fuseのサンプルプログラム

fusetest.c

/*
* fuseのサンプルプログラム
* リンクは実装しない
* 起動は sudo ./fusetest <mountpoint>
* 終了は sudo umount <mountpoint>
*/

#define FUSE_USE_VERSION 28

#include <string.h>
#include <libgen.h>
#include <errno.h>
#include <fuse.h>
#include <time.h>
#include <syslog.h>

#define ENTRY_MAX_DATA 128
#define ENTRY_MAX_NAME 16

//struct entryのフラグ
#define FLAG_TYPE_MASK 0x1
#define FLAG_TYPE_DIR 0x0
#define FLAG_TYPE_FILE 0x1
#define FLAG_ENTRY_USED 0x100

#define NUM_OF_ENTRIES 100

#define for_each_entry(i) for(i=0;i<NUM_OF_ENTRIES;i++) if(entries[i].flags & FLAG_ENTRY_USED)

//ファイルまたはディレクトリを表す
struct entry{
	int flags, size;		//sizeはdataのサイズ
	char data[ENTRY_MAX_DATA];	//ファイルを表すときのみ使う
	char name[ENTRY_MAX_NAME];
	struct entry *parent;
	mode_t mode;			//パーミッションとか
};
//flagsとmodeの役割分担がやや曖昧

struct entry entries[NUM_OF_ENTRIES];

static void entry_init(struct entry *e,struct entry *parent, char *name, int flags, mode_t mode)
{
	e->flags = flags | FLAG_ENTRY_USED;
	e->size = 0;
	if(strlen(name) >= ENTRY_MAX_NAME){
		//ENAMETOOLONGだが、面倒なので無視
	}
	strncpy(e->name, name, ENTRY_MAX_NAME);
	e->parent = parent;
	e->mode = mode;
}

static int entry_is_dir(struct entry *e)
{
	return (e->flags & FLAG_TYPE_MASK) == FLAG_TYPE_DIR;
}

static int entry_is_file(struct entry *e)
{
	return (e->flags & FLAG_TYPE_MASK) == FLAG_TYPE_FILE;
}

static struct entry *get_unused_entry()
{
	int i;
	for(i=0;i<NUM_OF_ENTRIES;i++){
		if((entries[i].flags & FLAG_ENTRY_USED) == 0){
			return entries + i;
		}
	}
	return NULL;
}

//名前の重複は確認しない
static int entry_mkdir(struct entry *parent, char *name, mode_t mode)
{
	struct entry *e = get_unused_entry();
	if(e){
		entry_init(e, parent, name, FLAG_TYPE_DIR, mode);
		return 0;
	}
	else return -ENOSPC;
}

static int create_file(struct entry *parent, char *name, mode_t mode)
{
	struct entry *e = get_unused_entry();
        if(e){
                entry_init(e, parent, name, FLAG_TYPE_FILE, mode);
                return 0;
        }
        else return -ENOSPC;
}

static int entry_is_root(struct entry *e)
{
	return e->parent == NULL;
}

/*
* 引数のnはバッファのサイズ(sizeof(buf))
* 成功: strlen(buf)を返す
* エラー: -1を返す
*/
static int entry_get_path(struct entry *e, char *buf, int n)
{
	int i, len;
	if(entry_is_root(e) && n >= 2){
		strcpy(buf, "/");
		return 1;
	}
	i = entry_get_path(e->parent, buf, n);
	//buf == "/" のとき、"//abc"のようにならないよう気をつける
	if(i == 1){
		i = 0;
	}
	len = strlen(e->name);
	if(i != -1 && i + len + 2 <= n){//+2は '/' '\0'の分
		buf[i++] = '/';
		strncpy(buf + i, e->name, n - i);
		return i + len;
	}
	else return -1;
}

