|
1
34 package smallsql.database;
35
36 import java.io.*;
37 import java.sql.SQLException  ;
38
39
40
43 public class Identity extends Number {
44
45 final private long filePos;
46 final private RandomAccessFile raFile;
47 final private byte[] page = new byte[8];
48 final private Table table;
49 private long value;
50
51 public Identity(Table table, RandomAccessFile raFile, long filePos) throws IOException{
52 synchronized(raFile){
53 raFile.seek(filePos);
54 raFile.read(page);
55 }
56 value = ((long)(page[ 0 ]) << 56) |
57 ((long)(page[ 1 ] & 0xFF) << 48) |
58 ((long)(page[ 2 ] & 0xFF) << 40) |
59 ((long)(page[ 3 ] & 0xFF) << 32) |
60 ((long)(page[ 4 ] & 0xFF) << 24) |
61 ((page[ 5 ] & 0xFF) << 16) |
62 ((page[ 6 ] & 0xFF) << 8) |
63 ((page[ 7 ] & 0xFF));
64 this.table = table;
65 this.raFile = raFile;
66 this.filePos = filePos;
67 }
68
69 private StorePage createStorePage(){
70 page[ 0 ] = (byte)(value >> 56);
71 page[ 1 ] = (byte)(value >> 48);
72 page[ 2 ] = (byte)(value >> 40);
73 page[ 3 ] = (byte)(value >> 32);
74 page[ 4 ] = (byte)(value >> 24);
75 page[ 5 ] = (byte)(value >> 16);
76 page[ 6 ] = (byte)(value >> 8);
77 page[ 7 ] = (byte)(value);
78 return new StorePage( page, 8, raFile, filePos);
79 }
80
81 void createNextValue(SSConnection con) throws SQLException {
82 value++;
83 con.add( createStorePage() );
84 }
85
86
87 void setNextValue(Expression expr) throws Exception {
88 if(expr.isNull()) return;
89 long newValue = expr.getLong();
90 if(newValue > value){
91 value = newValue;
92 createStorePage().commit();
93 }
94 }
95
96 public float floatValue() {
97 return value;
98 }
99
100 public double doubleValue() {
101 return value;
102 }
103
104 public int intValue() {
105 return (int)value;
106 }
107
108 public long longValue() {
109 return value;
110 }
111
112 }
113 |
Popular Tags |
Java API By Example, From Geeks To Geeks.