key, type, bitWidth, position);
}
static Value int8(int key, int value) {

97
tests/JavaTest.java
View File

@@ -12,6 +12,10 @@ import com.google.flatbuffers.FlexBuffers;
import com.google.flatbuffers.FlexBuffersBuilder;
import com.google.flatbuffers.StringVector;
import com.google.flatbuffers.UnionVector;
import com.google.flatbuffers.FlexBuffers.FlexBufferException;
import com.google.flatbuffers.FlexBuffers.Reference;
import com.google.flatbuffers.FlexBuffers.Vector;
import java.io.*;
import java.math.BigInteger;
import java.nio.ByteBuffer;
@@ -694,6 +698,60 @@ class JavaTest {
TestEq(mymap.get("blob").toString(), "\"AC\"");
}
public static void testFlexBufferVectorStrings() {
FlexBuffersBuilder builder = new FlexBuffersBuilder(ByteBuffer.allocate(10000000));
int size = 3000;
StringBuilder sb = new StringBuilder();
for (int i=0; i< size; i++) {
sb.append("a");
}
String text = sb.toString();
TestEq(text.length(), size);
int pos = builder.startVector();
for (int i=0; i<size; i++) {
builder.putString(text);
}
try {
builder.endVector(null, pos, true, false);
// this should raise an exception as
// typed vector of string was deprecated
assert false;
} catch(FlexBufferException fb) {
// no op
}
// we finish the vector again as non-typed
builder.endVector(null, pos, false, false);
ByteBuffer b = builder.finish();
Vector v = FlexBuffers.getRoot(b).asVector();
TestEq(v.size(), size);
for (int i=0; i<size; i++) {
TestEq(v.get(i).asString().length(), size);
TestEq(v.get(i).asString(), text);
}
}
public static void testDeprecatedTypedVectorString() {
// tests whether we are able to support reading deprecated typed vector string
// data is equivalent to [ "abc", "abc", "abc", "abc"]
byte[] data = new byte[] {0x03, 0x61, 0x62, 0x63, 0x00, 0x03, 0x61, 0x62, 0x63, 0x00,
0x03, 0x61, 0x62, 0x63, 0x00, 0x03, 0x61, 0x62, 0x63, 0x00, 0x04, 0x14, 0x10,
0x0c, 0x08, 0x04, 0x3c, 0x01};
Reference ref = FlexBuffers.getRoot(ByteBuffer.wrap(data));
TestEq(ref.getType(), FlexBuffers.FBT_VECTOR_STRING_DEPRECATED);
TestEq(ref.isTypedVector(), true);
Vector vec = ref.asVector();
for (int i=0; i< vec.size(); i++) {
TestEq("abc", vec.get(i).asString());
}
}
public static void testSingleElementBoolean() {
FlexBuffersBuilder builder = new FlexBuffersBuilder(ByteBuffer.allocate(100));
builder.putBoolean(true);
@@ -743,13 +801,32 @@ class JavaTest {
TestEq(Double.compare(Double.MAX_VALUE, FlexBuffers.getRoot(b).asFloat()), 0);
}
public static void testSingleElementString() {
FlexBuffersBuilder builder = new FlexBuffersBuilder();
builder.putString("wow");
public static void testSingleElementBigString() {
FlexBuffersBuilder builder = new FlexBuffersBuilder(ByteBuffer.allocate(10000));
StringBuilder sb = new StringBuilder();
for (int i=0; i< 3000; i++) {
sb.append("a");
}
builder.putString(sb.toString());
ByteBuffer b = builder.finish();
FlexBuffers.Reference r = FlexBuffers.getRoot(b);
TestEq(FlexBuffers.FBT_STRING, r.getType());
TestEq(sb.toString(), r.asString());
}
public static void testSingleElementSmallString() {
FlexBuffersBuilder builder = new FlexBuffersBuilder(ByteBuffer.allocate(10000));
builder.putString("aa");
ByteBuffer b = builder.finish();
FlexBuffers.Reference r = FlexBuffers.getRoot(b);
TestEq(FlexBuffers.FBT_STRING, r.getType());
TestEq("wow", r.asString());
TestEq("aa", r.asString());
}
public static void testSingleElementBlob() {
@@ -813,12 +890,6 @@ class JavaTest {
}
builder.endVector("floats", vecPos, true, false);
vecPos = builder.startVector();
for (final String i : strings) {
builder.putString(i);
}
builder.endVector("strings", vecPos, true, false);
vecPos = builder.startVector();
for (final boolean i : booleans) {
builder.putBoolean(i);
@@ -832,7 +903,6 @@ class JavaTest {
FlexBuffers.Reference r = FlexBuffers.getRoot(b);
assert(r.asMap().get("ints").isTypedVector());
assert(r.asMap().get("floats").isTypedVector());
assert(r.asMap().get("strings").isTypedVector());
assert(r.asMap().get("booleans").isTypedVector());
}
@@ -944,7 +1014,8 @@ class JavaTest {
testSingleElementLong();
testSingleElementFloat();
testSingleElementDouble();
testSingleElementString();
testSingleElementSmallString();
testSingleElementBigString();
testSingleElementBlob();
testSingleElementVector();
testSingleFixedTypeVector();
@@ -955,6 +1026,8 @@ class JavaTest {
testFlexBuffersTest();
testHashMapToMap();
testFlexBuferEmpty();
testFlexBufferVectorStrings();
testDeprecatedTypedVectorString();
}
static void TestVectorOfBytes() {