/*********************************************************************
*               SEGGER MICROCONTROLLER GmbH & Co. KG                 *
*       Solutions for real time microcontroller applications         *
**********************************************************************
*                                                                    *
*       (c) 2014 - 2015  SEGGER Microcontroller GmbH & Co. KG        *
*                                                                    *
*       www.segger.com     Support: support@segger.com               *
*                                                                    *
**********************************************************************
*                                                                    *
* All rights reserved.                                               *
*                                                                    *
* * This software may in its unmodified form be freely redistributed *
*   in source form.                                                  *
* * The source code may be modified, provided the source code        *
*   retains the above copyright notice, this list of conditions and  *
*   the following disclaimer.                                        *
* * Modified versions of this software in source or linkable form    *
*   may not be distributed without prior consent of SEGGER.          *
* * This software may only be used for communication with SEGGER     *
*   J-Link debug probes.                                             *
*                                                                    *
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND             *
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,        *
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF           *
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE           *
* DISCLAIMED. IN NO EVENT SHALL SEGGER Microcontroller BE LIABLE FOR *
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR           *
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT  *
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;    *
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF      *
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT          *
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE  *
* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH   *
* DAMAGE.                                                            *
*                                                                    *
**********************************************************************
---------------------------END-OF-HEADER------------------------------
File    : SEGGER_RTT.c
Purpose : Implementation of SEGGER real-time transfer (RTT) which
          allows real-time communication on targets which support
          debugger memory accesses while the CPU is running.

Additional information:
          Type "int" is assumed to be 32-bits in size
          H->T    Host to target communication
          T->H    Target to host communication

          RTT channel 0 is always present and reserved for Terminal usage.
          Name is fixed to "Terminal"

----------------------------------------------------------------------
*/

#include "SEGGER_RTT.h"

#include <string.h>                 // for memcpy

/*********************************************************************
*
*       Configuration, default values
*
**********************************************************************
*/

#ifndef   BUFFER_SIZE_UP
  #define BUFFER_SIZE_UP                                  1024  // Size of the buffer for terminal output of target, up to host
#endif

#ifndef   BUFFER_SIZE_DOWN
  #define BUFFER_SIZE_DOWN                                16    // Size of the buffer for terminal input to target from host (Usually keyboard input)
#endif

#ifndef   SEGGER_RTT_MAX_NUM_UP_BUFFERS
  #define SEGGER_RTT_MAX_NUM_UP_BUFFERS                    2    // Number of up-buffers (T->H) available on this target
#endif

#ifndef   SEGGER_RTT_MAX_NUM_DOWN_BUFFERS
  #define SEGGER_RTT_MAX_NUM_DOWN_BUFFERS                  2    // Number of down-buffers (H->T) available on this target
#endif

#ifndef   SEGGER_RTT_MODE_DEFAULT
  #define SEGGER_RTT_MODE_DEFAULT                         SEGGER_RTT_MODE_NO_BLOCK_SKIP
#endif

#ifndef   SEGGER_RTT_LOCK
  #define SEGGER_RTT_LOCK(SavedState)
#endif

#ifndef   SEGGER_RTT_UNLOCK
  #define SEGGER_RTT_UNLOCK(SavedState)
#endif

#ifndef   STRLEN
  #define STRLEN(a)                                       strlen((a))
#endif

#ifndef   MEMCPY
  #define MEMCPY(pDest, pSrc, NumBytes)                   memcpy((pDest), (pSrc), (NumBytes))
#endif

#ifndef   MIN
  #define MIN(a, b)         (((a) < (b)) ? (a) : (b))
#endif

#ifndef   MAX
  #define MAX(a, b)         (((a) > (b)) ? (a) : (b))
#endif
//
// For some environments, NULL may not be defined until certain headers are included
//
#ifndef NULL
  #define NULL 0
#endif

/*********************************************************************
*
*       Static const data
*
**********************************************************************
*/

static unsigned char _aTerminalId[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

/*********************************************************************
*
*       Static data
*
**********************************************************************
*/
//
// Allocate buffers for channel 0
//
static char _acUpBuffer  [BUFFER_SIZE_UP];
static char _acDownBuffer[BUFFER_SIZE_DOWN];
//
// Initialize SEGGER Real-time-Terminal control block (CB)
//
SEGGER_RTT_CB _SEGGER_RTT;

static char _ActiveTerminal;

/*********************************************************************
*
*       Static functions
*
**********************************************************************
*/

