/*
  Copyright 2008 Larry Gritz and the other authors and contributors.
  All Rights Reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
  * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
  * Neither the name of the software's owners nor the names of its
    contributors may be used to endorse or promote products derived from
    this software without specific prior written permission.
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  (This is the Modified BSD License)
*/

// clang-format off

/////////////////////////////////////////////////////////////////////////
/// @file  strutil.h
///
/// @brief String-related utilities, all in namespace Strutil.
/////////////////////////////////////////////////////////////////////////



#pragma once

#include <cstdio>
#include <map>
#include <string>
#include <vector>

#include <OpenImageIO/export.h>
#include <OpenImageIO/hash.h>
#include <OpenImageIO/oiioversion.h>
#include <OpenImageIO/platform.h>
#include <OpenImageIO/string_view.h>

// For now, let a prior set of OIIO_USE_FMT=0 cause us to fall back to
// tinyformat.
#ifndef OIIO_USE_FMT
#    define OIIO_USE_FMT
#endif

#if OIIO_GNUC_VERSION >= 70000
#    pragma GCC diagnostic push
#    pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif
#ifndef FMT_HEADER_ONLY
#    define FMT_HEADER_ONLY
#endif
#include "fmt/ostream.h"
#include "fmt/format.h"
#include "fmt/printf.h"
#if OIIO_GNUC_VERSION >= 70000
#    pragma GCC diagnostic pop
#endif

// Allow client software to know if this version of OIIO as Strutil::sprintf
#define OIIO_HAS_SPRINTF 1

// Allow client software to know if this version of OIIO has Strutil::format
// behave like sprintf (OIIO_FORMAT_IS_FMT==0) or like python / {fmt} /
// C++20ish std::format (OIIO_FORMAT_IS_FMT==1).
#define OIIO_FORMAT_IS_FMT 0

// Allow client software to know that at this moment, the fmt-based string
// formatting is not correctly locale-independent. We will change this value
// to 1 when the fmt bugs are fixed.
#define OIIO_FMT_LOCALE_INDEPENDENT 0

#ifndef TINYFORMAT_USE_VARIADIC_TEMPLATES
#    define TINYFORMAT_USE_VARIADIC_TEMPLATES
#endif
#include <OpenImageIO/tinyformat.h>

#ifndef OPENIMAGEIO_PRINTF_ARGS
#   ifndef __GNUC__
#       define __attribute__(x)
#   endif
    // Enable printf-like warnings with gcc by attaching
    // OPENIMAGEIO_PRINTF_ARGS to printf-like functions.  Eg:
    //
    // void foo (const char* fmt, ...) OPENIMAGEIO_PRINTF_ARGS(1,2);
    //
    // The arguments specify the positions of the format string and the the
    // beginning of the varargs parameter list respectively.
    //
    // For member functions with arguments like the example above, you need
    // OPENIMAGEIO_PRINTF_ARGS(2,3) instead.  (gcc includes the implicit this
    // pointer when it counts member function arguments.)
#   define OPENIMAGEIO_PRINTF_ARGS(fmtarg_pos, vararg_pos) \
        __attribute__ ((format (printf, fmtarg_pos, vararg_pos) ))
#endif


OIIO_NAMESPACE_BEGIN
/// @namespace Strutil
///
/// @brief     String-related utilities.
namespace Strutil {

/// Output the string to the file/stream in a synchronized fashion, so that
/// buffers are flushed and internal mutex is used to prevent threads from
/// clobbering each other -- output strings coming from concurrent threads
/// may be interleaved, but each string is "atomic" and will never splice
/// each other character-by-character.
void OIIO_API sync_output (FILE *file, string_view str);
void OIIO_API sync_output (std::ostream &file, string_view str);


