transmission/libtransmission/utils.cc

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// This file Copyright © Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
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#include <algorithm> // for std::sort, std::transform
#include <array> // std::array
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#include <cctype>
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#include <cfloat> // DBL_DIG
#include <chrono>
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#include <cstdint> // SIZE_MAX
#include <cstdlib> // getenv()
#include <cstring> /* strerror() */
#include <ctime>
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#include <exception>
#include <iostream>
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#include <iterator> // for std::back_inserter
#include <locale>
#include <memory>
#include <optional>
#include <set>
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#include <stdexcept> // std::runtime_error
#include <string>
#include <string_view>
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#include <system_error>
#include <type_traits>
#include <vector>
#ifdef _WIN32
#include <windows.h> /* Sleep(), GetEnvironmentVariable() */
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#include <ws2tcpip.h> /* htonl(), ntohl() */
#include <shellapi.h> /* CommandLineToArgv() */
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#else
#include <arpa/inet.h>
#endif
#define UTF_CPP_CPLUSPLUS 201703L
#include <utf8.h>
#include <curl/curl.h>
#include <fmt/core.h>
#include <fast_float/fast_float.h>
#include <wildmat.h>
#include "libtransmission/transmission.h"
#include "libtransmission/error-types.h"
#include "libtransmission/error.h"
#include "libtransmission/file.h"
#include "libtransmission/log.h"
#include "libtransmission/mime-types.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/tr-strbuf.h"
#include "libtransmission/utils.h"
#include "libtransmission/values.h"
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using namespace std::literals;
using namespace libtransmission::Values;
time_t libtransmission::detail::tr_time::current_time = {};
// ---
namespace libtransmission::Values
{
// default values; can be overridden by client apps
Config::Units<MemoryUnits> Config::Memory{ Config::Base::Kibi, "B"sv, "KiB"sv, "MiB"sv, "GiB"sv, "TiB"sv };
Config::Units<SpeedUnits> Config::Speed{ Config::Base::Kilo, "B/s"sv, "kB/s"sv, "MB/s"sv, "GB/s"sv, "TB/s"sv };
Config::Units<StorageUnits> Config::Storage{ Config::Base::Kilo, "B"sv, "kB"sv, "MB"sv, "GB"sv, "TB"sv };
} // namespace libtransmission::Values
// ---
std::optional<std::locale> tr_locale_set_global(char const* locale_name) noexcept
{
try
{
return tr_locale_set_global(std::locale{ locale_name });
}
catch (std::runtime_error const&)
{
return {};
}
}
std::optional<std::locale> tr_locale_set_global(std::locale const& locale) noexcept
{
try
{
auto old_locale = std::locale::global(locale);
std::cout.imbue(std::locale{});
std::cerr.imbue(std::locale{});
return old_locale;
}
catch (std::exception const&)
{
return {};
}
}
// ---
bool tr_file_read(std::string_view filename, std::vector<char>& contents, tr_error* error)
{
auto const szfilename = tr_pathbuf{ filename };
/* try to stat the file */
auto local_error = tr_error{};
if (error == nullptr)
{
error = &local_error;
}
auto const info = tr_sys_path_get_info(szfilename, 0, error);
if (*error)
{
tr_logAddError(fmt::format(
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_("Couldn't read '{path}': {error} ({error_code})"),
fmt::arg("path", filename),
fmt::arg("error", error->message()),
fmt::arg("error_code", error->code())));
return false;
}
if (!info || !info->isFile())
{
tr_logAddError(fmt::format(_("Couldn't read '{path}': Not a regular file"), fmt::arg("path", filename)));
error->set(TR_ERROR_EISDIR, "Not a regular file"sv);
return false;
}
/* Load the torrent file into our buffer */
auto const fd = tr_sys_file_open(szfilename, TR_SYS_FILE_READ | TR_SYS_FILE_SEQUENTIAL, 0, error);
if (fd == TR_BAD_SYS_FILE)
{
tr_logAddError(fmt::format(
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_("Couldn't read '{path}': {error} ({error_code})"),
fmt::arg("path", filename),
fmt::arg("error", error->message()),
fmt::arg("error_code", error->code())));
return false;
}
contents.resize(info->size);
if (!tr_sys_file_read(fd, std::data(contents), info->size, nullptr, error))
{
tr_logAddError(fmt::format(
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_("Couldn't read '{path}': {error} ({error_code})"),
fmt::arg("path", filename),
fmt::arg("error", error->message()),
fmt::arg("error_code", error->code())));
tr_sys_file_close(fd);
return false;
}
tr_sys_file_close(fd);
return true;
}
bool tr_file_save(std::string_view filename, std::string_view contents, tr_error* error)
{
// follow symlinks to find the "real" file, to make sure the temporary
// we build with tr_sys_file_open_temp() is created on the right partition
if (auto const realname = tr_sys_path_resolve(filename); !std::empty(realname) && realname != filename)
{
return tr_file_save(realname, contents, error);
}
// Write it to a temp file first.
