scaledrafile.java

来自「纯Java的数据库」· Java 代码 · 共 525 行 · 第 1/2 页

        try {
            long fileLength = file.length();

            if (seekPosition >= fileLength) {
                return -1;
            }

            if (bufferDirty || seekPosition < bufferOffset
                    || seekPosition >= bufferOffset + buffer.length) {
                readIntoBuffer();
            } else {
                cacheHit++;
            }

            ba.reset();
            ba.skip(seekPosition - bufferOffset);

            int val = ba.read();

            seekPosition++;

            return val;
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public long readLong() throws IOException {

        try {
            if (bufferDirty || seekPosition < bufferOffset
                    || seekPosition >= bufferOffset + buffer.length) {
                readIntoBuffer();
            } else {
                cacheHit++;
            }

            ba.reset();

            if (seekPosition - bufferOffset
                    != ba.skip(seekPosition - bufferOffset)) {
                throw new EOFException();
            }

            long val;

            try {
                val = ba.readLong();
            } catch (EOFException e) {
                file.seek(seekPosition);

                val          = file.readLong();
                realPosition = file.getFilePointer();
            }

            seekPosition += 8;

            return val;
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public int readInt() throws IOException {

        try {
            if (bufferDirty || seekPosition < bufferOffset
                    || seekPosition >= bufferOffset + buffer.length) {
                readIntoBuffer();
            } else {
                cacheHit++;
            }

            ba.reset();

            if (seekPosition - bufferOffset
                    != ba.skip(seekPosition - bufferOffset)) {
                throw new EOFException();
            }

            int val;

            try {
                val = ba.readInt();
            } catch (EOFException e) {
                file.seek(seekPosition);

                val          = file.readInt();
                realPosition = file.getFilePointer();
            }

            seekPosition += 4;

            return val;
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public void read(byte[] b, int offset, int length) throws IOException {

        try {
            if (bufferDirty || seekPosition < bufferOffset
                    || seekPosition >= bufferOffset + buffer.length) {
                readIntoBuffer();
            } else {
                cacheHit++;
            }

            ba.reset();

            if (seekPosition - bufferOffset
                    != ba.skip(seekPosition - bufferOffset)) {
                throw new EOFException();
            }

            int bytesRead = ba.read(b, offset, length);

            seekPosition += bytesRead;

            if (bytesRead < length) {
                if (seekPosition != realPosition) {
                    file.seek(seekPosition);
                }

                file.readFully(b, offset + bytesRead, length - bytesRead);

                seekPosition += (length - bytesRead);
                realPosition = seekPosition;
            }
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public void write(byte[] b, int off, int len) throws IOException {

        try {
            if (realPosition != seekPosition) {
                file.seek(seekPosition);

                realPosition = seekPosition;
            }

            if (seekPosition >= bufferOffset
                    && seekPosition < bufferOffset + buffer.length) {
                bufferDirty = true;
            }

            file.write(b, off, len);

            seekPosition += len;
            realPosition = seekPosition;
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public void writeInt(int i) throws IOException {

        try {
            if (realPosition != seekPosition) {
                file.seek(seekPosition);

                realPosition = seekPosition;
            }

            if (seekPosition >= bufferOffset
                    && seekPosition < bufferOffset + buffer.length) {
                bufferDirty = true;
            }

            file.writeInt(i);

            seekPosition += 4;
            realPosition = seekPosition;
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public void writeLong(long i) throws IOException {

        try {
            if (realPosition != seekPosition) {
                file.seek(seekPosition);

                realPosition = seekPosition;
            }

            if (seekPosition >= bufferOffset
                    && seekPosition < bufferOffset + buffer.length) {
                bufferDirty = true;
            }

            file.writeLong(i);

            seekPosition += 8;
            realPosition = seekPosition;
        } catch (IOException e) {
            resetPointer();
            appLog.logContext(e, null);

            throw e;
        }
    }

    public void close() throws IOException {
        Trace.printSystemOut("cache hit " + cacheHit);
        file.close();
    }

    public boolean isReadOnly() {
        return readOnly;
    }

    public boolean wasNio() {
        return false;
    }

    public boolean canAccess(int length) {
        return true;
    }

    public boolean canSeek(long position) {
        return true;
    }

    public Database getDatabase() {
        return null;
    }

    private void resetPointer() {

        try {
            bufferDirty = true;

            file.seek(seekPosition);

            realPosition = seekPosition;
        } catch (Throwable e) {}
    }
}