driver/filesystem: filesystem interface
mostly from FUSE (https://github.com/libfuse/libfuse/blob/master/include/fuse.h)
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driver/filesystem/filesystem.hpp
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driver/filesystem/filesystem.hpp
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#pragma once
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#include "../../cppruntime/runtime.hpp"
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namespace helos {
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// Filesystems are created per-mount.
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//
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// Paths always begin with "/".
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// Functions return negative numbers on error.
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class Filesystem {
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public:
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typedef uint16_t uid_t, gid_t; // User and group ID types
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typedef uint16_t mode_t; // UNIX permission mode type
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enum OpenFlag {
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O_APPEND = 1 << 0, // File opened in append mode
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O_ASYNC = 1 << 1, // Enable signal-driver I/O
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O_CREAT = 1 << 2, // Create the file if it does not exist
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O_DIRECTORY = 1 << 3, // Fail if not a directory
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O_DSYNC = 1 << 4, // Operation data synced on return
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O_EXCL = 1 << 5, // Fail if the file exists in conjunction with O_CREAT
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O_LARGEFILE = 1 << 6, // Allow use of off64_t
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O_NOCTTY = 1 << 7, // Does not switch process's controlling terminal
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O_NOFOLLOW = 1 << 8, // Does not follow symbolic link on the trailing component (basename)
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O_NONBLOCK = 1 << 9, // Open file in nonblocking mode
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O_SYNC = 1 << 10, // Writes synced by file on return
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O_TRUNC = 1 << 11, // Thuncate existing file to size 0 if it exists
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O_RDONLY = 1 << 12, // Read-only
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O_WRONLY = 1 << 13, // Write-only
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O_RDWR = O_RDONLY | O_WRONLY, // Read and write
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O_EXEC = 1 << 14, // Execute
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};
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public:
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static constexpr char Seperator = '/';
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// Error enums are positive, so use something like "return -EPERM;"
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enum Error {
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EPERM = 1, // Operation not permitted
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ENOENT = 2, // No such file or directory
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EAGAIN = 11, // Resource temporarily unavailable
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EACCES = 13, // Permission denied
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ENOTBLK = 15, // Blockdevice required
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EBUSY = 16, // Device or resource busy
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EEXIST = 17, // File exists
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EXDEV = 18, // No such device
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ENODEV = 19, // No such device
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ENOTDIR = 20, // Not a directory
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EISDIR = 21, // Is a directory
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EINVAL = 22, // Invalid argument
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ETXTBSY = 26, // Text file busy
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EFBIG = 27, // File too large
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ENOSPC = 28, // No space left on device
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ESPIPE = 29, // Illegal seek
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EROFS = 30, // Read-only file system
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EMLINK = 31, // Too many links
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EPIPE = 32, // Broken pipe
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ENAMETOOLONG = 36, // File name too long
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ENOLCK = 37, // No locks available
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ENOSYS = 38, // Function not implemented
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ENOTEMPTY = 39, // Directory not empty
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ELOOP = 40, // Too many levels of symbolic links
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EWOULDBLOCK = 11, // Resource temporarily unavailable (call would block)
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};
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// Configuration passed to New() from the kernel.
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struct Config {
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bool setgid, setuid; // If true, GID/UID of each file is overwritten with gid/uid.
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gid_t gid;
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uid_t uid;
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bool setfmask, setdmask; // If true, file/directory permissions are masked with the given values.
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mode_t fmask, dmask; // (Corresponding bits cleared)
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};
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// Information on an open file.
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struct OpenFile {
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// File open flags.
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OpenFlag flags;
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// Filled in by open(), to indicate the file is not seekable.
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bool nonseekable : 1;
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unsigned int padding : 31;
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unsigned int padding2 : 32;
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// File handle. Filled in by Create(), Open(), Opendir().
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uint64_t handle;
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};
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enum RenameType {
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Rename_Exchange, // Atomically swaps the 2 files if the target file exists.
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Rename_NoReplace, // Return with error if the target file exists.
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};
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// POSIX file types
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static constexpr mode_t S_IFMT = 0170000; // Bit mask for the file type bit field
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static constexpr mode_t S_IFIFO = 0010000; // FIFO
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static constexpr mode_t S_IFCHR = 0020000; // Character device
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static constexpr mode_t S_IFDIR = 0040000; // Directory
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static constexpr mode_t S_IFBLK = 0060000; // Block device
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static constexpr mode_t S_IFREG = 0100000; // Regular file
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static constexpr mode_t S_IFLNK = 0120000; // Symbolic link
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static constexpr mode_t S_IFSOCK = 0140000; // Socket
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// File status
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struct Stat {
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mode_t Mode; // File type and mode
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uint32_t NumLinks; // Number of hard links on the same file
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uid_t Uid; // User ID of owner
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gid_t Gid; // Group ID of owner
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uint64_t Size; // Total size of file in bytes
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uint64_t Blocks; // Number of 512Byte blocks allocated
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uint64_t TimeAccess, TimeModification; // UNIX time of last access/modification
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};
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// New is called to create a new Filesystem instance from a given source.
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//
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// The source paramater is quite special.
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// Beginning with "/" means a local file source (device or image).
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// Beginning with a "//" means a network target (URL).
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// Otherwise, this string is non-canonical and its behavior is implementation-depedent.