/*********************************************************************
*
*       _DoInit()
*
*  Function description
*    Initializes the control block an buffers.
*    May only be called via INIT() to avoid overriding settings.
*
*/
#define INIT()  do {                                            \
                  if (_SEGGER_RTT.acID[0] == '\0') { _DoInit(); }  \
                } while (0)
static void _DoInit(void) {
  SEGGER_RTT_CB* p;
  //
  // Initialize control block
  //
  p = &_SEGGER_RTT;
  p->MaxNumUpBuffers    = SEGGER_RTT_MAX_NUM_UP_BUFFERS;
  p->MaxNumDownBuffers  = SEGGER_RTT_MAX_NUM_DOWN_BUFFERS;
  //
  // Initialize up buffer 0
  //
  p->aUp[0].sName         = "Terminal";
  p->aUp[0].pBuffer       = _acUpBuffer;
  p->aUp[0].SizeOfBuffer  = sizeof(_acUpBuffer);
  p->aUp[0].RdOff         = 0u;
  p->aUp[0].WrOff         = 0u;
  p->aUp[0].Flags         = SEGGER_RTT_MODE_DEFAULT;
  //
  // Initialize down buffer 0
  //
  p->aDown[0].sName         = "Terminal";
  p->aDown[0].pBuffer       = _acDownBuffer;
  p->aDown[0].SizeOfBuffer  = sizeof(_acDownBuffer);
  p->aDown[0].RdOff         = 0u;
  p->aDown[0].WrOff         = 0u;
  p->aDown[0].Flags         = SEGGER_RTT_MODE_DEFAULT;
  //
  // Finish initialization of the control block.
  // Copy Id string in three steps to make sure "SEGGER RTT" is not found
  // in initializer memory (usually flash) by J-Link
  //
  strcpy(&p->acID[7], "RTT");
  strcpy(&p->acID[0], "SEGGER");
  p->acID[6] = ' ';
}

/*********************************************************************
*
*       _WriteBlocking()
*
*  Function description
*    Stores a specified number of characters in SEGGER RTT ring buffer
*    and updates the associated write pointer which is periodically
*    read by the host.
*    The caller is responsible for managing the write chunk sizes as
*    _WriteBlocking() will block until all data has been posted successfully.
*
*  Parameters
*    pRing        Ring buffer to post to.
*    pBuffer      Pointer to character array. Does not need to point to a \0 terminated string.
*    NumBytes     Number of bytes to be stored in the SEGGER RTT control block.
*
*  Return value
*    >= 0 - Number of bytes written into buffer.
*/
static unsigned _WriteBlocking(SEGGER_RTT_RING_BUFFER *pRing, const char* pBuffer, unsigned NumBytes) {
  unsigned NumBytesToWrite;
  unsigned NumBytesWritten;
  unsigned RdOff;
  unsigned WrOff;
  //
  // Write data to buffer and handle wrap-around if necessary
  //
  NumBytesWritten = 0u;
  WrOff = pRing->WrOff;
  do {
    RdOff = pRing->RdOff;                         // May be changed by host (debug probe) in the meantime
    if (RdOff > WrOff) {
      NumBytesToWrite = RdOff - WrOff - 1u;
    } else {
      NumBytesToWrite = pRing->SizeOfBuffer - (WrOff - RdOff + 1u);
    }
    NumBytesToWrite = MIN(NumBytesToWrite, (pRing->SizeOfBuffer - WrOff));      // Number of bytes that can be written until buffer wrap-around
    NumBytesToWrite = MIN(NumBytesToWrite, NumBytes);
    memcpy(pRing->pBuffer + WrOff, pBuffer, NumBytesToWrite);
    NumBytesWritten += NumBytesToWrite;
    pBuffer         += NumBytesToWrite;
    NumBytes        -= NumBytesToWrite;
    WrOff           += NumBytesToWrite;
    if (WrOff == pRing->SizeOfBuffer) {
      WrOff = 0u;
    }
    pRing->WrOff = WrOff;
  } while (NumBytes);
  //
  return NumBytesWritten;
}

/*********************************************************************
*
*       _WriteNoCheck()
*
*  Function description
*    Stores a specified number of characters in SEGGER RTT ring buffer
*    and updates the associated write pointer which is periodically
*    read by the host.
*    It is callers responsibility to make sure data actually fits in buffer.
*
*  Parameters
*    pRing        Ring buffer to post to.
*    pBuffer      Pointer to character array. Does not need to point to a \0 terminated string.
*    NumBytes     Number of bytes to be stored in the SEGGER RTT control block.
*
*  Notes
*    (1) If there might not be enough space in the "Up"-buffer, call _WriteBlocking
*/
static void _WriteNoCheck(SEGGER_RTT_RING_BUFFER *pRing, const char* pData, unsigned NumBytes) {
  unsigned NumBytesAtOnce;
  unsigned WrOff;
  unsigned Rem;