//パスの文字列を比較して探す
//検索にハッシュを使ったほうがいいかも
static struct entry *get_entry(const char *path)
{
	char buf[512];//十分大きく
	int i, err;
	for_each_entry(i){
		err = entry_get_path(entries+i, buf, sizeof(buf));
		if(err != -1 && strcmp(buf, path) == 0){
			return entries + i;
		}
	}
	return NULL;
}


static int fusetest_getattr(const char *path, struct stat *stbuf)
{
	struct entry *e = get_entry(path);

	syslog(LOG_INFO, "getattr: %s\n", path);

        if(!e) return -ENOENT;

	memset(stbuf, 0, sizeof(struct stat));
	switch(e->flags & FLAG_TYPE_MASK){
	case FLAG_TYPE_DIR:
		stbuf->st_mode = S_IFDIR | e->mode;
		stbuf->st_nlink = 2;
		break;
	case FLAG_TYPE_FILE:
		stbuf->st_mode = S_IFREG | e->mode;
		stbuf->st_nlink = 1;
		stbuf->st_size = e->size;
		break;
	default:
		return -ENOENT;
	}
	//タイムスタンプ
	//面倒なので、現在時刻を用いる
	stbuf->st_atime = stbuf->st_mtime = stbuf->st_ctime = time(NULL);
	return 0;
}

static int fusetest_readdir(const char *path,
                         void *buf,
                         fuse_fill_dir_t filler,
                         off_t offset,
                         struct fuse_file_info *fi)
{
	struct entry *e = get_entry(path);
	int i;
	if(!e || !entry_is_dir(e)) return -ENOENT;
	filler(buf, ".",  NULL, 0);
	filler(buf, "..", NULL, 0);
	for_each_entry(i){
		if(entries[i].parent == e){
			filler(buf, entries[i].name, NULL, 0);
		}
	}
	return 0;
}

static int fusetest_open(const char *path, struct fuse_file_info *fi)
{
	struct entry *e = get_entry(path);
	syslog(LOG_INFO, "open: flags = %x\n", fi->flags);
	if(!e || !entry_is_file(e)) return -ENOENT;
	return 0;
}

static int fusetest_read(const char *path,
                      char *buf,
                      size_t size,
                      off_t offset,
                      struct fuse_file_info *fi)
{
	struct entry *e = get_entry(path);
	if(!e || !entry_is_file(e)){
		return -ENOENT;
	}
	if(offset > e->size) return 0;

	if(offset + size > e->size)
		size = e->size - offset;

	memcpy(buf, e->data + offset, size);
	return size;
}

static int fusetest_write(const char *path,
                      const char *buf,
                      size_t size,
                      off_t offset,
                      struct fuse_file_info *fi)
{
	struct entry *e = get_entry(path);
	if(!e || !entry_is_file(e)){
		return -ENOENT;
	}
	if(offset >= ENTRY_MAX_DATA)
		return -ENOSPC;

	if(offset + size > ENTRY_MAX_DATA)
		size = ENTRY_MAX_DATA - offset;

	memcpy(e->data + offset, buf, size);
	e->size = offset + size;

	return size;
}

static int fusetest_mkdir(const char *path, mode_t mode)
{
	char tmp[512];
	struct entry *parent;

	syslog(LOG_INFO, "mkdir: %o\n", mode);

	if(strlen(path) >= sizeof(tmp)) return -ENAMETOOLONG;

	strncpy(tmp, path, sizeof(tmp));
	parent = get_entry(dirname(tmp));

	if(get_entry(path)) return -EEXIST;
	if(!parent) return -ENOENT;
	if(!entry_is_dir(parent)) return -ENOTDIR;

	strncpy(tmp, path, sizeof(tmp));
	return entry_mkdir(parent, basename(tmp), mode);
}

static int fusetest_rmdir(const char *path)
{
	struct entry *e = get_entry(path);
	if(!e) return -ENOENT;
	if(!entry_is_dir(e)) return -ENOTDIR;
	int i;
	for_each_entry(i){
		if(entries[i].parent == e) return -ENOTEMPTY;
	}