/// Construct a std::string in a printf-like fashion.  For example:
///
///    std::string s = Strutil::sprintf ("blah %d %g", (int)foo, (float)bar);
///
/// Uses the tinyformat or fmt library underneath, so it's fully type-safe, and
/// works with any types that understand stream output via '<<'.
/// The formatting of the string will always use the classic "C" locale
/// conventions (in particular, '.' as decimal separator for float values).
template<typename... Args>
inline std::string sprintf (const char* fmt, const Args&... args)
{
    // Have to fall back on tinyformat rather than fmt::format, because
    // fmt::format is not correctly locale-independent for floating point
    // values. As soon as they fix it, we will upgrade, then change this
    // implementation to use `::fmt::sprintf(fmt, args...)` if it is faster.
#if 1
    return tinyformat::format (fmt, args...);
#else
    return ::fmt::sprintf (fmt, args...);
#endif
}



/// format() constructs formatted strings. Note that this is in transition!
///
/// Strutil::old::format() uses printf conventions and matches format() used
/// in OIIO 1.x. It is equivalent to Strutil::sprintf().
///
///    std::string s = Strutil::old::sprintf ("blah %d %g", (int)foo, (float)bar);
///
/// Strutil::fmt::format() uses "Python" conventions, in the style of string
/// formatting being planned for C++20 and implemented today in the {fmt}
/// package (https://github.com/fmtlib/fmt). For example:
///
///    std::string s = Strutil::format ("blah {}  {}", (int)foo, (float)bar);
///
/// Straight-up Strutil::format is today aliased to old::format for the sake
/// of back-compatibility, but will someday be switched to fmt::format.
///
/// Recommended strategy for users:
/// * If you want printf conventions, switch to Strutil::sprintf().
/// * If you want to use the python conventions prior to the big switch,
///   use Strutil::fmt::format() explicitly (but see the caveat below).
/// * Use of unspecified Strutil::format() is, for back compatibility,
///   currently equivalent to sprintf, but beware that some point it will
///   switch to the future-standard formatting rules.
///
/// Caveat: BEWARE using fmt::format on floating point values if there is
/// any chance you could be running with a global non-C locale, because fmt
/// does not yet correctly produce locale-independent output! We will
/// upgrade as soon as they get that fixed.

namespace fmt {
template<typename... Args>
inline std::string format (const char* fmt, const Args&... args)
{
    return ::fmt::format (fmt, args...);
}
} // namespace fmt

namespace old {
template<typename... Args>
inline std::string format (const char* fmt, const Args&... args)
{
    return Strutil::sprintf (fmt, args...);
}

// DEPRECATED(2.0) string_view version. Phasing this out because
// std::string_view won't have a c_str() method.
template<typename... Args>
inline std::string format (string_view fmt, const Args&... args)
{
    return format (fmt.c_str(), args...);
}
} // namespace old



using old::format;



/// Strutil::print (fmt, ...)
/// Strutil::fprint (FILE*, fmt, ...)
/// Strutil::fprint (ostream& fmt, ...)
///
/// Output formatted strings to stdout, a FILE*, or a stream, respectively.
/// All use printf-like formatting rules, are type-safe, are thread-safe
/// (the outputs are "atomic", at least versus other calls to
/// Strutil::*printf), and automatically flush their outputs. They are all
/// locale-independent (forcing classic "C" locale).

template<typename... Args>
inline void printf (const char* fmt, const Args&... args)
{
    sync_output (stdout, Strutil::sprintf(fmt, args...));
}

template<typename... Args>
inline void fprintf (FILE *file, const char* fmt, const Args&... args)
{
    sync_output (file, Strutil::sprintf(fmt, args...));
}

template<typename... Args>
inline void fprintf (std::ostream &file, const char* fmt, const Args&... args)
{
    sync_output (file, Strutil::sprintf(fmt, args...));
}



/// Strutil::print (fmt, ...)
/// Strutil::print (FILE*, fmt, ...)
/// Strutil::print (ostream& fmt, ...)
///
/// Output formatted strings to stdout, a FILE*, or a stream, respectively.
/// All use "Python-like" formatting description (as {fmt} does, and some
/// day, std::format), are type-safe, are thread-safe (the outputs are
/// "atomic", at least versus other calls to Strutil::*printf), and
/// automatically flush their outputs. They are all locale-independent by
/// default (use {:n} for locale-aware formatting).

