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//===- Format.h - Efficient printf-style formatting for streams -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the format() function, which can be used with other
// LLVM subsystems to provide printf-style formatting. This gives all the power
// and risk of printf. This can be used like this (with raw_ostreams as an
// example):
//
// OS << "mynumber: " << format("%4.5f", 1234.412) << '\n';
//
// Or if you prefer:
//
// OS << format("mynumber: %4.5f\n", 1234.412);
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_FORMAT_H
#define LLVM_SUPPORT_FORMAT_H
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/DataTypes.h"
#include <cassert>
#include <cstdio>
#include <tuple>
namespace llvm {
/// This is a helper class used for handling formatted output. It is the
/// abstract base class of a templated derived class.
class format_object_base {
protected:
const char *Fmt;
~format_object_base() = default; // Disallow polymorphic deletion.
format_object_base(const format_object_base &) = default;
virtual void home(); // Out of line virtual method.
/// Call snprintf() for this object, on the given buffer and size.
virtual int snprint(char *Buffer, unsigned BufferSize) const = 0;
public:
format_object_base(const char *fmt) : Fmt(fmt) {}
/// Format the object into the specified buffer. On success, this returns
/// the length of the formatted string. If the buffer is too small, this
/// returns a length to retry with, which will be larger than BufferSize.
unsigned print(char *Buffer, unsigned BufferSize) const {
assert(BufferSize && "Invalid buffer size!");
// Print the string, leaving room for the terminating null.
int N = snprint(Buffer, BufferSize);
// VC++ and old GlibC return negative on overflow, just double the size.
if (N < 0)
return BufferSize * 2;
// Other implementations yield number of bytes needed, not including the
// final '\0'.
if (unsigned(N) >= BufferSize)
return N + 1;
// Otherwise N is the length of output (not including the final '\0').
return N;
}
};
/// These are templated helper classes used by the format function that
/// capture the object to be formated and the format string. When actually
/// printed, this synthesizes the string into a temporary buffer provided and
/// returns whether or not it is big enough.
template <typename... Ts>
class format_object final : public format_object_base {
std::tuple<Ts...> Vals;
template <std::size_t... Is>
int snprint_tuple(char *Buffer, unsigned BufferSize,
index_sequence<Is...>) const {
#ifdef _MSC_VER
return _snprintf(Buffer, BufferSize, Fmt, std::get<Is>(Vals)...);
#else
return snprintf(Buffer, BufferSize, Fmt, std::get<Is>(Vals)...);
#endif
}
public:
format_object(const char *fmt, const Ts &... vals)
: format_object_base(fmt), Vals(vals...) {}
int snprint(char *Buffer, unsigned BufferSize) const override {
return snprint_tuple(Buffer, BufferSize, index_sequence_for<Ts...>());
}
};
/// These are helper functions used to produce formatted output. They use
/// template type deduction to construct the appropriate instance of the
/// format_object class to simplify their construction.
///
/// This is typically used like:
/// \code
/// OS << format("%0.4f", myfloat) << '\n';
/// \endcode
template <typename... Ts>
inline format_object<Ts...> format(const char *Fmt, const Ts &... Vals) {
return format_object<Ts...>(Fmt, Vals...);
}
/// This is a helper class used for left_justify() and right_justify().
class FormattedString {
StringRef Str;
unsigned Width;
bool RightJustify;
friend class raw_ostream;
public:
FormattedString(StringRef S, unsigned W, bool R)
: Str(S), Width(W), RightJustify(R) { }
};
/// left_justify - append spaces after string so total output is
/// \p Width characters. If \p Str is larger that \p Width, full string
/// is written with no padding.
inline FormattedString left_justify(StringRef Str, unsigned Width) {
return FormattedString(Str, Width, false);
}
/// right_justify - add spaces before string so total output is
/// \p Width characters. If \p Str is larger that \p Width, full string
/// is written with no padding.
inline FormattedString right_justify(StringRef Str, unsigned Width) {
return FormattedString(Str, Width, true);
}
/// This is a helper class used for format_hex() and format_decimal().
class FormattedNumber {
uint64_t HexValue;
int64_t DecValue;
unsigned Width;
bool Hex;
bool Upper;
bool HexPrefix;
friend class raw_ostream;
public:
FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U,
bool Prefix)
: HexValue(HV), DecValue(DV), Width(W), Hex(H), Upper(U),
HexPrefix(Prefix) {}
};
/// format_hex - Output \p N as a fixed width hexadecimal. If number will not
/// fit in width, full number is still printed. Examples:
/// OS << format_hex(255, 4) => 0xff
/// OS << format_hex(255, 4, true) => 0xFF
/// OS << format_hex(255, 6) => 0x00ff
/// OS << format_hex(255, 2) => 0xff
inline FormattedNumber format_hex(uint64_t N, unsigned Width,
bool Upper = false) {
assert(Width <= 18 && "hex width must be <= 18");
return FormattedNumber(N, 0, Width, true, Upper, true);
}
/// format_hex_no_prefix - Output \p N as a fixed width hexadecimal. Does not
/// prepend '0x' to the outputted string. If number will not fit in width,
/// full number is still printed. Examples:
/// OS << format_hex_no_prefix(255, 4) => ff
/// OS << format_hex_no_prefix(255, 4, true) => FF
/// OS << format_hex_no_prefix(255, 6) => 00ff
/// OS << format_hex_no_prefix(255, 2) => ff
inline FormattedNumber format_hex_no_prefix(uint64_t N, unsigned Width,
bool Upper = false) {
assert(Width <= 18 && "hex width must be <= 18");
return FormattedNumber(N, 0, Width, true, Upper, false);
}
/// format_decimal - Output \p N as a right justified, fixed-width decimal. If
/// number will not fit in width, full number is still printed. Examples:
/// OS << format_decimal(0, 5) => " 0"
/// OS << format_decimal(255, 5) => " 255"
/// OS << format_decimal(-1, 3) => " -1"
/// OS << format_decimal(12345, 3) => "12345"
inline FormattedNumber format_decimal(int64_t N, unsigned Width) {
return FormattedNumber(0, N, Width, false, false, false);
}
} // end namespace llvm
#endif
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