// This is a safeguard against edge cases, e.g. disk full, crash while writing, etc.
auto tmp = tr_pathbuf{ filename, ".tmp.XXXXXX"sv };
auto const fd = tr_sys_file_open_temp(std::data(tmp), error);
if (fd == TR_BAD_SYS_FILE)
{
return false;
}
// Save the contents. This might take >1 pass.
auto ok = bool{ true };
while (!std::empty(contents))
{
auto n_written = uint64_t{};
if (!tr_sys_file_write(fd, std::data(contents), std::size(contents), &n_written, error))
{
ok = false;
break;
}
contents.remove_prefix(n_written);
}
// If we saved it to disk successfully, move it from '.tmp' to the correct filename
if (!tr_sys_file_close(fd, error) || !ok || !tr_sys_path_rename(tmp, tr_pathbuf{ filename }, error))
{
return false;
}
tr_logAddTrace(fmt::format("Saved '{}'", filename));
return true;
}
// ---
size_t tr_strv_to_buf(std::string_view src, char* buf, size_t buflen)
{
size_t const len = std::size(src);
if (buflen >= len)
{
auto const out = std::copy(std::begin(src), std::end(src), buf);
if (buflen > len)
{
*out = '\0';
}
}
return len;
}
/* User-level routine. returns whether or not 'text' and 'p' matched */
bool tr_wildmat(std::string_view text, std::string_view pattern)
{
// TODO(ckerr): replace wildmat with base/strings/pattern.cc
// wildmat wants these to be zero-terminated.
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return pattern == "*"sv || DoMatch(std::string{ text }.c_str(), std::string{ pattern }.c_str()) > 0;
}
char const* tr_strerror(int errnum)
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{
if (char const* const ret = strerror(errnum); ret != nullptr)
{
return ret;
}
return "Unknown Error";
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}
// ---
std::string_view tr_strv_strip(std::string_view str)
{
auto constexpr Test = [](auto ch)
{
return isspace(static_cast<unsigned char>(ch));
};
auto const it = std::find_if_not(std::begin(str), std::end(str), Test);
str.remove_prefix(std::distance(std::begin(str), it));
auto const rit = std::find_if_not(std::rbegin(str), std::rend(str), Test);
str.remove_suffix(std::distance(std::rbegin(str), rit));
return str;
}
// ---
uint64_t tr_time_msec()
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{
return std::chrono::system_clock::now().time_since_epoch() / 1ms;
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}
// ---
double tr_getRatio(uint64_t numerator, uint64_t denominator)
{
if (denominator > 0)
{
return numerator / static_cast<double>(denominator);
}
if (numerator > 0)
{
return TR_RATIO_INF;
}
return TR_RATIO_NA;
}
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// ---
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#if !(defined(__APPLE__) && defined(__clang__))
std::string tr_strv_convert_utf8(std::string_view sv)
{
return tr_strv_replace_invalid(sv);
}
#endif
std::string tr_strv_replace_invalid(std::string_view sv, uint32_t replacement)
{
// stripping characters after first \0
if (auto first_null = sv.find('\0'); first_null != std::string::npos)
{
sv = { std::data(sv), first_null };
}
auto out = std::string{};
out.reserve(std::size(sv));
utf8::unchecked::replace_invalid(std::data(sv), std::data(sv) + std::size(sv), std::back_inserter(out), replacement);
return out;
}
#ifdef _WIN32
std::string tr_win32_native_to_utf8(std::wstring_view in)
{
auto out = std::string{};
out.resize(WideCharToMultiByte(CP_UTF8, 0, std::data(in), std::size(in), nullptr, 0, nullptr, nullptr));
