ZipEntry.java

/*
 * Copyright (c) 1995, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.util.zip;

import java.nio.file.attribute.FileTime;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Objects;
import java.util.concurrent.TimeUnit;

import static java.util.zip.ZipConstants64.EXTID_EXTT;
import static java.util.zip.ZipConstants64.EXTID_NTFS;
import static java.util.zip.ZipConstants64.EXTID_ZIP64;
import static java.util.zip.ZipUtils.WINDOWS_TIME_NOT_AVAILABLE;
import static java.util.zip.ZipUtils.extendedDosToJavaTime;
import static java.util.zip.ZipUtils.get16;
import static java.util.zip.ZipUtils.get32S;
import static java.util.zip.ZipUtils.get64;
import static java.util.zip.ZipUtils.javaToExtendedDosTime;
import static java.util.zip.ZipUtils.unixTimeToFileTime;
import static java.util.zip.ZipUtils.winTimeToFileTime;

/**
 * This class is used to represent a ZIP file entry.
 *
 * @author David Connelly
 * @since 1.1
 */
/*
 * 压缩包中的实体条目(并不代表文件内容)，每一个未压缩的文件/文件夹都会对应一个压缩后的条目。
 * ZipEntry内部的属性可能解析自zip文件第一部分的第1小节，也可能解析自zip文件的第二部分。
 */
public class ZipEntry implements ZipConstants, Cloneable {
    
    /**
     * Approximately 128 years, in milliseconds (ignoring leap years etc).
     *
     * This establish an approximate high-bound value for DOS times in
     * milliseconds since epoch, used to enable an efficient but
     * sufficient bounds check to avoid generating extended last modified
     * time entries.
     *
     * Calculating the exact number is locale dependent, would require loading
     * TimeZone data eagerly, and would make little practical sense. Since DOS
     * times theoretically go to 2107 - with compatibility not guaranteed
     * after 2099 - setting this to a time that is before but near 2099
     * should be sufficient.
     */
    private static final long UPPER_DOSTIME_BOUND = 128L * 365 * 24 * 60 * 60 * 1000;
    
    /**
     * DOS time constant for representing timestamps before 1980.
     */
    static final long DOSTIME_BEFORE_1980 = (1 << 21) | (1 << 16);
    
    /**
     * Compression method for uncompressed entries.
     */
    public static final int STORED = 0;     // 原始数据未压缩
    
    /**
     * Compression method for compressed (deflated) entries.
     */
    public static final int DEFLATED = 8;   // 原始数据使用了默认压缩方式
    
    int flag = 0;       // general purpose flag | 通用位标记
    
    int method = -1;    // compression method | 压缩方法
    
    // 文件最后修改时间(日期)
    long xdostime = -1; // last modification time (in extended DOS time, where milliseconds lost in conversion might be encoded into the upper half)
    
    // 以下三个参数在STORED模式下必须主动设置
    long crc = -1;      // crc-32 of entry data | crc-32校验码
    long size = -1;     // uncompressed size of entry data | 压缩前的大小
    long csize = -1;    // compressed size of entry data   | 压缩后的大小
    
    String name;        // entry name | 待压缩实体的名称（文件相对路径）
    
    // 文件最后修改时间(扩展区)
    FileTime mtime;     // last modification time, from extra field data
    // 文件最后访问时间(扩展区)
    FileTime atime;     // last access time, from extra field data
    // 文件创建时间(扩展区)
    FileTime ctime;     // creation time, from extra field data
    
    byte[] extra;       // optional extra field data for entry | 其他扩展区信息，使用小端法存储
    
    String comment;     // optional comment string for entry | 可选的注释信息
    
    
    
    /*▼ 构造器 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    /**
     * Creates a new un-initialized zip entry
     */
    ZipEntry() {
    }
    
