feat: Better no_std support (#44)

Signed-off-by: YXL <chenxin.lan.76@gmail.com>

Cargo.toml

@@ -15,8 +15,8 @@ edition = "2021"
 
 [dependencies]
 cfg-if = "1.0"
-hashbrown = { version = "0.11", default-features = false, features = ["ahash"] }
-serde = { version = "1.0", optional = true }
+hashbrown = { version = "0.12.0", default-features = false, features = ["ahash"] }
+serde = { version = "1.0", default-features = false, features = ["alloc"], optional = true }
 
 [dev-dependencies]
 serde_json = "1.0"
@@ -29,7 +29,7 @@ harness = false
 
 [features]
 default = ["std", "serde-1", "inline-more", "backends"]
-std = []
+std = ["serde/std"]
 
 # Enable this if you need `Serde` serialization and deserialization support.
 #

src/backend/bucket/fixed_str.rs

@@ -1,4 +1,6 @@
 use super::InternedStr;
+#[cfg(not(feature = "std"))]
+use alloc::string::String;
 
 #[derive(Debug, Default, Clone, PartialEq, Eq)]
 pub struct FixedString {

src/backend/bucket/interned_str.rs

@@ -50,7 +50,7 @@ mod tests {
 
     #[test]
     fn size_of() {
-        use std::mem;
+        use core::mem;
         assert_eq!(mem::size_of::<InternedStr>(), mem::size_of::<&str>());
     }
 }

src/backend/bucket/mod.rs

@@ -14,12 +14,13 @@ use crate::{
     DefaultSymbol,
     Symbol,
 };
+#[cfg(not(feature = "std"))]
+use alloc::string::String;
 use core::{
     iter::Enumerate,
     marker::PhantomData,
     slice,
 };
-
 /// An interner backend that reduces memory allocations by using string buckets.
 ///
 /// # Note

src/backend/buffer.rs

@@ -281,6 +281,8 @@ mod tests {
         decode_var_usize,
         encode_var_usize,
     };
+    #[cfg(not(feature = "std"))]
+    use alloc::vec::Vec;
 
     #[test]
     fn encode_var_usize_1_byte_works() {

src/lib.rs

@@ -121,6 +121,9 @@
 //!
 //! Never use this one for real use cases!
 
+#[cfg(not(feature = "std"))]
+extern crate alloc;
+
 #[cfg(feature = "serde-1")]
 mod serde_impl;
 

src/serde_impl.rs

@@ -3,6 +3,8 @@ use crate::{
     StringInterner,
     Symbol,
 };
+#[cfg(not(feature = "std"))]
+use alloc::boxed::Box;
 use core::{
     default::Default,
     fmt,