[[maybe_unused]] auto
len = WideCharToMultiByte(CP_UTF8, 0, std::data(in), std::size(in), std::data(out), std::size(out), nullptr, nullptr);
TR_ASSERT(len == std::size(out));
return out;
}
std::wstring tr_win32_utf8_to_native(std::string_view in)
{
auto out = std::wstring{};
out.resize(MultiByteToWideChar(CP_UTF8, 0, std::data(in), std::size(in), nullptr, 0));
[[maybe_unused]] auto len = MultiByteToWideChar(CP_UTF8, 0, std::data(in), std::size(in), std::data(out), std::size(out));
TR_ASSERT(len == std::size(out));
return out;
}
std::string tr_win32_format_message(uint32_t code)
{
wchar_t* wide_text = nullptr;
auto const wide_size = FormatMessageW(
FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
nullptr,
code,
0,
(LPWSTR)&wide_text,
0,
nullptr);
if (wide_size == 0)
{
return fmt::format("Unknown error ({:#08x})", code);
}
auto text = std::string{};
if (wide_size != 0 && wide_text != nullptr)
{
text = tr_win32_native_to_utf8({ wide_text, wide_size });
}
LocalFree(wide_text);
// Most (all?) messages contain "\r\n" in the end, chop it
while (!std::empty(text) && isspace(text.back()))
{
text.resize(text.size() - 1);
}
return text;
}
namespace
{
namespace tr_main_win32_impl
{
std::optional<std::vector<std::string>> win32MakeUtf8Argv()
{
int argc;
auto argv = std::vector<std::string>{};
if (wchar_t** wargv = CommandLineToArgvW(GetCommandLineW(), &argc); wargv != nullptr)
{
for (int i = 0; i < argc; ++i)
{
if (wargv[i] == nullptr)
{
break;
}
auto str = tr_win32_native_to_utf8(wargv[i]);
if (std::empty(str))
{
break;
}
argv.emplace_back(std::move(str));
}
LocalFree(wargv);
}
if (static_cast<int>(std::size(argv)) == argc)
{
return argv;
}
return {};
}
} // namespace tr_main_win32_impl
} // namespace
int tr_main_win32(int argc, char** argv, int (*real_main)(int, char**))
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{
using namespace tr_main_win32_impl;
SetConsoleCP(CP_UTF8);
SetConsoleOutputCP(CP_UTF8);
// build an argv from GetCommandLineW + CommandLineToArgvW
if (auto argv_strs = win32MakeUtf8Argv(); argv_strs)
{
auto argv_cstrs = std::vector<char*>{};
argv_cstrs.reserve(std::size(*argv_strs));
std::transform(
std::begin(*argv_strs),
std::end(*argv_strs),
std::back_inserter(argv_cstrs),
[](auto& str) { return std::data(str); });
argv_cstrs.push_back(nullptr); // argv is nullptr-terminated
return (*real_main)(std::size(*argv_strs), std::data(argv_cstrs));
}
return (*real_main)(argc, argv);
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}
#endif
// ---
namespace
{
namespace tr_num_parse_range_impl
{
struct number_range
{
int low;
int high;
};
/**
* This should be a single number (ex. "6") or a range (ex. "6-9").
* Anything else is an error and will return failure.
*/
bool parseNumberSection(std::string_view str, number_range& range)
{
auto constexpr Delimiter = "-"sv;
auto const first = tr_num_parse<int>(str, &str);
if (!first)
{
return false;
}
range.low = range.high = *first;
if (std::empty(str))
{
return true;
}
if (!tr_strv_starts_with(str, Delimiter))
{
return false;
}
str.remove_prefix(std::size(Delimiter));
auto const second = tr_num_parse<int>(str);
if (!second)
{
return false;
}
range.high = *second;
return true;
}
} // namespace tr_num_parse_range_impl
} // namespace
/**
* Given a string like "1-4" or "1-4,6,9,14-51", this allocates and returns an
* array of setmeCount ints of all the values in the array.
