Merge pull request #50 from ferrous-systems/leb

Move leb64 encoding and tests to its own file
knurling-rs · Aug 4, 2020 · 7dce165 · 7dce165
2 parents 36e5280 + 5f9426e
commit 7dce165
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Showing 3 changed files with 109 additions and 106 deletions.
diff --git a/src/leb.rs b/src/leb.rs
@@ -0,0 +1,107 @@
+/// # Unsafety
+/// `buf` must be large enough to hold the encoded value
+pub(crate) unsafe fn leb64(x: u64, buf: &mut [u8]) -> usize {
+    let mut low = x as u32;
+    let mut high = (x >> 32) as u32;
+
+    let mut i = 0;
+    loop {
+        let mut byte = (low & 0x7f) as u8;
+        low >>= 7;
+        if low != 0 {
+            byte |= 0x80;
+        }
+
+        *buf.get_unchecked_mut(i) = byte;
+        i += 1;
+        if low == 0 {
+            break;
+        }
+    }
+
+    if high == 0 {
+        return i;
+    }
+
+    for j in (i - 1)..4 {
+        *buf.get_unchecked_mut(j) = 0x80;
+    }
+
+    if i != 5 {
+        *buf.get_unchecked_mut(4) = 0;
+    }
+
+    i = 4;
+    *buf.get_unchecked_mut(i) |= (high as u8 & 0b111) << 4;
+    high >>= 3;
+
+    if high != 0 {
+        *buf.get_unchecked_mut(i) |= 0x80;
+    }
+
+    i += 1;
+
+    if high == 0 {
+        return i;
+    }
+
+    loop {
+        let mut byte = (high & 0x7f) as u8;
+        high >>= 7;
+        if high != 0 {
+            byte |= 0x80;
+        }
+
+        *buf.get_unchecked_mut(i) = byte;
+        i += 1;
+        if high == 0 {
+            return i;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn leb() {
+        let mut buf = [0x55; 10];
+
+        let i = unsafe { super::leb64(0, &mut buf) };
+        assert_eq!(buf[..i], [0]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64(1, &mut buf) };
+        assert_eq!(buf[..i], [1]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64((1 << 7) - 1, &mut buf) };
+        assert_eq!(buf[..i], [0x7f]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64(1 << 7, &mut buf) };
+        assert_eq!(buf[..i], [0x80, 1]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64((1 << 32) - 1, &mut buf) };
+        assert_eq!(buf[..i], [0xff, 0xff, 0xff, 0xff, 0xf]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64((1 << 35) - 1, &mut buf) };
+        assert_eq!(buf[..i], [0xff, 0xff, 0xff, 0xff, 0x7f]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64(1 << 35, &mut buf) };
+        assert_eq!(buf[..i], [0x80, 0x80, 0x80, 0x80, 0x80, 1]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64((1 << 42) - 1, &mut buf) };
+        assert_eq!(buf[..i], [0xff, 0xff, 0xff, 0xff, 0xff, 0x7f]);
+        buf.iter_mut().for_each(|b| *b = 0x55);
+
+        let i = unsafe { super::leb64(u64::max_value(), &mut buf) };
+        assert_eq!(
+            buf[..i],
+            [0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1]
+        );
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
@@ -5,6 +5,7 @@ use core::{mem::MaybeUninit, ptr::NonNull};
 #[doc(hidden)]
 pub mod export;
 mod impls;
+mod leb;
 #[cfg(test)]
 mod tests;
 
@@ -147,68 +148,6 @@ pub struct Formatter {
     bytes: Vec<u8>,
 }
 
-/// # Unsafety
-/// `buf` must be large enough to hold the encoded value
-unsafe fn leb64(x: u64, buf: &mut [u8]) -> usize {
-    let mut low = x as u32;
-    let mut high = (x >> 32) as u32;
-
-    let mut i = 0;
-    loop {
-        let mut byte = (low & 0x7f) as u8;
-        low >>= 7;
-        if low != 0 {
-            byte |= 0x80;
-        }
-
-        *buf.get_unchecked_mut(i) = byte;
-        i += 1;
-        if low == 0 {
-            break;
-        }
-    }
-
-    if high == 0 {
-        return i;
-    }
-
-    for j in (i - 1)..4 {
-        *buf.get_unchecked_mut(j) = 0x80;
-    }
-
-    if i != 5 {
-        *buf.get_unchecked_mut(4) = 0;
-    }
-
-    i = 4;
-    *buf.get_unchecked_mut(i) |= (high as u8 & 0b111) << 4;
-    high >>= 3;
-
-    if high != 0 {
-        *buf.get_unchecked_mut(i) |= 0x80;
-    }
-
-    i += 1;
-
-    if high == 0 {
-        return i;
-    }
-
-    loop {
-        let mut byte = (high & 0x7f) as u8;
-        high >>= 7;
-        if high != 0 {
-            byte |= 0x80;
-        }
-
-        *buf.get_unchecked_mut(i) = byte;
-        i += 1;
-        if high == 0 {
-            return i;
-        }
-    }
-}
-
 impl Formatter {
     /// Only for testing on x86_64
     #[cfg(target_arch = "x86_64")]
@@ -273,7 +212,7 @@ impl Formatter {
     #[doc(hidden)]
     pub fn leb64(&mut self, x: u64) {
         let mut buf: [u8; 10] = unsafe { MaybeUninit::uninit().assume_init() };
-        let i = unsafe { leb64(x, &mut buf) };
+        let i = unsafe { leb::leb64(x, &mut buf) };
         self.write(unsafe { buf.get_unchecked(..i) })
     }
 

diff --git a/src/tests.rs b/src/tests.rs
@@ -1,48 +1,5 @@
 use crate as binfmt;
 
-#[test]
-fn leb() {
-    let mut buf = [0x55; 10];
-
-    let i = unsafe { super::leb64(0, &mut buf) };
-    assert_eq!(buf[..i], [0]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64(1, &mut buf) };
-    assert_eq!(buf[..i], [1]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64((1 << 7) - 1, &mut buf) };
-    assert_eq!(buf[..i], [0x7f]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64(1 << 7, &mut buf) };
-    assert_eq!(buf[..i], [0x80, 1]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64((1 << 32) - 1, &mut buf) };
-    assert_eq!(buf[..i], [0xff, 0xff, 0xff, 0xff, 0xf]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64((1 << 35) - 1, &mut buf) };
-    assert_eq!(buf[..i], [0xff, 0xff, 0xff, 0xff, 0x7f]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64(1 << 35, &mut buf) };
-    assert_eq!(buf[..i], [0x80, 0x80, 0x80, 0x80, 0x80, 1]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64((1 << 42) - 1, &mut buf) };
-    assert_eq!(buf[..i], [0xff, 0xff, 0xff, 0xff, 0xff, 0x7f]);
-    buf.iter_mut().for_each(|b| *b = 0x55);
-
-    let i = unsafe { super::leb64(u64::max_value(), &mut buf) };
-    assert_eq!(
-        buf[..i],
-        [0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1]
-    );
-}
-
 #[test]
 fn log_levels() {
     // just make sure they build OK for now