When tokenizing a stream of bytes in Java, I need to extract information about indexes of the tokenized words. For example, given:
String "Hello world! Java8 program." -> stream -> ...
I would need something like:
[(Hello, 0, 5), (world, 6, 11), (Java8, 13, 18), (program, 19, 25)]
The problem is similar to Java NLP: Extracting Indicies When Tokenizing Text
The difference is the program input is stream with unknown length. I wanted to apply SimpleTokenizer to this task but unfortunately it accepts only String as an input. Since stream could be very long I can't directly transform stream into String (which would force program to stop until stream would be closed). I can't process stream in chunks evaluated on the char buffer since I can break the words in that process. Can you help me with finding suitable solution? Current code can perform only tokenization without including indexes:
public static void main(String[] args) throws IOException, ParseException {
final Reader input = initializeInput();
final Writer output = initializeOutput();
try {
final long count = process(input, output);
output.flush();
} finally {
input.close();
output.close();
}
}
protected static long process(Reader input, Writer output) throws IOException {
final StreamTokenizer st = new StreamTokenizer(input);
st.eolIsSignificant(false);
long count = 0;
int token;
while ((token = st.nextToken()) != StreamTokenizer.TT_EOF) {
if (token == StreamTokenizer.TT_WORD) {
final String word = st.sval;
count++;
output.write(word);
output.flush();
}
}
return count;
}
private static String asString(CharSequence stem) {
if (stem == null)
return "-";
return stem.toString();
}
private static Writer initializeOutput()
throws IOException, ParseException {
final Writer output;
output = new OutputStreamWriter(System.out, "UTF-8");
return output;
}
private static Reader initializeInput()
throws IOException {
final Reader input;
input = new InputStreamReader(System.in, "UTF-8");
return input;
}
For people in similar problem in the future:
I've modified implementation of StreamTokenizer. Unfortunately inheritance is not posissble here. getLastTokenStart() and getLastTokenEnd() returns indexes of token parsed after each parsing step. That was prepared for string and numbers only (didnt test it on CT_QUOTE, CT_COMMENT)
package wrapper;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.Arrays;
public class CustomStreamTokenizer {
private long lastTokenStart = 0;
private long lastTokenEnd = -1;
/* Only one of these will be non-null */
private Reader reader = null;
private InputStream input = null;
private char buf[] = new char[20];
private int peekc = NEED_CHAR;
private static final int NEED_CHAR = Integer.MAX_VALUE;
private static final int SKIP_LF = Integer.MAX_VALUE - 1;
private boolean pushedBack;
private boolean forceLower;
/** The line number of the last token read */
private int LINENO = 1;
private boolean eolIsSignificantP = false;
private boolean slashSlashCommentsP = false;
private boolean slashStarCommentsP = false;
private byte ctype[] = new byte[256];
private static final byte CT_WHITESPACE = 1;
private static final byte CT_DIGIT = 2;
private static final byte CT_ALPHA = 4;
private static final byte CT_QUOTE = 8;
private static final byte CT_COMMENT = 16;
/**
* After a call to the {@code nextToken} method, this field
* contains the type of the token just read. For a single character
* token, its value is the single character, converted to an integer.
* For a quoted string token, its value is the quote character.
* Otherwise, its value is one of the following:
* <ul>
* <li>{@code TT_WORD} indicates that the token is a word.
* <li>{@code TT_NUMBER} indicates that the token is a number.
* <li>{@code TT_EOL} indicates that the end of line has been read.
* The field can only have this value if the
* {@code eolIsSignificant} method has been called with the
* argument {@code true}.
* <li>{@code TT_EOF} indicates that the end of the input stream
* has been reached.
* </ul>
* <p>
* The initial value of this field is -4.
*
* @see java.io.StreamTokenizer#eolIsSignificant(boolean)
* @see java.io.StreamTokenizer#nextToken()
* @see java.io.StreamTokenizer#quoteChar(int)
* @see java.io.StreamTokenizer#TT_EOF
* @see java.io.StreamTokenizer#TT_EOL
* @see java.io.StreamTokenizer#TT_NUMBER
* @see java.io.StreamTokenizer#TT_WORD
*/
public int ttype = TT_NOTHING;
/**
* A constant indicating that the end of the stream has been read.
*/
public static final int TT_EOF = -1;
/**
* A constant indicating that the end of the line has been read.
*/
public static final int TT_EOL = '\n';
/**
* A constant indicating that a number token has been read.
