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Initial release: mcufont 0.1.0

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Faithful Rust port of Maurycy's mcufont.h — a 5x5 monospace pixel
font (~350 bytes of bitmap data) covering A-Z, a-z, 0-9, and the
punctuation set - + . , ? ! : = '.

- no_std, forbid(unsafe_code), zero deps with default features.
- Public glyph tables (UPPER / LOWER / DIGITS / SYMBOLS), SYM_*
  index constants, and a glyph(c: char) lookup.
- Each glyph row is packed in bits 7..=3 MSB-first so the bytes
  are byte-for-byte compatible with embedded_graphics::ImageRaw.
- Optional `embedded-graphics` feature exposes MCU_FONT
  (MonoFont<'static>), FONT_DATA, and McuGlyphMapping for drop-in
  use with MonoTextStyle / Text on any DrawTarget (SSD1306 over
  I²C, ST7735, etc.).
- Per-category feature flags (upper / lower / numbers / symbols,
  all on by default) so users can drop unused glyphs from flash.

Licensed CC BY-NC-SA 4.0, inherited from the upstream font data.
An email is out to the upstream author asking for a permissive
software license (MIT / Apache-2.0); if granted, the crate will
be relicensed and a new version published.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
swaitsandClaude Opus 4.7 committed 2026-04-29 13:36:29 -06:00
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.gitignore
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/target
/Cargo.lock
CHANGELOG.md
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# Changelog
All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
## [Unreleased]
### Pending
- **Relicense.** An email is out to the upstream author requesting a
permissive software license (MIT / Apache-2.0) on the original C
source. If granted, this crate will be relicensed and the next release
will reflect the new terms. Until then, CC BY-NC-SA 4.0 applies.
## [0.1.0] - 2026-04-29
### Added
- Initial release. Faithful Rust port of Maurycy's `mcufont.h`
(<https://maurycyz.com/projects/mcufont/>) — a 5×5 monospace pixel
font, ~350 bytes of bitmap data, covering `A–Z`, `a–z`, `0–9`, and
`- + . , ? ! : = '`.
- `no_std`, `forbid(unsafe_code)`, zero dependencies with default
features.
- Public glyph tables: `UPPER`, `LOWER`, `DIGITS`, `SYMBOLS`.
- `glyph(c: char) -> Option<&'static Glyph>` lookup function.
- `SYM_*` index constants for direct symbol-table access.
- Feature flags: `upper`, `lower`, `numbers`, `symbols` (all on by
default) — disable individually to save flash.
- Optional `embedded-graphics` feature exposing `eg::MCU_FONT`
(`MonoFont<'static>`), `eg::FONT_DATA`, and `eg::McuGlyphMapping` for
drop-in use with `MonoTextStyle` / `Text` on any `DrawTarget`
(SSD1306 over I²C, ST7735, etc.).
- Glyph bytes packed in bits 7..=3 (MSB-first), bits 2..=0 zero —
layout matches `embedded_graphics::image::ImageRaw` so the same data
serves both APIs.
### Licensed under
- CC BY-NC-SA 4.0 (inherited from the upstream font data; see
`LICENSE`). Non-commercial use only, ShareAlike. See README for
implications and the pending relicense note.
Cargo.toml
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[package]
name = "mcufont"
version = "0.1.0"
edition = "2024"
rust-version = "1.85"
description = "Tiny 5x5 monospace pixel font for microcontrollers — Rust port of Maurycy's mcufont, with optional embedded-graphics integration"
license = "CC-BY-NC-SA-4.0"
keywords = ["font", "embedded", "no-std", "pixel", "embedded-graphics"]
categories = ["embedded", "no-std", "graphics"]
readme = "README.md"
include = ["src/**/*", "Cargo.toml", "README.md", "CHANGELOG.md", "LICENSE"]
[package.metadata.docs.rs]
all-features = true
rustdoc-args = ["--cfg", "docsrs"]
[features]
default = ["upper", "lower", "numbers", "symbols"]
upper = []
lower = []
numbers = []
symbols = []
embedded-graphics = ["dep:embedded-graphics"]
[dependencies]
embedded-graphics = { version = "0.8", optional = true, default-features = false }
LICENSE
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README.md
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# mcufont
Tiny 5×5 monospace pixel font for microcontrollers. `no_std`, zero dependencies (with default features), ~350 bytes of font data.
Faithful Rust port of [Maurycy's `mcufont`](https://maurycyz.com/projects/mcufont/) C header. Covers `A–Z`, `a–z`, `0–9`, and the punctuation set `- + . , ? ! : = '`.