	e->flags = 0;
	return 0;
}

static int fusetest_create(const char *path, mode_t mode, struct fuse_file_info *fi)
{
	char tmp[512];
	struct entry *parent;

	syslog(LOG_INFO, "create: %o\n", mode);

	if(strlen(path) >= sizeof(tmp)) return -ENAMETOOLONG;

	strncpy(tmp, path, sizeof(tmp));
	parent = get_entry(dirname(tmp));

	if(get_entry(path)) return -EEXIST;
	if(!parent) return -ENOENT;

	strncpy(tmp, path, sizeof(tmp));
	return create_file(parent, basename(tmp), mode);
}

static int fusetest_unlink(const char *path)
{
	struct entry *e = get_entry(path);
	if(!e) return -ENOENT;
	if(entry_is_dir(e)) return -EISDIR;
	e->flags = 0;	//e->flags & FLAG_ENTRY_USED == 0 にする
	return 0;
}

static int fusetest_truncate(const char *path, off_t size)
{
	struct entry *e = get_entry(path);
	if(!e) return -ENOENT;
	if(entry_is_dir(e)) return -EISDIR;
	if(size > ENTRY_MAX_DATA || size < 0) return -EINVAL;

	e->size = size;
	return 0;
}

static int fusetest_chmod(const char *path, mode_t mode)
{
	struct entry *e = get_entry(path);
	if(!e) return -ENOENT;
	syslog(LOG_INFO, "chmod: %o\n", mode);
	e->mode = mode;
	return 0;
}

static int fusetest_chown(const char *path, uid_t uid, gid_t gid)
{
	syslog(LOG_INFO, "chown: uid = %d, gid = %d\n", uid, gid);
	return -ENOSYS;	//未実装としておく
}

//touchに必要
static int fusetest_utimens(const char *path, const struct timespec tv[2])
{
	syslog(LOG_INFO, "utimens: path = %s\n", path);
	syslog(LOG_INFO, "atime: %s .%09d\n", ctime(&tv[0].tv_sec), (int)tv[0].tv_nsec);
	syslog(LOG_INFO, "mtime: %s .%09d\n", ctime(&tv[1].tv_sec), (int)tv[1].tv_nsec);
//	return -ENOSYS;
	return 0;
}

//適当にファイルやディレクトリを作成しておく
static void *fusetest_init(struct fuse_conn_info *conn)
{
	entry_init(entries, NULL, "", FLAG_TYPE_DIR, 0755);
	entry_mkdir(entries, "dir1", 0755);
	create_file(entries, "hello.txt", 0644);
	struct entry *e = get_entry("/dir1");
	create_file(e, "aaa", 0644);
	e = get_entry("/hello.txt");
	e->size = 7;
	memcpy(e->data, "abcdefg", e->size);
	return NULL;
}

//http://fuse.sourceforge.net/doxygen/index.html 参照
//エラーコードはman 2 open, man 3 errnoなどで調べる
static struct fuse_operations fusetest_op = {
	.getattr = fusetest_getattr,
	.readdir = fusetest_readdir,
	.open	= fusetest_open,
	.read	= fusetest_read,
	.write	= fusetest_write,
	.mkdir	= fusetest_mkdir,
	.rmdir	= fusetest_rmdir,
	.create	= fusetest_create,
	.unlink	= fusetest_unlink,
	.truncate = fusetest_truncate,
	.chmod	= fusetest_chmod,
	.chown	= fusetest_chown,
	.utimens = fusetest_utimens,
	.init	= fusetest_init,
};
//destroyでファイルに保存、とかもできると思う

int main(int argc, char *argv[])
{
	openlog("fusetest", LOG_PID, LOG_USER);
	return fuse_main(argc, argv, &fusetest_op, NULL);
}

Makefile

all: fusetest

fusetest: fusetest.c
	gcc -Wall fusetest.c `PKG_CONFIG_PATH=/usr/lib/i386-linux-gnu/pkgconfig/ pkg-config fuse --cflags --libs` -o fusetest

.PHONY: clean
clean:
	rm -f fusetest