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(const 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(const 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(const char *target, const 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(const char *target, size_t targetLen, const char *terminator, size_t termLen) {
  if (terminator == NULL) {
    MultiTarget t[1] = {{target, targetLen, 0}};
    return findMulti(t, 1) == 0;
  } else {
    MultiTarget t[2] = {{target, targetLen, 0}, {terminator, termLen, 0}};
    return findMulti(t, 2) == 0;
  }
}

// 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 ((char)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') || (char)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;
  double value = 0.0;
  int c;
  double fraction = 1.0;

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

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

  if (isNegative) {
    value = -value;
  }

  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) {
  size_t index = 0;
  while (index < length) {
    int c = timedRead();
    if (c < 0 || (char)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 && (char)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 ((char)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 ((char)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;
}