/**************************************************************************
 *
 *  Copyright (c) 2019-2020 Diality Inc. - All Rights Reserved.
 *
 *  THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
 *  WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
 *
 *  @file CommBuffers.c
 *
 *  @date 08-Oct-2019
 *  @author S. Nash
 *
 *  @brief CommBuffers service module.  Provides data buffering functionality. \n
 *  Data coming in via CAN/UART Rx interrupts can be placed in a buffer to \n
 *  be processed at a later time.  Data is double buffered to prevent \n
 *  contention between Rx/Tx interrupts and the processing thread(s). \n
 *  Data to be transmitted via CAN/UART can be placed in a buffer to be sent \n
 *  when the transmitter becomes available. \n
 *  If a buffer becomes too full to service more data, a s/w fault is triggered.
 *
 **************************************************************************/

#include <string.h>     // for memcpy()

#include "CommBuffers.h"

// ********** private definitions **********

#define COMM_BUFFER_LENGTH              512     // max bytes in each comm buffer (double if you count double buffers)
#define DOUBLE_BUFFERS                  2       // need 2 buffers for double buffering

// ********** private data **********

static volatile U32 commBufferByteCount[ NUM_OF_COMM_BUFFERS ][ DOUBLE_BUFFERS ];      // for each buffer, how many bytes does it contain?  (also index to next available)
static volatile U32 activeDoubleBuffer[ NUM_OF_COMM_BUFFERS ];                         // for each buffer, which double buffer is being fed right now?
static U08 commBuffers[ NUM_OF_COMM_BUFFERS ][ DOUBLE_BUFFERS ][ COMM_BUFFER_LENGTH ]; // each is double buffered to avoid thread contention
static volatile BOOL bufferGetLock[ NUM_OF_COMM_BUFFERS ];                             // prevent getter from accessing active buffer while add in progress

// ********** private function prototypes **********

static U32 switchDoubleBuffer( COMM_BUFFER_T buffer );
static void getDataFromInactiveBuffer( COMM_BUFFER_T buffer, U08 *data, U32 len );

/*************************************************************************
 * @brief initCommBuffers
 * The initCommBuffers function initializes the CommBuffers module.
 * @details
 * Inputs : none
 * Outputs : CommBuffers module initialized.
 * @param none
 * @return none
 *************************************************************************/
void initCommBuffers( void )
{
    S32 b,d,i;

    // reset and zero out all buffers
    for ( b = 0; b < NUM_OF_COMM_BUFFERS; b++ )
    {
        activeDoubleBuffer[ b ] = 0;
        for ( d = 0; d < DOUBLE_BUFFERS; d++ )
        {
            commBufferByteCount[ b ][ d ] = 0;
            for ( i = 0; i < COMM_BUFFER_LENGTH; i++ )
            {
                commBuffers[ b ][ d ][ i ] = 0;
            }
        }
    }
}

/*************************************************************************
 * @brief addToCommBuffer
 * The addToCommBuffer function adds data of specified length to a specified \n
 * communication buffer.  S/W fault if buffer too full to add data. \n
 * This function will always add to the active double buffer. \n
 * This function should only be called from the background, general, or \n
 * priority tasks (BG or IRQ) for thread safety.
 * @details
 * Inputs : commBufferByteCount[], activeDoubleBuffer[]
 * Outputs : commBuffers[], commBufferByteCount[]
 * @param buffer : which comm buffer to add data to
 * @param data : pointer to byte array containing data to add
 * @param len : length of data (in bytes)
 * @return TRUE if data added to buffer successfully, FALSE if not
 *************************************************************************/
BOOL addToCommBuffer( COMM_BUFFER_T buffer, U08* data, U32 len )
{
    BOOL result = FALSE;

    // verify given buffer
    if ( buffer < NUM_OF_COMM_BUFFERS )
    {
        U32 activeBuffer;
        U32 currentActiveBufCount;  // where to start adding new data to buffer (after existing data)

        // add requires brief thread protection because there may be multiple sources for transmits trying to add data to a buffer.
        _disable_IRQ();
        bufferGetLock[ buffer ] = TRUE;

        activeBuffer = activeDoubleBuffer[ buffer ];
        currentActiveBufCount = commBufferByteCount[ buffer ][ activeBuffer ];

        // check to make sure buffer is not too full to service this add
        if ( len <= ( COMM_BUFFER_LENGTH - currentActiveBufCount ) )
        {
            U08 *buffPtr;  // buffer destination for added data

