5_pass_vlad_os

/**
 * @file os_assignment.c
 *
 * This is the file you will be working in. You will have to complete the (partial) implementation
 * given below. Any functions you have to complete are clearly marked as such.
 *
 * Good luck!
 */

#include "dfs.h"
#include "dfs-path.h"
#include "dfs-helpers.h"
#include "strdup.h"

#define FUSE_USE_VERSION 31
#include <fuse.h>

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/**
 * path = [<parent_path>/<entity_name>]
 * entity_name can be either the name of a file, or the name of a directory.
*/
static int split_path(const char *path, char *parent_path, char *entity_name) {
    char *last_slash = strrchr(path, '/'); // Obtain a pointer to the last occurence of "/"
    if (NULL == last_slash) { // No "/" in the provided path
        return -1;
    }
    size_t parent_len = last_slash - path;
    strncpy(parent_path, path, parent_len);
    parent_path[parent_len] = '\0';
    strcpy(entity_name, last_slash + 1);
    return 0;
}


/**
 * The root directory of the file system.
 */
DfsDir *root_dir;

/**
 * Initializes the default file system.
 *
 * This fills the DFS with a number of directories and files. Add, remove and rename some files
 * and directories, if you wish.
 *
 * Note how this creates a top-level directory root_dir. You will have to use this directory.
 */
void create_dfs(void) {
    // Define some directories
    root_dir = dfs_create_dir();

    DfsDir *files_dir = dfs_create_dir();
    DfsDir *pictures_dir = dfs_create_dir();
    DfsDir *important_files_dir = dfs_create_dir();
    assert(files_dir && pictures_dir && important_files_dir);

    // Define some files
    DfsFile *welcome_file = make_file("Welcome to the DFS.\n");
    DfsFile *budget_file = make_file(budget_text);
    DfsFile *hello_1_file = make_file("Hello there!\n");
    DfsFile *hello_2_file = make_file("Hei siell      !\n");
    DfsFile *image_1_file = make_binary_file(image_1, sizeof(image_1));
    DfsFile *image_2_file = make_binary_file(image_2, sizeof(image_2));
    assert(
        welcome_file && budget_file && hello_1_file && hello_2_file && image_1_file && image_2_file
    );

    // Add everything together
    assert_dfs_ok(dfs_add_dir(root_dir, "Files", files_dir));
    assert_dfs_ok(dfs_add_dir(root_dir, "Pictures", pictures_dir));

    assert_dfs_ok(dfs_add_dir(files_dir, "Important files", important_files_dir));

    assert_dfs_ok(dfs_add_file(root_dir, "README.txt", welcome_file));
    assert_dfs_ok(dfs_add_file(files_dir, "hello.txt", hello_1_file));
    assert_dfs_ok(dfs_add_file(files_dir, "hello2.txt", hello_2_file));
    assert_dfs_ok(dfs_add_file(important_files_dir, "budget.csv", budget_file));
    assert_dfs_ok(dfs_add_file(pictures_dir, "some image.png", image_1_file));
    assert_dfs_ok(dfs_add_file(pictures_dir, "some other image.png", image_2_file));
}

/**
 * @defgroup Assignment The assignment
 * These functions must be completed for the assignment.
 *
 * The functions here directly correspond to the syscall with the same name, unless noted otherwise.
 * @{
 */

/**
 * Lists files/directories available in a specific directory.
 *
 * This function is specific to FUSE; there is no directly corresponding system call.
 *
 * @param path directory which we are listing
 * @param buff buffer to fill with data
 * @param fill a function to help fill buffer
 * @param off not used
 * @param fi not used
 *
 * @return 0 or an appropriate error code
 */
static int os_readdir(
    const char *path, void *buff, fuse_fill_dir_t fill, off_t off, struct fuse_file_info *fi
) {
    // Example: this is how you find the required directory.
    DfsDir *dir;
    DfsStatus dir_status = dfs_find_dir_str(root_dir, path, &dir); // Writes address of found directory to `dir`
    // This could fail though! You should return an error if this is so, in other functions as well
    if (dir_status != DFS_OK) {
        return -ENOENT; // Error: no entity
    }
    // Other errors are also possible

    fill(buff, ".", NULL, 0);
    fill(buff, "..", NULL, 0);

    // Iterate over all entries in a dir
    size_t cursor = 0;
    const char *name;
    DfsEntry* entry;
    while (dfs_get_next(dir, &cursor, &name, &entry) == DFS_OK && name != NULL)
        fill(buff, name, NULL, 0);

