Loki/include/loki/SafeFormat.h

////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2005 by Andrei Alexandrescu
// Permission to use, copy, modify, distribute, and sell this software for any
//     purpose is hereby granted without fee, provided that the above copyright
//     notice appear in all copies and that both that copyright notice and this
//     permission notice appear in supporting documentation.
// The author makes no representations about the suitability of this software 
//     for any purpose. It is provided "as is" without express or implied 
//     warranty.
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
// This file contains definitions for SafePrintf. SafeScanf coming soon (the 
//   design is similar). 
// See Alexandrescu, Andrei: Type-safe Formatting, C/C++ Users Journal, Aug 2005
////////////////////////////////////////////////////////////////////////////////

#ifndef LOKI_SAFEFORMAT_H_
#define LOKI_SAFEFORMAT_H_

#include <cstdio>
#include <string>
#include <stdexcept>
#include <utility>
#include <cassert>
#include <locale>

namespace Loki
{

	// Crude writing method: writes straight to the file, unbuffered
	// Must be combined with a buffer to work properly (and efficiently)

	void write(std::FILE* f, const char* from, const char* to) {
		assert(from <= to);
		fwrite(from, 1, to - from, f);
	}

	// Write to a string

	void write(std::string& s, const char* from, const char* to) {
		assert(from <= to);
		s.append(from, to);
	}

	// Write to a fixed-size buffer

	template <class Char>
	void write(std::pair<Char*, std::size_t>& s, const Char* from, const Char* to) {
		assert(from <= to);
		if (from + s.second > to) throw std::overflow_error("");
		s.first = copy(from, to, s.first);
		s.second -= to - from;
	}

	////////////////////////////////////////////////////////////////////////////////
	// PrintfState class template
	// Holds the formatting state, and implements operator() to format stuff
	// Todo: make sure errors are handled properly
	////////////////////////////////////////////////////////////////////////////////

	template <class Device, class Char>
	struct PrintfState {
		PrintfState(Device dev, const Char * format) 
				: device_(dev)
				, format_(format)
				, result_(0) {
			Advance();
		}
	    
		~PrintfState() {
		}

		#define LOKI_PRINTF_STATE_FORWARD(type) \
			PrintfState& operator()(type par) {\
				return (*this)(static_cast< unsigned long >(par)); \
			}

		LOKI_PRINTF_STATE_FORWARD(bool)
		LOKI_PRINTF_STATE_FORWARD(char)
		LOKI_PRINTF_STATE_FORWARD(signed char)
		LOKI_PRINTF_STATE_FORWARD(unsigned char)
		LOKI_PRINTF_STATE_FORWARD(short)
		LOKI_PRINTF_STATE_FORWARD(unsigned short)
		LOKI_PRINTF_STATE_FORWARD(int)
		LOKI_PRINTF_STATE_FORWARD(unsigned)
		LOKI_PRINTF_STATE_FORWARD(long)

		// Print (or gobble in case of the "*" specifier) an int
		PrintfState& operator()(unsigned long i) {
			if (result_ == -1) return *this; // don't even bother
			// % [flags] [width] [.prec] [modifier] type_char
			// Fetch the flags 
			ReadFlags();
			if (*format_ == '*') {
				// read the width and get out
				SetWidth(static_cast<size_t>(i));
				++format_;
				return *this;
			}
			ReadWidth();
			// precision
			if (*format_ == '.') {
				// deal with precision
				if (format_[1] == '*') {
					// read the precision and get out
					SetPrec(static_cast<size_t>(i));
					format_ += 2;
					return *this;
				}
				ReadPrecision();
			}
			ReadModifiers();
			// input size modifier
			if (ForceShort()) {
				// short int
				const Char c = *format_;
				if (c == 'x' || c == 'X' || c == 'u' || c == 'o') {
					i = static_cast<unsigned long>(static_cast<unsigned short>(i));
				}
			}
			FormatWithCurrentFlags(i);
			return *this;
		}
	    
