printf.h

Go to the documentation of this file.

/*
 Formatting library for C++

 Copyright (c) 2012 - 2016, Victor Zverovich
 All rights reserved.

 For the license information refer to format.h.
 */

#ifndef FMT_PRINTF_H_
#define FMT_PRINTF_H_

#include <algorithm>  // std::fill_n
#include <limits>     // std::numeric_limits

#include "fmt/ostream.h"

namespace fmt {
namespace internal {

// Checks if a value fits in int - used to avoid warnings about comparing
// signed and unsigned integers.
template <bool IsSigned>
struct IntChecker {
  template <typename T>
  static bool fits_in_int(T value) {
    unsigned max = std::numeric_limits<int>::max();
    return value <= max;
  }
  static bool fits_in_int(bool) { return true; }
};

template <>
struct IntChecker<true> {
  template <typename T>
  static bool fits_in_int(T value) {
    return value >= std::numeric_limits<int>::min() &&
           value <= std::numeric_limits<int>::max();
  }
  static bool fits_in_int(int) { return true; }
};

class PrecisionHandler : public ArgVisitor<PrecisionHandler, int> {
 public:
  void report_unhandled_arg() {
    FMT_THROW(FormatError("precision is not integer"));
  }

  template <typename T>
  int visit_any_int(T value) {
    if (!IntChecker<std::numeric_limits<T>::is_signed>::fits_in_int(value))
      FMT_THROW(FormatError("number is too big"));
    return static_cast<int>(value);
  }
};

// IsZeroInt::visit(arg) returns true iff arg is a zero integer.
class IsZeroInt : public ArgVisitor<IsZeroInt, bool> {
 public:
  template <typename T>
  bool visit_any_int(T value) { return value == 0; }
};

template <typename T, typename U>
struct is_same {
  enum { value = 0 };
};

template <typename T>
struct is_same<T, T> {
  enum { value = 1 };
};

// An argument visitor that converts an integer argument to T for printf,
// if T is an integral type. If T is void, the argument is converted to
// corresponding signed or unsigned type depending on the type specifier:
// 'd' and 'i' - signed, other - unsigned)
template <typename T = void>
class ArgConverter : public ArgVisitor<ArgConverter<T>, void> {
 private:
  internal::Arg &arg_;
  wchar_t type_;

  FMT_DISALLOW_COPY_AND_ASSIGN(ArgConverter);

 public:
  ArgConverter(internal::Arg &arg, wchar_t type)
    : arg_(arg), type_(type) {}

  void visit_bool(bool value) {
    if (type_ != 's')
      visit_any_int(value);
  }

  template <typename U>
  void visit_any_int(U value) {
    bool is_signed = type_ == 'd' || type_ == 'i';
    using internal::Arg;
    typedef typename internal::Conditional<
        is_same<T, void>::value, U, T>::type TargetType;
    if (sizeof(TargetType) <= sizeof(int)) {
      // Extra casts are used to silence warnings.
      if (is_signed) {
        arg_.type = Arg::INT;
        arg_.int_value = static_cast<int>(static_cast<TargetType>(value));
      } else {
        arg_.type = Arg::UINT;
        typedef typename internal::MakeUnsigned<TargetType>::Type Unsigned;
        arg_.uint_value = static_cast<unsigned>(static_cast<Unsigned>(value));
      }
    } else {
      if (is_signed) {
        arg_.type = Arg::LONG_LONG;
        // glibc's printf doesn't sign extend arguments of smaller types:
        //   std::printf("%lld", -42);  // prints "4294967254"
        // but we don't have to do the same because it's a UB.
        arg_.long_long_value = static_cast<LongLong>(value);
      } else {
        arg_.type = Arg::ULONG_LONG;
        arg_.ulong_long_value =
            static_cast<typename internal::MakeUnsigned<U>::Type>(value);
      }
    }
  }
};

// Converts an integer argument to char for printf.
class CharConverter : public ArgVisitor<CharConverter, void> {
 private:
  internal::Arg &arg_;

  FMT_DISALLOW_COPY_AND_ASSIGN(CharConverter);

 public:
  explicit CharConverter(internal::Arg &arg) : arg_(arg) {}

  template <typename T>
  void visit_any_int(T value) {
    arg_.type = internal::Arg::CHAR;
    arg_.int_value = static_cast<char>(value);
  }
};

// Checks if an argument is a valid printf width specifier and sets
// left alignment if it is negative.
class WidthHandler : public ArgVisitor<WidthHandler, unsigned> {
 private:
  FormatSpec &spec_;