*/
public static final int TT_NUMBER = -2;
/**
* A constant indicating that a word token has been read.
*/
public static final int TT_WORD = -3;
/* A constant indicating that no token has been read, used for
* initializing ttype. FIXME This could be made public and
* made available as the part of the API in a future release.
*/
private static final int TT_NOTHING = -4;
/**
* If the current token is a word token, this field contains a
* string giving the characters of the word token. When the current
* token is a quoted string token, this field contains the body of
* the string.
* <p>
* The current token is a word when the value of the
* {@code ttype} field is {@code TT_WORD}. The current token is
* a quoted string token when the value of the {@code ttype} field is
* a quote character.
* <p>
* The initial value of this field is null.
*
* @see java.io.StreamTokenizer#quoteChar(int)
* @see java.io.StreamTokenizer#TT_WORD
* @see java.io.StreamTokenizer#ttype
*/
public String sval;
/**
* If the current token is a number, this field contains the value
* of that number. The current token is a number when the value of
* the {@code ttype} field is {@code TT_NUMBER}.
* <p>
* The initial value of this field is 0.0.
*
* @see java.io.StreamTokenizer#TT_NUMBER
* @see java.io.StreamTokenizer#ttype
*/
public double nval;
/** Private constructor that initializes everything except the streams. */
private CustomStreamTokenizer() {
wordChars('a', 'z');
wordChars('A', 'Z');
wordChars(128 + 32, 255);
whitespaceChars(0, ' ');
commentChar('/');
quoteChar('"');
quoteChar('\'');
parseNumbers();
}
/**
* Create a tokenizer that parses the given character stream.
*
* @param r a Reader object providing the input stream.
* @since JDK1.1
*/
public CustomStreamTokenizer(Reader r) {
this();
if (r == null) {
throw new NullPointerException();
}
reader = r;
}
/**
* Resets this tokenizer's syntax table so that all characters are
* "ordinary." See the {@code ordinaryChar} method
* for more information on a character being ordinary.
*
* @see java.io.StreamTokenizer#ordinaryChar(int)
*/
public void resetSyntax() {
for (int i = ctype.length; --i >= 0;)
ctype[i] = 0;
}
/**
* Specifies that all characters <i>c</i> in the range
* <code>low <= <i>c</i> <= high</code>
* are word constituents. A word token consists of a word constituent
* followed by zero or more word constituents or number constituents.
*
* @param low the low end of the range.
* @param hi the high end of the range.
*/
public void wordChars(int low, int hi) {
if (low < 0)
low = 0;
if (hi >= ctype.length)
hi = ctype.length - 1;
while (low <= hi)
ctype[low++] |= CT_ALPHA;
}
/**
* Specifies that all characters <i>c</i> in the range
* <code>low <= <i>c</i> <= high</code>
* are white space characters. White space characters serve only to
* separate tokens in the input stream.
*
* <p>Any other attribute settings for the characters in the specified
* range are cleared.
*
* @param low the low end of the range.
* @param hi the high end of the range.
*/
public void whitespaceChars(int low, int hi) {
if (low < 0)
low = 0;
if (hi >= ctype.length)
hi = ctype.length - 1;
while (low <= hi)
ctype[low++] = CT_WHITESPACE;
}
/**
* Specifies that all characters <i>c</i> in the range
* <code>low <= <i>c</i> <= high</code>
* are "ordinary" in this tokenizer. See the
* {@code ordinaryChar} method for more information on a
* character being ordinary.
*
* @param low the low end of the range.
* @param hi the high end of the range.
* @see java.io.StreamTokenizer#ordinaryChar(int)
*/
public void ordinaryChars(int low, int hi) {
if (low < 0)
low = 0;
if (hi >= ctype.length)
hi = ctype.length - 1;
while (low <= hi)
ctype[low++] = 0;
}
/**
* Specifies that the character argument is "ordinary"
* in this tokenizer. It removes any special significance the
* character has as a comment character, word component, string
* delimiter, white space, or number character. When such a character
* is encountered by the parser, the parser treats it as a
* single-character token and sets {@code ttype} field to the
* character value.
*
* <p>Making a line terminator character "ordinary" may interfere
* with the ability of a {@code CustomStreamTokenizer} to count
* lines. The {@code lineno} method may no longer reflect
* the presence of such terminator characters in its line count.
*
* @param ch the character.
