add no_std feature

Cargo.toml

@@ -10,4 +10,14 @@ documentation = "http://mrhooray.github.io/crc-rs/crc/index.html"
 license = "MIT"
 
 [dependencies]
-lazy_static = "0.2"
+
+[dependencies.build_const]
+version = "0.2"
+default-features = false
+
+[build-dependencies]
+build_const = "0.2"
+
+[features]
+std = []
+default = ["std"]

build.rs

@@ -0,0 +1,73 @@
+
+extern crate build_const;
+
+pub fn make_table_crc32(poly: u32) -> [u32; 256] {
+    let mut table = [0u32; 256];
+    for i in 0..256 {
+        let mut value = i as u32;
+        for _ in 0..8 {
+            value = if (value & 1) == 1 {
+                (value >> 1) ^ poly
+            } else {
+                value >> 1
+            }
+        }
+        table[i] = value;
+    }
+    table
+}
+
+pub fn make_table_crc64(poly: u64) -> [u64; 256] {
+    let mut table = [0u64; 256];
+    for i in 0..256 {
+        let mut value = i as u64;
+        for _ in 0..8 {
+            value = if (value & 1) == 1 {
+                (value >> 1) ^ poly
+            } else {
+                value >> 1
+            }
+        }
+        table[i] = value;
+    }
+    table
+}
+
+#[allow(non_snake_case)]
+fn create_constants() {
+    let mut crc32 = build_const::ConstWriter::for_build("crc32_constants")
+        .unwrap()
+        .finish_dependencies();
+    let CASTAGNOLI: u32 = 0x82f63b78;
+    crc32.add_value("CASTAGNOLI", "u32", CASTAGNOLI);
+    crc32.add_array("CASTAGNOLI_TABLE", "u32", &make_table_crc32(CASTAGNOLI));
+
+    let IEEE: u32 = 0xedb88320;
+    crc32.add_value("IEEE", "u32", IEEE);
+    crc32.add_array("IEEE_TABLE", "u32", &make_table_crc32(IEEE));
+
+    let KOOPMAN: u32 = 0xeb31d82e;
+    crc32.add_value("KOOPMAN", "u32", KOOPMAN);
+    crc32.add_array("KOOPMAN_TABLE", "u32", &make_table_crc32(KOOPMAN));
+
+    crc32.finish();
+
+    let mut crc64 = build_const::ConstWriter::for_build("crc64_constants")
+        .unwrap()
+        .finish_dependencies();
+
+    let ECMA: u64 = 0xc96c5795d7870f42;
+    crc64.add_value("ECMA", "u64", ECMA);
+    crc64.add_array("ECMA_TABLE", "u64", &make_table_crc64(ECMA));
+
+    let ISO: u64 = 0xd800000000000000;
+    crc64.add_value("ISO", "u64", ISO);
+    crc64.add_array("ISO_TABLE", "u64", &make_table_crc64(ISO));
+
+    crc64.finish();
+}
+
+fn main() {
+    create_constants();
+}
+

src/crc32.rs

@@ -1,14 +1,9 @@
+#[cfg(feature = "std")]
 use std::hash::Hasher;
+#[cfg(not(feature = "std"))]
+use core::hash::Hasher;
 
-pub const CASTAGNOLI: u32 = 0x82f63b78;
-pub const IEEE: u32 = 0xedb88320;
-pub const KOOPMAN: u32 = 0xeb31d82e;
-
-lazy_static! {
-    pub static ref IEEE_TABLE: [u32; 256] = make_table(IEEE);
-    pub static ref CASTAGNOLI_TABLE: [u32; 256] = make_table(CASTAGNOLI);
-    pub static ref KOOPMAN_TABLE: [u32; 256] = make_table(KOOPMAN);
-}
+build_const!("crc32_constants");
 
 pub struct Digest {
     table: [u32; 256],

src/crc64.rs

@@ -1,12 +1,9 @@
+#[cfg(feature = "std")]
 use std::hash::Hasher;
+#[cfg(not(feature = "std"))]
+use core::hash::Hasher;
 
-pub const ECMA: u64 = 0xc96c5795d7870f42;
-pub const ISO: u64 = 0xd800000000000000;
-
-lazy_static! {
-    pub static ref ECMA_TABLE: [u64; 256] = make_table(ECMA);
-    pub static ref ISO_TABLE: [u64; 256] = make_table(ISO);
-}
+build_const!("crc64_constants");
 
 pub struct Digest {
     table: [u64; 256],

src/lib.rs

@@ -40,8 +40,10 @@
 //! assert_eq!(digest.sum64(), 0x995dc9bbdf1939fa);
 //! ```
 
+#![cfg_attr(not(feature = "std"), no_std)]
+
 #[macro_use]
-extern crate lazy_static;
+extern crate build_const;
 
 pub mod crc32;
 pub mod crc64;