custom-format

This crate extends the standard formatting syntax with custom format specifiers, by providing custom formatting macros.

It uses : (a space and a colon) as a separator before the format specifier, which is not a syntax currently accepted and allows supporting standard specifiers in addition to custom specifiers.

Example

```rust use custom_format::{CustomFormat, CustomFormatter};

use core::fmt;

pub struct DateTime { year: i32, month: u8, month_day: u8, hour: u8, minute: u8, second: u8, nanoseconds: u32, }

impl CustomFormat for DateTime { fn fmt(&self, f: &mut fmt::Formatter, spec: &str) -> fmt::Result { match spec { // Year with pad for at least 4 digits "%Y" => write!(f, "{:04}", self.year), // Year % 100 (00..99) "%y" => write!(f, "{:02}", (self.year % 100).abs()), // Month of the year, zero-padded (01..12) "%m" => write!(f, "{:02}", self.month), // Day of the month, zero-padded (01..31) "%d" => write!(f, "{:02}", self.month_day), // Hour of the day, 24-hour clock, zero-padded (00..23) "%H" => write!(f, "{:02}", self.hour), // Minute of the hour (00..59) "%M" => write!(f, "{:02}", self.minute), // Second of the minute (00..60) "%S" => write!(f, "{:02}", self.second), // Nanosecond (9 digits) "%9N" => write!(f, "{:09}", self.nanoseconds), // Date (%m/%d/%y) "%D" => write!( f, "{}/{}/{}", CustomFormatter::new(self, "%m"), CustomFormatter::new(self, "%d"), CustomFormatter::new(self, "%y") ), // The ISO 8601 date format (%Y-%m-%d) "%F" => write!( f, "{}-{}-{}", CustomFormatter::new(self, "%Y"), CustomFormatter::new(self, "%m"), CustomFormatter::new(self, "%d") ), // 24-hour time (%H:%M:%S) "%T" => write!( f, "{}:{}:{}", CustomFormatter::new(self, "%H"), CustomFormatter::new(self, "%M"), CustomFormatter::new(self, "%S") ), // Incorrect format _ => Err(fmt::Error), } } }

fn main() { let datetime = DateTime { year: 1836, month: 5, monthday: 18, hour: 23, minute: 45, second: 54, nanoseconds: 123456789, };

// Expands to:
//
// match (&(date_time), &("The date time is")) {
//     (arg0, arg1) => {
//         ::std::println!(
//             "{0}: {1}-{2}-{3} {4}:{5}:{6}.{7}",
//             arg1,
//             ::custom_format::CustomFormatter::new(arg0, "%Y"),
//             ::custom_format::CustomFormatter::new(arg0, "%m"),
//             ::custom_format::CustomFormatter::new(arg0, "%d"),
//             ::custom_format::CustomFormatter::new(arg0, "%H"),
//             ::custom_format::CustomFormatter::new(arg0, "%M"),
//             ::custom_format::CustomFormatter::new(arg0, "%S"),
//             ::custom_format::CustomFormatter::new(arg0, "%9N")
//         )
//     }
// }
//
// Output: "The date time is: 1836-05-18 23:45:54.123456789"
//
custom_format::println!(
    "{1}: {0 :%Y}-{0 :%m}-{0 :%d} {0 :%H}:{0 :%M}:{0 :%S}.{0 :%9N}",
    date_time,
    "The date time is"
);

} ```