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#![deny(missing_docs)]
use libc::c_char;
use std::fmt;
use std::io::Write;
#[derive(Debug, Default, Clone, Copy)]
#[repr(transparent)]
pub struct GPoint<Float>(
pub Float,
);
impl std::fmt::Display for GPoint<f64> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt_g(f, self.0)
}
}
impl std::fmt::Display for GPoint<f32> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt_g(f, self.0 as f64)
}
}
const FORMAT_SIZE: usize = 20;
const NUMSTR_SIZE: usize = 200;
fn fmt_g(formatter: &mut fmt::Formatter<'_>, value: f64) -> fmt::Result {
let mut format = [0u8; FORMAT_SIZE];
let numstr = [0u8; NUMSTR_SIZE];
let mut fmtbuf = std::io::Cursor::new(&mut format[..FORMAT_SIZE - 1]);
let zero_pad = if formatter.sign_aware_zero_pad() {
"0"
} else {
""
};
let sign_pad = if formatter.sign_minus() {
"-"
} else if formatter.sign_plus() {
"+"
} else {
""
};
let alternate = if formatter.alternate() { "#" } else { "" };
match (formatter.width(), formatter.precision()) {
(None, None) => write!(fmtbuf, "%{}{}g", alternate, sign_pad),
(Some(w), None) => write!(fmtbuf, "%{}{}{}{}g", alternate, sign_pad, zero_pad, w),
(None, Some(p)) => write!(fmtbuf, "%{}.{}g", alternate, p),
(Some(w), Some(p)) => write!(fmtbuf, "%{}{}{}{}.{}g", alternate, sign_pad, zero_pad, w, p),
}
.map_err(|_| fmt::Error)?;
let nbchars = unsafe {
libc::snprintf(
numstr.as_ptr() as *mut c_char,
NUMSTR_SIZE,
format.as_ptr() as *const c_char,
value,
)
};
if nbchars < 0 || nbchars >= NUMSTR_SIZE as i32 {
return Err(fmt::Error);
}
let numstr = &numstr[..nbchars as usize];
formatter.write_str(unsafe { std::str::from_utf8_unchecked(numstr) })
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn simple() {
for (num, res) in [
(42., "42"),
(f64::NAN, "nan"),
(-f64::INFINITY, "-inf"),
(f64::INFINITY, "inf"),
] {
let num = GPoint(num);
assert_eq!(&format!("{}", num), res);
}
}
#[test]
fn pad() {
for (num, res) in [
(42., " 42"),
(f64::NAN, " nan"),
(-f64::INFINITY, " -inf"),
(f64::INFINITY, " inf"),
] {
let num = GPoint(num);
assert_eq!(&format!("{:8}", num), res);
}
}
#[test]
fn zero_pad() {
for (num, res) in [
(42., "00000042"),
(-1.01, "-0001.01"),
(f64::NAN, " nan"),
(-f64::INFINITY, " -inf"),
(f64::INFINITY, " inf"),
] {
let num = GPoint(num);
assert_eq!(&format!("{:08}", num), res);
}
}
#[test]
fn minus_pad() {
for (num, res) in [
(42., "42 "),
(-1.01, "-1.01 "),
(f64::NAN, "nan "),
(-f64::INFINITY, "-inf "),
(f64::INFINITY, "inf "),
] {
let num = GPoint(num);
assert_eq!(&format!("{:-8}", num), res);
}
}
#[test]
fn plus() {
for (num, res) in [
(42., "+42"),
(-1.01, "-1.01"),
(f64::NAN, "+nan"),
(-f64::INFINITY, "-inf"),
(f64::INFINITY, "+inf"),
] {
let num = GPoint(num);
assert_eq!(&format!("{:+}", num), res);
}
}
#[test]
fn plus_pad() {
for (num, res) in [
(42., " +42"),
(-1.01, " -1.01"),
(f64::NAN, " +nan"),
(-f64::INFINITY, " -inf"),
(f64::INFINITY, " +inf"),
] {
let num = GPoint(num);
assert_eq!(&format!("{:+8}", num), res);
}
}
#[test]
fn prec() {
for (num, res) in [
(42., "42"),
(-1.012345678901, "-1.01"),
(-42.8952, "-42.9"),
(4321., "4.32e+03"),
] {
let num = GPoint(num);
assert_eq!(&format!("{:.3}", num), res);
}
}
#[test]
fn alt() {
for (num, res) in [
(42., "42.0000"),
(-1.012345678901, "-1.01235"),
(432100., "432100."),
] {
let num = GPoint(num);
assert_eq!(&format!("{:#}", num), res);
}
}
#[test]
fn in_context() {
assert_eq!(&format!("answer={}!", GPoint(42.)), "answer=42!");
}
}