    // Returning 0 means all-ok.
    return 0;
}

/**
 * Creates a new directory.
 *
 * @param path the path to the new directory
 * @param mode the mode (permissions) of the new directory. Can be ignored
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 mkdir`](https://linux.die.net/man/2/mkdir)
 */
static int os_mkdir(const char *path, mode_t mode) {
    // Example: this is how you find the required directory.
    char dir_name[1024] = {0};
    char parent_path[1024] = {0};

    if (split_path(path, parent_path, dir_name) != 0)
        return -ENOENT;

    DfsDir *parent_dir;

    DfsStatus dir_status = dfs_find_dir_str(root_dir, parent_path, &parent_dir); // Writes address of found directory to `parent_dir`
    if (dir_status != DFS_OK)
        return -ENOENT; // Error: no entity


    DfsDir *new_dir = dfs_create_dir(); // Create new directory
    if (!new_dir)
        return -ENOENT;

    // Add it to parent directory
    DfsStatus add_dir_status = dfs_add_entry(parent_dir, dir_name, (DfsDir*) new_dir);
    if (add_dir_status != DFS_OK) {
        dfs_destroy_dir(new_dir);
        return -EEXIST; // Error: Did already exists -> dir name conflict
    }

    return 0;

}

/**
 * Removes a directory.
 *
 * This must return an error if the directory is not empty.
 *
 * @param path the path to the directory to remove
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 rmdir`](https://linux.die.net/man/2/rmdir)
 */
static int os_rmdir(const char *path) {

    char parent_path[1024] = {0};
    char dir_name[1024] = {0};

    if (split_path(path, parent_path, dir_name) != 0)
        return -ENOENT;

    DfsDir *parent_dir;
        DfsStatus dir_status = dfs_find_dir_str(root_dir, parent_path, &parent_dir); // Writes address of found directory to `parent_dir`
    if (dir_status != DFS_OK)
        return -ENOENT; // Error: no entity

    DfsDir *dir_removed;
    DfsStatus find_dir = dfs_get_dir(parent_dir, dir_name, &dir_removed);
    if (find_dir != DFS_OK)
        return -ENOENT;

    size_t cursor = 0;
    const char *next_name;
    DfsEntry* entry;
    if (dfs_get_next(dir_removed, &cursor, &next_name, NULL) == DFS_OK) // not empty
        return -ENOTEMPTY;

    dfs_remove_dir(parent_dir, dir_name, NULL);
    return 0;
}

/**
 * Reads (part of) a file.
 *
 * This may return fewer bytes than requested, but only if the end of the file was reached. Note
 * that the system call behaves differently!
 *
 * @param path the path to the file
 * @param buff where to write the read data
 * @param size the number of bytes to read
 * @param off where to start reading from
 * @param fi can be ignored
 *
 * @return the number of bytes read or an appropriate error code
 *
 * @see [`man 2 read`](https://linux.die.net/man/2/read)
 */
static int os_read(
    const char *path, char *buff, size_t size, off_t off, struct fuse_file_info *fi
) {
    DfsFile *file;
    DfsStatus find_file_status = dfs_find_file_str(root_dir, path, &file); // , find the file to read from
    if (find_file_status != DFS_OK) {
        return -ENOENT; // Error: no entity
    }

    // try to write after EOF
    if (off >= file->length)
        return 0;

    size_t read_size = size;
    if (off + size > file->length)
        read_size = file->length - off;

    memcpy(buff, file->contents + off, read_size); //  copy the chunk of bytes to the buffer; TODO: Check if resize of buff neede

    return read_size; // return # of bytes read
}

/**
 * Writes (part of) a file.
 *
 * This must write all given bytes. Note that the system call behaves differently!
 *
 * @param path the path to the file
 * @param buff the data to write
 * @param size the number of bytes to write
 * @param off where to start writing from
 * @param fi can be ignored
 *
 * @return the number of bytes written or an appropriate error code
 *
 * @see [`man 2 write`](https://linux.die.net/man/2/write)
 */
static int os_write(
    const char *path, const char *buff, size_t size, off_t off, struct fuse_file_info *fi
) {
    DfsFile *file;
    DfsStatus find_file_status = dfs_find_file_str(root_dir, path, &file); // , find the file to read from
    if (find_file_status != DFS_OK) {
        return -ENOENT; // Error: no entity
    }

    if (file->length < off + size) { // file too short
        char* copy_contents = realloc(file->contents, off + size);
        if (!copy_contents)
            return -ENOMEM;
        memset(copy_contents + file->length, 0, (off + size) - file->length);

        file->contents = copy_contents;
        file->length = off + size;
    }

    memcpy(file->contents + off, buff, size);
    return size; // Return # of written bytes
}