  WrOff = pRing->WrOff;
  Rem = pRing->SizeOfBuffer - WrOff;
  if (Rem > NumBytes) {
    //
    // All data fits before wrap around
    //
    memcpy(pRing->pBuffer + WrOff, pData, NumBytes);
    pRing->WrOff = WrOff + NumBytes;
  } else {
    //
    // We reach the end of the buffer, so need to wrap around
    //
    NumBytesAtOnce = Rem;
    memcpy(pRing->pBuffer + WrOff, pData, NumBytesAtOnce);
    NumBytesAtOnce = NumBytes - Rem;
    memcpy(pRing->pBuffer, pData + Rem, NumBytesAtOnce);
    pRing->WrOff = NumBytesAtOnce;
  }
}

/*********************************************************************
*
*       _PostTerminalSwitch()
*
*  Function description
*    Switch terminal to the given terminal ID.  It is the caller's
*    responsibility to ensure the terminal ID is correct and there is
*    enough space in the buffer for this to complete successfully.
*
*  Parameters
*    pRing        Ring buffer to post to.
*    TerminalId   Terminal ID to switch to.
*/
static void _PostTerminalSwitch(SEGGER_RTT_RING_BUFFER *pRing, char TerminalId) {
  char ac[2];

  ac[0] = 0xFFu;
  ac[1] = _aTerminalId[(unsigned char)TerminalId];  // Caller made already sure that TerminalId does not exceed our terminal limit
  _WriteBlocking(pRing, ac, 2u);
}

/*********************************************************************
*
*       _GetAvailWriteSpace()
*
*  Function description
*    Returns the number of bytes that can be written to the ring
*    buffer without blocking.
*
*  Parameters
*    pRing        Ring buffer to check.
*
*  Return value
*    Number of bytes that are free in the buffer.
*/
static unsigned _GetAvailWriteSpace(SEGGER_RTT_RING_BUFFER *pRing) {
  unsigned RdOff;
  unsigned WrOff;
  unsigned r;
  //
  // Avoid warnings regarding volatile access order.  It's not a problem
  // in this case, but dampen compiler enthusiasm.
  //
  RdOff = pRing->RdOff;
  WrOff = pRing->WrOff;
  if (RdOff <= WrOff) {
    r = pRing->SizeOfBuffer - 1u - WrOff + RdOff;
  } else {
    r = RdOff - WrOff - 1u;
  }
  return r;
}

/*********************************************************************
*
*       Public code
*
**********************************************************************
*/
/*********************************************************************
*
*       SEGGER_RTT_ReadNoLock()
*
*  Function description
*    Reads characters from SEGGER real-time-terminal control block
*    which have been previously stored by the host.
*    Do not lock against interrupts and multiple access.
*
*  Parameters
*    BufferIndex  Index of Down-buffer to be used (e.g. 0 for "Terminal").
*    pBuffer      Pointer to buffer provided by target application, to copy characters from RTT-down-buffer to.
*    BufferSize   Size of the target application buffer.
*
*  Return value
*    Number of bytes that have been read.
*/
unsigned SEGGER_RTT_ReadNoLock(unsigned BufferIndex, void* pData, unsigned BufferSize) {
  unsigned NumBytesRem;
  unsigned NumBytesRead;
  unsigned RdOff;
  unsigned WrOff;
  unsigned char* pBuffer;
  SEGGER_RTT_RING_BUFFER* pRing;
  //
  INIT();
  pRing = &_SEGGER_RTT.aDown[BufferIndex];
  pBuffer = (unsigned char*)pData;
  RdOff = pRing->RdOff;
  WrOff = pRing->WrOff;
  NumBytesRead = 0u;
  //
  // Read from current read position to wrap-around of buffer, first
  //
  if (RdOff > WrOff) {
    NumBytesRem = pRing->SizeOfBuffer - RdOff;
    NumBytesRem = MIN(NumBytesRem, BufferSize);
    memcpy(pBuffer, pRing->pBuffer + RdOff, NumBytesRem);
    NumBytesRead += NumBytesRem;
    pBuffer      += NumBytesRem;
    BufferSize   -= NumBytesRem;
    RdOff        += NumBytesRem;
    //
    // Handle wrap-around of buffer
    //
    if (RdOff == pRing->SizeOfBuffer) {
      RdOff = 0u;
    }
  }
  //
  // Read remaining items of buffer
  //
  NumBytesRem = WrOff - RdOff;
  NumBytesRem = MIN(NumBytesRem, BufferSize);
  if (NumBytesRem > 0u) {
    memcpy(pBuffer, pRing->pBuffer + RdOff, NumBytesRem);
    NumBytesRead += NumBytesRem;
    pBuffer      += NumBytesRem;
    BufferSize   -= NumBytesRem;
    RdOff        += NumBytesRem;
  }
  if (NumBytesRead) {
    pRing->RdOff = RdOff;
  }
  //
  return NumBytesRead;
}