## Usage — raw
```rust
use mcufont::{glyph, GLYPH_WIDTH, GLYPH_HEIGHT};
if let Some(g) = glyph('A') {
for row in g {
// bit 7 = leftmost pixel, bit 3 = rightmost; bits 2..=0 are zero.
for x in 0..GLYPH_WIDTH {
let on = (row >> (7 - x)) & 1 == 1;
// ... blit to your framebuffer
}
}
}
```
The static tables `UPPER`, `LOWER`, `DIGITS`, `SYMBOLS` are also public — index them directly if you don't need the lookup function.
## Usage — `embedded-graphics`
Enable the `embedded-graphics` feature in `Cargo.toml`:
```toml
mcufont = { version = "0.1", features = ["embedded-graphics"] }
```
Then drop `MCU_FONT` into a `MonoTextStyle`:
```rust
use embedded_graphics::{
mono_font::MonoTextStyle, pixelcolor::BinaryColor,
prelude::*, text::Text,
};
use mcufont::eg::MCU_FONT;
let style = MonoTextStyle::new(&MCU_FONT, BinaryColor::On);
Text::new("Hello", Point::new(0, 5), style).draw(&mut display)?;
```
Works with any `embedded-graphics` `DrawTarget` — SSD1306 over I²C, SH1106, ST7735, fbink, etc.
## Features
| Feature | Default | What it adds |
| ------------------- | ------- | ---------------------------------------------------------------- |
| `upper` | yes | `A–Z` (130 bytes) |
| `lower` | yes | `a–z` (130 bytes) |
| `numbers` | yes | `0–9` (50 bytes) |
| `symbols` | yes | `- + . , ? ! : = '` (45 bytes) |
| `embedded-graphics` | no | `MonoFont` integration + concatenated strip (~2× the flash cost) |
Disable any category you don't need to save flash. With all four enabled the raw tables sum to ~355 bytes.
## Glyph format
Each glyph is `[u8; 5]` — one byte per row. Pixels are packed in **bits 7..=3 MSB-first** (bit 7 = leftmost pixel); bits 2..=0 are always zero. This layout matches `embedded_graphics::image::ImageRaw` byte ordering for a 5-pixel-wide row, so the same bytes drive both the raw API and the `embedded-graphics` integration with no transformation.
```text
byte = 0b A B C D E _ _ _ → row pixels = A B C D E
```
## Embedded targets
Plain `static` arrays land in `.rodata`, which is mapped to flash on the common embedded Rust targets — Cortex-M, RISC-V, ESP32, etc. The crate is `no_std` and uses no allocator. AVR's Harvard architecture (`PROGMEM`) is **not** addressed; AVR Rust support is nightly-only and out of scope for this crate.
## License — read this
This crate is currently licensed **CC BY-NC-SA 4.0** — the only license offered for the upstream font data on the source page. That means:
- **Non-commercial use only.** You cannot ship this crate (or work derived from its font data) in a product you sell.
- **ShareAlike.** Any derivative work that incorporates the font data must also be licensed under CC BY-NC-SA 4.0.
- This is **not** an OSI-approved open-source license. It is incompatible with most permissive and copyleft software licenses.
If those terms don't fit your project, this crate is not for you.
Full license text: [`LICENSE`](./LICENSE) — see also <https://creativecommons.org/licenses/by-nc-sa/4.0/>.
### Pending relicense
We've reached out to the upstream author asking for a permissive software license (MIT or Apache-2.0) on the original C source. If granted, this crate will be relicensed accordingly and a new version published. Until then the inherited CC BY-NC-SA 4.0 license stands.
Watch the [CHANGELOG](./CHANGELOG.md) for the relicense, if and when it lands.
## Attribution
- 5×5 font data and original C implementation: <https://maurycyz.com/projects/mcufont/>
- Original 5×6 `font-inline.h` it was based on: lcamtuf, <https://lcamtuf.coredump.cx/soft/embedded/font-inline.h>
- Lineage further traces to the ZX Spectrum 8×8 system font.
This Rust crate (scaffolding, `embedded-graphics` integration, tests) is itself a derivative work and is therefore also CC BY-NC-SA 4.0.
src/eg.rs
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//! `embedded-graphics` integration. Enable the `embedded-graphics` feature.
//!
//! ```ignore
//! use embedded_graphics::{
//! mono_font::MonoTextStyle, pixelcolor::BinaryColor,
//! prelude::*, text::Text,
//! };
//! use mcufont::eg::MCU_FONT;
//!