template<typename... Args>
inline void print (const char* fmt, const Args&... args)
{
    sync_output (stdout, Strutil::fmt::format(fmt, args...));
}

template<typename... Args>
inline void print (FILE *file, const char* fmt, const Args&... args)
{
    sync_output (file, Strutil::fmt::format(fmt, args...));
}

template<typename... Args>
inline void print (std::ostream &file, const char* fmt, const Args&... args)
{
    sync_output (file, Strutil::fmt::format(fmt, args...));
}




/// Return a std::string formatted from printf-like arguments -- passed
/// already as a va_list.  This is not guaranteed type-safe and is not
/// extensible like format(). Use with caution!
std::string OIIO_API vsprintf (const char *fmt, va_list ap)
                                         OPENIMAGEIO_PRINTF_ARGS(1,0);

/// Return a std::string formatted like Strutil::format, but passed
/// already as a va_list.  This is not guaranteed type-safe and is not
/// extensible like format(). Use with caution!
std::string OIIO_API vformat (const char *fmt, va_list ap)
                                         OPENIMAGEIO_PRINTF_ARGS(1,0);

/// Return a string expressing a number of bytes, in human readable form.
///  - memformat(153)           -> "153 B"
///  - memformat(15300)         -> "14.9 KB"
///  - memformat(15300000)      -> "14.6 MB"
///  - memformat(15300000000LL) -> "14.2 GB"
std::string OIIO_API memformat (long long bytes, int digits=1);

/// Return a string expressing an elapsed time, in human readable form.
/// e.g. "0:35.2"
std::string OIIO_API timeintervalformat (double secs, int digits=1);


/// Get a map with RESTful arguments extracted from the given string 'str'.
/// Add it into the 'result' argument (Warning: the 'result' argument may
/// be changed even if 'get_rest_arguments ()' return an error!).
/// Return true on success, false on error.
/// Acceptable forms:
///  - text?arg1=val1&arg2=val2...
///  - ?arg1=val1&arg2=val2...
/// Everything before question mark will be saved into the 'base' argument.
bool OIIO_API get_rest_arguments (const std::string &str, std::string &base,
                                   std::map<std::string, std::string> &result);

/// Take a string that may have embedded newlines, tabs, etc., and turn
/// those characters into escape sequences like \n, \t, \v, \b, \r, \f,
/// \a, \\, \".
std::string OIIO_API escape_chars (string_view unescaped);

/// Take a string that has embedded escape sequences (\\, \", \n, etc.)
/// and collapse them into the 'real' characters.
std::string OIIO_API unescape_chars (string_view escaped);

/// Word-wrap string `src` to no more than `columns` width, starting with an
/// assumed position of `prefix` on the first line and intending by `prefix`
/// blanks before all lines other than the first.
///
/// Words may be split AT any characters in `sep` or immediately AFTER any
/// characters in `presep`. After the break, any extra `sep` characters will
/// be deleted.
///
/// By illustration,
///     wordwrap("0 1 2 3 4 5 6 7 8", 10, 4)
/// should return:
///     "0 1 2\n    3 4 5\n    6 7 8"
std::string OIIO_API wordwrap (string_view src, int columns = 80,
                               int prefix = 0, string_view sep = " ",
                               string_view presep = "");

/// Hash a string_view.
inline size_t
strhash (string_view s)
{
    return s.length() ? farmhash::Hash (s) : 0;
}



/// Case-insensitive comparison of strings.  For speed, this always uses
/// a static locale that doesn't require a mutex.
bool OIIO_API iequals (string_view a, string_view b);

/// Case-insensitive ordered comparison of strings.  For speed, this always
/// uses a static locale that doesn't require a mutex.
bool OIIO_API iless (string_view a, string_view b);

/// Does 'a' start with the string 'b', with a case-sensitive comparison?
bool OIIO_API starts_with (string_view a, string_view b);

/// Does 'a' start with the string 'b', with a case-insensitive comparison?
/// For speed, this always uses a static locale that doesn't require a mutex.
bool OIIO_API istarts_with (string_view a, string_view b);

