FileSystem.h

#ifndef _FILESYSTEM_H
#define _FILESYSTEM_H

#include "RefCounted.h"
#include "StringRange.h"
#include "ByteRange.h"
#include <string>
#include <vector>
#include <deque>
#include <memory>

/*
 * Functionality:
 *   - Overlay multiple file sources (directories and archives)
 *     in a single virtual file system.
 *   - Enumerate entries from that combined virtual file system.
 *   - Read a file from the virtual file system.
 *   - Determine the path of the application's installed files.
 *   - Determine a sensible path for application configuration files.
 */

namespace FileSystem {

	class FileSource;
	class FileData;
	class FileSourceFS;
	class FileSourceUnion;

	void Init();
	void Uninit();

	extern FileSourceUnion gameDataFiles;
	extern FileSourceFS rawFileSystem;

	std::string GetUserDir(const char *subdir = 0);
	std::string GetDataDir(const char *subdir = 0);

	/// Create path <a>/<b>, coping with 'a' or 'b' being empty,
	/// 'b' being an absolute path, or 'a' not having a trailing separator
	std::string JoinPath(const std::string &a, const std::string &b);

	/// Create path <base>/<path> ensuring that the result points
	/// to a path at or below <base>
	/// throws an exception (std::invalid_argument) if the path tries to escape
	/// <base> must not be empty
	std::string JoinPathBelow(const std::string &base, const std::string &path);

	/// Collapse redundant path separators, and '.' and '..' components
	/// NB: this does not interpret symlinks, so the result may refer to
	/// an entirely different file than the input
	/// throws std::invalid_argument if the input path resolves to a 'negative' path
	/// (e.g., "a/../.." resolves to a negative path)
	std::string NormalisePath(const std::string &path);

	class FileInfo {
		friend class FileSource;
	public:
		FileInfo(): m_source(0), m_dirLen(0), m_type(FT_NON_EXISTENT) {}

		enum FileType {
			// note: order here affects sort-order of FileInfo
			FT_DIR,
			FT_FILE,
			FT_NON_EXISTENT,
			FT_SPECIAL
		};

		enum FileType GetType() const { return m_type; }
		bool Exists() const { return (m_type != FT_NON_EXISTENT); }
		bool IsDir() const { return (m_type == FT_DIR); }
		bool IsFile() const { return (m_type == FT_FILE); }
		bool IsSpecial() const { return (m_type == FT_SPECIAL); }

		const std::string &GetPath() const { return m_path; }
		std::string GetName() const { return m_path.substr(m_dirLen); }
		std::string GetDir() const { return m_path.substr(0, m_dirLen); }
		std::string GetAbsoluteDir() const;
		std::string GetAbsolutePath() const;

		const FileSource &GetSource() const { return *m_source; }

		RefCountedPtr<FileData> Read() const;

		friend bool operator==(const FileInfo &a, const FileInfo &b)
		{ return (a.m_source == b.m_source && a.m_type == b.m_type && a.m_path == b.m_path); }
		friend bool operator!=(const FileInfo &a, const FileInfo &b)
		{ return (a.m_source != b.m_source || a.m_type != b.m_type || a.m_path != b.m_path); }
		friend bool operator< (const FileInfo &a, const FileInfo &b)
		{
			int c = a.m_path.compare(b.m_path);
			if (c != 0) { return (c < 0); }
			if (a.m_type != b.m_type) { return (a.m_type < b.m_type); }
			return (a.m_source < b.m_source);
		}
		friend bool operator<=(const FileInfo &a, const FileInfo &b)
		{
			int c = a.m_path.compare(b.m_path);
			if (c != 0) { return (c < 0); }
			if (a.m_type != b.m_type) { return (a.m_type < b.m_type); }
			return (a.m_source <= b.m_source);
		}
		friend bool operator> (const FileInfo &a, const FileInfo &b) { return (b < a); }
		friend bool operator>=(const FileInfo &a, const FileInfo &b) { return (b <= a); }

	private:
		// use FileSource::MakeFileInfo to create your FileInfos
		FileInfo(FileSource *source, const std::string &path, FileType type);