    /**
     * Creates a new zip entry with the specified name.
     *
     * @param name The entry name
     *
     * @throws NullPointerException     if the entry name is null
     * @throws IllegalArgumentException if the entry name is longer than
     *                                  0xFFFF bytes
     */
    public ZipEntry(String name) {
        Objects.requireNonNull(name, "name");
        
        if(name.length()>0xFFFF) {
            throw new IllegalArgumentException("entry name too long");
        }
        
        this.name = name;
    }
    
    /**
     * Creates a new zip entry with fields taken from the specified
     * zip entry.
     *
     * @param e A zip Entry object
     *
     * @throws NullPointerException if the entry object is null
     */
    public ZipEntry(ZipEntry e) {
        Objects.requireNonNull(e, "entry");
        
        name = e.name;
        xdostime = e.xdostime;
        mtime = e.mtime;
        atime = e.atime;
        ctime = e.ctime;
        crc = e.crc;
        size = e.size;
        csize = e.csize;
        method = e.method;
        flag = e.flag;
        extra = e.extra;
        comment = e.comment;
    }
    
    /*▲ 构造器 ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼ set ████████████████████████████████████████████████████████████████████████████████┓ */
    
    /**
     * Sets the compression method for the entry.
     *
     * @param method the compression method, either STORED or DEFLATED
     *
     * @throws IllegalArgumentException if the specified compression
     *                                  method is invalid
     * @see #getMethod()
     */
    // 设置对压缩实体的压缩方法
    public void setMethod(int method) {
        if(method != STORED && method != DEFLATED) {
            throw new IllegalArgumentException("invalid compression method");
        }
        this.method = method;
    }
    
    /**
     * Sets the last modification time of the entry.
     *
     * <p> If the entry is output to a ZIP file or ZIP file formatted
     * output stream the last modification time set by this method will
     * be stored into the {@code date and time fields} of the zip file
     * entry and encoded in standard {@code MS-DOS date and time format}.
     * The {@link java.util.TimeZone#getDefault() default TimeZone} is
     * used to convert the epoch time to the MS-DOS data and time.
     *
     * @param time The last modification time of the entry in milliseconds
     *             since the epoch
     *
     * @see #getTime()
     * @see #getLastModifiedTime()
     */
    // 设置压缩实体的最后修改时间
    public void setTime(long time) {
        this.xdostime = javaToExtendedDosTime(time);
        
        // Avoid setting the mtime field if time is in the valid range for a DOS time
        if(xdostime != DOSTIME_BEFORE_1980 && time<=UPPER_DOSTIME_BOUND) {
            this.mtime = null;
        } else {
            this.mtime = FileTime.from(time, TimeUnit.MILLISECONDS);
        }
    }
    
    /**
     * Sets the last modification time of the entry in local date-time.
     *
     * <p> If the entry is output to a ZIP file or ZIP file formatted
     * output stream the last modification time set by this method will
     * be stored into the {@code date and time fields} of the zip file
     * entry and encoded in standard {@code MS-DOS date and time format}.
     * If the date-time set is out of the range of the standard {@code
     * MS-DOS date and time format}, the time will also be stored into
     * zip file entry's extended timestamp fields in {@code optional
     * extra data} in UTC time. The {@link java.time.ZoneId#systemDefault()
     * system default TimeZone} is used to convert the local date-time
     * to UTC time.
     *
     * <p> {@code LocalDateTime} uses a precision of nanoseconds, whereas
     * this class uses a precision of milliseconds. The conversion will
     * truncate any excess precision information as though the amount in
     * nanoseconds was subject to integer division by one million.
     *
     * @param time The last modification time of the entry in local date-time
     *
     * @see #getTimeLocal()
     * @since 9
     */
    // 设置压缩实体的最后修改时间
    public void setTimeLocal(LocalDateTime time) {
        int year = time.getYear() - 1980;
        
        if(year<0) {
            this.xdostime = DOSTIME_BEFORE_1980;
        } else {
            this.xdostime = ((year << 25 | time.getMonthValue() << 21 | time.getDayOfMonth() << 16 | time.getHour() << 11 | time.getMinute() << 5 | time.getSecond() >> 1) & 0xffffffffL)
                + ((long) (((time.getSecond() & 0x1) * 1000) + time.getNano() / 1000_000) << 32);
        }
        
        if(xdostime != DOSTIME_BEFORE_1980 && year<=0x7f) {
            this.mtime = null;
        } else {
            this.mtime = FileTime.from(ZonedDateTime.of(time, ZoneId.systemDefault()).toInstant());
        }
    }
    
