Initial commit with usize decimal format

.gitignore

+/target

Cargo.lock

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "mini-format"
+version = "0.1.0"

Cargo.toml

+[package]
+name = "mini-format"
+version = "0.1.0"
+edition = "2021"
+authors = ["Michaël Hauspie <michael.hauspie@univ-lille.fr>"]
+
+
+[dependencies]

README.md

+mini-format is a minimalist formating crate.
+
+Its main purpose is to be used in very small embedded systems in which
+you want to avoid use the [`core::fmt::Write`] trait for whatever
+reason.

src/lib.rs

+#![doc = include_str!("../README.md")]
+#![cfg_attr(not(test), no_std)]
+
+/// A trait that tells that a type can be formatted.
+///
+/// This is used to provide the [`format`] function
+/// that can be called on any type that implement the
+/// trait
+pub trait Format<F> where
+    F: FnMut(char)
+{
+    /// format to a decimal representation by using the provided
+    /// `putchar` closure to *output* subsequent char, whatever it may
+    /// mean
+    fn format_dec(&self, putchar: F);
+}
+
+
+/// format a value to a decimal representation by using the provided
+/// `putchar` closure to *output* subsequent char, whatever it may
+/// mean
+pub fn format_dec<T,F>(value: T, putchar: F) where
+    T: Format<F>,
+    F: FnMut(char)
+{
+    value.format_dec(putchar);
+}
+
+
+impl<F:FnMut(char)> Format<F> for usize {
+    fn format_dec(&self, mut putchar: F) {
+        let mut max_pow = 1;				
+	let mut val = *self;					
+
+	while val / max_pow >= 10 {
+            max_pow *= 10;
+        }
+	while max_pow >= 1 {
+            let char_val: char = char::from_u32((val / max_pow) as u32 + '0' as u32).unwrap_or(' ');
+            putchar(char_val);
+	    val = val % max_pow;
+            max_pow /= 10
+	}
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn format_dec_ok() {
+        let x = 124567891354654;
+        let mut s = String::new();
+        format_dec(x, |c| {
+            s.push(c)
+        });
+        assert_eq!(s, format!("{x}"));
+    }
+}