global: snapshot

crates/brk_core/src/structs/mod.rs

@@ -36,6 +36,7 @@ mod txidprefix;
 mod txindex;
 mod txversion;
 mod unit;
+mod version;
 mod vin;
 mod vout;
 mod weekindex;
@@ -80,6 +81,7 @@ pub use txidprefix::*;
 pub use txindex::*;
 pub use txversion::*;
 pub use unit::*;
+pub use version::*;
 pub use vin::*;
 pub use vout::*;
 pub use weekindex::*;

crates/brk_core/src/structs/version.rs

@@ -0,0 +1,72 @@
+use std::{
+    fs,
+    io::{self, Read},
+    ops::Add,
+    path::Path,
+};
+
+use zerocopy::{FromBytes, IntoBytes};
+use zerocopy_derive::{FromBytes, Immutable, IntoBytes, KnownLayout};
+
+use crate::{Error, Result};
+
+#[derive(
+    Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, FromBytes, IntoBytes, Immutable, KnownLayout,
+)]
+pub struct Version(u64);
+
+impl Version {
+    pub const ZERO: Self = Self(0);
+    pub const ONE: Self = Self(1);
+    pub const TWO: Self = Self(2);
+
+    pub const fn new(v: u64) -> Self {
+        Self(v)
+    }
+
+    pub fn write(&self, path: &Path) -> Result<(), io::Error> {
+        fs::write(path, self.as_bytes())
+    }
+
+    pub fn swap_bytes(self) -> Self {
+        Self(self.0.swap_bytes())
+    }
+
+    pub fn validate(&self, path: &Path) -> Result<()> {
+        if let Ok(prev_version) = Version::try_from(path) {
+            if prev_version != *self {
+                if prev_version.swap_bytes() == *self {
+                    return Err(Error::WrongEndian);
+                }
+                return Err(Error::DifferentVersion {
+                    found: prev_version,
+                    expected: *self,
+                });
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl From<u64> for Version {
+    fn from(value: u64) -> Self {
+        Self(value)
+    }
+}
+
+impl TryFrom<&Path> for Version {
+    type Error = Error;
+    fn try_from(value: &Path) -> Result<Self, Self::Error> {
+        let mut buf = [0; 8];
+        fs::read(value)?.as_slice().read_exact(&mut buf)?;
+        Ok(*(Self::ref_from_bytes(&buf)?))
+    }
+}
+
+impl Add<Version> for Version {
+    type Output = Self;
+    fn add(self, rhs: Version) -> Self::Output {
+        Self(self.0 + rhs.0)
+    }
+}