    /**
     * Sets the last modification time of the entry.
     *
     * <p> When output to a ZIP file or ZIP file formatted output stream
     * the last modification time set by this method will be stored into
     * zip file entry's {@code date and time fields} in {@code standard
     * MS-DOS date and time format}), and the extended timestamp fields
     * in {@code optional extra data} in UTC time.
     *
     * @param time The last modification time of the entry
     *
     * @return This zip entry
     *
     * @throws NullPointerException if the {@code time} is null
     * @see #getLastModifiedTime()
     * @since 1.8
     */
    // 设置压缩实体的最后修改时间
    public ZipEntry setLastModifiedTime(FileTime time) {
        this.mtime = Objects.requireNonNull(time, "lastModifiedTime");
        this.xdostime = javaToExtendedDosTime(time.to(TimeUnit.MILLISECONDS));
        return this;
    }
    
    /**
     * Sets the last access time of the entry.
     *
     * <p> If set, the last access time will be stored into the extended
     * timestamp fields of entry's {@code optional extra data}, when output
     * to a ZIP file or ZIP file formatted stream.
     *
     * @param time The last access time of the entry
     *
     * @return This zip entry
     *
     * @throws NullPointerException if the {@code time} is null
     * @see #getLastAccessTime()
     * @since 1.8
     */
    // 设置压缩实体的最后访问时间
    public ZipEntry setLastAccessTime(FileTime time) {
        this.atime = Objects.requireNonNull(time, "lastAccessTime");
        return this;
    }
    
    /**
     * Sets the creation time of the entry.
     *
     * <p> If set, the creation time will be stored into the extended
     * timestamp fields of entry's {@code optional extra data}, when
     * output to a ZIP file or ZIP file formatted stream.
     *
     * @param time The creation time of the entry
     *
     * @return This zip entry
     *
     * @throws NullPointerException if the {@code time} is null
     * @see #getCreationTime()
     * @since 1.8
     */
    // 设置压缩实体的创建时间
    public ZipEntry setCreationTime(FileTime time) {
        this.ctime = Objects.requireNonNull(time, "creationTime");
        return this;
    }
    
    /**
     * Sets the CRC-32 checksum of the uncompressed entry data.
     *
     * @param crc the CRC-32 value
     *
     * @throws IllegalArgumentException if the specified CRC-32 value is
     *                                  less than 0 or greater than 0xFFFFFFFF
     * @see #getCrc()
     */
    // 设置crc-32校验码
    public void setCrc(long crc) {
        if(crc<0 || crc>0xFFFFFFFFL) {
            throw new IllegalArgumentException("invalid entry crc-32");
        }
        this.crc = crc;
    }
    
    /**
     * Sets the uncompressed size of the entry data.
     *
     * @param size the uncompressed size in bytes
     *
     * @throws IllegalArgumentException if the specified size is less
     *                                  than 0, is greater than 0xFFFFFFFF when
     *                                  <a href="package-summary.html#zip64">ZIP64 format</a> is not supported,
     *                                  or is less than 0 when ZIP64 is supported
     * @see #getSize()
     */
    // 设置压缩实体压缩前的大小
    public void setSize(long size) {
        if(size<0) {
            throw new IllegalArgumentException("invalid entry size");
        }
        this.size = size;
    }
    
    /**
     * Sets the size of the compressed entry data.
     *
     * @param csize the compressed size to set
     *
     * @see #getCompressedSize()
     */
    // 设置压缩实体压缩后的大小
    public void setCompressedSize(long csize) {
        this.csize = csize;
    }
    