/// Does 'a' end with the string 'b', with a case-sensitive comparison?
bool OIIO_API ends_with (string_view a, string_view b);

/// Does 'a' end with the string 'b', with a case-insensitive comparison?
/// For speed, this always uses a static locale that doesn't require a mutex.
bool OIIO_API iends_with (string_view a, string_view b);

/// Does 'a' contain the string 'b' within it?
bool OIIO_API contains (string_view a, string_view b);

/// Does 'a' contain the string 'b' within it, using a case-insensitive
/// comparison?
bool OIIO_API icontains (string_view a, string_view b);

/// Convert to upper case, faster than std::toupper because we use
/// a static locale that doesn't require a mutex lock.
void OIIO_API to_lower (std::string &a);

/// Convert to upper case, faster than std::toupper because we use
/// a static locale that doesn't require a mutex lock.
void OIIO_API to_upper (std::string &a);



/// Return a reference to the section of str that has all consecutive
/// characters in chars removed from the beginning and ending.  If chars is
/// empty, it will be interpreted as " \t\n\r\f\v" (whitespace).
string_view OIIO_API strip (string_view str, string_view chars=string_view());

/// Fills the "result" list with the words in the string, using sep as
/// the delimiter string.  If maxsplit is > -1, at most maxsplit splits
/// are done. If sep is "", any whitespace string is a separator.
void OIIO_API split (string_view str, std::vector<string_view> &result,
                     string_view sep = string_view(), int maxsplit = -1);
void OIIO_API split (string_view str, std::vector<std::string> &result,
                     string_view sep = string_view(), int maxsplit = -1);

/// Split the contents of `str` using `sep` as the delimiter string (if
/// `sep` is "", any whitespace string is a separator). If `maxsplit > -1`,
/// at most `maxsplit` splits are performed. The result is returned as a
/// vector of std::string (for `splits()`) or a vector of string_view (for
/// `splitsv()`).
OIIO_API std::vector<std::string>
splits (string_view str, string_view sep = "", int maxsplit = -1);
OIIO_API std::vector<string_view>
splitsv (string_view str, string_view sep = "", int maxsplit = -1);

/// Join all the strings in 'seq' into one big string, separated by the
/// 'sep' string. The Sequence can be any iterable collection of items that
/// are able to convert to string via stream output. Examples include:
/// std::vector<string_view>, std::vector<std::string>, std::set<ustring>,
/// std::vector<int>, etc.
template<class Sequence>
std::string join (const Sequence& seq, string_view sep="")
{
    std::ostringstream out;
    bool first = true;
    for (auto&& s : seq) {
        if (! first && sep.size())
            out << sep;
        out << s;
        first = false;
    }
    return out.str();
}

/// Repeat a string formed by concatenating str n times.
std::string OIIO_API repeat (string_view str, int n);

/// Replace a pattern inside a string and return the result. If global is
/// true, replace all instances of the pattern, otherwise just the first.
std::string OIIO_API replace (string_view str, string_view pattern,
                              string_view replacement, bool global=false);


/// strtod/strtof equivalents that are "locale-independent", always using
/// '.' as the decimal separator. This should be preferred for I/O and other
/// situations where you want the same standard formatting regardless of
/// locale.
float OIIO_API strtof (const char *nptr, char **endptr = nullptr);
double OIIO_API strtod (const char *nptr, char **endptr = nullptr);


// stoi() returns the int conversion of text from a string.
// No exceptions or errors -- parsing errors just return 0, over/underflow
// gets clamped to int range. No locale consideration.
OIIO_API int stoi (string_view s, size_t* pos=0, int base=10);

// stoui() returns the unsigned int conversion of text from a string.
// No exceptions or errors -- parsing errors just return 0. Negative
// values are cast, overflow is clamped. No locale considerations.
inline unsigned int stoui (string_view s, size_t* pos=0, int base=10) {
    return static_cast<unsigned int>(stoi (s, pos, base));
}