* @see java.io.StreamTokenizer#ttype
*/
public void ordinaryChar(int ch) {
if (ch >= 0 && ch < ctype.length)
ctype[ch] = 0;
}
/**
* Specified that the character argument starts a single-line
* comment. All characters from the comment character to the end of
* the line are ignored by this stream tokenizer.
*
* <p>Any other attribute settings for the specified character are cleared.
*
* @param ch the character.
*/
public void commentChar(int ch) {
if (ch >= 0 && ch < ctype.length)
ctype[ch] = CT_COMMENT;
}
/**
* Specifies that matching pairs of this character delimit string
* constants in this tokenizer.
* <p>
* When the {@code nextToken} method encounters a string
* constant, the {@code ttype} field is set to the string
* delimiter and the {@code sval} field is set to the body of
* the string.
* <p>
* If a string quote character is encountered, then a string is
* recognized, consisting of all characters after (but not including)
* the string quote character, up to (but not including) the next
* occurrence of that same string quote character, or a line
* terminator, or end of file. The usual escape sequences such as
* {@code "\u005Cn"} and {@code "\u005Ct"} are recognized and
* converted to single characters as the string is parsed.
*
* <p>Any other attribute settings for the specified character are cleared.
*
* @param ch the character.
* @see java.io.StreamTokenizer#nextToken()
* @see java.io.StreamTokenizer#sval
* @see java.io.StreamTokenizer#ttype
*/
public void quoteChar(int ch) {
if (ch >= 0 && ch < ctype.length)
ctype[ch] = CT_QUOTE;
}
/**
* Specifies that numbers should be parsed by this tokenizer. The
* syntax table of this tokenizer is modified so that each of the twelve
* characters:
* <blockquote><pre>
* 0 1 2 3 4 5 6 7 8 9 . -
* </pre></blockquote>
* <p>
* has the "numeric" attribute.
* <p>
* When the parser encounters a word token that has the format of a
* double precision floating-point number, it treats the token as a
* number rather than a word, by setting the {@code ttype}
* field to the value {@code TT_NUMBER} and putting the numeric
* value of the token into the {@code nval} field.
*
* @see java.io.StreamTokenizer#nval
* @see java.io.StreamTokenizer#TT_NUMBER
* @see java.io.StreamTokenizer#ttype
*/
public void parseNumbers() {
for (int i = '0'; i <= '9'; i++)
ctype[i] |= CT_DIGIT;
ctype['.'] |= CT_DIGIT;
ctype['-'] |= CT_DIGIT;
}
/**
* Determines whether or not ends of line are treated as tokens.
* If the flag argument is true, this tokenizer treats end of lines
* as tokens; the {@code nextToken} method returns
* {@code TT_EOL} and also sets the {@code ttype} field to
* this value when an end of line is read.
* <p>
* A line is a sequence of characters ending with either a
* carriage-return character ({@code '\u005Cr'}) or a newline
* character ({@code '\u005Cn'}). In addition, a carriage-return
* character followed immediately by a newline character is treated
* as a single end-of-line token.
* <p>
* If the {@code flag} is false, end-of-line characters are
* treated as white space and serve only to separate tokens.
*
* @param flag {@code true} indicates that end-of-line characters
* are separate tokens; {@code false} indicates that
* end-of-line characters are white space.
* @see java.io.StreamTokenizer#nextToken()
* @see java.io.StreamTokenizer#ttype
* @see java.io.StreamTokenizer#TT_EOL
*/
public void eolIsSignificant(boolean flag) {
eolIsSignificantP = flag;
}
/**
* Determines whether or not the tokenizer recognizes C-style comments.
* If the flag argument is {@code true}, this stream tokenizer
* recognizes C-style comments. All text between successive
* occurrences of {@code /*} and <code>*/</code> are discarded.
* <p>
* If the flag argument is {@code false}, then C-style comments
* are not treated specially.
*
* @param flag {@code true} indicates to recognize and ignore
* C-style comments.
*/
public void slashStarComments(boolean flag) {
slashStarCommentsP = flag;
}
/**
* Determines whether or not the tokenizer recognizes C++-style comments.
* If the flag argument is {@code true}, this stream tokenizer
* recognizes C++-style comments. Any occurrence of two consecutive
* slash characters ({@code '/'}) is treated as the beginning of
* a comment that extends to the end of the line.
* <p>
* If the flag argument is {@code false}, then C++-style
* comments are not treated specially.
*
* @param flag {@code true} indicates to recognize and ignore
* C++-style comments.
*/
public void slashSlashComments(boolean flag) {
slashSlashCommentsP = flag;
}
/**
* Determines whether or not word token are automatically lowercased.
