Stream.cpp

/*
 Stream.cpp - adds parsing methods to Stream class
 Copyright (c) 2008 David A. Mellis.  All right reserved.

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 Created July 2011
 parsing functions based on TextFinder library by Michael Margolis

 findMulti/findUntil routines written by Jim Leonard/Xuth
 */

#include "Arduino.h"
#include "Stream.h"

#define PARSE_TIMEOUT 1000 // default number of milli-seconds to wait

// private method to read stream with timeout
int Stream::timedRead()
{
  int c;
  _startMillis = millis();
  do
  {
    c = read();
    if (c >= 0)
      return c;
  } while (millis() - _startMillis < _timeout);
  return -1; // -1 indicates timeout
}

// private method to peek stream with timeout
int Stream::timedPeek()
{
  int c;
  _startMillis = millis();
  do
  {
    c = peek();
    if (c >= 0)
      return c;
  } while (millis() - _startMillis < _timeout);
  return -1; // -1 indicates timeout
}

// returns peek of the next digit in the stream or -1 if timeout
// discards non-numeric characters
int Stream::peekNextDigit(LookaheadMode lookahead, bool detectDecimal)
{
  int c;
  while (1)
  {
    c = timedPeek();

    if (c < 0 ||
        c == '-' ||
        (c >= '0' && c <= '9') ||
        (detectDecimal && c == '.'))
      return c;

    switch (lookahead)
    {
    case SKIP_NONE:
      return -1; // Fail code.
    case SKIP_WHITESPACE:
      switch (c)
      {
      case ' ':
      case '\t':
      case '\r':
      case '\n':
        break;
      default:
        return -1; // Fail code.
      }
    case SKIP_ALL:
      break;
    }
    read(); // discard non-numeric
  }
}

// Public Methods
//////////////////////////////////////////////////////////////

void Stream::setTimeout(unsigned long timeout) // sets the maximum number of milliseconds to wait
{
  _timeout = timeout;
}

// find returns true if the target string is found
bool Stream::find(char *target)
{
  return findUntil(target, strlen(target), NULL, 0);
}

// reads data from the stream until the target string of given length is found
// returns true if target string is found, false if timed out
bool Stream::find(char *target, size_t length)
{
  return findUntil(target, length, NULL, 0);
}

// as find but search ends if the terminator string is found
bool Stream::findUntil(char *target, char *terminator)
{
  return findUntil(target, strlen(target), terminator, strlen(terminator));
}

// reads data from the stream until the target string of the given length is found
// search terminated if the terminator string is found
// returns true if target string is found, false if terminated or timed out
bool Stream::findUntil(char *target, size_t targetLen, char *terminator, size_t termLen)
{
  if (terminator == NULL)
  {
    MultiTarget t[1] = {{target, targetLen, 0}};
    return findMulti(t, 1) == 0 ? true : false;
  }
  else
  {
    MultiTarget t[2] = {{target, targetLen, 0}, {terminator, termLen, 0}};
    return findMulti(t, 2) == 0 ? true : false;
  }
}

// returns the first valid (long) integer value from the current position.
// lookahead determines how parseInt looks ahead in the stream.
// See LookaheadMode enumeration at the top of the file.
// Lookahead is terminated by the first character that is not a valid part of an integer.
// Once parsing commences, 'ignore' will be skipped in the stream.
long Stream::parseInt(LookaheadMode lookahead, char ignore)
{
  bool isNegative = false;
  long value = 0;
  int c;

  c = peekNextDigit(lookahead, false);
  // ignore non numeric leading characters
  if (c < 0)
    return 0; // zero returned if timeout

  do
  {
    if (c == ignore)
      ; // ignore this character
    else if (c == '-')
      isNegative = true;
    else if (c >= '0' && c <= '9') // is c a digit?
      value = value * 10 + c - '0';
    read(); // consume the character we got with peek
    c = timedPeek();
  } while ((c >= '0' && c <= '9') || c == ignore);

