cfg

Cargo.toml

@@ -13,3 +13,8 @@ edition = "2021"
 
 [dependencies]
 mono-fmt-macro = { path = "./mono-fmt-macro" }
+
+[features]
+alloc = []
+std = ["alloc"]
+default = ["std"]

src/formatter.rs

@@ -6,11 +6,11 @@ pub struct Formatter<W, O> {
 }
 
 impl<W: Write, O: FmtOpts> core::fmt::Write for Formatter<W, O> {
-    fn write_char(&mut self, c: char) -> std::fmt::Result {
-        self.buf.write_char(c).map_err(|_| std::fmt::Error)
+    fn write_char(&mut self, c: char) -> core::fmt::Result {
+        self.buf.write_char(c).map_err(|_| core::fmt::Error)
     }
-    fn write_str(&mut self, s: &str) -> std::fmt::Result {
-        self.buf.write_str(s).map_err(|_| std::fmt::Error)
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        self.buf.write_str(s).map_err(|_| core::fmt::Error)
     }
 }
 

src/lib.rs

@@ -1,5 +1,8 @@
+#![cfg_attr(not(feature = "std"), no_std)]
 #![allow(dead_code)]
 
+extern crate alloc;
+
 mod args;
 mod formatter;
 mod opts;
@@ -19,7 +22,7 @@ pub use crate::{
     opts::FmtOpts,
 };
 
-pub type Result = std::result::Result<(), Error>;
+pub type Result = core::result::Result<(), Error>;
 
 #[derive(Debug, Clone, Copy)]
 pub struct Error;
@@ -34,6 +37,9 @@ pub trait Write {
 }
 
 pub mod helpers {
+    #[cfg(feature = "alloc")]
+    use alloc::string::String;
+
     use crate::{Arguments, Formatter, Result, Write};
 
     pub fn write<W: Write, A: Arguments>(buffer: W, args: A) -> Result {
@@ -41,6 +47,7 @@ pub mod helpers {
         args.fmt(&mut fmt)
     }
 
+    #[cfg(feature = "alloc")]
     pub fn format<A: Arguments>(args: A) -> String {
         let mut string = String::new();
         write(&mut string, args).unwrap();
@@ -59,6 +66,7 @@ pub mod _private {
     };
 }
 
+#[cfg(feature = "alloc")]
 #[macro_export]
 macro_rules! format {
     ($($tt:tt)*) => {

src/rust_core_impl/aggregated.rs

@@ -92,8 +92,21 @@ mod char {
 }
 
 mod strings {
+    #[cfg(feature = "alloc")]
+    use alloc::string::String;
+
     use super::impl_prelude::*;
 
+    #[cfg(feature = "alloc")]
+    impl Debug for String {
+        fn fmt<W: Write, O: FmtOpts>(&self, f: &mut Formatter<W, O>) -> Result {
+            f.write_char('"')?;
+            f.write_str(self)?;
+            f.write_char('"')
+        }
+    }
+
+    #[cfg(feature = "alloc")]
     impl Display for String {
         fn fmt<W: Write, O: FmtOpts>(&self, f: &mut Formatter<W, O>) -> Result {
             f.write_str(self)
@@ -113,12 +126,4 @@ mod strings {
             f.write_char('"')
         }
     }
-
-    impl Debug for String {
-        fn fmt<W: Write, O: FmtOpts>(&self, f: &mut Formatter<W, O>) -> Result {
-            f.write_char('"')?;
-            f.write_str(self)?;
-            f.write_char('"')
-        }
-    }
 }

src/rust_core_impl/mod.rs

@@ -249,7 +249,7 @@ impl<W: Write, O: FmtOpts> Formatter<W, O> {
         default: Alignment,
         self_fill: char,
         self_align: Alignment,
-    ) -> std::result::Result<PostPadding, Error> {
+    ) -> core::result::Result<PostPadding, Error> {
         // WARN: We might have `self` in an invalid state, don't touch `self` opts
         let align = match self_align {
             Alignment::Unknown => default,
@@ -279,7 +279,7 @@ impl<W: Write, O: FmtOpts> Formatter<W, O> {
             // in a bad value for `buf` into `numfmt::to_shortest_str` since it is a
             // public function.
             // FIXME: Determine whether this could result in UB.
-            buf.write_str(unsafe { std::str::from_utf8_unchecked(s) })
+            buf.write_str(unsafe { core::str::from_utf8_unchecked(s) })
         }
 
         if !formatted.sign.is_empty() {

src/rust_core_impl/num.rs

@@ -1,6 +1,6 @@
 //! Integer and floating-point number formatting
 
-use std::{
+use core::{
     mem::MaybeUninit,
     ops::{Div, Rem, Sub},
     ptr, slice, str,
@@ -223,7 +223,7 @@ macro_rules! impl_Display {
             // is safe to access.
             unsafe {
                 // need at least 16 bits for the 4-characters-at-a-time to work.
-                assert!(std::mem::size_of::<$u>() >= 2);
+                assert!(core::mem::size_of::<$u>() >= 2);
 