/*********************************************************************
*
*       SEGGER_RTT_Read
*
*  Function description
*    Reads characters from SEGGER real-time-terminal control block
*    which have been previously stored by the host.
*
*  Parameters
*    BufferIndex  Index of Down-buffer to be used (e.g. 0 for "Terminal").
*    pBuffer      Pointer to buffer provided by target application, to copy characters from RTT-down-buffer to.
*    BufferSize   Size of the target application buffer.
*
*  Return value
*    Number of bytes that have been read.
*/
unsigned SEGGER_RTT_Read(unsigned BufferIndex, void* pBuffer, unsigned BufferSize) {
  unsigned NumBytesRead;
  volatile unsigned SavedState;
  //
  SEGGER_RTT_LOCK(SavedState);
  //
  // Call the non-locking read function
  //
  NumBytesRead = SEGGER_RTT_ReadNoLock(BufferIndex, pBuffer, BufferSize);
  //
  // Finish up.
  //
  SEGGER_RTT_UNLOCK(SavedState);
  //
  return NumBytesRead;
}

/*********************************************************************
*
*       SEGGER_RTT_WriteSkipNoLock
*
*  Function description
*    Stores a specified number of characters in SEGGER RTT
*    control block which is then read by the host.
*    SEGGER_RTT_WriteSkipNoLock does not lock the application and
*    skips all data, if the data does not fit into the buffer.
*
*  Parameters
*    BufferIndex  Index of "Up"-buffer to be used (e.g. 0 for "Terminal").
*    pBuffer      Pointer to character array. Does not need to point to a \0 terminated string.
*    NumBytes     Number of bytes to be stored in the SEGGER RTT control block.
*
*  Return value
*    Number of bytes which have been stored in the "Up"-buffer.
*
*  Notes
*    (1) If there is not enough space in the "Up"-buffer, all data is dropped.
*    (2) For performance reasons this function does not call Init()
*        and may only be called after RTT has been initialized.
*        Either by calling SEGGER_RTT_Init() or calling another RTT API function first.
*/
unsigned SEGGER_RTT_WriteSkipNoLock(unsigned BufferIndex, const void* pBuffer, unsigned NumBytes) {
  const char*  pData;
  SEGGER_RTT_RING_BUFFER* pRing;
  unsigned     Avail;
  unsigned     RdOff;
  unsigned     WrOff;
  unsigned     Rem;

  pData = (const char *)pBuffer;
  //
  // Get "to-host" ring buffer and copy some elements into local variables.
  //
  pRing = &_SEGGER_RTT.aUp[BufferIndex];
  RdOff = pRing->RdOff;
  WrOff = pRing->WrOff;
  //
  // Handle the most common cases fastest.
  // Which is:
  //    RdOff <= WrOff -> Space until wrap around is free.
  //  AND
  //    WrOff + NumBytes < SizeOfBuffer -> No Wrap around necessary.
  //
  //  OR
  //
  //    RdOff > WrOff -> Space until RdOff - 1 is free.
  //  AND
  //    WrOff + NumBytes < RdOff -> Data fits into buffer
  //
  if (RdOff <= WrOff) {
    //
    // Get space until WrOff will be at wrap around.
    //
    Avail = pRing->SizeOfBuffer - 1u - WrOff ;
    if (Avail >= NumBytes) {
      memcpy(pRing->pBuffer + WrOff, pData, NumBytes);
      pRing->WrOff = WrOff + NumBytes;
      return 1;
    }
    //
    // If data did not fit into space until wrap around calculate complete space in buffer.
    //
    Avail += RdOff;
    //
    // If there is still no space for the whole of this output, don't bother.
    //
    if (Avail >= NumBytes) {
      //
      //  OK, we have enough space in buffer. Copy in one or 2 chunks
      //
      Rem = pRing->SizeOfBuffer - WrOff;      // Space until end of buffer
      if (Rem > NumBytes) {
        memcpy(pRing->pBuffer + WrOff, pData, NumBytes);
        pRing->WrOff = WrOff + NumBytes;
      } else {
        //
        // We reach the end of the buffer, so need to wrap around
        //
        memcpy(pRing->pBuffer + WrOff, pData, Rem);
        memcpy(pRing->pBuffer, pData + Rem, NumBytes - Rem);
        pRing->WrOff = NumBytes - Rem;
      }
      return 1;
    }
  } else {
    Avail = RdOff - WrOff - 1u;
    if (Avail >= NumBytes) {
      memcpy(pRing->pBuffer + WrOff, pData, NumBytes);
      pRing->WrOff = WrOff + NumBytes;
      return 1;
    }
  }
  //
  // If we reach this point no data has been written
  //
  return 0;
}

