vec: compression part 1

crates/brk_vec/src/structs/length.rs

@@ -0,0 +1,71 @@
+use std::{
+    fs,
+    io::{self, Read},
+    ops::{AddAssign, Deref, DerefMut},
+    path::Path,
+};
+
+use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout};
+
+use crate::{Error, Result};
+
+#[derive(
+    Debug,
+    Default,
+    Clone,
+    Copy,
+    PartialEq,
+    Eq,
+    PartialOrd,
+    Ord,
+    FromBytes,
+    IntoBytes,
+    Immutable,
+    KnownLayout,
+)]
+pub struct Length(usize);
+
+impl Length {
+    pub fn write(&self, path: &Path) -> Result<(), io::Error> {
+        fs::write(path, self.as_bytes())
+    }
+}
+
+impl From<usize> for Length {
+    fn from(value: usize) -> Self {
+        Self(value)
+    }
+}
+
+impl Deref for Length {
+    type Target = usize;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for Length {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl TryFrom<&Path> for Length {
+    type Error = Error;
+    fn try_from(value: &Path) -> Result<Self, Self::Error> {
+        let mut buf = [0; 8];
+        if let Ok(bytes) = fs::read(value) {
+            bytes.as_slice().read_exact(&mut buf)?;
+            Ok(*(Self::ref_from_bytes(&buf)?))
+        } else {
+            Ok(Self::default())
+        }
+    }
+}
+
+impl AddAssign<usize> for Length {
+    fn add_assign(&mut self, rhs: usize) {
+        self.0 += rhs;
+    }
+}