wordclock/games/tetris/bucket.c

/**
 * \addtogroup tetris
 * @{
 */

/**
 * @file bucket.c
 * @brief Implementation of Tetris' game logic.
 * @author Christian Kroll
 */

#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <stdint.h>
#include "../../compat/pgmspace.h"
#include "../../config.h"
#include "bucket.h"
#include "piece.h"

/***************************
 * non-interface functions *
 ***************************/

/**
 * detects if piece collides with s.th. at a given position
 * @param pBucket bucket to perform action on
 * @param nColumn column where the piece should be moved
 * @param nRow row where the piece should be moved
 * @return 1 for collision, 0 otherwise
 */
static uint8_t tetris_bucket_collision(tetris_bucket_t *pBucket,
                                       int8_t nCol,
                                       int8_t nRow)
{
	// A piece is represented by 16 bits (4 bits per row where the LSB marks the
	// left most position). The part of the bucket which is covered by the piece
	// is converted to this format (including the bucket borders) so that a
	// simple bitwise 'AND' tells us if the piece and the dump overlap.

	// only allow coordinates which are within sane ranges
	assert(pBucket != NULL);
	assert((nCol > -4) && (nCol < pBucket->nWidth));
	assert((nRow > -4) && (nRow < pBucket->nHeight));

	// left and right borders
	uint16_t const nPieceMap = tetris_piece_getBitmap(pBucket->pPiece);
	uint16_t nBucketPart = 0;
	if (nCol < 0)
	{
		static uint16_t const nLeftPart[] PROGMEM = {0x7777, 0x3333, 0x1111};
		nBucketPart = pgm_read_word(&nLeftPart[nCol + 3]);
	}
	else if (nCol >= pBucket->nWidth - 3)
	{
		static uint16_t const nRightPart[] PROGMEM = {0xEEEE, 0xCCCC, 0x8888};
		nBucketPart = pgm_read_word(&nRightPart[pBucket->nWidth - nCol - 1]);
	}
	// lower border
	if (nRow > pBucket->nHeight - 4)
	{
		nBucketPart |= 0xFFFF << ((pBucket->nHeight - nRow) * 4);
	}

	// return if the piece already collides with the border
	if (nPieceMap & nBucketPart)
	{
		// collision
		return 1;
	}

	// range for inspecting the piece row by row (starting at the bottom)
	int8_t const nStart = nRow + tetris_piece_getBottomOffset(nPieceMap);
	int8_t const nStop = nRow >= 0 ? nRow : 0;
	// mask those blocks which are not covered by the piece
	uint16_t const nDumpMask = nCol >= 0 ? 0x000Fu << nCol : 0x000Fu >> -nCol;
	// value for shifting blocks to the corresponding part of the piece
	int8_t nShift = 12 - nCol - 4 * (nRow + 3 - nStart);
	// compare piece with dump
	for (int8_t y = nStart; y >= nStop; --y)
	{
		uint16_t nTemp = pBucket->dump[y] & nDumpMask;
		nBucketPart |= nShift >= 0 ? nTemp << nShift : nTemp >> -nShift;
		if (nPieceMap & nBucketPart)
		{
			// collision
			return 1;
		}
		nShift -= 4;
	}

	// if we reach here, no collision was detected
	return 0;
}


/**
 * determines if piece is either hovering or gliding and sets the bucket's state
 * @param pBucket the bucket we want information from
 */
static void tetris_bucket_hoverStatus(tetris_bucket_t *pBucket)
{
	assert(pBucket != NULL);

	// status depends on whether the piece touches the dump or not
	// NOTE: 0 == TETRIS_BUS_HOVERING, 1 == TETRIS_BUS_GLIDING,
	//       tetris_bucket_collision(...) either returns 0 or 1
	pBucket->status = tetris_bucket_collision(pBucket, pBucket->nColumn,
			pBucket->nRow + 1);
}


/****************************
 * construction/destruction *
 ****************************/

tetris_bucket_t *tetris_bucket_construct(int8_t nWidth,
                                         int8_t nHeight)
{
	assert((nWidth >= 4) && (nWidth <= TETRIS_BUCKET_MAX_COLUMNS));
	assert((nHeight >= 4) && (nHeight <= TETRIS_BUCKET_MAX_ROWS));

	// allocating memory
	tetris_bucket_t *pBucket =
			(tetris_bucket_t *)malloc(sizeof(tetris_bucket_t));
	assert(pBucket != NULL);
	pBucket->dump = (uint16_t *)calloc((size_t)nHeight, sizeof(uint16_t));
	assert(pBucket->dump != NULL);

