1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
// Generated by re2java
// re2java $INPUT -o $OUTPUT
import java.io.*;
import java.nio.file.*;
import java.util.Arrays;
class Lexer {
static final int YYMAXFILL = 1;
public static final int BUFSIZE = 4096;
private BufferedInputStream stream;
private byte[] yyinput;
private int yycursor;
private int yylimit;
private int token;
private boolean eof;
public Lexer(File file) throws FileNotFoundException {
stream = new BufferedInputStream(new FileInputStream(file));
// Prepare lexer state: all offsets are at the end of buffer.
// This immediately triggers YYFILL, as the YYLESSTHAN condition is true.
yyinput = new byte[BUFSIZE + YYMAXFILL];
yycursor = yylimit = token = BUFSIZE;
eof = false;
}
private int fill(int need) throws IOException {
if (eof) { return -1; } // unexpected EOF
// Error: lexeme too long. In real life can reallocate a larger buffer.
if (token < need) { return -2; }
// Shift buffer contents (discard everything up to the current token).
System.arraycopy(yyinput, token, yyinput, 0, yylimit - token);
yycursor -= token;
yylimit -= token;
token = 0;
// Fill free space at the end of buffer with new data from file.
yylimit += stream.read(yyinput, yylimit, BUFSIZE - yylimit);
yyinput[yylimit] = 0; // append sentinel symbol
// If read less than expected, this is the end of input.
if (yylimit < BUFSIZE) {
eof = true;
Arrays.fill(yyinput, yylimit, yylimit + YYMAXFILL, (byte)0);
yylimit += YYMAXFILL;
}
return 0;
}
// Expects a null-terminated string.
public int lex() throws IOException {
int count = 0;
loop: while (true) {
token = yycursor;
{
int yych = 0;
int yystate = 0;
yyl: while (true) {
switch (yystate) {
case 0:
if (yylimit <= yycursor) {
if (fill(1) != 0) { return -2; }
}
yych = Byte.toUnsignedInt(yyinput[yycursor]);
yycursor += 1;
switch (yych) {
case 0x00:
yystate = 1;
continue yyl;
case 0x20:
yystate = 3;
continue yyl;
case 0x27:
yystate = 5;
continue yyl;
default:
yystate = 2;
continue yyl;
}
case 1:
{
// Check that it is the sentinel, not some unexpected null.
return (token == yylimit - YYMAXFILL) ? count : -1;
}
case 2:
{ return -1; }
case 3:
if (yylimit <= yycursor) {
if (fill(1) != 0) { return -2; }
}
yych = Byte.toUnsignedInt(yyinput[yycursor]);
switch (yych) {
case 0x20:
yycursor += 1;
yystate = 3;
continue yyl;
default:
yystate = 4;
continue yyl;
}
case 4:
{ continue loop; }
case 5:
if (yylimit <= yycursor) {
if (fill(1) != 0) { return -2; }
}
yych = Byte.toUnsignedInt(yyinput[yycursor]);
yycursor += 1;
switch (yych) {
case 0x27:
yystate = 6;
continue yyl;
case 0x5C:
yystate = 7;
continue yyl;
default:
yystate = 5;
continue yyl;
}
case 6:
{ count += 1; continue loop; }
case 7:
if (yylimit <= yycursor) {
if (fill(1) != 0) { return -2; }
}
yycursor += 1;
yystate = 5;
continue yyl;
default:
throw new IllegalStateException("internal lexer error");
}
}
}
}
}
public static void main(String []args) throws FileNotFoundException, IOException {
String fname = "input";
String content = "'qu\0tes' 'are' 'fine: \\'' ".repeat(Lexer.BUFSIZE);
// Prepare input file: a few times the size of the buffer, containing
// strings with zeroes and escaped quotes.
Files.writeString(Paths.get(fname), content);
int count = 3 * Lexer.BUFSIZE; // number of quoted strings written to file
// Prepare lexer state: all offsets are at the end of buffer.
File file = new File(".", fname);
Lexer lexer = new Lexer(file);
// Run the lexer.
int n = lexer.lex();
assert n == count;
// Cleanup: remove input file.
file.delete();
}
};
|