/**
 * Creates a file.
 *
 * @param path the path to the file
 * @param mode the mode (permissions) of the new file. Can be ignored
 * @param fi can be ignored
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 creat`](https://linux.die.net/man/2/creat) (that is not a typo)
 */
static int os_create(const char *path, mode_t mode, struct fuse_file_info *fi) {
    char file_name[1024];
    char parent_path[1024];

    if (split_path(path, parent_path, file_name) != 0)
        return -ENOENT;

    DfsDir *parent_dir;

    DfsStatus dir_status = dfs_find_dir_str(root_dir, parent_path, &parent_dir); // Writes address of found directory to `parent_dir`
    if (dir_status != DFS_OK)
        return -ENOENT; // Error: no entity


    DfsFile *new_file = dfs_create_file(); // Create new file
    if (!new_file)
        return -ENOSPC; // mem. not allocd

    // Add it to parent directory
    DfsStatus add_file_status = dfs_add_file(parent_dir, file_name, new_file);
    if (add_file_status != DFS_OK) {
        dfs_destroy_file(new_file);
        return -EEXIST; // Error: File already exists -> dir name conflict
    }

    return 0;
}

/**
 * Unlinks (deletes) a file.
 *
 * @param path the path to the file
 *
 * @return 0 or appropriate error code
 *
 * @see [`man 2 unlink`](https://linux.die.net/man/2/unlink)
 */
static int os_unlink(const char *path) {

    char file_name[1024] = {0};
    char parent_path[1024] = {0};

    if (split_path(path, parent_path, file_name) != 0)
        return -ENOENT;


    DfsDir *parent_dir;

    DfsStatus dir_status = dfs_find_dir_str(root_dir, parent_path, &parent_dir); // Writes address of found directory to `parent_dir`
    if (dir_status != DFS_OK)
        return -ENOENT; // Error: no entity


    DfsStatus removed_status = dfs_remove_file(parent_dir, file_name, NULL);
    if (removed_status != DFS_OK)
        return -ENOENT;

    return 0;
}

/// @}
/**
 * @defgroup Predefined Predefined functions
 * You do not have to modify these for the assignment.
 * @{
 */

/**
 * Counts the number of (direct) subdirectories of a directory.
 *
 * @param dir the directory to scan
 *
 * @return the number of subdirectories
 */
static size_t os_count_subdirs(DfsDir *dir) {
    size_t cursor = 0;
    size_t num_subdirs = 0;
    DfsEntry *entry;
    for (;;) {
        DfsStatus get_next_status = dfs_get_next(dir, &cursor, NULL, &entry);
        if (get_next_status == DFS_E_NO_MORE_ENTRIES) break;
        if (entry->type == DFS_ENT_DIR) ++num_subdirs;
    }

    return num_subdirs;
}

/**
 * Retrieves file/directory attributes.
 *
 * @param path the path for which attributes are requested
 * @param st struct to be filled with attributes
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 stat`](https://linux.die.net/man/2/stat)
 */
static int os_getattr(const char *path, struct stat *st) {
    DfsEntry *entry;
    DfsStatus entry_status = dfs_find_entry_str(root_dir, path, &entry);
    if (entry_status == DFS_E_MALLOC_FAILURE) return -ENOMEM;
    if (entry_status == DFS_E_ENTRY_DOES_NOT_EXIST) return -ENOENT;

    st->st_uid = entry->user;
    st->st_gid = entry->group;
    st->st_ctime = entry->ctime.tv_sec;
    st->st_mtime = entry->mtime.tv_sec;
    st->st_atime = entry->atime.tv_sec;

    if (entry->type == DFS_ENT_FILE) {
        DfsFile *file = (DfsFile *) entry;
        st->st_mode = S_IFREG | entry->mode; // Requested item is (probably) a regular file
        st->st_nlink = 1; // Number of hard links: a file has at least one
        st->st_size = file->length;
    } else if (entry->type == DFS_ENT_DIR) {
        DfsDir *dir = (DfsDir *) entry;
        st->st_mode = S_IFDIR | entry->mode;
        st->st_nlink = os_count_subdirs(dir) + 1;
        st->st_size = dfs_get_dir_size(dir) * 32; // Estimate :)
    }