* If the flag argument is {@code true}, then the value in the
* {@code sval} field is lowercased whenever a word token is
* returned (the {@code ttype} field has the
* value {@code TT_WORD} by the {@code nextToken} method
* of this tokenizer.
* <p>
* If the flag argument is {@code false}, then the
* {@code sval} field is not modified.
*
* @param fl {@code true} indicates that all word tokens should
* be lowercased.
* @see java.io.StreamTokenizer#nextToken()
* @see java.io.StreamTokenizer#ttype
* @see java.io.StreamTokenizer#TT_WORD
*/
public void lowerCaseMode(boolean fl) {
forceLower = fl;
}
/** Read the next character */
private int read() throws IOException {
lastTokenEnd++;
if (reader != null)
return reader.read();
else if (input != null)
return input.read();
else
throw new IllegalStateException();
}
/**
* Parses the next token from the input stream of this tokenizer.
* The type of the next token is returned in the {@code ttype}
* field. Additional information about the token may be in the
* {@code nval} field or the {@code sval} field of this
* tokenizer.
* <p>
* Typical clients of this
* class first set up the syntax tables and then sit in a loop
* calling nextToken to parse successive tokens until TT_EOF
* is returned.
*
* @return the value of the {@code ttype} field.
* @exception IOException if an I/O error occurs.
* @see java.io.StreamTokenizer#nval
* @see java.io.StreamTokenizer#sval
* @see java.io.StreamTokenizer#ttype
*/
public int nextToken() throws IOException {
if (pushedBack) {
pushedBack = false;
return ttype;
}
byte ct[] = ctype;
sval = null;
int c = peekc;
if (c < 0)
c = NEED_CHAR;
if (c == SKIP_LF) {
c = read();
if (c < 0)
return ttype = TT_EOF;
if (c == '\n')
c = NEED_CHAR;
}
if (c == NEED_CHAR) {
c = read();
if (c < 0)
return ttype = TT_EOF;
}
ttype = c; /* Just to be safe */
/* Set peekc so that the next invocation of nextToken will read
* another character unless peekc is reset in this invocation
*/
peekc = NEED_CHAR;
int ctype = c < 256 ? ct[c] : CT_ALPHA;
while ((ctype & CT_WHITESPACE) != 0) {
if (c == '\r') {
LINENO++;
if (eolIsSignificantP) {
peekc = SKIP_LF;
return ttype = TT_EOL;
}
c = read();
if (c == '\n')
c = read();
} else {
if (c == '\n') {
LINENO++;
if (eolIsSignificantP) {
return ttype = TT_EOL;
}
}
c = read();
}
if (c < 0)
return ttype = TT_EOF;
ctype = c < 256 ? ct[c] : CT_ALPHA;
}
lastTokenStart = lastTokenEnd;
if ((ctype & CT_DIGIT) != 0) {
boolean neg = false;
if (c == '-') {
c = read();
if (c != '.' && (c < '0' || c > '9')) {
peekc = c;
return ttype = '-';
}
neg = true;
}
double v = 0;
int decexp = 0;
int seendot = 0;
while (true) {
if (c == '.' && seendot == 0)
seendot = 1;
else if ('0' <= c && c <= '9') {
v = v * 10 + (c - '0');
decexp += seendot;
} else
break;
c = read();
}
peekc = c;
if (decexp != 0) {
double denom = 10;
decexp--;
while (decexp > 0) {
denom *= 10;
decexp--;
}
/* Do one division of a likely-to-be-more-accurate number */
v = v / denom;
}
nval = neg ? -v : v;
return ttype = TT_NUMBER;
}
if ((ctype & CT_ALPHA) != 0) {
int i = 0;
do {
if (i >= buf.length) {
buf = Arrays.copyOf(buf, buf.length * 2);
}
buf[i++] = (char) c;
c = read();
ctype = c < 0 ? CT_WHITESPACE : c < 256 ? ct[c] : CT_ALPHA;
} while ((ctype & (CT_ALPHA | CT_DIGIT)) != 0);
peekc = c;
sval = String.copyValueOf(buf, 0, i);
if (forceLower)
sval = sval.toLowerCase();
return ttype = TT_WORD;
}
if ((ctype & CT_QUOTE) != 0) {
ttype = c;
int i = 0;
/* Invariants (because \Octal needs a lookahead):
* (i) c contains char value
* (ii) d contains the lookahead
*/
int d = read();
while (d >= 0 && d != ttype && d != '\n' && d != '\r') {
if (d == '\\') {
c = read();
int first = c; /* To allow \377, but not \477 */
if (c >= '0' && c <= '7') {
c = c - '0';
int c2 = read();
if ('0' <= c2 && c2 <= '7') {
c = (c << 3) + (c2 - '0');
c2 = read();
if ('0' <= c2 && c2 <= '7' && first <= '3') {
c = (c << 3) + (c2 - '0');
d = read();
} else
d = c2;
} else
d = c2;
} else {
switch (c) {
case 'a':
c = 0x7;
break;
case 'b':
c = '\b';
break;
case 'f':
c = 0xC;
break;
case 'n':
c = '\n';
break;
case 'r':
c = '\r';
break;
case 't':
c = '\t';
break;
case 'v':
c = 0xB;
break;
}
d = read();
}
} else {
c = d;
d = read();
}
if (i >= buf.length) {
buf = Arrays.copyOf(buf, buf.length * 2);
}
buf[i++] = (char)c;
}
/* If we broke out of the loop because we found a matching quote
* character then arrange to read a new character next time
* around; otherwise, save the character.