		PrintfState& operator()(double n) {
			if (result_ == -1) return *this; // don't even bother
			PrintFloatingPoint(n);
			return *this;
		}

		PrintfState& operator()(long double n) {
			if (result_ == -1) return *this; // don't even bother
			PrintFloatingPoint(n);
			return *this;
		}

		// Store the number of characters printed so far
		PrintfState& operator()(int * pi) {
			return StoreCountHelper(pi);
		}
	    
		// Store the number of characters printed so far
		PrintfState& operator()(short * pi) {
			return StoreCountHelper(pi);
		}
	    
		// Store the number of characters printed so far
		PrintfState& operator()(long * pi) {
			return StoreCountHelper(pi);
		}
	    
		PrintfState& operator()(const char *const s) {
			if (result_ == -1) return *this;
			ReadLeaders();
			const char fmt = *format_;
			if (fmt == 'p') {
				FormatWithCurrentFlags(reinterpret_cast<uintptr_t>(s));
				return *this;
			}
			if (fmt != 's') {
				result_ = -1;
				return *this;
			}
			const size_t len = std::min(strlen(s), prec_);
			if (width_ > len) {
				if (LeftJustify()) {
					Write(s, s + len);
					Fill(' ', width_ - len);
				} else {
					Fill(' ', width_ - len);
					Write(s, s + len);
				}
			} else {
				Write(s, s + len);
			}
			Next();
			return *this;
		}
	    
		PrintfState& operator()(const void *const p) {
			return (*this)(reinterpret_cast<uintptr_t>(p));
		}
	    
		// read the result
		operator int() const {
			return result_;
		}
	    
	private:
		PrintfState& operator=(const PrintfState&);
		template <typename T>
		PrintfState& StoreCountHelper(T *const pi) {
			if (result_ == -1) return *this; // don't even bother
			ReadLeaders();
			const char fmt = *format_;
			if (fmt == 'p') { // pointer
				FormatWithCurrentFlags(reinterpret_cast<unsigned long>(pi));
				return *this;
			}
			if (fmt != 'n') {
				result_ = -1;
				return *this;
			}
			assert(pi != 0);
			*pi = result_;
			Next();
			return *this;
		}

		void FormatWithCurrentFlags(const unsigned long i) {
			// look at the format character
			Char formatChar = *format_;
			bool isSigned = formatChar == 'd' || formatChar == 'i';
			if (formatChar == 'p') {
				formatChar = 'x'; // pointers go to hex
				SetAlternateForm(); // printed with '0x' in front
				isSigned = true; // that's what gcc does
			}
			if (!strchr("cdiuoxX", formatChar)) {
				result_ = -1;
				return;
			}
			Char buf[
				sizeof(unsigned long) * 3 // digits
				+ 1 // sign or ' '
				+ 2 // 0x or 0X
				+ 1]; // terminating zero
			const Char *const bufEnd = buf + (sizeof(buf) / sizeof(Char));
			Char * bufLast = buf + (sizeof(buf) / sizeof(Char) - 1);
			Char signChar = 0;
			unsigned int base = 10;
	        