/// stof() returns the float conversion of text from several string types.
/// No exceptions or errors -- parsing errors just return 0.0. These always
/// use '.' for the decimal mark (versus atof and std::strtof, which are
/// locale-dependent).
OIIO_API float stof (string_view s, size_t* pos=0);
#define OIIO_STRUTIL_HAS_STOF 1  /* be able to test this */

// Temporary fix: allow separate std::string and char* versions, to avoid
// string_view allocation on some platforms. This will be deprecated once
// we can count on all supported compilers using short string optimization.
OIIO_API float stof (const std::string& s, size_t* pos=0);
OIIO_API float stof (const char* s, size_t* pos=0);
// N.B. For users of ustring, there's a stof(ustring) defined in ustring.h.

OIIO_API double stod (string_view s, size_t* pos=0);
OIIO_API double stod (const std::string& s, size_t* pos=0);
OIIO_API double stod (const char* s, size_t* pos=0);



/// Return true if the string is exactly (other than leading  and trailing
/// whitespace) a valid int.
OIIO_API bool string_is_int (string_view s);

/// Return true if the string is exactly (other than leading or trailing
/// whitespace) a valid float. This operations in a locale-independent
/// manner, i.e., it assumes '.' as the decimal mark.
OIIO_API bool string_is_float (string_view s);



// Helper template to convert from generic type to string. Used when you
// want stoX but you're in a template. Rigged to use "C" locale.
template<typename T>
inline T from_string (string_view s) {
    return T(s); // Generic: assume there is an explicit converter
}
// Special case for int
template<> inline int from_string<int> (string_view s) {
    return Strutil::stoi(s);
}
// Special case for uint
template<> inline unsigned int from_string<unsigned int> (string_view s) {
    return Strutil::stoui(s);
}
// Special case for float -- note that by using Strutil::strtof, this
// always treats '.' as the decimal mark.
template<> inline float from_string<float> (string_view s) {
    return Strutil::stof(s);
}



// Template function to convert any type to a string. The default
// implementation is just to use sprintf. The template can be
// overloaded if there is a better method for particular types.
// Eventually, we want this to use fmt::to_string, but for now that doesn't
// work because {fmt} doesn't correctly support locale-independent
// formatting of floating-point types.
template<typename T>
inline std::string to_string (const T& value) {
    return Strutil::sprintf("%s",value);
}

template<> inline std::string to_string (const std::string& value) { return value; }
template<> inline std::string to_string (const string_view& value) { return value; }
inline std::string to_string (const char* value) { return value; }

// Int types are SO much faster with fmt than tinyformat, specialize. Can't
// do it for floats yet because of the locale-dependence.
inline std::string to_string (int value) { return ::fmt::to_string(value); }
inline std::string to_string (size_t value) { return ::fmt::to_string(value); }




// Helper template to test if a string is a generic type. Used instead of
// string_is_X, but when you're inside templated code.
template<typename T>
inline bool string_is (string_view /*s*/) {
    return false; // Generic: assume there is an explicit specialization
}
// Special case for int
template <> inline bool string_is<int> (string_view s) {
    return string_is_int (s);
}
// Special case for float. Note that by using Strutil::stof, this always
// treats '.' as the decimal character.
template <> inline bool string_is<float> (string_view s) {
    return string_is_float (s);
}




/// Given a string containing values separated by a comma (or optionally
/// another separator), extract the individual values, placing them into
/// vals[] which is presumed to already contain defaults.  If only a single
/// value was in the list, replace all elements of vals[] with the value.
/// Otherwise, replace them in the same order.  A missing value will simply
/// not be replaced. Return the number of values found in the list
/// (including blank or malformed ones). If the vals vector was empty
/// initially, grow it as necessary.
///
/// For example, if T=float, suppose initially, vals[] = {0, 1, 2}, then
///   "3.14"       results in vals[] = {3.14, 3.14, 3.14}
///   "3.14,,-2.0" results in vals[] = {3.14, 1, -2.0}
///
/// This can work for type T = int, float, or any type for that has
/// an explicit constructor from a std::string.
template<class T>
int extract_from_list_string (std::vector<T> &vals,
                              string_view list,
                              string_view sep = ",")
{
    size_t nvals = vals.size();
    std::vector<string_view> valuestrings;
    Strutil::split (list, valuestrings, sep);
    for (size_t i = 0, e = valuestrings.size(); i < e; ++i) {
        T v = from_string<T> (valuestrings[i]);
        if (nvals == 0)
            vals.push_back (v);
        else if (valuestrings[i].size()) {
            if (vals.size() > i)  // don't replace non-existnt entries
                vals[i] = from_string<T> (valuestrings[i]);
        }
        /* Otherwise, empty space between commas, so leave default alone */
    }
    if (valuestrings.size() == 1 && nvals > 0) {
        vals.resize (1);
        vals.resize (nvals, vals[0]);
    }
    return list.size() ? (int) valuestrings.size() : 0;
}


