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1
21 package com.db4o.header;
22
23 import java.io.*;
24
25 import com.db4o.*;
26 import com.db4o.inside.*;
27
28
29
32 public abstract class FileHeader {
33
34 private static final FileHeader[] AVAILABLE_FILE_HEADERS = new FileHeader[]{
35 new FileHeader0(),
36 new FileHeader1()
37 };
38
39 private static int readerLength(){
40 int length = AVAILABLE_FILE_HEADERS[0].length();
41 for (int i = 1; i < AVAILABLE_FILE_HEADERS.length; i++) {
42 length = YInt.max(length, AVAILABLE_FILE_HEADERS[i].length());
43 }
44 return length;
45 }
46
47 public static FileHeader readFixedPart(YapFile file) throws IOException{
48 YapReader reader = prepareFileHeaderReader(file);
49 FileHeader header = detectFileHeader(file, reader);
50 if(header == null){
51 Exceptions4.throwRuntimeException(17);
52 } else {
53 header.readFixedPart(file, reader);
54 }
55 return header;
56 }
57
58 private static YapReader prepareFileHeaderReader(YapFile file) {
59 YapReader reader = new YapReader(readerLength());
60 reader.read(file, 0, 0);
61 return reader;
62 }
63
64 private static FileHeader detectFileHeader(YapFile file, YapReader reader) {
65 for (int i = 0; i < AVAILABLE_FILE_HEADERS.length; i++) {
66 reader.seek(0);
67 FileHeader result = AVAILABLE_FILE_HEADERS[i].newOnSignatureMatch(file, reader);
68 if(result != null) {
69 return result;
70 }
71 }
72 return null;
73 }
74
75 public abstract void close() throws IOException;
76
77 public abstract void initNew(YapFile file) throws IOException;
78
79 public abstract Transaction interruptedTransaction();
80
81 public abstract int length();
82
83 protected abstract FileHeader newOnSignatureMatch(YapFile file, YapReader reader);
84
85 protected long timeToWrite(long time, boolean shuttingDown) {
86 return shuttingDown ? 0 : time;
87 }
88
89 protected abstract void readFixedPart(YapFile file, YapReader reader) throws IOException;
90
91 public abstract void readVariablePart(YapFile file);
92
93 protected boolean signatureMatches(YapReader reader, byte[] signature, byte version){
94 for (int i = 0; i < signature.length; i++) {
95 if(reader.readByte() != signature[i]){
96 return false;
97 }
98 }
99 return reader.readByte() == version;
100 }
101
102 public abstract void writeFixedPart(
104 YapFile file, boolean shuttingDown, YapWriter writer, int blockSize, int freespaceID);
105
106 public abstract void writeTransactionPointer(Transaction systemTransaction, int transactionAddress);
107
108 protected void writeTransactionPointer(Transaction systemTransaction, int transactionAddress, final int address, final int offset) {
109 YapWriter bytes = new YapWriter(systemTransaction, address, YapConst.INT_LENGTH * 2);
110 bytes.moveForward(offset);
111 bytes.writeInt(transactionAddress);
112 bytes.writeInt(transactionAddress);
113 if (Debug.xbytes && Deploy.overwrite) {
114 bytes.setID(YapConst.IGNORE_ID);
115 }
116 bytes.write();
117 }
118
119 public abstract void writeVariablePart(YapFile file, int part);
120
121 protected void readClassCollectionAndFreeSpace(YapFile file, YapReader reader) {
122 SystemData systemData = file.systemData();
123 systemData.classCollectionID(reader.readInt());
124 systemData.freespaceID(reader.readInt());
125 }
126
127 }
128 |
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