javacc之路3---CharStream

字符流类
根据各种选项的组合生成4 种不同类型的CharStream类。

NB 以上类都不能用于以混合模式读取字符，即一些字符以 1 字节字符给出，而另一些字符为 2 字节字符。为此，您需要将USER_CHAR_STREAM选项设置为true并定义您自己的CharStream.

在以下部分中，我们将使用XXXCharStream代表上述 4 个类中的任何一个的符号。

构造函数

/**
 * Takes an input stream, starting line and column numbers
 * and constructs a CharStream object. It also creates buffers
 * of initial size 4K for buffering the characters and also for
 * line and column numbers for each of those characters.
 */
public XXXCharStream(java.io.InputStream dstream, int startline, int startcolumn)
/**
 * Takes an input stream, starting line and column numbers
 * and constructs a CharStream object. It also creates buffers
 * of initial size buffsize for buffering the characters and also
 * for line and column numbers for each of those characters.
 */
public XXXCharStream(java.io.InputStream dstream, int startline, int startcolumn, int buffersize)
1
2
3
4
5
6
7
8
9
10
11
12
13
14

因此，当您对可能出现的任何令牌的最大大小进行估计时，您可以使用该大小来优化缓冲区大小。请注意，这些尺寸只是初始尺寸，它们将在需要时扩展（以 2K 为步长）。

方法
以下所有方法将是静态的或非静态的，具体取决于STATIC选项是在生成时true还是false在生成时。此外，此处仅记录了用户可以在其词法操作中使用的那些方法（使用input_stream词法分析器的变量）。

其余（公共）方法与词法分析器的实现紧密耦合，因此不应在词法操作中使用。将来我们将通过使接口的那部分成为词法分析器的内部类来简化它。

/**
 * This method returns the next "character" in the input according
 * to the rules of the CharStream class as described above. It will
 * throw java.io.IOException if it reaches EOF during the process
 * of "constructing" the character. It also updates the line and
 * column number and buffers the character for any possible
 * backtracking that may be required later. It also stores the
 * line and column numbers for the same purpose.
 */
public final char readChar() throws java.io.IOException
/**
 * This method returns the line number for the beginning of the current match.
 */
public final int getBeginLine()
/**
 * This method returns the column number for the beginning of the current match.
 */
public final int getBeginColumn()
/**
 * This method returns the line number for the ending of the current match.
 */
public final int getEndLine()
/**
 * This method returns the column number for the ending of the current match.
 */
public final int getEndColumn()
/**
 * This method puts back amount number of characters into the stream.
 *
 * N.B. The amount indicates the number of characters as constructed
 * by readChar. Since the buffers used are circular buffers, it cannot
 * check for illegal amount values, it just wraps around. So it is the
 * user's responsibility to make sure that those many characters are
 * really produced before a call to this method.
 */
public final void backup(int amount)
/**
 * Returns the image of the current match. As far as the XXXCharStream
 * is concerned, all characters after the last call to the private
 * method BeginToken are considered a part of the current match.
 */
public final String GetImage()
/**
 * This method reinitializes the XXXCharStream classes with a
 * (possibly new) input stream and starting line and column numbers.
 */
public void ReInit(java.io.InputStream dstream, int startline, int startcolumn)
/**
 * This method reinitializes the XXXCharStream classes with a
 * (possibly new) input stream and starting line and column numbers
 * and adjusts the size of the buffers to buffersize, by extending them.
 *
 * N.B. If the value of buffersize is less than the current buffer sizes,
 * they remain unchanged.
 */
public void ReInit(java.io.InputStream dstream, int startline, int startcolumn, int buffersize)

/**
 * This method adjusts the line and column number of the beginning
 * of the current match to newLine and newCol and also adjusts the
 * line and column numbers for all the characters in the lookahead buffer.
 */
public void adjustBeginLineColumn(int newLine, int newCol)
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