Fix builds in no_std environments

Cargo.toml

@@ -16,7 +16,7 @@ edition = "2021"
 name = "elf"
 
 [dependencies]
-hashbrown = { version = "0.14.0", optional = true }
+hashbrown = { version = "0.14.0", optional = true, default-features = false }
 
 [features]
 default = ["std", "to_str"]

src/elf_stream.rs

@@ -1,9 +1,9 @@
 use core::ops::Range;
 
 #[cfg(not(feature = "std"))]
-use hashbrown::HashMap;
+use alloc::{boxed::Box, collections::BTreeMap as BufferMap, vec, vec::Vec};
 #[cfg(feature = "std")]
-use std::collections::HashMap;
+use std::collections::BTreeMap as BufferMap;
 
 use crate::abi;
 use crate::compression::CompressionHeader;
@@ -683,7 +683,7 @@ impl<E: EndianParse, S: Read + Seek> ElfStream<E, S> {
 struct CachingReader<R: Read + Seek> {
     reader: R,
     stream_len: u64,
-    bufs: HashMap<(usize, usize), Box<[u8]>>,
+    bufs: BufferMap<(usize, usize), Box<[u8]>>,
 }
 
 impl<R: Read + Seek> CachingReader<R> {
@@ -694,7 +694,7 @@ impl<R: Read + Seek> CachingReader<R> {
         Ok(CachingReader {
             reader,
             stream_len,
-            bufs: HashMap::<(usize, usize), Box<[u8]>>::default(),
+            bufs: BufferMap::<(usize, usize), Box<[u8]>>::default(),
         })
     }
 

src/io_traits.rs

@@ -1,6 +1,8 @@
 #[cfg(feature = "std")]
 pub type StreamError = std::io::Error;
+
 #[cfg(not(feature = "std"))]
+#[derive(Debug)]
 pub struct StreamError {
     pub message: &'static str,
 }

src/lib.rs

@@ -130,6 +130,9 @@
 #![warn(rust_2018_idioms)]
 #![deny(missing_debug_implementations)]
 
+#[cfg(not(feature = "std"))]
+extern crate alloc;
+
 pub mod abi;
 
 pub mod compression;