Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/qoi/src/utils.rs

@@ -0,0 +1,107 @@
+#[cfg(feature = "std")]
+use std::io::Write;
+
+use crate::error::Result;
+
+#[inline(always)]
+#[cold]
+pub const fn cold() {}
+
+#[inline(always)]
+#[allow(unused)]
+pub const fn likely(b: bool) -> bool {
+    if !b {
+        cold();
+    }
+    b
+}
+
+#[inline(always)]
+pub const fn unlikely(b: bool) -> bool {
+    if b {
+        cold();
+    }
+    b
+}
+
+pub trait Writer: Sized {
+    fn write_one(self, v: u8) -> Result<Self>;
+    fn write_many(self, v: &[u8]) -> Result<Self>;
+    fn capacity(&self) -> usize;
+}
+
+pub struct BytesMut<'a>(&'a mut [u8]);
+
+impl<'a> BytesMut<'a> {
+    pub fn new(buf: &'a mut [u8]) -> Self {
+        Self(buf)
+    }
+
+    #[inline]
+    pub fn write_one(self, v: u8) -> Self {
+        if let Some((first, tail)) = self.0.split_first_mut() {
+            *first = v;
+            Self(tail)
+        } else {
+            unreachable!()
+        }
+    }
+
+    #[inline]
+    pub fn write_many(self, v: &[u8]) -> Self {
+        if v.len() <= self.0.len() {
+            let (head, tail) = self.0.split_at_mut(v.len());
+            head.copy_from_slice(v);
+            Self(tail)
+        } else {
+            unreachable!()
+        }
+    }
+}
+
+impl<'a> Writer for BytesMut<'a> {
+    #[inline]
+    fn write_one(self, v: u8) -> Result<Self> {
+        Ok(BytesMut::write_one(self, v))
+    }
+
+    #[inline]
+    fn write_many(self, v: &[u8]) -> Result<Self> {
+        Ok(BytesMut::write_many(self, v))
+    }
+
+    #[inline]
+    fn capacity(&self) -> usize {
+        self.0.len()
+    }
+}
+
+#[cfg(feature = "std")]
+pub struct GenericWriter<W> {
+    writer: W,
+    n_written: usize,
+}
+
+#[cfg(feature = "std")]
+impl<W: Write> GenericWriter<W> {
+    pub const fn new(writer: W) -> Self {
+        Self { writer, n_written: 0 }
+    }
+}
+
+#[cfg(feature = "std")]
+impl<W: Write> Writer for GenericWriter<W> {
+    fn write_one(mut self, v: u8) -> Result<Self> {
+        self.n_written += 1;
+        self.writer.write_all(&[v]).map(|_| self).map_err(Into::into)
+    }
+
+    fn write_many(mut self, v: &[u8]) -> Result<Self> {
+        self.n_written += v.len();
+        self.writer.write_all(v).map(|_| self).map_err(Into::into)
+    }
+
+    fn capacity(&self) -> usize {
+        usize::MAX - self.n_written
+    }
+}