/*********************************************************************
*
*       SEGGER_RTT_WriteNoLock
*
*  Function description
*    Stores a specified number of characters in SEGGER RTT
*    control block which is then read by the host.
*    SEGGER_RTT_WriteNoLock does not lock the application.
*
*  Parameters
*    BufferIndex  Index of "Up"-buffer to be used (e.g. 0 for "Terminal").
*    pBuffer      Pointer to character array. Does not need to point to a \0 terminated string.
*    NumBytes     Number of bytes to be stored in the SEGGER RTT control block.
*
*  Return value
*    Number of bytes which have been stored in the "Up"-buffer.
*
*  Notes
*    (1) If there is not enough space in the "Up"-buffer, remaining characters of pBuffer are dropped.
*    (2) For performance reasons this function does not call Init()
*        and may only be called after RTT has been initialized.
*        Either by calling SEGGER_RTT_Init() or calling another RTT API function first.
*/
unsigned SEGGER_RTT_WriteNoLock(unsigned BufferIndex, const void* pBuffer, unsigned NumBytes) {
  unsigned Status;
  unsigned Avail;
  const char*  pData;
  SEGGER_RTT_RING_BUFFER *pRing;

  pData = (const char *)pBuffer;
  //
  // Get "to-host" ring buffer.
  //
  pRing = &_SEGGER_RTT.aUp[BufferIndex];
  //
  // How we output depends upon the mode...
  //
  switch (pRing->Flags) {
  case SEGGER_RTT_MODE_NO_BLOCK_SKIP:
    //
    // If we are in skip mode and there is no space for the whole
    // of this output, don't bother.
    //
    Avail = _GetAvailWriteSpace(pRing);
    if (Avail < NumBytes) {
      Status = 0u;
    } else {
      Status = NumBytes;
      _WriteNoCheck(pRing, pData, NumBytes);
    }
    break;
  case SEGGER_RTT_MODE_NO_BLOCK_TRIM:
    //
    // If we are in trim mode, trim to what we can output without blocking.
    //
    Avail = _GetAvailWriteSpace(pRing);
    Status = Avail < NumBytes ? Avail : NumBytes;
    _WriteNoCheck(pRing, pData, Status);
    break;
  case SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL:
    //
    // If we are in blocking mode, output everything.
    //
    Status = _WriteBlocking(pRing, pData, NumBytes);
    break;
  default:
    Status = 0u;
    break;
  }
  //
  // Finish up.
  //
  return Status;
}

/*********************************************************************
*
*       SEGGER_RTT_Write
*
*  Function description
*    Stores a specified number of characters in SEGGER RTT
*    control block which is then read by the host.
*
*  Parameters
*    BufferIndex  Index of "Up"-buffer to be used (e.g. 0 for "Terminal").
*    pBuffer      Pointer to character array. Does not need to point to a \0 terminated string.
*    NumBytes     Number of bytes to be stored in the SEGGER RTT control block.
*
*  Return value
*    Number of bytes which have been stored in the "Up"-buffer.
*
*  Notes
*    (1) If there is not enough space in the "Up"-buffer, remaining characters of pBuffer are dropped.
*/
unsigned SEGGER_RTT_Write(unsigned BufferIndex, const void* pBuffer, unsigned NumBytes) {
  unsigned Status;
  volatile unsigned SavedState;
  //
  INIT();
  SEGGER_RTT_LOCK(SavedState);
  //
  // Call the non-locking write function
  //
  Status = SEGGER_RTT_WriteNoLock(BufferIndex, pBuffer, NumBytes);
  //
  // Finish up.
  //
  SEGGER_RTT_UNLOCK(SavedState);
  //
  return Status;
}