	// setting requested attributes
	pBucket->nHeight = pBucket->nFirstTaintedRow = nHeight;
	pBucket->nWidth = nWidth;

	// bit mask of a full row
	pBucket->nFullRow = 0xFFFF >> (16 - pBucket->nWidth);

	tetris_bucket_reset(pBucket);

	return pBucket;
}


/*******************************
 * bucket related functions *
 *******************************/

void tetris_bucket_reset(tetris_bucket_t *pBucket)
{
	assert(pBucket != NULL);
	assert(pBucket->dump != NULL);

	pBucket->pPiece = NULL;
	pBucket->nColumn = 0;
	pBucket->nRow = 0;
	pBucket->nRowMask = 0;
	pBucket->status = TETRIS_BUS_READY;

	// clear dump
	memset(pBucket->dump, 0, (size_t)pBucket->nHeight * sizeof(uint16_t));
}


tetris_piece_t *tetris_bucket_insertPiece(tetris_bucket_t *pBucket,
                                          tetris_piece_t *pPiece)
{
	assert((pBucket != NULL) && (pPiece != NULL));

	// a piece can only be inserted in state TETRIS_BUS_READY
	assert(pBucket->status == TETRIS_BUS_READY);

	// row mask is now meaningless
	pBucket->nRowMask = 0;

	// set horizontal start position (in the middle of the top line)
	pBucket->nColumn = (pBucket->nWidth - 2) / 2;

	// set vertical start position (first piece row with matter at pos. 1)
	pBucket->nRow =
			1 - tetris_piece_getBottomOffset(tetris_piece_getBitmap(pPiece));

	// replace old piece
	tetris_piece_t *pOldPiece = pBucket->pPiece;
	pBucket->pPiece = pPiece;

	// did we already collide with something?
	if (tetris_bucket_collision(pBucket, pBucket->nColumn, pBucket->nRow))
	{
		// game over man, game over!!
		pBucket->status = TETRIS_BUS_GAMEOVER;
	}
	else
	{
		// bring it on!
		tetris_bucket_hoverStatus(pBucket);
	}
	return pOldPiece;
}


void tetris_bucket_advancePiece(tetris_bucket_t *pBucket)
{
	assert(pBucket != NULL);
	// a piece can only be lowered if it is hovering or gliding
	assert ((pBucket->status == TETRIS_BUS_HOVERING) ||
		(pBucket->status == TETRIS_BUS_GLIDING));

	// collision detected? check if we can embed the piece into the bucket...
	if (tetris_bucket_collision(pBucket, pBucket->nColumn, pBucket->nRow + 1))
	{
		uint16_t nPieceMap = tetris_piece_getBitmap(pBucket->pPiece);
		// determine first row of the piece (skipping empty lines at the top)
		int8_t nPieceTop = pBucket->nRow + tetris_piece_getTopRow(nPieceMap);

		// Is the bucket filled up?
		if (nPieceTop < 0)
		{
			pBucket->status = TETRIS_BUS_GAMEOVER;
		}
		else
		{
			// update value for the first tainted row
			pBucket->nFirstTaintedRow = pBucket->nFirstTaintedRow > nPieceTop ?
					nPieceTop : pBucket->nFirstTaintedRow;

			// embed piece into the dump
			int8_t nStopRow = (pBucket->nRow + 3) >= pBucket->nHeight ?
					pBucket->nHeight - 1 : pBucket->nRow + 3;
			nPieceMap >>= (nPieceTop - pBucket->nRow) * 4;
			while (nPieceTop <= nStopRow)
			{
				uint16_t nTemp = nPieceMap & 0x000F;
				pBucket->dump[nPieceTop++] ^= pBucket->nColumn >= 0 ?
						nTemp << pBucket->nColumn : nTemp >> -pBucket->nColumn;
				nPieceMap >>= 4;
			}

			// the piece has finally been docked
			pBucket->status = TETRIS_BUS_DOCKED;
		}
	}
	else
	{
		// no collision: piece may continue its travel to the ground...
		pBucket->nRow++;
		// are we gliding?
		tetris_bucket_hoverStatus(pBucket);
	}
}


uint8_t tetris_bucket_movePiece(tetris_bucket_t *pBucket,
                                tetris_bucket_direction_t nDirection)
{
	assert(pBucket != NULL);

	// a piece can only be moved if it is still hovering or gliding
	assert((pBucket->status == TETRIS_BUS_HOVERING) ||
		(pBucket->status == TETRIS_BUS_GLIDING));
	// only the values of the direction enumeration are allowed
	assert((nDirection == TETRIS_BUD_LEFT) || (nDirection = TETRIS_BUD_RIGHT));

	if (tetris_bucket_collision(pBucket, pBucket->nColumn + nDirection,
			pBucket->nRow) == 0)
	{
		pBucket->nColumn += nDirection;

