Path: new class "Path" wraps filesystem path strings

1 files changed, 207 insertions, 0 deletions

diff --git a/src/Path.hxx b/src/Path.hxx
index db3f95961..5c76e4b87 100644
--- a/src/Path.hxx
+++ b/src/Path.hxx
@@ -21,7 +21,14 @@
 #define MPD_PATH_HXX
 
 #include "check.h"
+#include "gcc.h"
 
+#include <glib.h>
+
+#include <algorithm>
+
+#include <assert.h>
+#include <string.h>
 #include <limits.h>
 
 #if !defined(MPD_PATH_MAX)
@@ -54,4 +61,204 @@ utf8_to_fs_charset(const char *path_utf8);
 
 const char *path_get_fs_charset();
 
+/**
+ * A path name in the native file system character set.
+ */
+class Path {
+public:
+	typedef char value_type;
+	typedef value_type *pointer;
+	typedef const value_type *const_pointer;
+
+private:
+	pointer value;
+
+	struct Donate {};
+
+	/**
+	 * Donate the allocated pointer to a new #Path object.
+	 */
+	constexpr Path(Donate, pointer _value):value(_value) {}
+
+	/**
+	 * Release memory allocated by the value, but do not clear the
+	 * value pointer.
+	 */
+	void Free() {
+		/* free() can be optimized by gcc, while g_free() can
+		   not: when the compiler knows that the value is
+		   nullptr, it will not emit a free() call in the
+		   inlined destructor; however on Windows, we need to
+		   call g_free(), because the value has been allocated
+		   by GLib, and on Windows, this matters */
+#ifdef WIN32
+		g_free(value);
+#else
+		free(value);
+#endif
+	}
+
+public:
+	/**
+	 * Copy a #Path object.
+	 */
+	Path(const Path &other)
+		:value(g_strdup(other.value)) {}
+
+	/**
+	 * Move a #Path object.
+	 */
+	Path(Path &&other):value(other.value) {
+		other.value = nullptr;
+	}
+
+	~Path() {
+		Free();
+	}
+
+	/**
+	 * Return a "nulled" instance.  Its IsNull() method will
+	 * return true.  Such an object must not be used.
+	 *
+	 * @see IsNull()
+	 */
+	gcc_const
+	static Path Null() {
+		return Path(Donate(), nullptr);
+	}
+
+	/**
+	 * Join two path components with the path separator.
+	 */
+	gcc_pure gcc_nonnull_all
+	static Path Build(const_pointer a, const_pointer b) {
+		return Path(Donate(), g_build_filename(a, b, nullptr));
+	}
+
+	gcc_pure gcc_nonnull_all
+	static Path Build(const_pointer a, const Path &b) {
+		return Build(a, b.c_str());
+	}
+
+	gcc_pure gcc_nonnull_all
+	static Path Build(const Path &a, const_pointer b) {
+		return Build(a.c_str(), b);
+	}
+
+	gcc_pure
+	static Path Build(const Path &a, const Path &b) {
+		return Build(a.c_str(), b.c_str());
+	}
+
+	/**
+	 * Convert a C string that is already in the filesystem
+	 * character set to a #Path instance.
+	 */
+	gcc_pure
+	static Path FromFS(const_pointer fs) {
+		return Path(Donate(), g_strdup(fs));
+	}
+
+	/**
+	 * Convert a UTF-8 C string to a #Path instance.
+	 *
+	 * TODO: return a "nulled" instance on error and add checks to
+	 * all callers
+	 */
+	gcc_pure
+	static Path FromUTF8(const char *utf8) {
+		return Path(Donate(), utf8_to_fs_charset(utf8));
+	}
+
+	/**
+	 * Copy a #Path object.
+	 */
+	Path &operator=(const Path &other) {
+		if (this != &other) {
+			Free();
+			value = g_strdup(other.value);
+		}
+
+		return *this;
+	}
+
+	/**
+	 * Move a #Path object.
+	 */
+	Path &operator=(Path &&other) {
+		std::swap(value, other.value);
+		return *this;
+	}
+
+	/**
+	 * Steal the allocated value.  This object has an undefined
+	 * value, and the caller is response for freeing this method's
+	 * return value.
+	 */
+	pointer Steal() {
+		pointer result = value;
+		value = nullptr;
+		return result;
+	}
+
+	/**
+	 * Check if this is a "nulled" instance.  A "nulled" instance
+	 * must not be used.
+	 */
+	bool IsNull() const {
+		return value == nullptr;
+	}
+
+	/**
+	 * Clear this object's value, make it "nulled".
+	 *
+	 * @see IsNull()
+	 */
+	void SetNull() {
+		Free();
+		value = nullptr;
+	}
+
+	gcc_pure
+	bool empty() const {
+		assert(value != nullptr);
+
+		return *value == 0;
+	}
+
+	/**
+	 * @return the length of this string in number of "value_type"
+	 * elements (which may not be the number of characters).
+	 */
+	gcc_pure
+	size_t length() const {
+		assert(value != nullptr);
+
+		return strlen(value);
+	}
+
+	/**
+	 * Returns the value as a const C string.  The returned
+	 * pointer is invalidated whenever the value of life of this
+	 * instance ends.
+	 */
+	gcc_pure
+	const_pointer c_str() const {
+		assert(value != nullptr);
+
+		return value;
+	}
+
+	/**
+	 * Convert the path to UTF-8.  The caller is responsible for
+	 * freeing the return value with g_free().  Returns nullptr on
+	 * error.
+	 */
+	char *ToUTF8() const {
+		return value != nullptr
+			? fs_charset_to_utf8(value)
+			: nullptr;
+	}
+};
+
 #endif