* For example, "5-8" will return [ 5, 6, 7, 8 ] and setmeCount will be 4.
* If a fragment of the string can't be parsed, nullptr is returned.
*/
std::vector<int> tr_num_parse_range(std::string_view str)
{
using namespace tr_num_parse_range_impl;
auto values = std::set<int>{};
auto token = std::string_view{};
auto range = number_range{};
while (tr_strv_sep(&str, &token, ',') && parseNumberSection(token, range))
{
for (auto i = range.low; i <= range.high; ++i)
{
values.insert(i);
}
}
return { std::begin(values), std::end(values) };
}
// ---
double tr_truncd(double x, int decimal_places)
{
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auto buf = std::array<char, 128>{};
auto const [out, len] = fmt::format_to_n(std::data(buf), std::size(buf) - 1, "{:.{}f}", x, DBL_DIG);
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*out = '\0';
if (auto* const pt = strchr(std::data(buf), '.'); pt != nullptr)
{
pt[decimal_places != 0 ? decimal_places + 1 : 0] = '\0';
}
return tr_num_parse<double>(std::data(buf)).value_or(0.0);
}
std::string tr_strpercent(double x)
{
if (x < 5.0)
{
return fmt::format("{:.2Lf}", tr_truncd(x, 2));
}
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if (x < 100.0)
{
return fmt::format("{:.1Lf}", tr_truncd(x, 1));
}
return fmt::format("{:.0Lf}", x);
}
std::string tr_strratio(double ratio, char const* infinity)
{
if ((int)ratio == TR_RATIO_NA)
{
return _("None");
}
if ((int)ratio == TR_RATIO_INF)
{
return infinity != nullptr ? infinity : "";
}
return tr_strpercent(ratio);
}
// ---
bool tr_file_move(std::string_view oldpath_in, std::string_view newpath_in, tr_error* error)
{
auto const oldpath = tr_pathbuf{ oldpath_in };
auto const newpath = tr_pathbuf{ newpath_in };
auto local_error = tr_error{};
if (error == nullptr)
{
error = &local_error;
}
// make sure the old file exists
auto const info = tr_sys_path_get_info(oldpath, 0, error);
if (!info)
{
error->prefix_message("Unable to get information on old file: ");
return false;
}
if (!info->isFile())
{
error->set(TR_ERROR_EINVAL, "Old path does not point to a file."sv);
return false;
}
// ensure the target directory exists
auto newdir = tr_pathbuf{ newpath.sv() };
newdir.popdir();
if (!tr_sys_dir_create(newdir, TR_SYS_DIR_CREATE_PARENTS, 0777, error))
{
error->prefix_message("Unable to create directory for new file: ");
return false;
}
/* they might be on the same filesystem... */
if (tr_sys_path_rename(oldpath, newpath))
{
return true;
}
Add in-kernel file copying for several platforms. (#1092) * Add in-kernel copying support for Linux (sendfile64(2), copy_file_range(2)), FreeBSD 13 (copy_file_range(2)), MacOS (copyfile(2)), and Windows (CopyFileExA). * Fix macro name USE_COPY_FILE_RANGE. * Minor bugfixes for userspace fallback. * Fix linux sendfile64 bugs. * Remove some overzealous asserts. * Allow transmission-test-copy to take an optional argument for an external reference file. * Fix return value error of tr_sys_path_copy. * Use COPYFILE_ALL for Macs without COPYFILE_CLONE. * Add in-kernel file copying for several platforms. Numerous operating systems now have support for copying files directly in the kernel, which is generally more efficient than copying in a userspace read(2)/ write(2) loop. (This becomes particularly relevant for 4th gen PCI-E storage, which approaches the latency of DRAM.) For Linux I use sendfile64(2), and, for later kernels, copy_file_range(2). FreeBSD 13 will also support copy_file_range(2). MacOS has copyfile(2), and Windows has CopyFileExA. Operating systems lacking such a syscall continue to use the existing read(2)/write(2) loop. * Appease uncrustify. * Appease uncrustify. * copy-test: generate random content at run time. * copy-test: Stylistic changes and more check()s. * copy-test: files_are_identical should follow test idioms * tr_sys_path_copy: numerous tweaks as requested by review. * s/old file/source file; s/new file/destination file. * tr_sys_path_copy: handle win32 wide characters in paths. * Uncrustify. * test-copy: Use non-string create_file_with_contents. * tr_sys_path_copy: numerous fixes. Per review: generate test file content at runtime; tidy use of check(); fix style; re-measure file sizes in the copy; define a macro when the system does not provide it; use Unicode APIs on Windows; and fix documentation. * Updated as per comments. * Rebase kernel-copy changes onto 3.0 with gtest. * Undo irrelevant comment change. * Fix syntax error. * Use tr_malloc() instead of tr_valloc(). * Use EXPECT instead of TR_ASSERT in gtest. * Add error handling. * Acceptable coding style has changed again. Now it's camelCase. Also use nullptr instead of NULL, etc. * Fix east/west const. Co-authored-by: Mike Gelfand <mikedld@users.noreply.github.com>
2021-08-07 09:04:03 +00:00
/* Otherwise, copy the file. */
if (!tr_sys_path_copy(oldpath, newpath, error))
{
error->prefix_message("Unable to copy: ");
return false;
}
if (auto log_error = tr_error{}; !tr_sys_path_remove(oldpath, &log_error))
{
tr_logAddError(fmt::format(
_("Couldn't remove '{path}': {error} ({error_code})"),
fmt::arg("path", oldpath),
fmt::arg("error", log_error.message()),
fmt::arg("error_code", log_error.code())));
}
return true;
}
// ---
uint64_t tr_htonll(uint64_t hostlonglong)
{
#ifdef HAVE_HTONLL
return htonll(hostlonglong);
#else
/* fallback code by bdonlan at https://stackoverflow.com/questions/809902/64-bit-ntohl-in-c/875505#875505 */
union
{
std::array<uint32_t, 2> lx;
uint64_t llx;
} u = {};
u.lx[0] = htonl(hostlonglong >> 32);
u.lx[1] = htonl(hostlonglong & 0xFFFFFFFFULL);
return u.llx;
#endif
}
uint64_t tr_ntohll(uint64_t netlonglong)
{
#ifdef HAVE_NTOHLL
return ntohll(netlonglong);
#else
/* fallback code by bdonlan at https://stackoverflow.com/questions/809902/64-bit-ntohl-in-c/875505#875505 */
union
{
std::array<uint32_t, 2> lx;
uint64_t llx;
} u = {};
u.llx = netlonglong;
return ((uint64_t)ntohl(u.lx[0]) << 32) | (uint64_t)ntohl(u.lx[1]);
#endif
}
// --- ENVIRONMENT
bool tr_env_key_exists(char const* key)
{
TR_ASSERT(key != nullptr);
#ifdef _WIN32
return GetEnvironmentVariableA(key, nullptr, 0) != 0;
#else
return getenv(key) != nullptr;
#endif
}
std::string tr_env_get_string(std::string_view key, std::string_view default_value)
{
#ifdef _WIN32
if (auto const wide_key = tr_win32_utf8_to_native(key); !std::empty(wide_key))
{
if (auto const size = GetEnvironmentVariableW(wide_key.c_str(), nullptr, 0); size != 0)
{
auto wide_val = std::wstring{};
wide_val.resize(size);
if (GetEnvironmentVariableW(wide_key.c_str(), std::data(wide_val), std::size(wide_val)) == std::size(wide_val) - 1)
{
TR_ASSERT(wide_val.back() == L'\0');
wide_val.resize(std::size(wide_val) - 1);
return tr_win32_native_to_utf8(wide_val);
}
}
}
#else
auto const szkey = tr_strbuf<char, 256>{ key };
if (auto const* const value = getenv(szkey); value != nullptr)
{
return value;
}
#endif
return std::string{ default_value };
}
// ---
tr_net_init_mgr::tr_net_init_mgr()
{
// try to init curl with default settings (currently ssl support + win32 sockets)
// but if that fails, we need to init win32 sockets as a bare minimum
if (curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK)
{
curl_global_init(CURL_GLOBAL_WIN32);
}
}
tr_net_init_mgr::~tr_net_init_mgr()
{
curl_global_cleanup();
}
std::unique_ptr<tr_net_init_mgr> tr_net_init_mgr::create()
{
if (!initialised)
{
initialised = true;
return std::unique_ptr<tr_net_init_mgr>{ new tr_net_init_mgr };
}
return {};
}
bool tr_net_init_mgr::initialised = false;
std::unique_ptr<tr_net_init_mgr> tr_lib_init()
{
return tr_net_init_mgr::create();
}
// --- mime-type
std::string_view tr_get_mime_type_for_filename(std::string_view filename)