		// are we gliding?
		tetris_bucket_hoverStatus(pBucket);
		return 1;
	}

	return 0;
}


uint8_t tetris_bucket_rotatePiece(tetris_bucket_t *pBucket,
                                  tetris_piece_rotation_t rotation)
{
	assert(pBucket != NULL);

	// a piece can only be rotated if it is still hovering or gliding
	assert((pBucket->status == TETRIS_BUS_HOVERING) ||
			(pBucket->status == TETRIS_BUS_GLIDING));

	tetris_piece_rotate(pBucket->pPiece, rotation);

	// does the rotated piece collide with something?
	if (tetris_bucket_collision(pBucket, pBucket->nColumn, pBucket->nRow))
	{
		// in that case we revert the rotation
		tetris_piece_rotate(pBucket->pPiece, rotation == TETRIS_PC_ROT_CW ?
				TETRIS_PC_ROT_CCW : TETRIS_PC_ROT_CW);
		return 0;
	}

	// are we gliding?
	tetris_bucket_hoverStatus(pBucket);
	return 1;
}


void tetris_bucket_removeCompleteLines(tetris_bucket_t *pBucket)
{
	assert(pBucket != NULL);

	// rows can only be removed if we are in state TETRIS_BUS_DOCKED
	assert(pBucket->status == TETRIS_BUS_DOCKED);

	// bit mask (only 4 bits) that tells us if the n-th row after the
	// current nRow is complete (n-th bit set to 1, LSB represents nRow itself)
	pBucket->nRowMask = 0;

	// only consider rows which are affected by the piece (from low to high)
	//   for incomplete rows, both i and nShiftIndex will be decremented
	//   for complete rows, only i gets decremented
	int8_t nLowestRow = (pBucket->nRow + 3) < pBucket->nHeight ?
			pBucket->nRow + 3 : pBucket->nHeight - 1;
	int8_t nShiftIndex = nLowestRow;
	for (int8_t i = nLowestRow; i >= pBucket->nFirstTaintedRow; --i)
	{
		// is current row a full row?
		if ((pBucket->nFullRow & pBucket->dump[i]) == pBucket->nFullRow)
		{
			// set corresponding bit for the row mask
			pBucket->nRowMask |= 0x01 <<  (i - pBucket->nRow);
		}
		else
		{
			// if nShiftIndex and i differ, the dump has to be shifted
			if (i < nShiftIndex)
			{
				pBucket->dump[nShiftIndex] = pBucket->dump[i];
			}
			// if there were no completed lines within the range covered by the
			// piece, we don't need to look for those any further
			else if ((nLowestRow - i) >= 3)
			{
				break;
			}
			--nShiftIndex;
		}
	}
	// any completed rows removed?
	if (pBucket->nRowMask != 0)
	{
		// clear space from which the rows have been shifted away
		for (int8_t i = nShiftIndex; i >= pBucket->nFirstTaintedRow; --i)
		{
			pBucket->dump[i] = 0;
		}
		pBucket->nFirstTaintedRow = nShiftIndex + 1;
	}

	// ready to get the next piece
	pBucket->status = TETRIS_BUS_READY;
}


#ifdef GAME_BASTET

int8_t tetris_bucket_predictDeepestRow(tetris_bucket_t *pBucket,
                                       tetris_piece_t *pPiece,
                                       int8_t nStartRow,
                                       int8_t nColumn)
{
	assert(pBucket != NULL);
	assert(pPiece != NULL);
	assert(nStartRow > TETRIS_BUCKET_INVALID && nStartRow < pBucket->nHeight);
	assert(nColumn > TETRIS_BUCKET_INVALID && nColumn < pBucket->nWidth);

	// exchange current piece of the bucket (to use its collision detection)
	tetris_piece_t *pActualPiece = pBucket->pPiece;
	pBucket->pPiece = pPiece;

	// skip empty rows at the bottom of the piece which may overlap the dump
	uint16_t nMap = tetris_piece_getBitmap(pPiece);
	nStartRow -= tetris_piece_getBottomOffset(nMap);

	// check if the piece collides with one of the side borders
	if (nStartRow >= -3)
	{
		while (!tetris_bucket_collision(pBucket, nColumn, nStartRow + 1))
		{
			++nStartRow;
		}
		// bucket overflow?
		if (nStartRow < 0 && ((0xFFFF >> (((4 + nStartRow) * 4))) & nMap))
		{
			nStartRow = TETRIS_BUCKET_INVALID;
		}
	}

