Add --check-index subcommand to passively check the index file.

src/index.rs

@@ -178,16 +178,8 @@ impl Index {
       }
     };
 
-    if let Ok(mut file) = fs::OpenOptions::new().read(true).open(&path) {
-      // use cberner's quick hack to check the redb recovery bit
-      // https://github.com/cberner/redb/issues/639#issuecomment-1628037591
-      const MAGICNUMBER: [u8; 9] = [b'r', b'e', b'd', b'b', 0x1A, 0x0A, 0xA9, 0x0D, 0x0A];
-      const RECOVERY_REQUIRED: u8 = 2;
-
-      let mut buffer = [0; MAGICNUMBER.len() + 1];
-      file.read_exact(&mut buffer).unwrap();
-
-      if buffer[MAGICNUMBER.len()] & RECOVERY_REQUIRED != 0 {
+    if let Ok(file) = fs::OpenOptions::new().read(true).open(&path) {
+      if Self::is_index_file_corrupted(file) {
         println!("Index file {:?} needs recovery. This can take a long time, especially for the --index-sats index.", path);
       }
     }
@@ -1337,6 +1329,16 @@ impl Index {
 
     Ok(result)
   }
+
+  pub(crate) fn is_index_file_corrupted(mut file: File) -> bool {
+    // use cberner's quick hack to check the redb recovery bit
+    // https://github.com/cberner/redb/issues/639#issuecomment-1628037591
+    const MAGICNUMBER: [u8; 9] = [b'r', b'e', b'd', b'b', 0x1A, 0x0A, 0xA9, 0x0D, 0x0A];
+    const RECOVERY_REQUIRED: u8 = 2;
+
+    let mut buffer = [0; MAGICNUMBER.len() + 1];
+    file.read_exact(&mut buffer).is_err() || buffer[MAGICNUMBER.len()] & RECOVERY_REQUIRED != 0
+  }
 }
 
 #[cfg(test)]

src/subcommand.rs

@@ -1,5 +1,6 @@
 use super::*;
 
+pub mod check_index;
 pub mod decode;
 pub mod epochs;
 pub mod find;
@@ -24,6 +25,8 @@ fn print_json(output: impl Serialize) -> Result {
 
 #[derive(Debug, Parser)]
 pub(crate) enum Subcommand {
+  #[clap(about = "Check whether the index file needs recovery without attempting recovery")]
+  CheckIndex(check_index::CheckIndex),
   #[clap(about = "Decode inscription data from a transaction output")]
   Decode(decode::Decode),
   #[clap(about = "List the first satoshis of each reward epoch")]
@@ -59,6 +62,7 @@ pub(crate) enum Subcommand {
 impl Subcommand {
   pub(crate) fn run(self, options: Options) -> Result {
     match self {
+      Self::CheckIndex(check_index) => check_index.run(options),
       Self::Decode(decode) => decode.run(options),
       Self::Epochs => epochs::run(),
       Self::Preview(preview) => preview.run(),

src/subcommand/check_index.rs

@@ -0,0 +1,27 @@
+use super::*;
+
+#[derive(Debug, Parser)]
+pub(crate) struct CheckIndex {
+}
+
+impl CheckIndex {
+  pub(crate) fn run(self, options: Options) -> Result {
+    let path = if let Some(path) = &options.index {
+      path.clone()
+    } else {
+      options.data_dir()?.join("index.redb")
+    };
+
+    if let Ok(file) = fs::OpenOptions::new().read(true).open(&path) {
+      if Index::is_index_file_corrupted(file) {
+        println!("Index file {:?} needs recovery.", path);
+      } else {
+        println!("Index file {:?} doesn't need recovery.", path);
+      }
+    } else {
+      println!("Can't open {:?} for reading", path);
+    }
+
+    Ok(())
+  }
+}