    /**
     * Sets the optional extra field data for the entry.
     *
     * <p> Invoking this method may change this entry's last modification
     * time, last access time and creation time, if the {@code extra} field
     * data includes the extensible timestamp fields, such as {@code NTFS tag
     * 0x0001} or {@code Info-ZIP Extended Timestamp}, as specified in
     * <a href="http://www.info-zip.org/doc/appnote-19970311-iz.zip">Info-ZIP
     * Application Note 970311</a>.
     *
     * @param extra The extra field data bytes
     *
     * @throws IllegalArgumentException if the length of the specified
     *                                  extra field data is greater than 0xFFFF bytes
     * @see #getExtra()
     */
    // 为当前实体设置附加信息
    public void setExtra(byte[] extra) {
        setExtra0(extra, false);
    }
    
    /**
     * Sets the optional comment string for the entry.
     *
     * <p>ZIP entry comments have maximum length of 0xffff. If the length of the
     * specified comment string is greater than 0xFFFF bytes after encoding, only
     * the first 0xFFFF bytes are output to the ZIP file entry.
     *
     * @param comment the comment string
     *
     * @see #getComment()
     */
    // 为当前实体设置注释信息
    public void setComment(String comment) {
        this.comment = comment;
    }
    
    /*▲ set ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼ get ████████████████████████████████████████████████████████████████████████████████┓ */
    
    /**
     * Returns the compression method of the entry.
     *
     * @return the compression method of the entry, or -1 if not specified
     *
     * @see #setMethod(int)
     */
    // 返回对压缩实体的压缩方法
    public int getMethod() {
        return method;
    }
    
    /**
     * Returns the last modification time of the entry.
     *
     * <p> If the entry is read from a ZIP file or ZIP file formatted
     * input stream, this is the last modification time from the {@code
     * date and time fields} of the zip file entry. The
     * {@link java.util.TimeZone#getDefault() default TimeZone} is used
     * to convert the standard MS-DOS formatted date and time to the
     * epoch time.
     *
     * @return The last modification time of the entry in milliseconds
     * since the epoch, or -1 if not specified
     *
     * @see #setTime(long)
     * @see #setLastModifiedTime(FileTime)
     */
    // 返回压缩实体的最后修改时间
    public long getTime() {
        if(mtime != null) {
            return mtime.toMillis();
        }
        
        return (xdostime != -1) ? extendedDosToJavaTime(xdostime) : -1;
    }
    
    /**
     * Returns the last modification time of the entry in local date-time.
     *
     * <p> If the entry is read from a ZIP file or ZIP file formatted
     * input stream, this is the last modification time from the zip
     * file entry's {@code optional extra data} if the extended timestamp
     * fields are present. Otherwise, the last modification time is read
     * from entry's standard MS-DOS formatted {@code date and time fields}.
     *
     * <p> The {@link java.time.ZoneId#systemDefault() system default TimeZone}
     * is used to convert the UTC time to local date-time.
     *
     * @return The last modification time of the entry in local date-time
     *
     * @see #setTimeLocal(LocalDateTime)
     * @since 9
     */
    // 返回压缩实体的最后修改时间
    public LocalDateTime getTimeLocal() {
        if(mtime != null) {
            return LocalDateTime.ofInstant(mtime.toInstant(), ZoneId.systemDefault());
        }
        
        int ms = (int) (xdostime >> 32);
        return LocalDateTime.of(
            (int) (((xdostime >> 25) & 0x7f) + 1980),
            (int) ((xdostime >> 21) & 0x0f),
            (int) ((xdostime >> 16) & 0x1f),
            (int) ((xdostime >> 11) & 0x1f),
            (int) ((xdostime >> 5) & 0x3f),
            (int) ((xdostime << 1) & 0x3e) + ms / 1000,
            (ms % 1000) * 1000_000);
    }
    
