textcache.java

纯Java的数据库

        if (row != null) {
            return;
        }

        row = cache.release(pos);

        clearRowImage(row);
        release(pos);
    }

    private void clearRowImage(CachedObject row) throws IOException {

        int length = row.getStorageSize()
                     - ScriptWriterText.BYTES_LINE_SEP.length;

        rowOut.reset();

        HsqlByteArrayOutputStream out = rowOut.getOutputStream();

        out.fill(' ', length);
        out.write(ScriptWriterText.BYTES_LINE_SEP);
        dataFile.seek(row.getPos());
        dataFile.write(out.getBuffer(), 0, out.size());
    }

    public synchronized void removePersistence(int pos,
            PersistentStore store) throws IOException {

        CachedObject row = (CachedObject) uncommittedCache.get(pos);

        if (row != null) {
            return;
        }

        row = cache.get(pos);

        clearRowImage(row);
    }

    protected synchronized RowInputInterface readObject(int pos)
    throws IOException {

        ByteArray buffer   = new ByteArray(80);
        boolean   complete = false;
        boolean   wasCR    = false;
        int       c;
        boolean   hasQuote  = false;
        boolean   wasNormal = false;

        pos = findNextUsedLinePos(pos);

        if (pos == -1) {
            return null;
        }

        dataFile.seek(pos);

        while (!complete) {
            wasNormal = false;
            c         = dataFile.read();

            if (c == -1) {
                if (buffer.length() == 0) {
                    return null;
                }

                complete = true;

                if (wasCR) {
                    break;
                }

                if (!cacheReadonly) {
                    dataFile.write(ScriptWriterText.BYTES_LINE_SEP, 0,
                                   ScriptWriterText.BYTES_LINE_SEP.length);
                }

                break;
            }

            switch (c) {

                case DOUBLE_QUOTE_CHAR :
                    wasNormal = true;
                    complete  = wasCR;
                    wasCR     = false;

                    if (isQuoted) {
                        hasQuote = !hasQuote;
                    }
                    break;

                case CR_CHAR :
                    wasCR = !hasQuote;
                    break;

                case LF_CHAR :
                    complete = !hasQuote;
                    break;

                default :
                    wasNormal = true;
                    complete  = wasCR;
                    wasCR     = false;
            }

            buffer.append(c);
        }

        if (complete) {
            int length = (int) dataFile.getFilePointer() - pos;

            if (wasNormal) {
                length--;
            }

            ((RowInputText) rowIn).setSource(buffer.toString(), pos, length);

            return rowIn;
        }

        return null;
    }

    public int readHeaderLine() throws HsqlException {

        boolean   complete  = false;
        boolean   wasCR     = false;
        boolean   wasNormal = false;
        ByteArray buffer    = new ByteArray(80);

        while (!complete) {
            wasNormal = false;

            int c;

            try {
                c = dataFile.read();

                if (c == -1) {
                    if (buffer.length() == 0) {
                        return 0;
                    }

                    complete = true;

                    if (!cacheReadonly) {
                        dataFile.write(ScriptWriterText.BYTES_LINE_SEP, 0,
                                       ScriptWriterText.BYTES_LINE_SEP.length);
                    }

                    break;
                }
            } catch (IOException e) {
                throw Trace.error(Trace.TEXT_FILE);
            }

            switch (c) {

                case CR_CHAR :
                    wasCR = true;
                    break;

                case LF_CHAR :
                    complete = true;
                    break;

                default :
                    wasNormal = true;
                    complete  = wasCR;
                    wasCR     = false;
            }

            buffer.append(c);
        }

        header = buffer.toString();

        try {
            int length = (int) dataFile.getFilePointer();

            if (wasNormal) {
                length--;
            }

            return length;
        } catch (IOException e) {
            throw Trace.error(Trace.TEXT_FILE);
        }
    }