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typedef Filesystem *(*New)(const char *source, Config *config);
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public:
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// Filesystem implementation capabilitiy bits
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enum Capability {
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Capability_AtomicTruncate = 1 << 0, // supports O_TRUNC open flag. If disabled, kernel calls Truncate() and Open() on O_TRUNC.
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Capability_Export = 1 << 1, // supports lookup of "." and "..".
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Capability_NoOpen = 1 << 2, // does not use Open() (returning ENOSYS), using stateless file I/O
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};
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virtual Capability Capabilities() { return Capability_NoOpen; }
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public:
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virtual ~Filesystem() {}
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// Getattr is similar to stat(), returning file status.
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//
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// file is NULL if the file is not opened, but may too be NULL
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// if the file is opened.
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virtual int Getattr(const char *path, Stat *stat, OpenFile *file) { return -ENOSYS; }
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// Readlink reads the target of a symbolic link.
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//
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// If the linkname is too long to fit in the target, it should be truncated,
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// returning the required size of the new buffer.
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//
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// Returns 0 on success.
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virtual int Readlink(const char *link, char *buffer, uint64_t bufferSize) { return -ENOSYS; }
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// Create a new file node (empty file), without opening it.
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//
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// This is called for non-directory, non-symlink nodes.
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virtual int Mknod(const char *file, mode_t mode) { return -ENOSYS; }
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// Create a new directory.
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//
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// The mode argument might not have the S_IFDIR bits set.
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virtual int Mkdir(const char *path, mode_t mode) { return -ENOSYS; }
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// Remove a file or node.
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virtual int Unlink(const char *path) { return -ENOSYS; }
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// Remove an empty directory.
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virtual int Rmdir(const char *path) { return -ENOSYS; }
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// Create a symbolic link.
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virtual int Symlink(const char *target, const char *path) { return -ENOSYS; }
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// Rename (move) a file.
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//
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// The Type argument should be honored.
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virtual int Rename(const char *from, const char *to, RenameType type) { return -ENOSYS; }
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// Create a hard link to file.
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virtual int Link(const char *from, const char *to) { return -ENOSYS; }
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// Change the owner/group of a file.
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//
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// file is NULL if the file is not opened, but may too be NULL
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// if the file is opened.
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//
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// This function is never called if setuid/gid bits are set.
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virtual int Chown(const char *path, uid_t uid, gid_t gid, OpenFile *file) { return -ENOSYS; }
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// Change the permissions of a file.
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//
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// file is NULL if the file is not opened, but may too be NULL
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// if the file is opened.
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virtual int Chmod(const char *path, mode_t mode, OpenFile *file) { return -ENOSYS; }
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// Change the size of a file.
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//
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// file is NULL if the file is not opened, but may too be NULL
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// if the file is opened.
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virtual int Truncate(const char *path, uint64_t size, OpenFile *file) { return -ENOSYS; }
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// Opens a file, with flags in file->flags.
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//
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// - Creation flags (O_CREAT, O_EXCL, O_NOCTTY) are handled by the kernel and filtered out.
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// - Access modes (O_RDONLY, O_WRONLY,O_RDWR,O_EXEC) should be checked if the operation is permitted.
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//
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// Driver may store arbitrary value in file->handle and other flags to change the way the file is opened.
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virtual int Open(const char *path, OpenFile *file) { return -ENOSYS; }
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// Read data from an open file.
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//
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// Read should return exactly the number of bytes requested except
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// on EOF or error, when the rest of the data will be zeroed.
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virtual int Read(const char *path, char *buffer, uint64_t count, uint64_t offset, OpenFile *file) { return -ENOSYS; }
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// Write data to an open file.
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// Read should return exactly the number of bytes requested except on error.
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virtual int Write(const char *path, const char *buffer, uint64_t count, uint64_t offset, OpenFile *file) { return -ENOSYS; }
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// Syncs file data to disk.
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//
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// If syncOnlyUserData is true, sync only user data, not the metadata
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virtual int Fsync(const char *path, bool syncOnlyUserData, OpenFile *file) { return -ENOSYS; }
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// Closes an open file.
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//
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// For each Open() call there is exactly one Close() call with the same file->flags/handle.
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// It is possible that one same file has been opened several times.
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virtual int Close(const char *path, OpenFile *file) { return -ENOSYS; }
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// Open a directory for reading.
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//
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// This function should check for permissions in file->flags.
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virtual int Opendir(const char *path, OpenFile *file) { return -ENOSYS; }
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enum Readdir_CallbackFlags {
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Readdir_CallbackFlags_StatValid = 1 << 0, // All stat members are valid
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};
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// typedef of the callback Readdir() uses to emit directory entries
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typedef int (*Readdir_Callback)(void *user, const char *name, const Stat *stat, Readdir_CallbackFlags flags);
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// Read an open directory.
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//
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// The implementation calls Callback() on all directory entries.
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virtual int Readdir(const char *path, void *user, Readdir_Callback callback, OpenFile *file) { return -ENOSYS; }
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// Syncs the contents of a directory.
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//
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// If syncOnlyUserData is true, sync only user data, not the metadata
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virtual int Fsyncdir(const char *path, bool syncOnlyUserData, OpenFile *file) { return -ENOSYS; }
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// Close an open directory.
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virtual int Closedir(const char *path, OpenFile *file) { return -ENOSYS; }
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};
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} // namespace helos
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