  FMT_DISALLOW_COPY_AND_ASSIGN(WidthHandler);

 public:
  explicit WidthHandler(FormatSpec &spec) : spec_(spec) {}

  void report_unhandled_arg() {
    FMT_THROW(FormatError("width is not integer"));
  }

  template <typename T>
  unsigned visit_any_int(T value) {
    typedef typename internal::IntTraits<T>::MainType UnsignedType;
    UnsignedType width = static_cast<UnsignedType>(value);
    if (internal::is_negative(value)) {
      spec_.align_ = ALIGN_LEFT;
      width = 0 - width;
    }
    unsigned int_max = std::numeric_limits<int>::max();
    if (width > int_max)
      FMT_THROW(FormatError("number is too big"));
    return static_cast<unsigned>(width);
  }
};
}  // namespace internal

template <typename Impl, typename Char>
class BasicPrintfArgFormatter : public internal::ArgFormatterBase<Impl, Char> {
 private:
  void write_null_pointer() {
    this->spec().type_ = 0;
    this->write("(nil)");
  }

  typedef internal::ArgFormatterBase<Impl, Char> Base;

 public:
  BasicPrintfArgFormatter(BasicWriter<Char> &writer, FormatSpec &spec)
  : internal::ArgFormatterBase<Impl, Char>(writer, spec) {}

  void visit_bool(bool value) {
    FormatSpec &fmt_spec = this->spec();
    if (fmt_spec.type_ != 's')
      return this->visit_any_int(value);
    fmt_spec.type_ = 0;
    this->write(value);
  }

  void visit_char(int value) {
    const FormatSpec &fmt_spec = this->spec();
    BasicWriter<Char> &w = this->writer();
    if (fmt_spec.type_ && fmt_spec.type_ != 'c')
      w.write_int(value, fmt_spec);
    typedef typename BasicWriter<Char>::CharPtr CharPtr;
    CharPtr out = CharPtr();
    if (fmt_spec.width_ > 1) {
      Char fill = ' ';
      out = w.grow_buffer(fmt_spec.width_);
      if (fmt_spec.align_ != ALIGN_LEFT) {
        std::fill_n(out, fmt_spec.width_ - 1, fill);
        out += fmt_spec.width_ - 1;
      } else {
        std::fill_n(out + 1, fmt_spec.width_ - 1, fill);
      }
    } else {
      out = w.grow_buffer(1);
    }
    *out = static_cast<Char>(value);
  }

  void visit_cstring(const char *value) {
    if (value)
      Base::visit_cstring(value);
    else if (this->spec().type_ == 'p')
      write_null_pointer();
    else
      this->write("(null)");
  }

  void visit_pointer(const void *value) {
    if (value)
      return Base::visit_pointer(value);
    this->spec().type_ = 0;
    write_null_pointer();
  }

  void visit_custom(internal::Arg::CustomValue c) {
    BasicFormatter<Char> formatter(ArgList(), this->writer());
    const Char format_str[] = {'}', 0};
    const Char *format = format_str;
    c.format(&formatter, c.value, &format);
  }
};

template <typename Char>
class PrintfArgFormatter
    : public BasicPrintfArgFormatter<PrintfArgFormatter<Char>, Char> {
 public:
  PrintfArgFormatter(BasicWriter<Char> &w, FormatSpec &s)
  : BasicPrintfArgFormatter<PrintfArgFormatter<Char>, Char>(w, s) {}
};

template <typename Char, typename ArgFormatter = PrintfArgFormatter<Char> >
class PrintfFormatter : private internal::FormatterBase {
 private:
  BasicWriter<Char> &writer_;

  void parse_flags(FormatSpec &spec, const Char *&s);

  // Returns the argument with specified index or, if arg_index is equal
  // to the maximum unsigned value, the next argument.
  internal::Arg get_arg(
      const Char *s,
      unsigned arg_index = (std::numeric_limits<unsigned>::max)());

  // Parses argument index, flags and width and returns the argument index.
  unsigned parse_header(const Char *&s, FormatSpec &spec);

 public:
  explicit PrintfFormatter(const ArgList &args, BasicWriter<Char> &w)
    : FormatterBase(args), writer_(w) {}

  FMT_API void format(BasicCStringRef<Char> format_str);
};

template <typename Char, typename AF>
void PrintfFormatter<Char, AF>::parse_flags(FormatSpec &spec, const Char *&s) {
  for (;;) {
    switch (*s++) {
      case '-':
        spec.align_ = ALIGN_LEFT;
        break;
      case '+':
        spec.flags_ |= SIGN_FLAG | PLUS_FLAG;
        break;
      case '0':
        spec.fill_ = '0';
        break;
      case ' ':
        spec.flags_ |= SIGN_FLAG;
        break;
      case '#':
        spec.flags_ |= HASH_FLAG;
        break;
      default:
        --s;
        return;
    }
  }
}

template <typename Char, typename AF>
internal::Arg PrintfFormatter<Char, AF>::get_arg(const Char *s,
                                                 unsigned arg_index) {
  (void)s;
  const char *error = 0;
  internal::Arg arg = arg_index == std::numeric_limits<unsigned>::max() ?
    next_arg(error) : FormatterBase::get_arg(arg_index - 1, error);
  if (error)
    FMT_THROW(FormatError(!*s ? "invalid format string" : error));
  return arg;
}