/*********************************************************************
*
*       SEGGER_RTT_WriteString
*
*  Function description
*    Stores string in SEGGER RTT control block.
*    This data is read by the host.
*
*  Parameters
*    BufferIndex  Index of "Up"-buffer to be used (e.g. 0 for "Terminal").
*    s            Pointer to string.
*
*  Return value
*    Number of bytes which have been stored in the "Up"-buffer.
*
*  Notes
*    (1) If there is not enough space in the "Up"-buffer, depending on configuration,
*        remaining characters may be dropped or RTT module waits until there is more space in the buffer.
*    (2) String passed to this function has to be \0 terminated
*    (3) \0 termination character is *not* stored in RTT buffer
*/
unsigned SEGGER_RTT_WriteString(unsigned BufferIndex, const char* s) {
  unsigned Len;

  Len = STRLEN(s);
  return SEGGER_RTT_Write(BufferIndex, s, Len);
}

/*********************************************************************
*
*       SEGGER_RTT_GetKey
*
*  Function description
*    Reads one character from the SEGGER RTT buffer.
*    Host has previously stored data there.
*
*  Return value
*    <  0 -   No character available (buffer empty).
*    >= 0 -   Character which has been read. (Possible values: 0 - 255)
*
*  Notes
*    (1) This function is only specified for accesses to RTT buffer 0.
*/
int SEGGER_RTT_GetKey(void) {
  char c;
  int r;

  r = (int)SEGGER_RTT_Read(0u, &c, 1u);
  if (r == 1) {
    r = (int)(unsigned char)c;
  } else {
    r = -1;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_WaitKey
*
*  Function description
*    Waits until at least one character is avaible in the SEGGER RTT buffer.
*    Once a character is available, it is read and this function returns.
*
*  Return value
*    >=0 -   Character which has been read.
*
*  Notes
*    (1) This function is only specified for accesses to RTT buffer 0
*    (2) This function is blocking if no character is present in RTT buffer
*/
int SEGGER_RTT_WaitKey(void) {
  int r;

  do {
    r = SEGGER_RTT_GetKey();
  } while (r < 0);
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_HasKey
*
*  Function description
*    Checks if at least one character for reading is available in the SEGGER RTT buffer.
*
*  Return value
*    == 0 -     No characters are available to read.
*    == 1 -     At least one character is available.
*
*  Notes
*    (1) This function is only specified for accesses to RTT buffer 0
*/
int SEGGER_RTT_HasKey(void) {
  unsigned RdOff;
  int r;

  INIT();
  RdOff = _SEGGER_RTT.aDown[0].RdOff;
  if (RdOff != _SEGGER_RTT.aDown[0].WrOff) {
    r = 1;
  } else {
    r = 0;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_HasData
*
*  Function description
*    Check if there is data from the host in the given buffer.
*
*  Return value:
*  ==0:  No data
*  !=0:  Data in buffer
*
*/
unsigned SEGGER_RTT_HasData(unsigned BufferIndex) {
  SEGGER_RTT_RING_BUFFER *pRing;
  unsigned v;

  pRing = &_SEGGER_RTT.aDown[BufferIndex];
  v = pRing->WrOff;
  return v - pRing->RdOff;
}


/*********************************************************************
*
*       SEGGER_RTT_ConfigUpBuffer
*
*  Function description
*    Run-time configuration of a specific up-buffer (T->H).
*    Buffer to be configured is specified by index.
*    This includes: Buffer address, size, name, flags, ...
*
*  Parameters
*    BufferIndex  Index of the buffer to configure.
*    sName        Pointer to a constant name string.
*    pBuffer      Pointer to a buffer to be used.
*    BufferSize   Size of the buffer.
*    Flags        Operating modes. Define behavior if buffer is full (not enough space for entire message).
*
*  Return value
*    >= 0 - O.K.
*     < 0 - Error
*/
int SEGGER_RTT_ConfigUpBuffer(unsigned BufferIndex, const char* sName, void* pBuffer, unsigned BufferSize, unsigned Flags) {
  int r;
  volatile unsigned SavedState;