{
auto constexpr Compare = [](mime_type_suffix const& entry, auto const& suffix)
{
return entry.suffix < suffix;
};
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if (auto const pos = filename.rfind('.'); pos != std::string_view::npos)
{
auto const suffix_lc = tr_strlower(filename.substr(pos + 1));
auto const it = std::lower_bound(std::begin(mime_type_suffixes), std::end(mime_type_suffixes), suffix_lc, Compare);
if (it != std::end(mime_type_suffixes) && suffix_lc == it->suffix)
{
return it->mime_type;
}
}
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types
// application/octet-stream is the default value.
// An unknown file type should use this type.
auto constexpr Fallback = "application/octet-stream"sv;
return Fallback;
}
// --- parseNum()
#if defined(__GNUC__) && !__has_include(<charconv>)
#include <iomanip> // std::setbase
#include <sstream>
template<typename T, std::enable_if_t<std::is_integral_v<T>, bool> = true>
[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* remainder, int base)
{
auto val = T{};
auto const tmpstr = std::string(std::data(str), std::min(std::size(str), size_t{ 64 }));
auto sstream = std::stringstream{ tmpstr };
auto const oldpos = sstream.tellg();
/* The base parameter only works for bases 8, 10 and 16.
All other bases will be converted to 0 which activates the
prefix based parsing and therefore decimal in our usual cases.
This differs from the from_chars solution below. */
sstream >> std::setbase(base) >> val;
auto const newpos = sstream.tellg();
if ((newpos == oldpos) || (sstream.fail() && !sstream.eof()))
{
return std::nullopt;
}
if (remainder != nullptr)
{
*remainder = str;
remainder->remove_prefix(sstream.eof() ? std::size(str) : newpos - oldpos);
}
return val;
}
#else // #if defined(__GNUC__) && !__has_include(<charconv>)
#include <charconv> // std::from_chars()
template<typename T, std::enable_if_t<std::is_integral_v<T>, bool>>
[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* remainder, int base)
{
auto val = T{};
auto const* const begin_ch = std::data(str);
auto const* const end_ch = begin_ch + std::size(str);
/* The base parameter works for any base from 2 to 36 (inclusive).
This is different from the behaviour of the stringstream
based solution above. */
auto const result = std::from_chars(begin_ch, end_ch, val, base);
if (result.ec != std::errc{})
{
return std::nullopt;
}
if (remainder != nullptr)
{
*remainder = str;
remainder->remove_prefix(result.ptr - std::data(str));
}
return val;
}
#endif // #if defined(__GNUC__) && !__has_include(<charconv>)
template std::optional<long long> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<long> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<int> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<char> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<unsigned long long> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<unsigned long> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<unsigned int> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<unsigned short> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template std::optional<unsigned char> tr_num_parse(std::string_view str, std::string_view* remainder, int base);
template<typename T, std::enable_if_t<std::is_floating_point_v<T>, bool>>
[[nodiscard]] std::optional<T> tr_num_parse(std::string_view str, std::string_view* remainder)
{
auto const* const begin_ch = std::data(str);
auto const* const end_ch = begin_ch + std::size(str);
auto val = T{};
auto const result = fast_float::from_chars(begin_ch, end_ch, val);
if (result.ec != std::errc{})
{
return std::nullopt;
}
if (remainder != nullptr)
{
*remainder = str;
remainder->remove_prefix(result.ptr - std::data(str));
}
return val;
}
template std::optional<double> tr_num_parse(std::string_view sv, std::string_view* remainder);