Unclear algorithm for StaticBuffer::setDirtyBit

[SaintNerevar]

The algorithm doesn't state what happens if the call to StaticBuffer::getBufferNum fails i.e the block in question isn't in the buffer. If this scenario never happens due to design, the docs should make it clear.

[gokulsreekumar]

OLD:

int StaticBuffer::setDirtyBit(int blockNum) {
    // Check if blockNum is valid (non zero and less than number of disk blocks)
    // and return E_OUTOFBOUND if not valid.

    // find the buffer number corresponding to the block using getBufferNum().

    // set the dirty flag of that buffer in metaInfo to true

    // return SUCCESS

}

POSSIBLE NEW CHANGE:

int StaticBuffer::setDirtyBit(int blockNum) {
    // Check if blockNum is valid (non zero and less than number of disk blocks)
    // and return E_OUTOFBOUND if not valid.

    // find the buffer number corresponding to the block using getBufferNum().
          // if it returns FAILURE, then Block is not loaded to any buffer. Hence return FAILURE (or a new ERROR?).

    // set the dirty flag of that buffer in metaInfo to true

    // return SUCCESS

}

Note:

• I think this check should be placed, because, by proper design it may not happen, but, if student is calling setDirtyBit in static buffer without allocating buffer in first place, then throwing such an error will be easier for them to debug. Also helps in making the method complete in itself.

[gokulsreekumar]

@jessiyajoy please verify

[gokulsreekumar]

Do setDirtyBit function has to be public? is it being called anywhere else, other than its friend classes.

[jessiyajoy]

@jessiyajoy please verify

Return E_BLOCKNOTINBUFFER(new constant to be added)

[gokulsreekumar]

• New Algo returns two error conditions
• The caller of this method will return that error code to upper layer

  int StaticBuffer::setDirtyBit(int blockNum) {
  //find the buffer index corresponding to the block using the getBufferNum().
  int ret = getBufferNum(blockNum);
  // if Buffer is valid, bufferNum != E_BLOCKNOTINBUFFER
  if (ret != E_BLOCKNOTINBUFFER) {
      int bufferNum = ret;
      // set the dirty bit of that buffer in the metaInfo to true.
      metainfo[bufferNum].dirty = true;
  } else {
      // E_OUTOFBOUND - blockNum is invalid
      // E_BLOCKNOTINBUFFER - block with blockNum is not present in Buffer
      return ret;
  }
  // return SUCCESS
  return SUCCESS;
  }