Susimail: Add RegexOutputStream util

WIP, prep for enhancements to follow

apps/susimail/src/src/i2p/susi/util/RegexOutputStream.java

@@ -0,0 +1,143 @@
+package i2p.susi.util;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import net.i2p.I2PAppContext;
+import net.i2p.data.DataHelper;
+import net.i2p.util.Log;
+
+/**
+ * Replace patterns with a simple regex on the fly.
+ *
+ * @since 0.9.62
+ */
+public class RegexOutputStream extends FilterOutputStream {
+    
+    private final String match, repl;
+    /** parse in progress */
+    private final StringBuilder buf;
+    private final String noMatch;
+    private final Log _log;
+    private boolean found;
+    int idx;
+
+    /**
+     *  @param out MUST be buffered because this writes one byte at a time
+     *  @param pattern the only special char recognized is '*' and cannot be at the beginning or end
+     *                 or have two in a row. ASCII-only, no UTF-8.
+     *  @param replace ASCII-only, no UTF-8.
+     *  @param onNoMatch force output of this at the end if no replacement made, or null
+     */
+    public RegexOutputStream(OutputStream out, String pattern, String replace, String onNoMatch) {
+        super(out);
+        if (pattern.length() == 0 || pattern.startsWith("*") || pattern.endsWith("*") || pattern.contains("**"))
+            throw new IllegalArgumentException();
+        match = pattern;
+        repl = replace;
+        noMatch = onNoMatch;
+        buf = new StringBuilder(64);
+	_log = I2PAppContext.getGlobalContext().logManager().getLog(RegexOutputStream.class);
+        if (_log.shouldDebug())
+            _log.debug("New regex replace '" + match + "' with '" + repl + "'");
+    }
+    
+    @Override
+    public void write(int val) throws IOException {
+        char c = (char) val;
+        char m = match.charAt(idx);
+        if (c == '\r' || c == '\n') {
+            flushit();
+            out.write(val);
+        } else if (m == '*') {
+            pushit(c);
+            char d = match.charAt(idx + 1);
+            if (c == d) {
+                idx += 2;
+                if (idx == match.length()) {
+                    replaceit();
+                    found = true;
+                }
+            }
+        } else if (m == c) {
+            pushit(c);
+            idx++;
+            if (idx == match.length()) {
+                replaceit();
+                found = true;
+            }
+        } else {
+            flushit();
+            out.write(val);
+        }
+    }
+
+
+    /**
+     *  put in the pending parse buf
+     */
+    private void pushit(char c) {
+        buf.append(c);
+        //if (_log.shouldDebug())
+        //    _log.debug("Push, buf now '" + buf + "'");
+    }
+
+    /**
+     *  flush buf to out, start over
+     */
+    private void flushit() throws IOException {
+        int len = buf.length();
+        if (len > 0) {
+            for (int i = 0; i < len; i++) {
+                out.write(buf.charAt(i));
+            }
+            clearit();
+        }
+        //if (_log.shouldDebug())
+        //    _log.debug("Flush");
+    }
+    /**
+     *  Throw out inbuf, output replacement, start over
+     */
+    private void replaceit() throws IOException {
+        int len = repl.length();
+        if (len > 0) {
+            for (int i = 0; i < len; i++) {
+                out.write(repl.charAt(i));
+            }
+        }
+        if (_log.shouldInfo())
+            _log.info("Replaced '" + match + "' with '" + repl + "' buf: '" + buf + "'");
+        clearit();
+    }
+
+    /**
+     *  Start over
+     */
+    private void clearit() {
+        buf.setLength(0);
+        idx = 0;
+    }
+
+    @Override
+    public void close() throws IOException {
+        flushit();
+        if (!found && noMatch != null) {
+            if (_log.shouldInfo())
+                _log.info("No match, appending '" + noMatch + "'");
+            out.write(DataHelper.getASCII(noMatch));
+        }
+        super.close();
+    }
+
+/****
+*/
+    public static void main(String[] args) throws Exception {
+        OutputStream out = new RegexOutputStream(System.out, args[0], args[1], null);
+        net.i2p.data.DataHelper.copy(System.in, out);
+        out.flush();
+    }
+/*
+****/
+}