Turn crate into no_std using core + alloc

Extensions are also made an optional feature to not require depending on HashMap

Cargo.toml

@@ -27,6 +27,14 @@ rust-version = "1.49.0"
 bytes = "1"
 fnv = "1.0.5"
 itoa = "1"
+ahash = { version = "0.7", default-features = false }
+hashbrown = { version = "0.12", optional = true }
+
+[features]
+default = ["std", "extensions"]
+std = []
+hashmap = ["hashbrown"]
+extensions = ["hashmap"]
 
 [dev-dependencies]
 indexmap = "<=1.8"

src/byte_str.rs

@@ -1,6 +1,6 @@
+use alloc::string::String;
 use bytes::Bytes;
-
-use std::{ops, str};
+use core::{ops, str};
 
 #[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub(crate) struct ByteStr {

src/convert.rs

@@ -1,17 +1,17 @@
 macro_rules! if_downcast_into {
-    ($in_ty:ty, $out_ty:ty, $val:ident, $body:expr) => ({
-        if std::any::TypeId::of::<$in_ty>() == std::any::TypeId::of::<$out_ty>() {
+    ($in_ty:ty, $out_ty:ty, $val:ident, $body:expr) => {{
+        if core::any::TypeId::of::<$in_ty>() == core::any::TypeId::of::<$out_ty>() {
             // Store the value in an `Option` so we can `take`
             // it after casting to `&mut dyn Any`.
             let mut slot = Some($val);
             // Re-write the `$val` ident with the downcasted value.
-            let $val = (&mut slot as &mut dyn std::any::Any)
+            let $val = (&mut slot as &mut dyn core::any::Any)
                 .downcast_mut::<Option<$out_ty>>()
                 .unwrap()
                 .take()
                 .unwrap();
             // Run the $body in scope of the replaced val.
             $body
         }
-    })
+    }};
 }

src/error.rs

@@ -1,6 +1,7 @@
+use core::fmt;
+use core::result;
+#[cfg(feature = "std")]
 use std::error;
-use std::fmt;
-use std::result;
 
 use crate::header;
 use crate::method;
@@ -31,19 +32,38 @@ enum ErrorKind {
 
 impl fmt::Debug for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use ErrorKind::*;
+        let e: &dyn fmt::Debug = match self.inner {
+            StatusCode(ref e) => e,
+            Method(ref e) => e,
+            Uri(ref e) => e,
+            UriParts(ref e) => e,
+            HeaderName(ref e) => e,
+            HeaderValue(ref e) => e,
+        };
         f.debug_tuple("http::Error")
             // Skip the noise of the ErrorKind enum
-            .field(&self.get_ref())
+            .field(e)
             .finish()
     }
 }
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self.get_ref(), f)
+        use ErrorKind::*;
+        let e: &dyn fmt::Display = match self.inner {
+            StatusCode(ref e) => e,
+            Method(ref e) => e,
+            Uri(ref e) => e,
+            UriParts(ref e) => e,
+            HeaderName(ref e) => e,
+            HeaderValue(ref e) => e,
+        };
+        fmt::Display::fmt(e, f)
     }
 }
 
+#[cfg(feature = "std")]
 impl Error {
     /// Return true if the underlying error has the same type as T.
     pub fn is<T: error::Error + 'static>(&self) -> bool {
@@ -65,6 +85,7 @@ impl Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for Error {
     // Return any available cause from the inner error. Note the inner error is
     // not itself the cause.
@@ -121,13 +142,13 @@ impl From<header::InvalidHeaderValue> for Error {
     }
 }
 
-impl From<std::convert::Infallible> for Error {
-    fn from(err: std::convert::Infallible) -> Error {
+impl From<core::convert::Infallible> for Error {
+    fn from(err: core::convert::Infallible) -> Error {
         match err {}
     }
 }
 
-#[cfg(test)]
+#[cfg(all(test, feature = "std"))]
 mod tests {
     use super::*;
 

src/extensions.rs

@@ -1,7 +1,9 @@
-use std::any::{Any, TypeId};
-use std::collections::HashMap;
-use std::fmt;
-use std::hash::{BuildHasherDefault, Hasher};
+use core::any::{Any, TypeId};
+use core::fmt;
+use core::hash::{BuildHasherDefault, Hasher};
+use hashbrown::HashMap;
+
+use alloc::boxed::Box;
 
 type AnyMap = HashMap<TypeId, Box<dyn Any + Send + Sync>, BuildHasherDefault<IdHasher>>;
 
@@ -166,9 +168,7 @@ impl Extensions {
     /// ```
     #[inline]
     pub fn is_empty(&self) -> bool {
-        self.map
-            .as_ref()
-            .map_or(true, |map| map.is_empty())
+        self.map.as_ref().map_or(true, |map| map.is_empty())
     }
 
     /// Get the numer of extensions available.
@@ -184,28 +184,26 @@ impl Extensions {
     /// ```
     #[inline]
     pub fn len(&self) -> usize {
-        self.map
-            .as_ref()
-            .map_or(0, |map| map.len())
+        self.map.as_ref().map_or(0, |map| map.len())
     }
 
     /// Extends `self` with another `Extensions`.
     ///
     /// If an instance of a specific type exists in both, the one in `self` is overwritten with the
     /// one from `other`.
-    /// 
+    ///
     /// # Example
-    /// 
+    ///
     /// ```
     /// # use http::Extensions;
     /// let mut ext_a = Extensions::new();
     /// ext_a.insert(8u8);
     /// ext_a.insert(16u16);
-    /// 
+    ///
     /// let mut ext_b = Extensions::new();
     /// ext_b.insert(4u8);
     /// ext_b.insert("hello");
-    /// 
+    ///
     /// ext_a.extend(ext_b);
     /// assert_eq!(ext_a.len(), 3);
     /// assert_eq!(ext_a.get::<u8>(), Some(&4u8));