    // fredt - new method

    /**
     * Searches from file pointer, pos, and finds the beginning of the first
     * line that contains any non-space character. Increments the row counter
     * when a blank line is skipped.
     *
     * If none found return -1
     */
    int findNextUsedLinePos(int pos) throws IOException {

        int     firstPos   = pos;
        int     currentPos = pos;
        boolean wasCR      = false;

        dataFile.seek(pos);

        while (true) {
            int c = dataFile.read();

            currentPos++;

            switch (c) {

                case CR_CHAR :
                    wasCR = true;
                    break;

                case LF_CHAR :
                    wasCR = false;

                    ((RowInputText) rowIn).skippedLine();

                    firstPos = currentPos;
                    break;

                case ' ' :
                    if (wasCR) {
                        wasCR = false;

                        ((RowInputText) rowIn).skippedLine();
                    }
                    break;

                case -1 :
                    return -1;

                default :
                    return firstPos;
            }
        }
    }

    public synchronized void add(CachedObject object) throws IOException {
        super.add(object);
        clearRowImage(object);
    }

    public synchronized CachedObject get(int i, PersistentStore store,
                                         boolean keep) throws HsqlException {

        if (i < 0) {
            return null;
        }

        CachedObject o = (CachedObject) uncommittedCache.get(i);

        if (o == null) {
            o = super.get(i, store, keep);
        }

/*
        if (o == null) {
            o = super.get(i, store, keep);
        }
*/
        return o;
    }

    /**
     * This is called internally when old rows need to be removed from the
     * cache. Text table rows that have not been saved are those that have not
     * been committed yet. So we don't save them but add them to the
     * uncommitted cache until such time that they are committed or rolled
     * back- fredt
     */
    protected synchronized void saveRows(CachedObject[] rows, int offset,
                                         int count) throws IOException {

        if (count == 0) {
            return;
        }

        for (int i = offset; i < offset + count; i++) {
            CachedObject r = rows[i];

            uncommittedCache.put(r.getPos(), r);

            rows[i] = null;
        }
    }

    /**
     * In case the row has been moved to the uncommittedCache, removes it.
     * Then saves the row as normal.
     */
    public synchronized void saveRow(CachedObject row) throws IOException {
        uncommittedCache.remove(row.getPos());
        super.saveRow(row);
    }

    public String getHeader() {
        return header;
    }

    public void setHeader(String header) throws HsqlException {

        if (ignoreFirst && fileFreePosition == 0) {
            try {
                writeHeader(header);

                this.header = header;
            } catch (IOException e) {
                throw new HsqlException(
                    e, Trace.getMessage(Trace.GENERAL_IO_ERROR),
                    Trace.GENERAL_IO_ERROR);
            }

            return;
        }

        throw Trace.error(Trace.TEXT_TABLE_HEADER);
    }

    private void writeHeader(String header) throws IOException {

        byte[] buf       = null;
        String firstLine = header + NL;

        try {
            buf = firstLine.getBytes(stringEncoding);
        } catch (UnsupportedEncodingException e) {
            buf = firstLine.getBytes();
        }

        dataFile.write(buf, 0, buf.length);

        fileFreePosition = buf.length;
    }

    private class ByteArray {

        private byte[] buffer;
        private int    buflen;

        public ByteArray(int n) {
            buffer = new byte[n];
            buflen = 0;
        }

        public void append(int c) {

            if (buflen >= buffer.length) {
                byte[] newbuf = new byte[buflen + 80];

                System.arraycopy(buffer, 0, newbuf, 0, buflen);

                buffer = newbuf;
            }

            buffer[buflen] = (byte) c;

            buflen++;
        }

        public int length() {
            return buflen;
        }

        public void setLength(int l) {
            buflen = l;
        }

        public String toString() {

            try {
                return new String(buffer, 0, buflen, stringEncoding);
            } catch (UnsupportedEncodingException e) {
                return new String(buffer, 0, buflen);
            }
        }
    }

    public int getLineNumber() {
        return ((RowInputText) rowIn).getLineNumber();
    }

    protected void setFileModified() throws IOException {
        fileModified = true;
    }
}