                 // eagerly decode 4 characters at a time
                 while n >= 10000 {

src/write.rs

@@ -1,17 +1,5 @@
 use crate::{Result, Write};
 
-impl Write for String {
-    fn write_str(&mut self, str: &str) -> Result {
-        self.push_str(str);
-        Ok(())
-    }
-
-    fn write_char(&mut self, char: char) -> Result {
-        self.push(char);
-        Ok(())
-    }
-}
-
 impl<W: Write> Write for &mut W {
     fn write_str(&mut self, str: &str) -> Result {
         <W as Write>::write_str(self, str)
@@ -21,3 +9,110 @@ impl<W: Write> Write for &mut W {
         <W as Write>::write_char(self, char)
     }
 }
+
+impl Write for &'_ mut [u8] {
+    fn write_str(&mut self, str: &str) -> Result {
+        let data = str.as_bytes();
+        let amt = core::cmp::min(str.len(), self.len());
+        let (a, b) = core::mem::replace(self, &mut []).split_at_mut(amt);
+        a.copy_from_slice(&data[..amt]);
+        *self = b;
+        Ok(())
+    }
+}
+
+#[cfg(feature = "alloc")]
+mod alloc_impls {
+    use alloc::{boxed::Box, collections::VecDeque, string::String, vec::Vec};
+
+    use crate::{Result, Write};
+
+    impl Write for String {
+        fn write_str(&mut self, str: &str) -> Result {
+            self.push_str(str);
+            Ok(())
+        }
+
+        fn write_char(&mut self, char: char) -> Result {
+            self.push(char);
+            Ok(())
+        }
+    }
+
+    impl<W: Write> Write for Box<W> {
+        fn write_str(&mut self, str: &str) -> Result {
+            <W as Write>::write_str(self, str)
+        }
+
+        fn write_char(&mut self, char: char) -> Result {
+            <W as Write>::write_char(self, char)
+        }
+    }
+
+    impl Write for Vec<u8> {
+        fn write_str(&mut self, str: &str) -> Result {
+            self.extend(str.as_bytes());
+            Ok(())
+        }
+    }
+
+    impl Write for VecDeque<u8> {
+        fn write_str(&mut self, str: &str) -> Result {
+            self.extend(str.as_bytes());
+            Ok(())
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+mod std_impls {
+    use std::{
+        fs,
+        io::{self, Write as IoWrite},
+        net, process,
+    };
+
+    use crate::Result;
+
+    trait IoWriteForwad: IoWrite {
+        fn write_str(&mut self, str: &str) -> Result {
+            <Self as IoWrite>::write_all(self, str.as_bytes()).map_err(|_| crate::Error)
+        }
+
+        fn write_char(&mut self, char: char) -> Result {
+            let mut buf = [0; 4];
+
+            <Self as IoWrite>::write_all(self, char.encode_utf8(&mut buf).as_bytes())
+                .map_err(|_| crate::Error)
+        }
+    }
+
+    macro_rules! impl_io_forward {
+        ($($name:ty),* $(,)?) => {
+            $(
+                impl IoWriteForwad for $name {}
+            )*
+        };
+    }
+
+    impl_io_forward!(
+        fs::File,
+        net::TcpStream,
+        process::ChildStdin,
+        io::Cursor<&'_ mut [u8]>,
+        io::Sink,
+        io::Stderr,
+        io::StderrLock<'_>,
+        io::Stdout,
+        io::StdoutLock<'_>,
+        io::Cursor<&'_ mut Vec<u8>>,
+        io::Cursor<Box<[u8]>>,
+        io::Cursor<Vec<u8>>,
+        &fs::File,
+        &net::TcpStream,
+        &process::ChildStdin,
+        &io::Sink,
+        &io::Stderr,
+        &io::Stdout,
+    );
+}