    /**
     * Returns the last modification time of the entry.
     *
     * <p> If the entry is read from a ZIP file or ZIP file formatted
     * input stream, this is the last modification time from the zip
     * file entry's {@code optional extra data} if the extended timestamp
     * fields are present. Otherwise the last modification time is read
     * from the entry's {@code date and time fields}, the {@link
     * java.util.TimeZone#getDefault() default TimeZone} is used to convert
     * the standard MS-DOS formatted date and time to the epoch time.
     *
     * @return The last modification time of the entry, null if not specified
     *
     * @see #setLastModifiedTime(FileTime)
     * @since 1.8
     */
    // 返回压缩实体的最后修改时间
    public FileTime getLastModifiedTime() {
        if(mtime != null) {
            return mtime;
        }
        
        if(xdostime == -1) {
            return null;
        }
        
        return FileTime.from(getTime(), TimeUnit.MILLISECONDS);
    }
    
    /**
     * Returns the last access time of the entry.
     *
     * <p> The last access time is from the extended timestamp fields
     * of entry's {@code optional extra data} when read from a ZIP file
     * or ZIP file formatted stream.
     *
     * @return The last access time of the entry, null if not specified
     *
     * @see #setLastAccessTime(FileTime)
     * @since 1.8
     */
    // 返回压缩实体的最后访问时间
    public FileTime getLastAccessTime() {
        return atime;
    }
    
    /**
     * Returns the creation time of the entry.
     *
     * <p> The creation time is from the extended timestamp fields of
     * entry's {@code optional extra data} when read from a ZIP file
     * or ZIP file formatted stream.
     *
     * @return the creation time of the entry, null if not specified
     *
     * @see #setCreationTime(FileTime)
     * @since 1.8
     */
    // 返回压缩实体的创建时间
    public FileTime getCreationTime() {
        return ctime;
    }
    
    /**
     * Returns the CRC-32 checksum of the uncompressed entry data.
     *
     * @return the CRC-32 checksum of the uncompressed entry data, or -1 if
     * not known
     *
     * @see #setCrc(long)
     */
    // 返回crc-32校验码
    public long getCrc() {
        return crc;
    }
    
    /**
     * Returns the uncompressed size of the entry data.
     *
     * @return the uncompressed size of the entry data, or -1 if not known
     *
     * @see #setSize(long)
     */
    // 返回压缩实体压缩前的大小
    public long getSize() {
        return size;
    }
    
    /**
     * Returns the size of the compressed entry data.
     *
     * <p> In the case of a stored entry, the compressed size will be the same
     * as the uncompressed size of the entry.
     *
     * @return the size of the compressed entry data, or -1 if not known
     *
     * @see #setCompressedSize(long)
     */
    // 返回压缩实体压缩后的大小
    public long getCompressedSize() {
        return csize;
    }
    
    /**
     * Returns the extra field data for the entry.
     *
     * @return the extra field data for the entry, or null if none
     *
     * @see #setExtra(byte[])
     */
    // 返回当前实体的附加信息
    public byte[] getExtra() {
        return extra;
    }
    
    /**
     * Returns the comment string for the entry.
     *
     * @return the comment string for the entry, or null if none
     *
     * @see #setComment(String)
     */
    // 返回当前实体的注释信息
    public String getComment() {
        return comment;
    }
    
    /**
     * Returns the name of the entry.
     *
     * @return the name of the entry
     */
    // 返回当前实体的名称
    public String getName() {
        return name;
    }
    
    /*▲ get ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼  ████████████████████████████████████████████████████████████████████████████████┓ */
    
    /**
     * Returns true if this is a directory entry.
     * A directory entry is defined to be one whose name ends with a '/'.
     *
     * @return true if this is a directory entry
     */
    // 判断当前实体是否为目录（很重要的一点：需要以/结尾）
    public boolean isDirectory() {
        return name.endsWith("/");
    }
    
    /*▲  ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /**
     * Returns a string representation of the ZIP entry.
     */
    public String toString() {
        return getName();
    }
    
    /**
     * Returns the hash code value for this entry.
     */
    public int hashCode() {
        return name.hashCode();
    }
    