			if (formatChar == 'c') {
				// Format only one character
				// The 'fill with zeros' flag is ignored
				ResetFillZeros();
				*bufLast = static_cast<char>(i);
			} else {
				// TODO: inefficient code, refactor
				const bool negative = isSigned && static_cast<long>(i) < 0;
				if (formatChar == 'o') base = 8;
				else if (formatChar == 'x' || formatChar == 'X') base = 16;
				bufLast = isSigned
					? RenderWithoutSign(static_cast<long>(i), bufLast, base,
						formatChar == 'X')
					: RenderWithoutSign(i, bufLast, base, 
						formatChar == 'X');
				// Add the sign
				if (isSigned) {
					negative ? signChar = '-'
					: ShowSignAlways() ? signChar = '+'
					: Blank() ? signChar = ' '
					: 0;
				}
			}
			// precision 
			size_t 
				countDigits = bufEnd - bufLast,
				countZeros = prec_ != size_t(-1) && countDigits < prec_ && 
						formatChar != 'c'
					? prec_ - countDigits 
					: 0,
				countBase = base != 10 && AlternateForm() && i != 0
					? (base == 16 ? 2 : countZeros > 0 ? 0 : 1)
					: 0,
				countSign = (signChar != 0),
				totalPrintable = countDigits + countZeros + countBase + countSign;
			size_t countPadLeft = 0, countPadRight = 0;
			if (width_ > totalPrintable) {
				if (LeftJustify()) {
					countPadRight = width_ - totalPrintable;
					countPadLeft = 0;
				} else {
					countPadLeft = width_ - totalPrintable;
					countPadRight = 0;
				}
			}
			if (FillZeros() && prec_ == size_t(-1)) {
				// pad with zeros and no precision - transfer padding to precision
				countZeros = countPadLeft;
				countPadLeft = 0;
			}
			// ok, all computed, ready to print to device
			Fill(' ', countPadLeft);
			if (signChar != 0) Write(&signChar, &signChar + 1);
			if (countBase > 0) Fill('0', 1);
			if (countBase == 2) Fill(formatChar, 1);
			Fill('0', countZeros);
			Write(bufLast, bufEnd);
			Fill(' ', countPadRight);
			// done, advance
			Next();
		}
	    
		void Write(const Char* b, const Char* e) {
			if (result_ < 0) return;
			const ptrdiff_t x = e - b;
			write(device_, b, e);
			result_ += x;
		}

		template <class Double>
		void PrintFloatingPoint(Double n) {
			const Char *const fmt = format_ - 1;
			assert(*fmt == '%');
			// enforce format string validity
			ReadLeaders();
			// enforce format spec
			if (!strchr("eEfgG", *format_)) {
				result_ = -1;
				return;
			}
			// format char validated, copy it to a temp and use legacy sprintf
			++format_;
			Char fmtBuf[128], resultBuf[1024];
			if (format_  >= fmt + sizeof(fmtBuf) / sizeof(Char)) {
				result_ = -1;
				return;
			}
			memcpy(fmtBuf, fmt, (format_ - fmt) * sizeof(Char));
			fmtBuf[format_ - fmt] = 0;
	#ifdef _MSC_VER
			const int stored = _snprintf(resultBuf, 
	#else
			const int stored = snprintf(resultBuf, 
	#endif        
				sizeof(resultBuf) / sizeof(Char), fmtBuf, n);
			if (stored < 0) {
				result_ = -1;
				return;
			}
			Write(resultBuf, resultBuf + strlen(resultBuf));
			Advance(); // output stuff to the next format directive
		}

		void Fill(const Char c, size_t n) {
			for (; n > 0; --n) {
				Write(&c, &c + 1);
			}
		}
	    
		Char* RenderWithoutSign(unsigned long n, char* bufLast, 
				unsigned int base, bool uppercase) {
			const Char hex1st = uppercase ? 'A' : 'a';
			for (;;) {
				const unsigned long next = n / base;
				Char c = n - next * base;
				c += (c <= 9) ? '0' : hex1st - 10;
				*bufLast = c;
				n = next;
				if (n == 0) break;
				--bufLast;
			}
			return bufLast;
		}
	    
		char* RenderWithoutSign(long n, char* bufLast, unsigned int base, 
				bool uppercase) {
			if (n != LONG_MIN) {
				return RenderWithoutSign(static_cast<unsigned long>(n < 0 ? -n : n),
					bufLast, base, uppercase);            
			}
			// annoying corner case
			char* save = bufLast;
			++n;
			bufLast = RenderWithoutSign(static_cast<unsigned long>(n),
				bufLast, base, uppercase);
			--(*save);
			return bufLast;
		}
	    
		void Next() {
			++format_;
			Advance();
		}
	    
		void Advance() {
			ResetAll();
			const Char* begin = format_;
			for (;;) {
				if (*format_ == '%') { 
					if (format_[1] != '%') { // It's a format specifier
						Write(begin, format_);
						++format_;
						break;
					}
					// It's a "%%"
					Write(begin, ++format_);
					begin = ++format_;
					continue; 
				}
				if (*format_ == 0) {
					Write(begin, format_);
					break;
				}
				++format_;
			}
		}
	    
