Implement no_std support (#34)

This implements no_std support for unicase. no_std support has been implemented for every Rust version starting with 1.36 which added stable support for the alloc crate. All of unicase's features are available on no_std.

.travis.yml

@@ -11,6 +11,11 @@ matrix:
         - rust: 1.3.0
         # verify `const fn`
         - rust: 1.31.0
+        # verify `no_std`
+        - rust: stable
+          script:
+            - rustup target add thumbv6m-none-eabi
+            - cargo build --target thumbv6m-none-eabi
 
 cache:
     apt: true

Cargo.toml

@@ -8,8 +8,8 @@ repository = "https://github.com/seanmonstar/unicase"
 documentation = "https://docs.rs/unicase"
 license = "MIT/Apache-2.0"
 readme = "README.md"
-keywords = ["lowercase", "case", "case-insensitive", "case-folding"]
-categories = ["internationalization", "text-processing"]
+keywords = ["lowercase", "case", "case-insensitive", "case-folding", "no_std"]
+categories = ["internationalization", "text-processing", "no-std"]
 
 exclude = [
     "scripts/*"

build.rs

@@ -12,4 +12,8 @@ fn main() {
     if rustc::is_min_version("1.31.0").map(|(is_min, _)| is_min).unwrap_or(true) {
         println!("cargo:rustc-cfg=__unicase__const_fns");
     }
+
+    if rustc::is_min_version("1.36.0").map(|(is_min, _)| is_min).unwrap_or(true) {
+        println!("cargo:rustc-cfg=__unicase__core_and_alloc");
+    }
 }

scripts/mapgen.py

@@ -135,7 +135,7 @@ def remove_useless_comparison(case_line):
 rs.write('// %s\n' % datetime.date.today())
 rs.write('\n')
 rs.write('use super::fold::Fold;\n\n')
-rs.write('use std::char;\n');
+rs.write('use core::char;\n');
 rs.write("pub fn lookup(orig: char) -> Fold {\n")
 rs.write('    // The code below is is intended to reduce the binary size from that of a simple 1:1 lookup table.\n')
 rs.write('    // It exploits two facts:\n')

src/ascii.rs

@@ -1,11 +1,13 @@
+use alloc::string::String;
+#[cfg(__unicase__iter_cmp)]
+use core::cmp::Ordering;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::ops::{Deref, DerefMut};
+use core::str::FromStr;
+#[cfg(not(__unicase__core_and_alloc))]
 #[allow(deprecated, unused)]
 use std::ascii::AsciiExt;
-#[cfg(__unicase__iter_cmp)]
-use std::cmp::Ordering;
-use std::fmt;
-use std::hash::{Hash, Hasher};
-use std::ops::{Deref, DerefMut};
-use std::str::FromStr;
 
 use super::{Ascii, Encoding, UniCase};
 

src/lib.rs

@@ -2,6 +2,13 @@
 #![cfg_attr(test, deny(warnings))]
 #![doc(html_root_url = "https://docs.rs/unicase/2.5.1")]
 #![cfg_attr(feature = "nightly", feature(test))]
+#![cfg_attr(
+    all(
+        __unicase__core_and_alloc,
+        not(test),
+    ),
+    no_std,
+)]
 
 //! # UniCase
 //!
@@ -45,13 +52,23 @@
 #[cfg(feature = "nightly")]
 extern crate test;
 
-use std::borrow::Cow;
+#[cfg(all(__unicase__core_and_alloc, not(test)))]
+extern crate alloc;
+#[cfg(all(__unicase__core_and_alloc, not(test)))]
+use alloc::string::String;
+
+#[cfg(not(all(__unicase__core_and_alloc, not(test))))]
+extern crate std as alloc;
+#[cfg(not(all(__unicase__core_and_alloc, not(test))))]
+extern crate std as core;
+
+use alloc::borrow::Cow;
 #[cfg(__unicase__iter_cmp)]
-use std::cmp::Ordering;
-use std::fmt;
-use std::hash::{Hash, Hasher};
-use std::ops::{Deref, DerefMut};
-use std::str::FromStr;
+use core::cmp::Ordering;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::ops::{Deref, DerefMut};
+use core::str::FromStr;
 
 use self::unicode::Unicode;
 
@@ -118,8 +135,10 @@ impl<S: AsRef<str>> UniCase<S> {
     ///
     /// Note: This scans the text to determine if it is all ASCII or not.
     pub fn new(s: S) -> UniCase<S> {
+        #[cfg(not(__unicase__core_and_alloc))]
         #[allow(deprecated, unused)]
         use std::ascii::AsciiExt;
+
         if s.as_ref().is_ascii() {
             UniCase(Encoding::Ascii(Ascii(s)))
         } else {

src/unicode/map.rs

@@ -3,7 +3,7 @@
 
 use super::fold::Fold;
 
-use std::char;
+use core::char;
 pub fn lookup(orig: char) -> Fold {
     // The code below is is intended to reduce the binary size from that of a simple 1:1 lookup table.
     // It exploits two facts:

src/unicode/mod.rs

@@ -1,6 +1,6 @@
 #[cfg(__unicase__iter_cmp)]
-use std::cmp::Ordering;
-use std::hash::{Hash, Hasher};
+use core::cmp::Ordering;
+use core::hash::{Hash, Hasher};
 
 use self::map::lookup;
 mod map;