Function format_integer_str 

pub fn format_integer_str(x: &Integer, fmt: &str) -> Option<String>

Formats an Integer according to a GMP-style printf format string, for strict compatibility with GMP’s gmp_printf family.

The format string should contain a single conversion consuming the Integer, written %[flags][width][.precision]Z[conv], with any surrounding literal text (a literal % is written %%). The pieces are:

• flags: any of - (left-justify within the field), + (always show a sign), space (show a space before a nonnegative value), # (alternate form: prefix hexadecimal output with 0x or 0X and octal output with 0, unless the digits already begin with a zero), and 0 (pad the field with leading zeros). The ' flag is accepted but, as in GMP, has no effect on GMP types.
• width: the minimum field width, as a decimal integer.
• precision: following a ., the minimum number of digits, the absolute value being padded with leading zeros to reach it; a zero value formatted with a precision of 0 produces no digits at all. By default all necessary digits are printed.
• Z: marks the argument as a multiple-precision integer (GMP’s type character).
• conv: the conversion — d, i, or u (decimal; unlike in C, all three are the same, and a negative value keeps its sign under every conversion), o (octal), or x/X (lowercase/uppercase hexadecimal).

A negative value is written as a - followed by the absolute value’s digits, under every conversion; with the # flag the sign precedes the base prefix, as in -0xff.

Returns None when the format string is not a single well-formed %Z integer conversion: for instance if it uses * for the width or precision (which would need an integer argument that this single-value entry point does not supply), contains no %Z conversion or more than one, contains a conversion of any other type, or requests a width or precision beyond i32::MAX (the range of the C int GMP itself stores them in).

Worst-case complexity

$T(n) = O(n (\log n)^2 \log\log n)$

$M(n) = O(n \log n)$

where $T$ is time, $M$ is additional memory, and $n$ is max(x.significant_bits(), p, w), with p and w the precision and field width requested by the format string.

Examples

use malachite_nz::integer::Integer;
use malachite_nz::integer::conversion::string::format_integer::format_integer_str;

let x = Integer::from(-255);
assert_eq!(format_integer_str(&x, "%Zd"), Some("-255".to_string()));
assert_eq!(format_integer_str(&x, "%#Zx"), Some("-0xff".to_string()));
assert_eq!(format_integer_str(&x, "%#ZX"), Some("-0XFF".to_string()));
assert_eq!(format_integer_str(&x, "%#Zo"), Some("-0377".to_string()));
assert_eq!(format_integer_str(&x, "%8Zd"), Some("    -255".to_string()));
assert_eq!(
    format_integer_str(&x, "%08Zd"),
    Some("-0000255".to_string())
);
assert_eq!(format_integer_str(&x, "%.6Zd"), Some("-000255".to_string()));

let x = Integer::from(255);
assert_eq!(format_integer_str(&x, "%+Zd"), Some("+255".to_string()));
assert_eq!(format_integer_str(&x, "% Zd"), Some(" 255".to_string()));
assert_eq!(
    format_integer_str(&x, "x = %Zd!"),
    Some("x = 255!".to_string())
);

// invalid or unsupported format strings
assert_eq!(format_integer_str(&x, "%d"), None);
assert_eq!(format_integer_str(&x, "%*Zd"), None);
assert_eq!(format_integer_str(&x, "%Zd %Zd"), None);

This is gmp_snprintf from printf/snprintf.c, GMP 6.3.0, where the format string contains a single %Z integer conversion and the buffer is always large enough.