            // set destination pointer to end of active buffer data
            buffPtr = &commBuffers[ buffer ][ activeBuffer ][ currentActiveBufCount ];
            // copy source data to destination buffer
            memcpy( buffPtr, data, len );
            // adjust buffer count per this data add (also reserves space to add data before releasing thread protection)
            commBufferByteCount[ buffer ][ activeBuffer ] += len;
            // release thread protection
            bufferGetLock[ buffer ] = FALSE;
            _enable_IRQ();
            // data successfully added to buffer
            result = TRUE;
        }
        else // buffer too full to add this much data
        {
            // release thread protection
            bufferGetLock[ buffer ] = FALSE;
            _enable_IRQ();
            SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, SW_FAULT_ID_COMM_BUFFERS_ADD_TOO_MUCH_DATA, len )
        }
    }
    else // invalid buffer given
    {
        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, SW_FAULT_ID_COMM_BUFFERS_ADD_INVALID_BUFFER, buffer )
    }

    return result;
}

/*************************************************************************
 * @brief getFromCommBuffer
 * The getFromCommBuffer function fills a given byte array with a given \n
 * number of bytes from a given buffer and returns the number of bytes \n
 * retrieved from the buffer. This function will draw from the inactive \n
 * double buffer first and, if needed, switch double buffers to draw the \n
 * rest of the requested data.
 * Only one function in one thread should be calling this function for a given \n
 * buffer.
 * @details
 * Inputs : commBuffers[], commBufferByteCount[], activeDoubleBuffer[]
 * Outputs : commBuffers[], commBufferByteCount[], activeDoubleBuffer[], \n
 * and the given data array is populated with data from the buffer.
 * @param buffer : which comm buffer to retrieve data from
 * @param data : pointer to byte array to stuff data into
 * @param len : # of bytes to retrieve into given data array.
 * @return the number of bytes retrieved.
 *************************************************************************/
U32 getFromCommBuffer( COMM_BUFFER_T buffer, U08* data, U32 len )
{
    U32 result = 0;

    // verify given buffer
    if ( buffer < NUM_OF_COMM_BUFFERS )
    {
        // verify requested # of bytes to get are in the buffer
        if ( ( len <= ( COMM_BUFFER_LENGTH * DOUBLE_BUFFERS ) ) && ( len <= numberOfBytesInCommBuffer( buffer ) ) )
        {
            U32 activeBuffer = activeDoubleBuffer[ buffer ];
            U32 inactiveBuffer = ( activeBuffer == 0 ? 1 : 0 );
            U32 bytesInInactiveBuffer = commBufferByteCount[ buffer ][ inactiveBuffer ];
            U32 sizeOfFirstConsumption = MIN( len, bytesInInactiveBuffer );

            // see what we can get from inactive buffer
            getDataFromInactiveBuffer( buffer, data, sizeOfFirstConsumption );  // will switch double buffers if we empty inactive buffer
            // will return # of bytes consumed
            result = sizeOfFirstConsumption;
            // do we need more from active buffer?
            if ( len > bytesInInactiveBuffer )
            {
                U32 remNumOfBytes = len - sizeOfFirstConsumption;
                U08 *remPtr = data + sizeOfFirstConsumption;

                getDataFromInactiveBuffer( buffer, remPtr, remNumOfBytes );
                // will return # of bytes consumed
                result += remNumOfBytes;
            }
        }
    }
    else // invalid buffer given
    {
        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, SW_FAULT_ID_COMM_BUFFERS_GET_INVALID_BUFFER, buffer )
    }

    return result;
}

/*************************************************************************
 * @brief peekFromCommBuffer
 * The peekFromCommBuffer function fills a given byte array with a given \n
 * number of bytes from a given buffer.  This function does NOT consume \n
 * the bytes - it only peeks at them. A call to numberOfBytesInCommBuffer() \n
 * should be made before calling this function to determine how many bytes \n
 * are currently in the buffer.  Do not call this function with a "len" \n
 * longer than what is currently in the buffer.
 * @details
 * Inputs : commBuffers[], commBufferByteCount[], activeDoubleBuffer[]
 * Outputs : given array populated with requested # of bytes from the buffer.
 * @param buffer : which comm buffer to retrieve data from
 * @param data : pointer to byte array to stuff data into
 * @param len : # of bytes to retrieve into given data array.
 * @return the number of bytes retrieved.
 *************************************************************************/
U32 peekFromCommBuffer( COMM_BUFFER_T buffer, U08 *data, U32 len )
{
    U32  numOfBytesPeeked = 0;

    // verify given buffer
    if ( buffer < NUM_OF_COMM_BUFFERS )
    {
        // verify requested # of bytes to peek are in the buffer
        if ( ( len <= ( COMM_BUFFER_LENGTH * DOUBLE_BUFFERS ) ) && ( len <= numberOfBytesInCommBuffer( buffer ) ) )
        {
            U32 activeBuffer = activeDoubleBuffer[ buffer ];
            U32 inactiveBuffer = ( activeBuffer == 0 ? 1 : 0 );
            U32 bytesInInactiveBuffer = commBufferByteCount[ buffer ][ inactiveBuffer ];

            if ( len <= bytesInInactiveBuffer )
            {
                memcpy( data, &commBuffers[ buffer ][ inactiveBuffer ][ 0 ], len );
                numOfBytesPeeked = len;
            }
            else // will need to get the rest from active buffer
            {
                U32 remNumOfBytes = len - bytesInInactiveBuffer;
                U08 *remPtr = data + bytesInInactiveBuffer;

