/*
|
* Copyright (C) 2008 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.dex;
|
|
import com.android.dex.util.ByteInput;
|
import com.android.dex.util.ByteOutput;
|
|
/**
|
* Reads and writes DWARFv3 LEB 128 signed and unsigned integers. See DWARF v3
|
* section 7.6.
|
*/
|
public final class Leb128 {
|
private Leb128() {
|
}
|
|
/**
|
* Gets the number of bytes in the unsigned LEB128 encoding of the
|
* given value.
|
*
|
* @param value the value in question
|
* @return its write size, in bytes
|
*/
|
public static int unsignedLeb128Size(int value) {
|
// TODO: This could be much cleverer.
|
|
int remaining = value >> 7;
|
int count = 0;
|
|
while (remaining != 0) {
|
remaining >>= 7;
|
count++;
|
}
|
|
return count + 1;
|
}
|
|
/**
|
* Reads an signed integer from {@code in}.
|
*/
|
public static int readSignedLeb128(ByteInput in) {
|
int result = 0;
|
int cur;
|
int count = 0;
|
int signBits = -1;
|
|
do {
|
cur = in.readByte() & 0xff;
|
result |= (cur & 0x7f) << (count * 7);
|
signBits <<= 7;
|
count++;
|
} while (((cur & 0x80) == 0x80) && count < 5);
|
|
if ((cur & 0x80) == 0x80) {
|
throw new DexException("invalid LEB128 sequence");
|
}
|
|
// Sign extend if appropriate
|
if (((signBits >> 1) & result) != 0 ) {
|
result |= signBits;
|
}
|
|
return result;
|
}
|
|
/**
|
* Reads an unsigned integer from {@code in}.
|
*/
|
public static int readUnsignedLeb128(ByteInput in) {
|
int result = 0;
|
int cur;
|
int count = 0;
|
|
do {
|
cur = in.readByte() & 0xff;
|
result |= (cur & 0x7f) << (count * 7);
|
count++;
|
} while (((cur & 0x80) == 0x80) && count < 5);
|
|
if ((cur & 0x80) == 0x80) {
|
throw new DexException("invalid LEB128 sequence");
|
}
|
|
return result;
|
}
|
|
/**
|
* Writes {@code value} as an unsigned integer to {@code out}, starting at
|
* {@code offset}. Returns the number of bytes written.
|
*/
|
public static void writeUnsignedLeb128(ByteOutput out, int value) {
|
int remaining = value >>> 7;
|
|
while (remaining != 0) {
|
out.writeByte((byte) ((value & 0x7f) | 0x80));
|
value = remaining;
|
remaining >>>= 7;
|
}
|
|
out.writeByte((byte) (value & 0x7f));
|
}
|
|
/**
|
* Writes {@code value} as a signed integer to {@code out}, starting at
|
* {@code offset}. Returns the number of bytes written.
|
*/
|
public static void writeSignedLeb128(ByteOutput out, int value) {
|
int remaining = value >> 7;
|
boolean hasMore = true;
|
int end = ((value & Integer.MIN_VALUE) == 0) ? 0 : -1;
|
|
while (hasMore) {
|
hasMore = (remaining != end)
|
|| ((remaining & 1) != ((value >> 6) & 1));
|
|
out.writeByte((byte) ((value & 0x7f) | (hasMore ? 0x80 : 0)));
|
value = remaining;
|
remaining >>= 7;
|
}
|
}
|
}
|