  INIT();
  if (BufferIndex < (unsigned)_SEGGER_RTT.MaxNumUpBuffers) {
    SEGGER_RTT_LOCK(SavedState);
    if (BufferIndex > 0u) {
      _SEGGER_RTT.aUp[BufferIndex].sName        = sName;
      _SEGGER_RTT.aUp[BufferIndex].pBuffer      = pBuffer;
      _SEGGER_RTT.aUp[BufferIndex].SizeOfBuffer = BufferSize;
      _SEGGER_RTT.aUp[BufferIndex].RdOff        = 0u;
      _SEGGER_RTT.aUp[BufferIndex].WrOff        = 0u;
    }
    _SEGGER_RTT.aUp[BufferIndex].Flags          = Flags;
    SEGGER_RTT_UNLOCK(SavedState);
    r =  0;
  } else {
    r = -1;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_ConfigDownBuffer
*
*  Function description
*    Run-time configuration of a specific down-buffer (H->T).
*    Buffer to be configured is specified by index.
*    This includes: Buffer address, size, name, flags, ...
*
*  Parameters
*    BufferIndex  Index of the buffer to configure.
*    sName        Pointer to a constant name string.
*    pBuffer      Pointer to a buffer to be used.
*    BufferSize   Size of the buffer.
*    Flags        Operating modes. Define behavior if buffer is full (not enough space for entire message).
*
*  Return value
*    >= 0  O.K.
*     < 0  Error
*/
int SEGGER_RTT_ConfigDownBuffer(unsigned BufferIndex, const char* sName, void* pBuffer, unsigned BufferSize, unsigned Flags) {
  int r;
  volatile unsigned SavedState;

  INIT();
  if (BufferIndex < (unsigned)_SEGGER_RTT.MaxNumDownBuffers) {
    SEGGER_RTT_LOCK(SavedState);
    if (BufferIndex > 0u) {
      _SEGGER_RTT.aDown[BufferIndex].sName        = sName;
      _SEGGER_RTT.aDown[BufferIndex].pBuffer      = pBuffer;
      _SEGGER_RTT.aDown[BufferIndex].SizeOfBuffer = BufferSize;
      _SEGGER_RTT.aDown[BufferIndex].RdOff        = 0u;
      _SEGGER_RTT.aDown[BufferIndex].WrOff        = 0u;
    }
    _SEGGER_RTT.aDown[BufferIndex].Flags          = Flags;
    SEGGER_RTT_UNLOCK(SavedState);
    r =  0;
  } else {
    r = -1;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_SetNameUpBuffer
*
*  Function description
*    Run-time configuration of a specific up-buffer name (T->H).
*    Buffer to be configured is specified by index.
*
*  Parameters
*    BufferIndex  Index of the buffer to renamed.
*    sName        Pointer to a constant name string.
*
*  Return value
*    >= 0  O.K.
*     < 0  Error
*/
int SEGGER_RTT_SetNameUpBuffer(unsigned BufferIndex, const char* sName) {
  int r;
  volatile unsigned SavedState;

  INIT();
  if (BufferIndex < (unsigned)_SEGGER_RTT.MaxNumUpBuffers) {
    SEGGER_RTT_LOCK(SavedState);
    _SEGGER_RTT.aUp[BufferIndex].sName = sName;
    SEGGER_RTT_UNLOCK(SavedState);
    r =  0;
  } else {
    r = -1;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_SetNameDownBuffer
*
*  Function description
*    Run-time configuration of a specific Down-buffer name (T->H).
*    Buffer to be configured is specified by index.
*
*  Parameters
*    BufferIndex  Index of the buffer to renamed.
*    sName        Pointer to a constant name string.
*
*  Return value
*    >= 0  O.K.
*     < 0  Error
*/
int SEGGER_RTT_SetNameDownBuffer(unsigned BufferIndex, const char* sName) {
  int r;
  volatile unsigned SavedState;

  INIT();
  if (BufferIndex < (unsigned)_SEGGER_RTT.MaxNumDownBuffers) {
    SEGGER_RTT_LOCK(SavedState);
    _SEGGER_RTT.aDown[BufferIndex].sName = sName;
    SEGGER_RTT_UNLOCK(SavedState);
    r =  0;
  } else {
    r = -1;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_Init
*
*  Function description
*    Initializes the RTT Control Block.
*    Should be used in RAM targets, at start of the application.
*
*/
void SEGGER_RTT_Init (void) {
  INIT();
}

