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/*
* Copyright (C) 2015 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.apkzlib.zip;
import java.io.IOException;
import javax.annotation.Nonnull;
/**
* General purpose bit flags. Contains the encoding of the zip's general purpose bits.
*
* <p>We don't really care about the method bit(s). These are bits 1 and 2. Here are the values:
* <ul>
* <li>0 (00): Normal (-en) compression option was used.
* <li>1 (01): Maximum (-exx/-ex) compression option was used.
* <li>2 (10): Fast (-ef) compression option was used.
* <li>3 (11): Super Fast (-es) compression option was used.
* </ul>
*/
class GPFlags {
/**
* Is the entry encrypted?
*/
private static final int BIT_ENCRYPTION = 1;
/**
* Has CRC computation been deferred and, therefore, does a data description block exist?
*/
private static final int BIT_DEFERRED_CRC = (1 << 3);
/**
* Is enhanced deflating used?
*/
private static final int BIT_ENHANCED_DEFLATING = (1 << 4);
/**
* Does the entry contain patched data?
*/
private static final int BIT_PATCHED_DATA = (1 << 5);
/**
* Is strong encryption used?
*/
private static final int BIT_STRONG_ENCRYPTION = (1 << 6) | (1 << 13);
/**
* If this bit is set the filename and comment fields for this file must be encoded using UTF-8.
*/
private static final int BIT_EFS = (1 << 11);
/**
* Unused bits.
*/
private static final int BIT_UNUSED = (1 << 7) | (1 << 8) | (1 << 9) | (1 << 10)
| (1 << 14) | (1 << 15);
/**
* Bit flag value.
*/
private final long value;
/**
* Has the CRC computation beeen deferred?
*/
private boolean deferredCrc;
/**
* Is the file name encoded in UTF-8?
*/
private boolean utf8FileName;
/**
* Creates a new flags object.
*
* @param value the value of the bit mask
*/
private GPFlags(long value) {
this.value = value;
deferredCrc = ((value & BIT_DEFERRED_CRC) != 0);
utf8FileName = ((value & BIT_EFS) != 0);
}
/**
* Obtains the flags value.
*
* @return the value of the bit mask
*/
public long getValue() {
return value;
}
/**
* Is the CRC computation deferred?
*
* @return is the CRC computation deferred?
*/
public boolean isDeferredCrc() {
return deferredCrc;
}
/**
* Is the file name encoded in UTF-8?
*
* @return is the file name encoded in UTF-8?
*/
public boolean isUtf8FileName() {
return utf8FileName;
}
/**
* Creates a new bit mask.
*
* @param utf8Encoding should UTF-8 encoding be used?
* @return the new bit mask
*/
@Nonnull
static GPFlags make(boolean utf8Encoding) {
long flags = 0;
if (utf8Encoding) {
flags |= BIT_EFS;
}
return new GPFlags(flags);
}
/**
* Creates the flag information from a byte. This method will also validate that only
* supported options are defined in the flag.
*
* @param bits the bit mask
* @return the created flag information
* @throws IOException unsupported options are used in the bit mask
*/
@Nonnull
static GPFlags from(long bits) throws IOException {
if ((bits & BIT_ENCRYPTION) != 0) {
throw new IOException("Zip files with encrypted of entries not supported.");
}
if ((bits & BIT_ENHANCED_DEFLATING) != 0) {
throw new IOException("Enhanced deflating not supported.");
}
if ((bits & BIT_PATCHED_DATA) != 0) {
throw new IOException("Compressed patched data not supported.");
}
if ((bits & BIT_STRONG_ENCRYPTION) != 0) {
throw new IOException("Strong encryption not supported.");
}
if ((bits & BIT_UNUSED) != 0) {
throw new IOException("Unused bits set in directory entry. Weird. I don't know what's "
+ "going on.");
}
if ((bits & 0xffffffff00000000L) != 0) {
throw new IOException("Unsupported bits after 32.");
}
return new GPFlags(bits);
}
}
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