		void ReadFlags() {
			for (;; ++format_) {
				switch (*format_) {
					case '-': SetLeftJustify(); break;
					case '+': SetShowSignAlways(); break;
					case ' ': SetBlank(); break;
					case '#': SetAlternateForm(); break;
					case '0': SetFillZeros(); break;
					default: return;
				}
			}
		}
	    
		void ParseDecimalSizeT(size_t& dest) {
			if (!std::isdigit(*format_, std::locale())) return;
			size_t r = 0;
			do {
				// TODO: inefficient - rewrite
				r *= 10;
				r += *format_ - '0';
				++format_;
			} while (std::isdigit(*format_, std::locale()));
			dest = r;
		}
	    
		void ReadWidth() {
			ParseDecimalSizeT(width_);
		}    
	    
		void ReadPrecision() {
			assert(*format_ == '.');
			++format_;
			ParseDecimalSizeT(prec_);
		}    
	    
		void ReadModifiers() {
			switch (*format_) {
				case 'h': SetForceShort(); ++format_; break;
				case 'l': ++format_; break;
				// more (C99 and platform-specific modifiers) to come
			}
		}
	    
		void ReadLeaders() {
			ReadFlags();
			ReadWidth();
			if (*format_ == '.') ReadPrecision();
			ReadModifiers();
		}
	    
		enum { 
			leftJustify = 1,
			showSignAlways = 2,
			blank = 4,
			alternateForm = 8,
			fillZeros = 16,
			forceShort = 32
		};
	    
		bool LeftJustify() const { return (flags_ & leftJustify) != 0; }
		bool ShowSignAlways() const { return (flags_ & showSignAlways) != 0; }
		void SetWidth(size_t w) { width_  = w; }
		void SetLeftJustify() { flags_  |= leftJustify; }
		void SetShowSignAlways() { flags_ |= showSignAlways; }
		bool Blank() const { return (flags_ & blank) != 0; }
		bool AlternateForm() const { return (flags_ & alternateForm) != 0; }
		bool FillZeros() const { return (flags_ & fillZeros) != 0; }
		bool ForceShort() const { return (flags_ & forceShort) != 0; }

		void SetPrec(size_t p) { prec_ = p; }
		void SetBlank() { flags_ |= blank; }
		void SetAlternateForm() { flags_ |=  alternateForm; }
		void SetFillZeros() { flags_ |= fillZeros; }
		void ResetFillZeros() { flags_ &= ~fillZeros; }
		void SetForceShort() { flags_ |= forceShort; }
	    
		void ResetAll() {
			assert(result_ != EOF);
			width_ = 0;
			prec_ = size_t(-1);
			flags_ = 0;
		}

		// state
		Device device_;
		const Char* format_;
		size_t width_;
		size_t prec_;
		unsigned int flags_;
		int result_;
	};

	PrintfState<std::FILE*, char> Printf(const char* format) {
		return PrintfState<std::FILE*, char>(stdout, format);
	}

	PrintfState<std::FILE*, char> FPrintf(FILE* f, const char* format) {
		return PrintfState<std::FILE*, char>(f, format);
	}

	PrintfState<std::string&, char> SPrintf(std::string& s, const char* format) {
		return PrintfState<std::string&, char>(s, format);
	}

	template <class T, class Char>
	PrintfState<T&, Char> XPrintf(T& device, const Char* format) {
		return PrintfState<T&, Char>(device, format);
	}

	template <class Char, std::size_t N>
	PrintfState<std::pair<Char*, std::size_t>, Char> 
	BufPrintf(Char (&buf)[N], const Char* format) {
		std::pair<Char*, std::size_t> temp(buf, N);
		return PrintfState<std::pair<Char*, std::size_t>, Char>(temp, format);
	}

}// namespace Loki

#endif //SAFEFORMAT_H_