Add and use DEFAULT_ROUNDING_MODE compile-time configuration

Author: akubera

build.rs

@@ -1,7 +1,7 @@
-#![allow(clippy::style)]
 
 use std::env;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+
 
 fn main() {
     let ac = autocfg::new();
@@ -15,11 +15,12 @@ fn main() {
 
     let outdir: PathBuf = std::env::var_os("OUT_DIR").unwrap().into();
     write_default_precision_file(&outdir);
+    write_default_rounding_mode(&outdir);
 }
 
 
 /// Create default_precision.rs, containg definition of constant DEFAULT_PRECISION loaded in src/lib.rs
-fn write_default_precision_file(outdir: &PathBuf) {
+fn write_default_precision_file(outdir: &Path) {
     let env_var = env::var("RUST_BIGDECIMAL_DEFAULT_PRECISION").unwrap_or_else(|_| "100".to_owned());
     println!("cargo:rerun-if-env-changed=RUST_BIGDECIMAL_DEFAULT_PRECISION");
 
@@ -34,3 +35,14 @@ fn write_default_precision_file(outdir: &PathBuf) {
 
     std::fs::write(rust_file_path, rust_file_contents).unwrap();
 }
+
+/// Create default_rounding_mode.rs, using value of RUST_BIGDECIMAL_DEFAULT_ROUNDING_MODE environment variable
+fn write_default_rounding_mode(outdir: &Path) {
+    let rounding_mode_name = env::var("RUST_BIGDECIMAL_DEFAULT_ROUNDING_MODE").unwrap_or_else(|_| "HalfEven".to_owned());
+    println!("cargo:rerun-if-env-changed=RUST_BIGDECIMAL_DEFAULT_ROUNDING_MODE");
+
+    let rust_file_path = outdir.join("default_rounding_mode.rs");
+    let rust_file_contents = format!("const DEFAULT_ROUNDING_MODE: RoundingMode = RoundingMode::{};", rounding_mode_name);
+
+    std::fs::write(rust_file_path, rust_file_contents).unwrap();
+}

src/context.rs

@@ -15,6 +15,8 @@ use crate::{
 
 // const DEFAULT_PRECISION: u64 = ${RUST_BIGDECIMAL_DEFAULT_PRECISION} or 100;
 include!(concat!(env!("OUT_DIR"), "/default_precision.rs"));
+// const DEFAULT_ROUNDING_MODE: RoundingMode = ${RUST_BIGDECIMAL_DEFAULT_ROUNDING_MODE} or HalfUp;
+include!(concat!(env!("OUT_DIR"), "/default_rounding_mode.rs"));
 
 /// Mathematical Context
 ///
@@ -111,7 +113,7 @@ impl stdlib::default::Default for Context {
     fn default() -> Self {
         Self {
             precision: NonZeroU64::new(DEFAULT_PRECISION).unwrap(),
-            rounding: RoundingMode::HalfEven,
+            rounding: DEFAULT_ROUNDING_MODE,
         }
     }
 }