/// Given a string containing values separated by a comma (or optionally
/// another separator), extract the individual values, returning them as a
/// std::vector<T>. The vector will be initialized with `nvals` elements
/// with default value `val`. If only a single value was in the list,
/// replace all elements of vals[] with the value. Otherwise, replace them
/// in the same order.  A missing value will simply not be replaced and
/// will retain the initialized default value. If the string contains more
/// then `nvals` values, they will append to grow the vector.
///
/// For example, if T=float,
///   extract_from_list_string ("", 3, 42.0f)
///       --> {42.0, 42.0, 42.0}
///   extract_from_list_string ("3.14", 3, 42.0f)
///       --> {3.14, 3.14, 3.14}
///   extract_from_list_string ("3.14,,-2.0", 3, 42.0f)
///       --> {3.14, 42.0, -2.0}
///   extract_from_list_string ("1,2,3,4", 3, 42.0f)
///       --> {1.0, 2.0, 3.0, 4.0}
///
/// This can work for type T = int, float, or any type for that has
/// an explicit constructor from a std::string.
template<class T>
std::vector<T>
extract_from_list_string (string_view list, size_t nvals=0, T val=T(),
                          string_view sep = ",")
{
    std::vector<T> vals (nvals, val);
    extract_from_list_string (vals, list, sep);
    return vals;
}




/// C++ functor wrapper class for using strhash for unordered_map or
/// unordered_set.  The way this is used, in conjunction with
/// StringEqual, to build an efficient hash map for char*'s or
/// std::string's is as follows:
/// \code
///    unordered_map <const char *, Key, Strutil::StringHash, Strutil::StringEqual>
/// \endcode
class StringHash {
public:
    size_t operator() (string_view s) const {
        return (size_t)Strutil::strhash(s);
    }
};



/// C++ functor for comparing two strings for equality of their characters.
struct OIIO_API StringEqual {
    bool operator() (const char *a, const char *b) const { return strcmp (a, b) == 0; }
    bool operator() (string_view a, string_view b) const { return a == b; }
};


/// C++ functor for comparing two strings for equality of their characters
/// in a case-insensitive and locale-insensitive way.
struct OIIO_API StringIEqual {
    bool operator() (const char *a, const char *b) const;
    bool operator() (string_view a, string_view b) const { return iequals (a, b); }
};


/// C++ functor for comparing the ordering of two strings.
struct OIIO_API StringLess {
    bool operator() (const char *a, const char *b) const { return strcmp (a, b) < 0; }
    bool operator() (string_view a, string_view b) const { return a < b; }
};


/// C++ functor for comparing the ordering of two strings in a
/// case-insensitive and locale-insensitive way.
struct OIIO_API StringILess {
    bool operator() (const char *a, const char *b) const;
    bool operator() (string_view a, string_view b) const { return a < b; }
};