    return 0;
}

/**
 * Resizes a file.
 *
 * @param path the path to the file
 * @param off the new size of the file in bytes
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 truncate`](https://linux.die.net/man/2/truncate)
 */
static int os_truncate(const char *path, off_t off) {
    DfsFile *file;
    DfsStatus file_status = dfs_find_file_str(root_dir, path, &file);
    if (file_status == DFS_E_MALLOC_FAILURE) return -ENOMEM;
    if (file_status == DFS_E_ENTRY_DOES_NOT_EXIST) return -ENOENT;
    if (file_status == DFS_E_NOT_A_FILE) return -EISDIR;

    if (off == 0) {
        free(file->contents);
        file->contents = NULL;
        file->length = 0;
        return 0;
    }

    char *new_contents = realloc(file->contents, off);
    if (!new_contents) return -ENOMEM;

    file->contents = new_contents;

    if ((size_t) off > file->length) {
        memset(file->contents + file->length, 0, off - file->length);
    }

    file->length = off;

    return 0;
}

/**
 * Sets extended attributes on an entry.
 *
 * This is currently not implemented (and you do not have to implement it yourself).
 *
 * @param path the path to the file
 * @param name the name of the attribute
 * @param value the value of the attribute
 * @param length the length of the attribute
 * @param flags any flags
 *
 * @return 0 or an appropriate error code
 */
static int os_setxattr(
    const char *path, const char *name, const char *value, size_t length, int flags
) {
    return -ENOTSUP;
}

/**
 * Changes the mode (permissions) of an entry.
 *
 * @param path the path to the file
 * @param mode the new mode
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 chmod`](https://linux.die.net/man/2/chmod)
 */
static int os_chmod(const char *path, mode_t mode) {
    DfsEntry *entry;
    DfsStatus entry_status = dfs_find_entry_str(root_dir, path, &entry);
    if (entry_status == DFS_E_MALLOC_FAILURE) return -ENOMEM;
    if (entry_status == DFS_E_ENTRY_DOES_NOT_EXIST) return -ENOENT;

    entry->mode = mode;

    return 0;
}

/**
 * Changes the owning user and group of an entry.
 *
 * @param path the path to the file
 * @param uid the new owning user
 * @param gid the new owning group
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 chown`](https://linux.die.net/man/2/chown)
 */
static int os_chown(const char *path, uid_t uid, gid_t gid) {
    DfsEntry *entry;
    DfsStatus entry_status = dfs_find_entry_str(root_dir, path, &entry);
    if (entry_status == DFS_E_MALLOC_FAILURE) return -ENOMEM;
    if (entry_status == DFS_E_ENTRY_DOES_NOT_EXIST) return -ENOENT;

    entry->user = uid;
    entry->group = gid;

    return 0;
}

/**
 * Changes the atime and mtime of an entry.
 *
 * @param path the path to the entry
 * @param tv the new atime and mtime values, respectively
 *
 * @return 0 or an appropriate error code
 *
 * @see [`man 2 utimensat`](https://linux.die.net/man/2/utimensat)
 */
static int os_utimens(const char *path, const struct timespec tv[2]) {
    DfsEntry *entry;
    DfsStatus entry_status = dfs_find_entry_str(root_dir, path, &entry);
    if (entry_status == DFS_E_MALLOC_FAILURE) return -ENOMEM;
    if (entry_status == DFS_E_ENTRY_DOES_NOT_EXIST) return -ENOENT;

    entry->atime = tv[0];
    entry->mtime = tv[1];

    return 0;
}

/**
 * Here we define the operations FUSE has access to.
 *
 * Not all members have been populated and you should not call those!
 */
static struct fuse_operations operations = {
    .getattr = os_getattr,
    .readdir = os_readdir,
    .read = os_read,
    .mkdir = os_mkdir,
    .rmdir = os_rmdir,
    .write = os_write,
    .setxattr = os_setxattr,
    .truncate = os_truncate,
    .chmod = os_chmod,
    .chown = os_chown,
    .utimens = os_utimens,
    .create = os_create,
    .unlink = os_unlink
};

/**
 * Main function.
 *
 * @param argc the number of arguments
 * @param argv the arguments
 */
int main(int argc, char **argv) {
    // Setup dumb file system
    create_dfs();

    // Pass arguments on to FUSE.
    return fuse_main(argc, argv, &operations, NULL);
}

/// @}