FMT

A lightweight, type-safe string formatting library for microcontroller, inspired by PEP-3101.

Features

• Type Info: no manual format specifier needed -- fmt("{}", 42) -> "42"
• Alignment: alignment, fill, width, and forced cut-off
• Integer fmt: binary, decimal, hex (with/without prefix), BCD
• Pointer and string formatting
• Positional arguments

Supported types

• bool
• i8 ~ i32
• u8 ~ u32
• char* (string)
• void* (pointer)

Syntax

replacement_field :=
`{` arg_idx [`:` [ [fill] align ] [ sign ] [ width [ `!` ] ] [ spec ] `}`
arg_idx :=
digit
fill :=
any character default = ` `
align :=
< -- align to left default
> -- align to right
^ -- align to center
sign :=
` ` -- ` ` or `-` number type ONLY
+ -- `+` or `-` number type ONLY
- -- `-` if value < 0 default, number type ONLY
width :=
digits
spec :=
b -- binary
D -- BCD same as hex, used for BCD values
d -- dec default
p -- pointer hex, lower-case
P -- pointer hex, upper-case
q prec -- quantized value (not implemented yet)
h -- hex
H -- hex upper-case
x -- hex with prefix `0x`
X -- hex with prefix `0X`, upper-case
prec :=
digits [`.` digits]
digits :=
one or more digit
digit :=
one of
0 1 2 3 4 5 6 7 8 9

Run examples

$ clang -std=c11 fmt.c examples.c -O2 -o examples && ./examples
fmt("{}", "Hello") ->"Hello"
fmt("{}", 42) -> 42
fmt("{:d}", 42) -> 42
fmt("{:h}", 42) -> 2a
fmt("{:x}", 42) -> 0x2a
fmt("{:>8d}", 42) ->| 42|
fmt("{:<8d}", 42) ->|42 |
fmt("{:^8d}", 42) ->| 42 |
fmt("{}", "QwQ") -> QwQ
fmt("{:p}", "QwQ") -> 0x2649538
fmt("0:{} 1:{} 1:{1} 0:{0}", 42, "QwQ") -> 0:42 1:QwQ 1:QwQ 0:42