template <typename Char, typename AF>
unsigned PrintfFormatter<Char, AF>::parse_header(
  const Char *&s, FormatSpec &spec) {
  unsigned arg_index = std::numeric_limits<unsigned>::max();
  Char c = *s;
  if (c >= '0' && c <= '9') {
    // Parse an argument index (if followed by '$') or a width possibly
    // preceded with '0' flag(s).
    unsigned value = internal::parse_nonnegative_int(s);
    if (*s == '$') {  // value is an argument index
      ++s;
      arg_index = value;
    } else {
      if (c == '0')
        spec.fill_ = '0';
      if (value != 0) {
        // Nonzero value means that we parsed width and don't need to
        // parse it or flags again, so return now.
        spec.width_ = value;
        return arg_index;
      }
    }
  }
  parse_flags(spec, s);
  // Parse width.
  if (*s >= '0' && *s <= '9') {
    spec.width_ = internal::parse_nonnegative_int(s);
  } else if (*s == '*') {
    ++s;
    spec.width_ = internal::WidthHandler(spec).visit(get_arg(s));
  }
  return arg_index;
}

template <typename Char, typename AF>
void PrintfFormatter<Char, AF>::format(BasicCStringRef<Char> format_str) {
  const Char *start = format_str.c_str();
  const Char *s = start;
  while (*s) {
    Char c = *s++;
    if (c != '%') continue;
    if (*s == c) {
      write(writer_, start, s);
      start = ++s;
      continue;
    }
    write(writer_, start, s - 1);

    FormatSpec spec;
    spec.align_ = ALIGN_RIGHT;

    // Parse argument index, flags and width.
    unsigned arg_index = parse_header(s, spec);

    // Parse precision.
    if (*s == '.') {
      ++s;
      if ('0' <= *s && *s <= '9') {
        spec.precision_ = static_cast<int>(internal::parse_nonnegative_int(s));
      } else if (*s == '*') {
        ++s;
        spec.precision_ = internal::PrecisionHandler().visit(get_arg(s));
      }
    }

    using internal::Arg;
    Arg arg = get_arg(s, arg_index);
    if (spec.flag(HASH_FLAG) && internal::IsZeroInt().visit(arg))
      spec.flags_ &= ~internal::to_unsigned<int>(HASH_FLAG);
    if (spec.fill_ == '0') {
      if (arg.type <= Arg::LAST_NUMERIC_TYPE)
        spec.align_ = ALIGN_NUMERIC;
      else
        spec.fill_ = ' ';  // Ignore '0' flag for non-numeric types.
    }

    // Parse length and convert the argument to the required type.
    using internal::ArgConverter;
    switch (*s++) {
    case 'h':
      if (*s == 'h')
        ArgConverter<signed char>(arg, *++s).visit(arg);
      else
        ArgConverter<short>(arg, *s).visit(arg);
      break;
    case 'l':
      if (*s == 'l')
        ArgConverter<fmt::LongLong>(arg, *++s).visit(arg);
      else
        ArgConverter<long>(arg, *s).visit(arg);
      break;
    case 'j':
      ArgConverter<intmax_t>(arg, *s).visit(arg);
      break;
    case 'z':
      ArgConverter<std::size_t>(arg, *s).visit(arg);
      break;
    case 't':
      ArgConverter<std::ptrdiff_t>(arg, *s).visit(arg);
      break;
    case 'L':
      // printf produces garbage when 'L' is omitted for long double, no
      // need to do the same.
      break;
    default:
      --s;
      ArgConverter<void>(arg, *s).visit(arg);
    }

    // Parse type.
    if (!*s)
      FMT_THROW(FormatError("invalid format string"));
    spec.type_ = static_cast<char>(*s++);
    if (arg.type <= Arg::LAST_INTEGER_TYPE) {
      // Normalize type.
      switch (spec.type_) {
      case 'i': case 'u':
        spec.type_ = 'd';
        break;
      case 'c':
        // TODO: handle wchar_t
        internal::CharConverter(arg).visit(arg);
        break;
      }
    }

    start = s;

    // Format argument.
    AF(writer_, spec).visit(arg);
  }
  write(writer_, start, s);
}

template <typename Char>
void printf(BasicWriter<Char> &w, BasicCStringRef<Char> format, ArgList args) {
  PrintfFormatter<Char>(args, w).format(format);
}

inline std::string sprintf(CStringRef format, ArgList args) {
  MemoryWriter w;
  printf(w, format, args);
  return w.str();
}
FMT_VARIADIC(std::string, sprintf, CStringRef)

inline std::wstring sprintf(WCStringRef format, ArgList args) {
  WMemoryWriter w;
  printf(w, format, args);
  return w.str();
}
FMT_VARIADIC_W(std::wstring, sprintf, WCStringRef)


FMT_API int fprintf(std::FILE *f, CStringRef format, ArgList args);
FMT_VARIADIC(int, fprintf, std::FILE *, CStringRef)


inline int printf(CStringRef format, ArgList args) {
  return fprintf(stdout, format, args);
}
FMT_VARIADIC(int, printf, CStringRef)


inline int fprintf(std::ostream &os, CStringRef format_str, ArgList args) {
  MemoryWriter w;
  printf(w, format_str, args);
  internal::write(os, w);
  return static_cast<int>(w.size());
}
FMT_VARIADIC(int, fprintf, std::ostream &, CStringRef)
}  // namespace fmt

#endif  // FMT_PRINTF_H_