  if (isNegative)
    value = -value;
  return value;
}

// as parseInt but returns a floating point value
float Stream::parseFloat(LookaheadMode lookahead, char ignore)
{
  bool isNegative = false;
  bool isFraction = false;
  long value = 0;
  int c;
  float fraction = 1.0;

  c = peekNextDigit(lookahead, true);
  // ignore non numeric leading characters
  if (c < 0)
    return 0; // zero returned if timeout

  do
  {
    if (c == ignore)
      ; // ignore
    else if (c == '-')
      isNegative = true;
    else if (c == '.')
      isFraction = true;
    else if (c >= '0' && c <= '9')
    { // is c a digit?
      value = value * 10 + c - '0';
      if (isFraction)
        fraction *= 0.1;
    }
    read(); // consume the character we got with peek
    c = timedPeek();
  } while ((c >= '0' && c <= '9') || (c == '.' && !isFraction) || c == ignore);

  if (isNegative)
    value = -value;
  if (isFraction)
    return value * fraction;
  else
    return value;
}

// read characters from stream into buffer
// terminates if length characters have been read, or timeout (see setTimeout)
// returns the number of characters placed in the buffer
// the buffer is NOT null terminated.
//
size_t Stream::readBytes(char *buffer, size_t length)
{
  size_t count = 0;
  while (count < length)
  {
    int c = timedRead();
    if (c < 0)
      break;
    *buffer++ = (char)c;
    count++;
  }
  return count;
}

// as readBytes with terminator character
// terminates if length characters have been read, timeout, or if the terminator character  detected
// returns the number of characters placed in the buffer (0 means no valid data found)

size_t Stream::readBytesUntil(char terminator, char *buffer, size_t length)
{
  if (length < 1)
    return 0;
  size_t index = 0;
  while (index < length)
  {
    int c = timedRead();
    if (c < 0 || c == terminator)
      break;
    *buffer++ = (char)c;
    index++;
  }
  return index; // return number of characters, not including null terminator
}

String Stream::readString()
{
  String ret;
  int c = timedRead();
  while (c >= 0)
  {
    ret += (char)c;
    c = timedRead();
  }
  return ret;
}

String Stream::readStringUntil(char terminator)
{
  String ret;
  int c = timedRead();
  while (c >= 0 && c != terminator)
  {
    ret += (char)c;
    c = timedRead();
  }
  return ret;
}

int Stream::findMulti(struct Stream::MultiTarget *targets, int tCount)
{
  // any zero length target string automatically matches and would make
  // a mess of the rest of the algorithm.
  for (struct MultiTarget *t = targets; t < targets + tCount; ++t)
  {
    if (t->len <= 0)
      return t - targets;
  }

  while (1)
  {
    int c = timedRead();
    if (c < 0)
      return -1;

    for (struct MultiTarget *t = targets; t < targets + tCount; ++t)
    {
      // the simple case is if we match, deal with that first.
      if (c == t->str[t->index])
      {
        if (++t->index == t->len)
          return t - targets;
        else
          continue;
      }

      // if not we need to walk back and see if we could have matched further
      // down the stream (ie '1112' doesn't match the first position in '11112'
      // but it will match the second position so we can't just reset the current
      // index to 0 when we find a mismatch.
      if (t->index == 0)
        continue;

      int origIndex = t->index;
      do
      {
        --t->index;
        // first check if current char works against the new current index
        if (c != t->str[t->index])
          continue;

        // if it's the only char then we're good, nothing more to check
        if (t->index == 0)
        {
          t->index++;
          break;
        }

        // otherwise we need to check the rest of the found string
        int diff = origIndex - t->index;
        size_t i;
        for (i = 0; i < t->index; ++i)
        {
          if (t->str[i] != t->str[i + diff])
            break;
        }

        // if we successfully got through the previous loop then our current
        // index is good.
        if (i == t->index)
        {
          t->index++;
          break;
        }

        // otherwise we just try the next index
      } while (t->index);
    }
  }
  // unreachable
  return -1;
}