	// restore actual bucket piece
	pBucket->pPiece = pActualPiece;

	return nStartRow;
}


int8_t tetris_bucket_predictCompleteLines(tetris_bucket_t *pBucket,
                                          tetris_piece_t *pPiece,
                                          int8_t nRow,
                                          int8_t nColumn)
{
	assert(pBucket != NULL);
	assert(pPiece != NULL);
	assert(nRow > TETRIS_BUCKET_INVALID && nRow < pBucket->nHeight);
	assert(nColumn > TETRIS_BUCKET_INVALID && nColumn < pBucket->nWidth);

	// initialization
	int8_t nCompleteRows = 0;
	uint16_t nPieceMap = tetris_piece_getBitmap(pPiece);
	int8_t nStartRow = nRow;
	int8_t const nStopRow = (nRow + 3) >= pBucket->nHeight ?
			pBucket->nHeight - 1 : nRow + 3;
	if (nRow < 0)
	{
		nPieceMap >>= -nRow * 4;
		nStartRow = 0;
	}

	for (int8_t y = nStartRow; y <= nStopRow; ++y)
	{
		uint16_t nTemp = nPieceMap & 0x000F;
		nTemp = nColumn >= 0 ? nTemp << nColumn : nTemp >> -nColumn;
		if ((pBucket->dump[y] ^ nTemp) == pBucket->nFullRow)
		{
			++nCompleteRows;
		}
		nPieceMap >>= 4;
	}

	return nCompleteRows;
}


uint16_t* tetris_bucket_predictBottomRow(tetris_bucket_iterator_t *pIt,
                                         tetris_bucket_t *pBucket,
                                         tetris_piece_t *pPiece,
                                         int8_t nRow,
                                         int8_t nColumn)
{
	assert(pIt != NULL);
	assert(pBucket != NULL);
	assert(pPiece != NULL);
	assert(nRow > TETRIS_BUCKET_INVALID && nRow < pBucket->nHeight);
	assert(nColumn > TETRIS_BUCKET_INVALID && nColumn < pBucket->nWidth);

	pIt->pBucket = pBucket;
	pIt->nCurrentRow = pBucket->nHeight - 1;
	pIt->nRowBuffer = 0;

	pIt->nPieceMap = tetris_piece_getBitmap(pPiece);

	// determine sane start and stop values for the piece's row indices
	pIt->nPieceTopRow = nRow + tetris_piece_getTopRow(pIt->nPieceMap);
	pIt->nPieceBottomRow = nRow + tetris_piece_getBottomOffset(pIt->nPieceMap);
	if (pIt->nPieceBottomRow >= pBucket->nHeight)
	{
		pIt->nPieceBottomRow = pBucket->nHeight - 1;
	}
	// accelerate detection of full rows
	pIt->nPieceMap <<= (nRow + 3 - pIt->nPieceBottomRow) * 4;
	pIt->nShift = nColumn - 12;

	// don't return any trailing rows which are empty, so we look for a stop row
	pIt->nStopRow = pBucket->nFirstTaintedRow < pIt->nPieceTopRow ?
			pBucket->nFirstTaintedRow : pIt->nPieceTopRow;
	pIt->nStopRow = pIt->nStopRow < 0 ? 0 : pIt->nStopRow;

	return tetris_bucket_predictNextRow(pIt);
}


uint16_t* tetris_bucket_predictNextRow(tetris_bucket_iterator_t *pIt)
{
	assert(pIt != NULL);

	if (pIt->nCurrentRow >= pIt->nStopRow)
	{
		uint16_t nTemp = 0;
		// embed piece if it is there
		if ((pIt->nCurrentRow <= pIt->nPieceBottomRow) &&
				(pIt->nCurrentRow >= pIt->nPieceTopRow))
		{
			nTemp = pIt->nPieceMap & 0xF000;
			nTemp = pIt->nShift >= 0 ?
					nTemp << pIt->nShift : nTemp >> -pIt->nShift;
			pIt->nPieceMap <<= 4;
		}
		pIt->nRowBuffer = pIt->pBucket->dump[pIt->nCurrentRow--] | nTemp;
		// don't return full (and therefore removed) rows
		if (pIt->nRowBuffer == pIt->pBucket->nFullRow)
		{
			// recursively determine next (?) row instead
			return tetris_bucket_predictNextRow(pIt);
		}
		// row isn't full
		else
		{
			return &pIt->nRowBuffer;
		}
	}
	else
	{
		return NULL;
	}
}

#endif /* GAME_BASTET */
/*@}*/