                memcpy( data, &commBuffers[ buffer ][ inactiveBuffer ][ 0 ], bytesInInactiveBuffer );
                memcpy( remPtr, &commBuffers[ buffer ][ activeBuffer ][ 0 ], remNumOfBytes );
                numOfBytesPeeked = bytesInInactiveBuffer + remNumOfBytes;
            }
        }
    }
    else // invalid buffer given
    {
        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, SW_FAULT_ID_COMM_BUFFERS_PEEK_INVALID_BUFFER, buffer )
    }

    return numOfBytesPeeked;
}

/*************************************************************************
 * @brief numberOfBytesInCommBuffer
 * The numberOfBytesInCommBuffer function determines how many bytes \n
 * are currently contained in a given comm buffer.  Both double buffers \n
 * are considered for this.
 * @details
 * Inputs : activeDoubleBuffer[], commBufferByteCount[]
 * Outputs : none
 * @param buffer : which comm buffer to get byte count for
 * @return the number of bytes in the given comm buffer.
 *************************************************************************/
U32 numberOfBytesInCommBuffer( COMM_BUFFER_T buffer )
{
    U32 result = 0;

    // verify given buffer
    if ( buffer < NUM_OF_COMM_BUFFERS )
    {
        U32 activeBuffer = activeDoubleBuffer[ buffer ];
        U32 inactiveBuffer = GET_TOGGLE( activeBuffer, 0, 1 );

        if ( FALSE == bufferGetLock[ buffer ] )
        {
            result = commBufferByteCount[ buffer ][ inactiveBuffer ] + commBufferByteCount[ buffer ][ activeBuffer ];
        }
        else
        {
            result = commBufferByteCount[ buffer ][ inactiveBuffer ];
        }
    }
    else // invalid buffer
    {
        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_SOFTWARE_FAULT, SW_FAULT_ID_COMM_BUFFERS_COUNT_INVALID_BUFFER, buffer )
    }

    return result;
}

/*************************************************************************
 * @brief switchDoubleBuffer
 * The switchDoubleBuffer function switches the active and inactive buffers \n
 * for the given buffer. \n
 * This function should only be called when the current inactive buffer has \n
 * been emptied.  Any unconsumed data in inactive buffer will be lost.
 * @details
 * Inputs : activeDoubleBuffer[]
 * Outputs : activeDoubleBuffer[], commBufferByteCount[]
 * @param buffer : which comm buffer to switch double buffers on
 * @return the new active buffer for the given buffer.
 *************************************************************************/
static U32 switchDoubleBuffer( COMM_BUFFER_T buffer )
{
    U32 activeBuffer = activeDoubleBuffer[ buffer ];
    U32 inactiveBuffer = ( activeBuffer == 0 ? 1 : 0 );

    // ensure inactive buffer is reset before making active
    commBufferByteCount[ buffer ][ inactiveBuffer ] = 0;
    // switch buffers
    activeDoubleBuffer[ buffer ] = inactiveBuffer;

    // return the new active buffer (was just inactive)
    return inactiveBuffer;
}

/*************************************************************************
 * @brief getDataFromInactiveBuffer
 * The getDataFromInactiveBuffer function retrieves a given number of bytes \n
 * from the inactive buffer of a given buffer.  This function should only be \n
 * called by getFromCommBuffer().  Params will be pre-validated there.
 * @details
 * Inputs : commBuffers[], activeDoubleBuffer[], commBufferByteCount[]
 * Outputs : commBuffers[], activeDoubleBuffer[], commBufferByteCount[]
 * @param buffer : which comm buffer get data from
 * @param data : pointer to byte array to populate with data
 * @param len : # of bytes to get from comm buffer
 * @return none
 *************************************************************************/
static void getDataFromInactiveBuffer( COMM_BUFFER_T buffer, U08 *data, U32 len )
{
    U32 activeBuffer = activeDoubleBuffer[ buffer ];
    U32 inactiveBuffer = ( activeBuffer == 0 ? 1 : 0 );
    U32 bytesInInactiveBuffer = commBufferByteCount[ buffer ][ inactiveBuffer ];

    // get the requested data from inactive buffer
    memcpy( data, &commBuffers[ buffer ][ inactiveBuffer ][ 0 ], len );

    if ( len < bytesInInactiveBuffer )
    {
        U08 *endPtr = (&commBuffers[ buffer ][ inactiveBuffer ][ 0 ] + len);

        // move un-consumed data in inactive buffer to start of inactive buffer
        memcpy( &commBuffers[ buffer ][ inactiveBuffer ][ 0 ], endPtr, ( bytesInInactiveBuffer - len ) );
        // reduce byte count for inactive buffer by # of bytes consumed
        commBufferByteCount[ buffer ][ inactiveBuffer ] -= len;
    }
    else
    {
        // inactive buffer has been emptied so switch double buffers
        switchDoubleBuffer( buffer );  // switch will zero count off inactive buffer
    }
}