Add support for no_std environments

This commit adds a default "std" feature that can be disabled to run
this crate in no_std environments. This allows for Zlib compression or
decompression to happen on embedded systems.

Rel: dfrg/swash#4

This is a breaking change, as anyone who is already importing yazi with
"default-features = false" and using the From<io::Error> impl on
yazi::Error will have their build break after this commit.

Signed-off-by: John Nunley <[email protected]>

Cargo.toml

@@ -11,4 +11,6 @@ repository = "https://github.com/dfrg/yazi"
 homepage = "https://github.com/dfrg/yazi"
 readme = "README.md"
 
-[dependencies]
+[features]
+default = ["std"]
+std = []

src/decode.rs

@@ -1,6 +1,10 @@
 //! RFC 1590 decompression implementation.
 
 use super::{Error, Format};
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+
+#[cfg(feature = "std")]
 use std::io::{self, Write};
 
 /// Stateful context for decompression.
@@ -27,6 +31,7 @@ impl Decoder {
     }
 
     /// Creates a decoder stream that will write into the specified writer.
+    #[cfg(feature = "std")]
     pub fn stream<'a, W: Write>(
         &'a mut self,
         writer: &'a mut W,
@@ -125,6 +130,7 @@ impl<'a, S: Sink> Drop for DecoderStream<'a, S> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a, S: Sink> Write for DecoderStream<'a, S> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         match self.ctx.inflate(buf, &mut self.sink, false) {
@@ -942,7 +948,7 @@ impl Bits {
         let len = bytes.len();
         let mut i = 0;
         while (i + 4) <= len {
-            use std::convert::TryInto;
+            use core::convert::TryInto;
             let v = u32::from_le_bytes((&bytes[i..i + 4]).try_into().unwrap()) as u64;
             self.bit_buffer |= v << self.bits_in;
             self.bits_in += 32;
@@ -1131,12 +1137,14 @@ impl<'a> Sink for BufSink<'a> {
     }
 }
 
+#[cfg(feature = "std")]
 struct WriterSink<W> {
     writer: W,
     ring: RingBuffer,
     written: u64,
 }
 
+#[cfg(feature = "std")]
 impl<W: Write> Sink for WriterSink<W> {
     fn written(&self) -> u64 {
         self.written

src/encode.rs

@@ -1,10 +1,12 @@
 //! RFC 1590 compression implementation.
 
 use super::{Adler32, Error, Format};
-use std::{
-    convert::TryInto,
-    io::{self, Write},
-};
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::convert::TryInto;
+
+#[cfg(feature = "std")]
+use std::io::{self, Write};
 
 /// The level of compression-- a compromise between speed and size.
 #[derive(Copy, Clone, PartialEq, Debug)]
@@ -142,6 +144,7 @@ impl Encoder {
     }
 
     /// Creates an encoder stream that will write into the specified writer.
+    #[cfg(feature = "std")]
     pub fn stream<'a, W: Write>(
         &'a mut self,
         writer: &'a mut W,
@@ -235,6 +238,7 @@ impl<'a, S: Sink> Drop for EncoderStream<'a, S> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<'a, S: Sink> Write for EncoderStream<'a, S> {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
         match self.ctx.deflate(buf, &mut self.sink, false) {
@@ -927,7 +931,7 @@ mod huffman {
                 new_syms[offsets[j] as usize] = *sym;
                 offsets[j] += 1;
             }
-            std::mem::swap(&mut cur_syms, &mut new_syms);
+            core::mem::swap(&mut cur_syms, &mut new_syms);
         }
         cur_syms
     }
@@ -1475,6 +1479,7 @@ impl<'a> Sink for VecSink<'a> {
     }
 }
 
+#[cfg(feature = "std")]
 struct WriterSink<W> {
     writer: W,
     buffer: [u8; OUT_BUFFER_SIZE],
@@ -1484,6 +1489,7 @@ struct WriterSink<W> {
     written: u64,
 }
 
+#[cfg(feature = "std")]
 impl<W> WriterSink<W> {
     fn new(writer: W) -> Self {
         Self {
@@ -1497,6 +1503,7 @@ impl<W> WriterSink<W> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<W: Write> Sink for WriterSink<W> {
     #[inline(always)]
     fn put_bits(&mut self, bits: u32, len: u32) -> Result<(), Error> {

src/lib.rs

@@ -230,9 +230,14 @@
 //! decompressor is based on the techniques in libdeflate (<https://github.com/ebiggers/libdeflate>)
 //! by Eric Biggers.
 
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate alloc;
+
 mod decode;
 mod encode;
 
+#[cfg(feature = "std")]
 use std::io;
 
 pub use decode::{decompress, Decoder, DecoderStream};
@@ -259,9 +264,13 @@ pub enum Error {
     /// Attempt to write into a finished stream.
     Finished,
     /// A system I/O error.
+    /// 
+    /// Only available with the `std` feature enabled.
+    #[cfg(feature = "std")]
     Io(io::Error),
 }
 
+#[cfg(feature = "std")]
 impl From<io::Error> for Error {
     fn from(error: io::Error) -> Self {
         Self::Io(error)
@@ -315,6 +324,7 @@ impl Default for Adler32 {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use alloc::vec::Vec;
 
     fn generate_bytes() -> Vec<u8> {
         const BYTES: &[u8; 26] = b"abcdefghijklmnopqrstuvwxyz";