paths: add expand query for paths

CMakeLists.txt

@@ -129,6 +129,7 @@ if (NOT WIN32)
         io_posix.hpp
         library_posix.hpp
         library_posix.cpp
+        paths_posix.cpp
         posix/fwd.hpp
         posix/interface.hpp
         posix/interface.cpp
@@ -152,6 +153,7 @@ if (WIN32)
         io_win32.hpp
         library_win32.cpp
         library_win32.hpp
+        paths_win32.cpp
         rand/system_win32.cpp
         rand/system_win32.hpp
         time_win32.cpp
@@ -473,6 +475,7 @@ list (
     parse/value.hpp
     parse/si.cpp
     parse/si.hpp
+    paths.hpp
     platform.hpp
     point.cpp
     point.hpp

paths.hpp

@@ -0,0 +1,17 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2020, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include <filesystem>
+
+
+namespace cruft::paths {
+    std::filesystem::path
+    expand (std::filesystem::path const&);
+}

paths_posix.cpp

@@ -0,0 +1,32 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2020, Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "paths.hpp"
+
+#include "posix/except.hpp"
+#include "debug/assert.hpp"
+
+#include <memory>
+
+#include <wordexp.h>
+
+
+///////////////////////////////////////////////////////////////////////////////
+std::filesystem::path
+cruft::paths::expand (std::filesystem::path const &val)
+{
+    wordexp_t words;
+    posix::error::try_call (wordexp, val.c_str (), &words, WRDE_NOCMD | WRDE_UNDEF);
+    std::unique_ptr<wordexp_t, decltype(&wordfree)> cleanup {&words, &wordfree};
+
+    if (words.we_wordc != 1)
+        throw std::runtime_error ("glob matches too many files");
+
+    CHECK_EQ (words.we_offs, 0u);
+    return words.we_wordv[0];
+}

paths_win32.cpp

@@ -0,0 +1,38 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2020, Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "paths.hpp"
+
+#include "win32/windows.hpp"
+#include "win32/except.hpp"
+
+#include <stdexcept>
+
+
+///////////////////////////////////////////////////////////////////////////////
+std::filesystem::path
+cruft::paths::expand (std::filesystem::path const &val)
+{
+    auto const required_size = ExpandEnvironmentStringsW (val.native ().data (), nullptr, 0) + 1;
+
+    std::wstring store (required_size, '\0');
+
+    auto const actual_size = ExpandEnvironmentStringsW (
+        val.native ().data (),
+        store.data (),
+        store.size ()
+    );
+
+    if (actual_size == 0)
+        win32::error::throw_code ();
+    if (actual_size > required_size)
+        throw std::runtime_error ("Unable to expand path");
+    store.resize (actual_size);
+
+    return store;
+}