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sexp.cpp

//
//  Zinnia: Online hand recognition system with machine learning
//
//  $Id: sexp.cpp 17 2009-04-05 11:40:32Z taku-ku $;
//
//  Copyright(C) 2008 Taku Kudo <taku@chasen.org>
//
#include <iostream>
#include <string>
#include "sexp.h"

namespace zinnia {

namespace {
void dump_cdr_internal(const Sexp::Cell *cell,
                       std::ostream *os);

void dump_internal(const Sexp::Cell *cell,
                   std::ostream *os) {
  if (!cell) {
    *os << "NIL";
  } else {
    if (cell->is_cons()) {
      *os << '(';
      dump_internal(cell->car(), os);
      dump_cdr_internal(cell->cdr(), os);
      *os << ')';
    } else if (cell->is_atom()) {
      *os << cell->atom();
    }
  }
}

void dump_cdr_internal(const Sexp::Cell *cell,
                       std::ostream *os) {
  if (!cell) {
    return;
  }
  if (cell->is_cons()) {
    *os << ' ';
    dump_internal(cell->car(), os);
    dump_cdr_internal(cell->cdr(), os);
  } else {
    *os << ' ';
    dump_internal(cell, os);
  }
}
}

const Sexp::Cell *Sexp::read(char **begin, const char *end) {
  comment(begin, end);
  if (*begin >= end) {
    return 0;
  }
  const int r = next_token(begin, end, '(');
  if (r == 1) {
    return read_car(begin, end);
  } else if (r == 0) {
    return read_atom(begin, end);
  }
  return 0;
}

void Sexp::dump(const Sexp::Cell *cell, std::ostream *os) {
  dump_internal(cell, os);
  *os << std::endl;
}

void Sexp::free() {
  cell_freelist_.free();
  char_freelist_.free();
}

int Sexp::next_token(char **begin, const char *end, const char n) {
  char c = 0;
  do {
    c = **begin;
    ++(*begin);
  } while (isspace(c));

  if (*begin >= end) {
    return -1;
  }

  if (c == n) {
    return 1;
  } else {
    --(*begin);
    return 0;
  }
}

void Sexp::comment(char **begin, const char *end) {
  const int r = next_token(begin, end, ';');
  if (r == 1) {
    while (*begin < end) {
      const char c = **begin;
      ++(*begin);
      if (c == '\r' || c == '\n') {
        break;
      }
    }
    return comment(begin, end);
  }
}

const Sexp::Cell *Sexp::read_cdr(char **begin, const char *end) {
  comment(begin, end);
  const int r = next_token(begin, end, ')');
  if (r == 1) {
    return 0;
  } else if (r == 0) {
    return read_car(begin, end);
  }
  return 0;
}

const Sexp::Cell *Sexp::read_car(char **begin, const char *end) {
  comment(begin, end);
  const int r = next_token(begin, end, ')');
  if (r == 1) {
    return 0;
  } else if (r == 0) {
    Cell *cell = cell_freelist_.alloc(1);
    cell->set_car(this->read(begin, end));
    cell->set_cdr(read_cdr(begin, end));
    return cell;
  }
  return 0;
}

const Sexp::Cell *Sexp::read_atom(char **begin, const char *end) {
  comment(begin, end);
  char c = **begin;
  const char *p = *begin;
  ++(*begin);
  if (isspace(c) || c == '(' || c == ')') {
    return 0;
  } else if (*begin >= end) {
    return 0;
  } else {
    while (true) {
      c = **begin;
      ++(*begin);
      if (isspace(c) || c == '(' || c == ')' || *begin >= end) {
        --(*begin);
        const size_t length = static_cast<size_t>(*begin - p);
        char *tmp = char_freelist_.alloc(length + 1);
        std::copy(p, p + length, tmp);
        tmp[length] = '\0';
        Cell *cell = cell_freelist_.alloc(1);
        cell->set_atom(tmp);
        return cell;
      }
    }
  }
  return 0;
}
}

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