/*********************************************************************
*
*       SEGGER_RTT_SetTerminal
*
*  Function description
*    Sets the terminal to be used for output on channel 0.
*
*  Parameters
*    TerminalId  Index of the terminal.
*
*  Return value
*    >= 0  O.K.
*     < 0  Error (e.g. if RTT is configured for non-blocking mode and there was no space in the buffer to set the new terminal Id)
*/
int SEGGER_RTT_SetTerminal (char TerminalId) {
  char ac[2];
  SEGGER_RTT_RING_BUFFER *pRing;
  volatile unsigned SavedState;
  unsigned Avail;
  int r;
  //
  INIT();
  //
  r = 0;
  ac[0] = 0xFFU;
  if (TerminalId < (char)sizeof(_aTerminalId)) { // We only support a certain number of channels
    ac[1] = _aTerminalId[(unsigned char)TerminalId];
    pRing = &_SEGGER_RTT.aUp[0];    // Buffer 0 is always reserved for terminal I/O, so we can use index 0 here, fixed
    SEGGER_RTT_LOCK(SavedState);    // Lock to make sure that no other task is writing into buffer, while we are and number of free bytes in buffer does not change downwards after checking and before writing
    if ((pRing->Flags & SEGGER_RTT_MODE_MASK) == SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL) {
      _ActiveTerminal = TerminalId;
      _WriteBlocking(pRing, ac, 2u);
    } else {                                                                            // Skipping mode or trim mode? => We cannot trim this command so handling is the same for both modes
      Avail = _GetAvailWriteSpace(pRing);
      if (Avail >= 2) {
        _ActiveTerminal = TerminalId;    // Only change active terminal in case of success
        _WriteNoCheck(pRing, ac, 2u);
      } else {
        r = -1;
      }
    }
    SEGGER_RTT_UNLOCK(SavedState);
  } else {
    r = -1;
  }
  return r;
}

/*********************************************************************
*
*       SEGGER_RTT_TerminalOut
*
*  Function description
*    Writes a string to the given terminal
*     without changing the terminal for channel 0.
*
*  Parameters
*    TerminalId   Index of the terminal.
*    s            String to be printed on the terminal.
*
*  Return value
*    >= 0 - Number of bytes written.
*     < 0 - Error.
*
*/
int SEGGER_RTT_TerminalOut (char TerminalId, const char* s) {
  int  Status;
  unsigned  FragLen;
  unsigned  Avail;
  SEGGER_RTT_RING_BUFFER *pRing;
  volatile unsigned SavedState;
  //
  INIT();
  //
  // Validate terminal ID.
  //
  if (TerminalId < (char)sizeof(_aTerminalId)) { // We only support a certain number of channels
    //
    // Get "to-host" ring buffer.
    //
    pRing = &_SEGGER_RTT.aUp[0];
    //
    // Need to be able to change terminal, write data, change back.
    // Compute the fixed and variable sizes.
    //
    FragLen = strlen(s);
    //
    // How we output depends upon the mode...
    //
    SEGGER_RTT_LOCK(SavedState);
    Avail = _GetAvailWriteSpace(pRing);
    switch (pRing->Flags & SEGGER_RTT_MODE_MASK) {
    case SEGGER_RTT_MODE_NO_BLOCK_SKIP:
      //
      // If we are in skip mode and there is no space for the whole
      // of this output, don't bother switching terminals at all.
      //
      if (Avail < (FragLen + 4u)) {
        Status = 0;
      } else {
        _PostTerminalSwitch(pRing, TerminalId);
        Status = (int)_WriteBlocking(pRing, s, FragLen);
        _PostTerminalSwitch(pRing, _ActiveTerminal);
      }
      break;
    case SEGGER_RTT_MODE_NO_BLOCK_TRIM:
      //
      // If we are in trim mode and there is not enough space for everything,
      // trim the output but always include the terminal switch.  If no room
      // for terminal switch, skip that totally.
      //
      if (Avail < 4u) {
        Status = -1;
      } else {
        _PostTerminalSwitch(pRing, TerminalId);
        Status = (int)_WriteBlocking(pRing, s, (FragLen < (Avail - 4u)) ? FragLen : (Avail - 4u));
        _PostTerminalSwitch(pRing, _ActiveTerminal);
      }
      break;
    case SEGGER_RTT_MODE_BLOCK_IF_FIFO_FULL:
      //
      // If we are in blocking mode, output everything.
      //
      _PostTerminalSwitch(pRing, TerminalId);
      Status = (int)_WriteBlocking(pRing, s, FragLen);
      _PostTerminalSwitch(pRing, _ActiveTerminal);
      break;
    default:
      Status = -1;
      break;
    }
    //
    // Finish up.
    //
    SEGGER_RTT_UNLOCK(SavedState);
  } else {
    Status = -1;
  }
  return Status;
}


/*************************** End of file ****************************/