*/
peekc = (d == ttype) ? NEED_CHAR : d;
sval = String.copyValueOf(buf, 0, i);
return ttype;
}
if (c == '/' && (slashSlashCommentsP || slashStarCommentsP)) {
c = read();
if (c == '*' && slashStarCommentsP) {
int prevc = 0;
while ((c = read()) != '/' || prevc != '*') {
if (c == '\r') {
LINENO++;
c = read();
if (c == '\n') {
c = read();
}
} else {
if (c == '\n') {
LINENO++;
c = read();
}
}
if (c < 0)
return ttype = TT_EOF;
prevc = c;
}
return nextToken();
} else if (c == '/' && slashSlashCommentsP) {
while ((c = read()) != '\n' && c != '\r' && c >= 0);
peekc = c;
return nextToken();
} else {
/* Now see if it is still a single line comment */
if ((ct['/'] & CT_COMMENT) != 0) {
while ((c = read()) != '\n' && c != '\r' && c >= 0);
peekc = c;
return nextToken();
} else {
peekc = c;
return ttype = '/';
}
}
}
if ((ctype & CT_COMMENT) != 0) {
while ((c = read()) != '\n' && c != '\r' && c >= 0);
peekc = c;
return nextToken();
}
return ttype = c;
}
/**
* Causes the next call to the {@code nextToken} method of this
* tokenizer to return the current value in the {@code ttype}
* field, and not to modify the value in the {@code nval} or
* {@code sval} field.
*
* @see java.io.StreamTokenizer#nextToken()
* @see java.io.StreamTokenizer#nval
* @see java.io.StreamTokenizer#sval
* @see java.io.StreamTokenizer#ttype
*/
public void pushBack() {
if (ttype != TT_NOTHING) /* No-op if nextToken() not called */
pushedBack = true;
}
/**
* Return the current line number.
*
* @return the current line number of this stream tokenizer.
*/
public int lineno() {
return LINENO;
}
/**
* Returns the string representation of the current stream token and
* the line number it occurs on.
*
* <p>The precise string returned is unspecified, although the following
* example can be considered typical:
*
* <blockquote><pre>Token['a'], line 10</pre></blockquote>
*
* @return a string representation of the token
* @see java.io.StreamTokenizer#nval
* @see java.io.StreamTokenizer#sval
* @see java.io.StreamTokenizer#ttype
*/
public String toString() {
String ret;
switch (ttype) {
case TT_EOF:
ret = "EOF";
break;
case TT_EOL:
ret = "EOL";
break;
case TT_WORD:
ret = sval;
break;
case TT_NUMBER:
ret = "n=" + nval;
break;
case TT_NOTHING:
ret = "NOTHING";
break;
default: {
/*
* ttype is the first character of either a quoted string or
* is an ordinary character. ttype can definitely not be less
* than 0, since those are reserved values used in the previous
* case statements
*/
if (ttype < 256 &&
((ctype[ttype] & CT_QUOTE) != 0)) {
ret = sval;
break;
}
char s[] = new char[3];
s[0] = s[2] = '\'';
s[1] = (char) ttype;
ret = new String(s);
break;
}
}
return "Token[" + ret + "], line " + LINENO;
}
public long getLastTokenStart() {
return lastTokenStart;
}
public long getLastTokenEnd() {
return lastTokenEnd;
}
}