feat: add file

src/file.rs

@@ -0,0 +1,39 @@
+use std::fs::File;
+use std::io::{Read, Write};
+
+use rust_util::{opt_result, simple_error, XResult};
+
+use crate::spec::TinyEncryptMeta;
+
+fn write_tiny_encrypt_meta<W: Write>(w: &mut W, meta: &TinyEncryptMeta) -> XResult<usize> {
+    let meta_json = opt_result!( serde_json::to_string(meta), "Meta to JSON failed: {}");
+    let meta_json_bytes = meta_json.as_bytes();
+    let meta_json_bytes_len = meta_json_bytes.len();
+
+    opt_result!(w.write_all(&((0x01) as u16).to_be_bytes()), "Write tag failed: {}");
+    opt_result!(w.write_all(&(meta_json_bytes_len as u32).to_be_bytes()), "Write length failed: {}");
+    opt_result!(w.write_all(&meta_json_bytes), "Write meta failed: {}");
+
+    Ok(meta_json_bytes_len + 2 + 4)
+}
+
+fn read_tiny_encrypt_meta<R: Read>(r: &mut R) -> XResult<TinyEncryptMeta> {
+    let mut tag_buff = [0_u8; 2];
+    opt_result!(r.read_exact(&mut tag_buff), "Read tag failed: {}");
+    let tag = u16::from_be_bytes(tag_buff);
+    if tag != 0x01 {
+        return simple_error!("Tag is not 0x01, but is: 0x{:x}", tag);
+    }
+
+    let mut length_buff = [0_u8; 4];
+    opt_result!(r.read_exact(&mut length_buff), "Read length failed: {}");
+    let length = u32::from_be_bytes(length_buff);
+    if length > 1024 * 1024 {
+        return simple_error!("Meta too large: {}", length);
+    }
+
+    let mut meta_buff = Vec::with_capacity(length as usize);
+    opt_result!( r.read_exact(meta_buff.as_mut_slice()), "Read meta failed: {}");
+
+    Ok(opt_result!(serde_json::from_slice(&meta_buff), "Parse meta failed: {}"))
+}