#ifdef _WIN32
/// Conversion functions between UTF-8 and UTF-16 for windows.
///
/// For historical reasons, the standard encoding for strings on windows is
/// UTF-16, whereas the unix world seems to have settled on UTF-8.  These two
/// encodings can be stored in std::string and std::wstring respectively, with
/// the caveat that they're both variable-width encodings, so not all the
/// standard string methods will make sense (for example std::string::size()
/// won't return the number of glyphs in a UTF-8 string, unless it happens to
/// be made up of only the 7-bit ASCII subset).
///
/// The standard windows API functions usually have two versions, a UTF-16
/// version with a 'W' suffix (using wchar_t* strings), and an ANSI version
/// with a 'A' suffix (using char* strings) which uses the current windows
/// code page to define the encoding.  (To make matters more confusing there is
/// also a further "TCHAR" version which is #defined to the UTF-16 or ANSI
/// version, depending on whether UNICODE is defined during compilation.
/// This is meant to make it possible to support compiling libraries in
/// either unicode or ansi mode from the same codebase.)
///
/// Using std::string as the string container (as in OIIO) implies that we
/// can't use UTF-16.  It also means we need a variable-width encoding to
/// represent characters in non-Latin alphabets in an unambiguous way; the
/// obvious candidate is UTF-8.  File paths in OIIO are considered to be
/// represented in UTF-8, and must be converted to UTF-16 before passing to
/// windows API file opening functions.

/// On the other hand, the encoding used for the ANSI versions of the windows
/// API is the current windows code page.  This is more compatible with the
/// default setup of the standard windows command prompt, and may be more
/// appropriate for error messages.

// Conversion to wide char
//
std::wstring OIIO_API utf8_to_utf16 (string_view utf8str);

// Conversion from wide char
//
std::string OIIO_API utf16_to_utf8(const std::wstring& utf16str);
#endif


/// Copy at most size characters (including terminating 0 character) from
/// src into dst[], filling any remaining characters with 0 values. Returns
/// dst. Note that this behavior is identical to strncpy, except that it
/// guarantees that there will be a termining 0 character.
OIIO_API char * safe_strcpy (char *dst, string_view src, size_t size);


/// Modify str to trim any whitespace (space, tab, linefeed, cr) from the
/// front.
void OIIO_API skip_whitespace (string_view &str);

/// If str's first character is c (or first non-whitespace char is c, if
/// skip_whitespace is true), return true and additionally modify str to
/// skip over that first character if eat is also true. Otherwise, if str
/// does not begin with character c, return false and don't modify str.
bool OIIO_API parse_char (string_view &str, char c,
                          bool skip_whitespace = true, bool eat=true);

/// Modify str to trim all characters up to (but not including) the first
/// occurrence of c, and return true if c was found or false if the whole
/// string was trimmed without ever finding c. But if eat is false, then
/// don't modify str, just return true if any c is found, false if no c
/// is found.
bool OIIO_API parse_until_char (string_view &str, char c, bool eat=true);

/// If str's first non-whitespace characters are the prefix, return true and
/// additionally modify str to skip over that prefix if eat is also true.
/// Otherwise, if str doesn't start with optional whitespace and the prefix,
/// return false and don't modify str.
bool OIIO_API parse_prefix (string_view &str, string_view prefix, bool eat=true);

/// If str's first non-whitespace characters form a valid integer, return
/// true, place the integer's value in val, and additionally modify str to
/// skip over the parsed integer if eat is also true. Otherwise, if no
/// integer is found at the beginning of str, return false and don't modify
/// val or str.
bool OIIO_API parse_int (string_view &str, int &val, bool eat=true);

/// If str's first non-whitespace characters form a valid float, return
/// true, place the float's value in val, and additionally modify str to
/// skip over the parsed float if eat is also true. Otherwise, if no float
/// is found at the beginning of str, return false and don't modify val or
/// str.
bool OIIO_API parse_float (string_view &str, float &val, bool eat=true);

enum QuoteBehavior { DeleteQuotes, KeepQuotes };
/// If str's first non-whitespace characters form a valid string (either a
/// single word separated by whitespace or anything inside a double-quoted
/// ("") or single-quoted ('') string, return true, place the string's value
/// (not including surrounding double quotes) in val, and additionally
/// modify str to skip over the parsed string if eat is also true.
/// Otherwise, if no string is found at the beginning of str, return false
/// and don't modify val or str. If keep_quotes is true, the surrounding
/// double quotes (if present) will be kept in val.
bool OIIO_API parse_string (string_view &str, string_view &val, bool eat=true,
                            QuoteBehavior keep_quotes=DeleteQuotes);

