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/*
* 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.dx.util;
/**
* Reads and writes DWARFv3 LEB 128 signed and unsigned integers. See DWARF v3
* section 7.6.
*/
public final class Leb128Utils {
/**
* This class is uninstantiable.
*/
private Leb128Utils() {
// This space intentionally left blank.
}
/**
* 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;
}
/**
* Gets the number of bytes in the signed LEB128 encoding of the
* given value.
*
* @param value the value in question
* @return its write size, in bytes
*/
public static int signedLeb128Size(int value) {
// TODO: This could be much cleverer.
int remaining = value >> 7;
int count = 0;
boolean hasMore = true;
int end = ((value & Integer.MIN_VALUE) == 0) ? 0 : -1;
while (hasMore) {
hasMore = (remaining != end)
|| ((remaining & 1) != ((value >> 6) & 1));
value = remaining;
remaining >>= 7;
count++;
}
return count;
}
/**
* 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;
}
}
}
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