001: /*
002: * gnu/regexp/REFilterInputStream.java
003: * Copyright (C) 1998 Wes Biggs
004: *
005: * This library is free software; you can redistribute it and/or modify
006: * it under the terms of the GNU Library General Public License as published
007: * by the Free Software Foundation; either version 2 of the License, or
008: * (at your option) any later version.
009: *
010: * This library is distributed in the hope that it will be useful,
011: * but WITHOUT ANY WARRANTY; without even the implied warranty of
012: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
013: * GNU Library General Public License for more details.
014: *
015: * You should have received a copy of the GNU Library General Public License
016: * along with this program; if not, write to the Free Software
017: * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
018: */
019:
020: package gnu.regexp;
021:
022: import java.io.FilterInputStream;
023: import java.io.InputStream;
024:
025: /**
026: * Replaces instances of a given RE with replacement text.
027: *
028: * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A>
029: * @since gnu.regexp 1.0.5
030: */
031:
032: public class REFilterInputStream extends FilterInputStream {
033:
034: private RE m_expr;
035: private String m_replace;
036: private String m_buffer;
037: private int m_bufpos;
038: private int m_offset;
039: private CharIndexedInputStream m_stream;
040:
041: /**
042: * Creates an REFilterInputStream. When reading from this stream,
043: * occurrences of patterns matching the supplied regular expression
044: * will be replaced with the supplied replacement text (the
045: * metacharacters $0 through $9 may be used to refer to the full
046: * match or subexpression matches.
047: *
048: * @param f_stream The InputStream to be filtered.
049: * @param f_expr The regular expression to search for.
050: * @param f_replace The text pattern to replace matches with.
051: */
052: public REFilterInputStream(InputStream f_stream, RE f_expr,
053: String f_replace) {
054: super (f_stream);
055: m_stream = new CharIndexedInputStream(f_stream, 0);
056: m_expr = f_expr;
057: m_replace = f_replace;
058: }
059:
060: /**
061: * Reads the next byte from the stream per the general contract of
062: * InputStream.read(). Returns -1 on error or end of stream.
063: */
064: public int read() {
065: // If we have buffered replace data, use it.
066: if ((m_buffer != null) && (m_bufpos < m_buffer.length())) {
067: return (int) m_buffer.charAt(m_bufpos++);
068: }
069:
070: // check if input is at a valid position
071: if (!m_stream.isValid())
072: return -1;
073:
074: REMatch mymatch = new REMatch(m_expr.getNumSubs(), m_offset);
075: int[] result = m_expr.match(m_stream, 0, 0, mymatch);
076: if (result != null) {
077: mymatch.end[0] = result[0];
078: mymatch.finish(m_stream);
079: m_stream.move(mymatch.toString().length());
080: m_offset += mymatch.toString().length();
081: m_buffer = mymatch.substituteInto(m_replace);
082: m_bufpos = 1;
083:
084: // This is prone to infinite loops if replace string turns out empty.
085: return m_buffer.charAt(0);
086: } else {
087: char ch = m_stream.charAt(0);
088: if (ch == CharIndexed.OUT_OF_BOUNDS)
089: return -1;
090: m_stream.move(1);
091: m_offset++;
092: return ch;
093: }
094: }
095:
096: /**
097: * Returns false. REFilterInputStream does not support mark() and
098: * reset() methods.
099: */
100: public boolean markSupported() {
101: return false;
102: }
103:
104: /** Reads from the stream into the provided array. */
105: public int read(byte[] b, int off, int len) {
106: int i;
107: int ok = 0;
108: while (len-- > 0) {
109: i = read();
110: if (i == -1)
111: return (ok == 0) ? -1 : ok;
112: b[off++] = (byte) i;
113: ok++;
114: }
115: return ok;
116: }
117:
118: /** Reads from the stream into the provided array. */
119: public int read(byte[] b) {
120: return read(b, 0, b.length);
121: }
122: }
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