fs: ext2: File operations

Introduced functions:
  - read
  - write
  - seek
  - tell

Signed-off-by: Franciszek Zdobylak <fzdobylak@antmicro.com>

subsys/fs/ext2/ext2_impl.c

@@ -549,6 +549,88 @@ static int64_t find_dir_entry(struct ext2_inode *inode, const char *name, size_t
 	return -EINVAL;
 }
 
+/* Inode operations --------------------------------------------------------- */
+
+ssize_t ext2_inode_read(struct ext2_inode *inode, void *buf, uint32_t offset, size_t nbytes)
+{
+	int rc = 0;
+	ssize_t read = 0;
+	uint32_t block_size = inode->i_fs->block_size;
+
+	while (read < nbytes && offset < inode->i_size) {
+
+		uint32_t block = offset / block_size;
+		uint32_t block_off = offset % block_size;
+
+		rc = ext2_fetch_inode_block(inode, block);
+		if (rc < 0) {
+			break;
+		}
+
+		uint32_t left_on_blk = block_size - block_off;
+		uint32_t left_in_file = inode->i_size - offset;
+		size_t to_read = MIN(nbytes, MIN(left_on_blk, left_in_file));
+
+		memcpy((uint8_t *)buf + read, inode_current_block_mem(inode) + block_off, to_read);
+
+		read += to_read;
+		offset += to_read;
+	}
+
+	if (rc < 0) {
+		return rc;
+	}
+	return read;
+}
+
+ssize_t ext2_inode_write(struct ext2_inode *inode, const void *buf, uint32_t offset, size_t nbytes)
+{
+	int rc = 0;
+	ssize_t written = 0;
+	uint32_t block_size = inode->i_fs->block_size;
+
+	while (written < nbytes) {
+		uint32_t block = offset / block_size;
+		uint32_t block_off = offset % block_size;
+
+		LOG_DBG("inode:%d Write to block %d (offset: %d-%zd/%d)",
+				inode->i_id, block, offset, offset + nbytes, inode->i_size);
+
+		rc = ext2_fetch_inode_block(inode, block);
+		if (rc < 0) {
+			break;
+		}
+
+		size_t to_write = MIN(nbytes, block_size - block_off);
+
+		memcpy(inode_current_block_mem(inode) + block_off, (uint8_t *)buf + written,
+				to_write);
+		LOG_DBG("Written %zd bytes at offset %d in block i%d", to_write, block_off, block);
+
+		rc = ext2_commit_inode_block(inode);
+		if (rc < 0) {
+			break;
+		}
+
+		written += to_write;
+	}
+
+	if (rc < 0) {
+		return rc;
+	}
+
+	if (offset + written > inode->i_size) {
+		LOG_DBG("New inode size: %d -> %zd", inode->i_size, offset + written);
+		inode->i_size = offset + written;
+		rc = ext2_commit_inode(inode);
+		if (rc < 0) {
+			return rc;
+		}
+	}
+
+	return written;
+}
+
 int ext2_get_direntry(struct ext2_dir *dir, struct fs_dirent *ent)
 {
 	if (dir->d_off >= dir->d_inode->i_size) {

subsys/fs/ext2/ext2_impl.h

@@ -156,6 +156,36 @@ struct ext2_lookup_args {
  */
 int ext2_lookup_inode(struct ext2_data *fs, struct ext2_lookup_args *args);
 
+/* Inode operations */
+
+/**
+ * @brief Read from inode at given offset
+ *
+ * @param inode Inode
+ * @param buf Buffer to hold read data
+ * @param offset Offset in inode
+ * @param nbytes Number of bytes to read
+ *
+ * @retval >=0 number of bytes read on success
+ * @retval <0 error code
+ */
+ssize_t ext2_inode_read(struct ext2_inode *inode, void *buf, uint32_t offset,
+			size_t nbytes);
+
+/**
+ * @brief Write to inode at given offset
+ *
+ * @param inode Inode
+ * @param buf Buffer with data to write
+ * @param offset Offset in inode
+ * @param nbytes Number of bytes to write
+ *
+ * @retval >=0 number of bytes read on success
+ * @retval <0 error code
+ */
+ssize_t ext2_inode_write(struct ext2_inode *inode, const void *buf,
+			 uint32_t offset, size_t nbytes);
+
 /* Directory operations */
 
 /**

subsys/fs/ext2/ext2_ops.c

@@ -125,6 +125,83 @@ out:
 	return rc;
 }
 
+static ssize_t ext2_read(struct fs_file_t *filp, void *dest, size_t nbytes)
+{
+	struct ext2_file *f = filp->filep;
+
+	if ((f->f_flags & FS_O_READ) == 0) {
+		return -EACCES;
+	}
+
+	ssize_t r = ext2_inode_read(f->f_inode, dest, f->f_off, nbytes);
+
+	if (r < 0) {
+		return r;
+	}
+	f->f_off += r;
+	return r;
+}
+
+static ssize_t ext2_write(struct fs_file_t *filp, const void *src, size_t nbytes)
+{
+	struct ext2_file *f = filp->filep;
+
+	if ((f->f_flags & FS_O_WRITE) == 0) {
+		return -EACCES;
+	}
+
+	if (f->f_flags & FS_O_APPEND) {
+		f->f_off = f->f_inode->i_size;
+	}
+
+	ssize_t r = ext2_inode_write(f->f_inode, src, f->f_off, nbytes);
+
+	if (r < 0) {
+		return r;
+	}
+
+	f->f_off += r;
+	return r;
+}
+
+static int ext2_lseek(struct fs_file_t *filp, off_t off, int whence)
+{
+	struct ext2_file *f = filp->filep;
+
+	uint32_t new_off = 0;
+
+	switch (whence) {
+	case FS_SEEK_SET:
+		new_off = off;
+		break;
+
+	case FS_SEEK_CUR:
+		new_off = f->f_off + off;
+		break;
+
+	case FS_SEEK_END:
+		new_off = f->f_inode->i_size + off;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	/* New offset not inside the file. */
+	if (new_off < 0 || new_off > f->f_inode->i_size) {
+		return -EINVAL;
+	}
+	f->f_off = new_off;
+	return 0;
+}
+
+static off_t ext2_tell(struct fs_file_t *filp)
+{
+	struct ext2_file *f = filp->filep;
+
+	return f->f_off;
+}
+
 /* Directory operations */
 
 static int ext2_mkdir(struct fs_mount_t *mountp, const char *name)
@@ -375,6 +452,10 @@ static int ext2_statvfs(struct fs_mount_t *mountp, const char *path, struct fs_s
 static const struct fs_file_system_t ext2_fs = {
 	.open = ext2_open,
 	.close = ext2_close,
+	.read = ext2_read,
+	.write = ext2_write,
+	.lseek = ext2_lseek,
+	.tell = ext2_tell,
 	.mkdir = ext2_mkdir,
 	.mount = ext2_mount,
 	.unmount = ext2_unmount,