    /**
     * Returns a copy of this entry.
     */
    public Object clone() {
        try {
            ZipEntry e = (ZipEntry) super.clone();
            e.extra = (extra == null) ? null : extra.clone();
            return e;
        } catch(CloneNotSupportedException e) {
            // This should never happen, since we are Cloneable
            throw new InternalError(e);
        }
    }
    
    
    
    /**
     * Sets the optional extra field data for the entry.
     *
     * @param extra   the extra field data bytes
     * @param doZIP64 if true, set size and csize from ZIP64 fields if present
     */
    // 为当前zip实体填充扩展信息
    void setExtra0(byte[] extra, boolean doZIP64) {
        if(extra != null) {
            // 附加数据不宜过长
            if(extra.length>0xFFFF) {
                throw new IllegalArgumentException("invalid extra field length");
            }
            
            // extra fields are in "HeaderID(2)DataSize(2)Data... format
            int off = 0;
            int len = extra.length;
            
            while(off + 4<len) {
                // 从extra的off处获取2个字节
                int tag = get16(extra, off);
                // 从extra的off + 2处获取2个字节
                int sz = get16(extra, off + 2);
                
                off += 4;
                
                if(off + sz>len) {
                    break;  // 无效数据
                }
                
                switch(tag) {
                    case EXTID_ZIP64:
                        if(doZIP64) {
                            /*
                             * LOC extra zip64 entry MUST include BOTH original and compressed file size fields.
                             * If invalid zip64 extra fields, simply skip.
                             * Even it's rare, it's possible the entry size happens to be the magic value
                             * and it "accidently" has some bytes in extra match the id.
                             */
                            if(sz >= 16) {
                                // 从extra的off处获取8个字节
                                size = get64(extra, off);
                                // 从extra的off+ 8处获取8个字节
                                csize = get64(extra, off + 8);
                            }
                        }
                        break;
                    case EXTID_NTFS:
                        // reserved  4 bytes + tag 2 bytes + size 2 bytes
                        if(sz<32) {
                            break;// m[a|c]time 24 bytes
                        }
                        
                        int pos = off + 4;               // reserved 4 bytes
                        if(get16(extra, pos) != 0x0001 || get16(extra, pos + 2) != 24) {
                            break;
                        }
                        
                        long wtime = get64(extra, pos + 4);
                        if(wtime != WINDOWS_TIME_NOT_AVAILABLE) {
                            mtime = winTimeToFileTime(wtime);
                        }
                        
                        wtime = get64(extra, pos + 12);
                        if(wtime != WINDOWS_TIME_NOT_AVAILABLE) {
                            atime = winTimeToFileTime(wtime);
                        }
                        
                        wtime = get64(extra, pos + 20);
                        if(wtime != WINDOWS_TIME_NOT_AVAILABLE) {
                            ctime = winTimeToFileTime(wtime);
                        }
                        break;
                    case EXTID_EXTT:
                        int flag = Byte.toUnsignedInt(extra[off]);
                        int sz0 = 1;
                        
                        /*
                         * The CEN-header extra field contains the modification time only, or no timestamp at all.
                         * 'sz' is used to flag its presence or absence.
                         * But if mtime is present in LOC it must be present in CEN as well.
                         */
                        if((flag & 0x1) != 0 && (sz0 + 4)<=sz) {
                            mtime = unixTimeToFileTime(get32S(extra, off + sz0));
                            sz0 += 4;
                        }
                        
                        if((flag & 0x2) != 0 && (sz0 + 4)<=sz) {
                            atime = unixTimeToFileTime(get32S(extra, off + sz0));
                            sz0 += 4;
                        }
                        
                        if((flag & 0x4) != 0 && (sz0 + 4)<=sz) {
                            ctime = unixTimeToFileTime(get32S(extra, off + sz0));
                            sz0 += 4;
                        }
                        break;
                    default:
                }
                
                off += sz;
            }
        }
        
        this.extra = extra;
    }
    
}