		FileSource *m_source;
		std::string m_path;
		int m_dirLen;
		FileType m_type;
	};

	class FileData : public RefCounted {
	public:
		virtual ~FileData() {}

		const FileInfo &GetInfo() const { return m_info; }
		size_t GetSize() const { return m_size; }
		const char *GetData() const { assert(m_info.IsFile()); return m_data; }
		StringRange AsStringRange() const { return StringRange(m_data, m_size); }
		ByteRange AsByteRange() const { return ByteRange(m_data, m_size); }

	protected:
		FileData(const FileInfo &info, size_t size, char *data):
			m_info(info), m_data(data), m_size(size) {}
		FileData(const FileInfo &info): m_info(info), m_data(0), m_size(0) {}

		FileInfo m_info;
		char *m_data;
		size_t m_size;
	};

	class FileDataMalloc : public FileData {
	public:
		FileDataMalloc(const FileInfo &info, size_t size):
			FileData(info, size, reinterpret_cast<char*>(std::malloc(size))) {}
		FileDataMalloc(const FileInfo &info, size_t size, char *data):
			FileData(info, size, data) {}
		virtual ~FileDataMalloc() { std::free(m_data); }
	};

	class FileSource {
	public:
		explicit FileSource(const std::string &root): m_root(root) {}
		virtual ~FileSource() {}

		const std::string &GetRoot() const { return m_root; }

		virtual FileInfo Lookup(const std::string &path) = 0;
		virtual RefCountedPtr<FileData> ReadFile(const std::string &path) = 0;
		virtual bool ReadDirectory(const std::string &path, std::vector<FileInfo> &output) = 0;

	protected:
		FileInfo MakeFileInfo(const std::string &path, FileInfo::FileType entryType);

	private:
		std::string m_root;
	};

	class FileSourceFS : public FileSource {
	public:
		explicit FileSourceFS(const std::string &root);
		~FileSourceFS();

		virtual FileInfo Lookup(const std::string &path);
		virtual RefCountedPtr<FileData> ReadFile(const std::string &path);
		virtual bool ReadDirectory(const std::string &path, std::vector<FileInfo> &output);

		bool MakeDirectory(const std::string &path);
	};

	class FileSourceUnion : public FileSource {
	public:
		FileSourceUnion();
		~FileSourceUnion();

		void PrependSource(FileSource *fs);
		void AppendSource(FileSource *fs);
		void RemoveSource(FileSource *fs);

		virtual FileInfo Lookup(const std::string &path);
		virtual RefCountedPtr<FileData> ReadFile(const std::string &path);
		virtual bool ReadDirectory(const std::string &path, std::vector<FileInfo> &output);

	private:
		std::vector<FileSource*> m_sources;
	};

	class FileEnumerator {
	public:
		enum Flags {
			IncludeDirs      = 1,
			IncludeSpecials  = 2,
			ExcludeFiles     = 4,
			Recurse          = 8
		};

		explicit FileEnumerator(FileSource &fs, int flags = 0);
		explicit FileEnumerator(FileSource &fs, const std::string &path, int flags = 0);
		~FileEnumerator();

		void AddSearchRoot(const std::string &path);

		bool Finished() const { return m_queue.empty(); }
		void Next();
		const FileInfo &Current() const { return m_queue.front(); }

	private:
		void ExpandDirQueue();
		void QueueDirectoryContents(const FileInfo &info);

		FileSource *m_source;
		std::deque<FileInfo> m_queue;
		std::deque<FileInfo> m_dirQueue;
		int m_flags;
	};

} // namespace FileSystem

inline std::string FileSystem::FileInfo::GetAbsoluteDir() const
{ return JoinPath(m_source->GetRoot(), GetDir()); }

inline std::string FileSystem::FileInfo::GetAbsolutePath() const
{ return JoinPath(m_source->GetRoot(), GetPath()); }

inline RefCountedPtr<FileSystem::FileData> FileSystem::FileInfo::Read() const
{ return m_source->ReadFile(m_path); }

#endif