/// Return the first "word" (set of contiguous alphabetical characters) in
/// str, and additionally modify str to skip over the parsed word if eat is
/// also true. Otherwise, if no word is found at the beginning of str,
/// return an empty string_view and don't modify str.
string_view OIIO_API parse_word (string_view &str, bool eat=true);

/// If str's first non-whitespace characters form a valid C-like identifier,
/// return the identifier, and additionally modify str to skip over the
/// parsed identifier if eat is also true. Otherwise, if no identifier is
/// found at the beginning of str, return an empty string_view and don't
/// modify str.
string_view OIIO_API parse_identifier (string_view &str, bool eat=true);

/// If str's first non-whitespace characters form a valid C-like identifier,
/// return the identifier, and additionally modify str to skip over the
/// parsed identifier if eat is also true. Otherwise, if no identifier is
/// found at the beginning of str, return an empty string_view and don't
/// modify str. The 'allowed' parameter may specify a additional characters
/// accepted that would not ordinarily be allowed in C identifiers, for
/// example, parse_identifier (blah, "$:") would allow "identifiers"
/// containing dollar signs and colons as well as the usual alphanumeric and
/// underscore characters.
string_view OIIO_API parse_identifier (string_view &str,
                                       string_view allowed, bool eat = true);

/// If the C-like identifier at the head of str exactly matches id,
/// return true, and also advance str if eat is true. If it is not a match
/// for id, return false and do not alter str.
bool OIIO_API parse_identifier_if (string_view &str, string_view id,
                                   bool eat=true);

/// Return the characters until any character in sep is found, storing it in
/// str, and additionally modify str to skip over the parsed section if eat
/// is also true. Otherwise, if no word is found at the beginning of str,
/// return an empty string_view and don't modify str.
string_view OIIO_API parse_until (string_view &str,
                                  string_view sep=" \t\r\n", bool eat=true);

/// Return the characters at the head of the string that match any in set,
/// and additionally modify str to skip over the parsed section if eat is
/// also true. Otherwise, if no `set` characters are found at the beginning
/// of str, return an empty string_view and don't modify str.
string_view OIIO_API parse_while (string_view &str,
                                  string_view set, bool eat=true);

/// Assuming the string str starts with either '(', '[', or '{', return the
/// head, up to and including the corresponding closing character (')', ']',
/// or '}', respectively), recognizing nesting structures. For example,
/// parse_nested("(a(b)c)d") should return "(a(b)c)", NOT "(a(b)". Return an
/// empty string if str doesn't start with one of those characters, or
/// doesn't contain a correctly matching nested pair. If eat==true, str will
/// be modified to trim off the part of the string that is returned as the
/// match.
string_view OIIO_API parse_nested (string_view &str, bool eat=true);


/// Look within `str` for the pattern:
///     head nonwhitespace_chars whitespace
/// Remove that full pattern from `str` and return the nonwhitespace
/// part that followed the head (or return the empty string and leave `str`
/// unmodified, if the head was never found).
OIIO_API std::string
excise_string_after_head (std::string& str, string_view head);


/// Converts utf-8 string to vector of unicode codepoints. This function
/// will not stop on invalid sequences. It will let through some invalid
/// utf-8 sequences like: 0xfdd0-0xfdef, 0x??fffe/0x??ffff. It does not
/// support 5-6 bytes long utf-8 sequences. Will skip trailing character if
/// there are not enough bytes for decoding a codepoint.
///
/// N.B. Following should probably return u32string instead of taking
/// vector, but C++11 support is not yet stabilized across compilers.
/// We will eventually add that and deprecate this one, after everybody
/// is caught up to C++11.
void OIIO_API utf8_to_unicode (string_view str, std::vector<uint32_t> &uvec);

/// Encode the string in base64.
/// https://en.wikipedia.org/wiki/Base64
std::string OIIO_API base64_encode (string_view str);

}  // namespace Strutil

OIIO_NAMESPACE_END