# File Node

### **File Node Overview**

The File node is a PIN path specifically designed for storing files. Through the File node, users can securely store files on the blockchain in the form of PINs, achieving decentralized file storage and management.

### **Data Format**

The PIN content for storing files follows this format:

```go
OP_FALSE
OP_IF
	metaid            
	create             
	/file/file-name-1.jpg     
	0                  
	OP_0               
	image/jpg;binary   
	<file data>        // Payload - Binary content of the file
OP_ENDIF
```

Here, **`<file data>`** contains the binary content of the file, and **`content-type`** specifies the file's data type (for example, image/jpg;binary indicates a JPEG image file).

### **File Node Path**

The path for the File node uses **`/file`** as the base path and can further distinguish different files through file names or sub-paths. Through the File node path, users can easily locate and retrieve specific file PINs in the MetaID tree structure, thereby achieving effective organization and management of files.

### **File Referencing**

In MetaID, file referencing is a fundamental business operation with critical importance. This feature allows users to reference existing on-chain **`file`** data in application protocols, enhancing data connectivity and user experience. To achieve this, we define a special file referencing rule.

#### **File Referencing Format**

When referencing a **`file`** in a sub-protocol, such as in the **`payload`**, we use the following format:

```arduino
metafile://{pinid}
```

Here, `PINID` is the unique identifier of the file to be referenced. This format allows us to establish a reference link from the current protocol to a specific **`file`**.

<figure><img src="https://1852888944-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FQqzh03Cj3B0aOuGYLJKs%2Fuploads%2FAxTDYpf4WQMaVWCRHtP8%2Fimage.png?alt=media&#x26;token=ce9c2ee8-71f7-454d-aee3-c61d55354347" alt=""><figcaption></figcaption></figure>

#### Example

For example, posting with an attached file:

```json
//Payload
{
	"content":"Hello bitcoin world!",
	"contentType":"text/plain",
	"createTime":1710741614716,
	"quoteTx":"",
	"attachment":[
		"metafile://{pinId}"
	]
}
```

The final on-chain content will be:

```json
OP_FALSE
OP_IF
	metaid                           // Protocol identifier
	create                          // Operation type
	/protocols/simplebuzz         // Path
	0                                // Encryption type (0 means no encryption)
	0                                // Version
	application/json;utf-8              // Content-type
	{"content":"Hello bitcoin world!","contentType":"text/plain","createTime":1710741614716,"quoteTx":"","attachment":["metafile://{pinId}"]}       // Payload
OP_ENDIF
```

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