no need to gate encoding behind std

src/encoding/block_header.rs

@@ -1,5 +1,5 @@
 use crate::blocks::block::BlockType;
-use std::vec::Vec;
+use alloc::vec::Vec;
 
 #[derive(Debug)]
 pub struct BlockHeader {
@@ -40,7 +40,7 @@ impl BlockHeader {
 mod tests {
     use super::BlockHeader;
     use crate::{blocks::block::BlockType, decoding::block_decoder};
-    use std::vec::Vec;
+    use alloc::vec::Vec;
 
     #[test]
     fn block_header_serialize() {

src/encoding/blocks/raw.rs

@@ -1,4 +1,4 @@
-use std::vec::Vec;
+use alloc::vec::Vec;
 
 /// Write the data from input into output. The data is not compressed.
 pub(crate) fn compress_raw_block(input: &[u8], output: &mut Vec<u8>) {

src/encoding/frame_encoder.rs

@@ -1,7 +1,7 @@
 //! Utilities and interfaces for encoding an entire frame.
 
+use alloc::vec::Vec;
 use core::convert::TryInto;
-use std::vec::Vec;
 
 use super::{block_header::BlockHeader, blocks::compress_raw_block, frame_header::FrameHeader};
 
@@ -126,7 +126,7 @@ impl<'input> FrameCompressor<'input> {
 mod tests {
     use super::FrameCompressor;
     use crate::frame::MAGIC_NUM;
-    use std::vec::Vec;
+    use alloc::vec::Vec;
 
     #[test]
     fn frame_starts_with_magic_num() {

src/encoding/frame_header.rs

@@ -4,7 +4,7 @@ use crate::encoding::{
     util::{find_min_size, minify_val},
 };
 use crate::frame;
-use std::vec::Vec;
+use alloc::vec::Vec;
 
 /// A header for a single Zstandard frame.
 ///
@@ -164,7 +164,7 @@ fn minify_val_fcs(val: u64) -> Vec<u8> {
 mod tests {
     use super::FrameHeader;
     use crate::frame::{read_frame_header, FrameDescriptor};
-    use std::vec::Vec;
+    use alloc::vec::Vec;
 
     #[test]
     fn frame_header_descriptor_decode() {

src/encoding/util.rs

@@ -1,4 +1,4 @@
-use std::vec::Vec;
+use alloc::vec::Vec;
 
 /// Returns the minimum number of bytes needed to represent this value, as
 /// either 1, 2, 4, or 8 bytes. A value of 0 will still return one byte.

src/lib.rs

@@ -35,7 +35,6 @@ macro_rules! vprintln {
 
 pub mod blocks;
 pub mod decoding;
-#[cfg(feature = "std")]
 pub mod encoding;
 pub mod frame;
 pub mod frame_decoder;