//! let style = MonoTextStyle::new(&MCU_FONT, BinaryColor::On);
//! Text::new("Hello", Point::new(0, 5), style).draw(&mut display)?;
//! ```
use embedded_graphics::{
geometry::Size,
image::ImageRaw,
mono_font::{DecorationDimensions, MonoFont, mapping::GlyphMapping},
pixelcolor::BinaryColor,
};
#[cfg(not(any(
feature = "upper",
feature = "lower",
feature = "numbers",
feature = "symbols",
)))]
compile_error!(
"the `embedded-graphics` feature requires at least one of `upper`, `lower`, `numbers`, `symbols`"
);
const fn upper_count() -> usize {
#[cfg(feature = "upper")]
{
26
}
#[cfg(not(feature = "upper"))]
{
0
}
}
const fn lower_count() -> usize {
#[cfg(feature = "lower")]
{
26
}
#[cfg(not(feature = "lower"))]
{
0
}
}
const fn digits_count() -> usize {
#[cfg(feature = "numbers")]
{
10
}
#[cfg(not(feature = "numbers"))]
{
0
}
}
const fn symbols_count() -> usize {
#[cfg(feature = "symbols")]
{
9
}
#[cfg(not(feature = "symbols"))]
{
0
}
}
const UPPER_OFFSET: usize = 0;
const LOWER_OFFSET: usize = UPPER_OFFSET + upper_count();
const DIGITS_OFFSET: usize = LOWER_OFFSET + lower_count();
const SYMBOLS_OFFSET: usize = DIGITS_OFFSET + digits_count();
const TOTAL_GLYPHS: usize = SYMBOLS_OFFSET + symbols_count();
const STRIP_BYTES: usize = TOTAL_GLYPHS * crate::GLYPH_HEIGHT;
const fn build_strip() -> [u8; STRIP_BYTES] {
let mut out = [0u8; STRIP_BYTES];
let mut i: usize = 0;
#[cfg(feature = "upper")]
{
let mut g = 0;
while g < 26 {
let mut r = 0;
while r < crate::GLYPH_HEIGHT {
out[i] = crate::UPPER[g][r];
i += 1;
r += 1;
}
g += 1;
}
}
#[cfg(feature = "lower")]
{
let mut g = 0;
while g < 26 {
let mut r = 0;
while r < crate::GLYPH_HEIGHT {
out[i] = crate::LOWER[g][r];
i += 1;
r += 1;
}
g += 1;
}
}
#[cfg(feature = "numbers")]
{
let mut g = 0;
while g < 10 {
let mut r = 0;
while r < crate::GLYPH_HEIGHT {
out[i] = crate::DIGITS[g][r];
i += 1;
r += 1;
}
g += 1;
}
}
#[cfg(feature = "symbols")]
{
let mut g = 0;
while g < 9 {
let mut r = 0;
while r < crate::GLYPH_HEIGHT {
out[i] = crate::SYMBOLS[g][r];
i += 1;
r += 1;
}
g += 1;
}
}
let _ = i;
out
}
/// All enabled glyphs concatenated as a 5-pixel-wide vertical strip,
/// in feature order: upper, lower, digits, symbols.
pub static FONT_DATA: [u8; STRIP_BYTES] = build_strip();
/// Maps ASCII chars to glyph indices in [`FONT_DATA`]. Unknown characters
/// fall back to `'?'` if the `symbols` feature is enabled, otherwise to
/// glyph 0.
pub struct McuGlyphMapping;
impl GlyphMapping for McuGlyphMapping {
fn index(&self, c: char) -> usize {
#[cfg(feature = "upper")]
if c.is_ascii_uppercase() {
return UPPER_OFFSET + (c as usize - 'A' as usize);
}
#[cfg(feature = "lower")]
if c.is_ascii_lowercase() {
return LOWER_OFFSET + (c as usize - 'a' as usize);
}
#[cfg(feature = "numbers")]
if c.is_ascii_digit() {
return DIGITS_OFFSET + (c as usize - '0' as usize);
}
#[cfg(feature = "symbols")]
match c {
'-' => return SYMBOLS_OFFSET + crate::SYM_MINUS,
'+' => return SYMBOLS_OFFSET + crate::SYM_PLUS,
'.' => return SYMBOLS_OFFSET + crate::SYM_DOT,
',' => return SYMBOLS_OFFSET + crate::SYM_COMMA,
'?' => return SYMBOLS_OFFSET + crate::SYM_QMARK,
'!' => return SYMBOLS_OFFSET + crate::SYM_EXMARK,
':' => return SYMBOLS_OFFSET + crate::SYM_COLON,
'=' => return SYMBOLS_OFFSET + crate::SYM_EQ,
'\'' => return SYMBOLS_OFFSET + crate::SYM_TICK,
_ => {}
}
let _ = c;
#[cfg(feature = "symbols")]
{
SYMBOLS_OFFSET + crate::SYM_QMARK
}
#[cfg(not(feature = "symbols"))]
{
0
}
}
}
static MAPPING: McuGlyphMapping = McuGlyphMapping;
/// Drop-in `MonoFont` for use with `MonoTextStyle`, `Text`, etc.
pub static MCU_FONT: MonoFont<'static> = MonoFont {
image: ImageRaw::<BinaryColor>::new(&FONT_DATA, crate::GLYPH_WIDTH as u32),
character_size: Size::new(crate::GLYPH_WIDTH as u32, crate::GLYPH_HEIGHT as u32),
character_spacing: 1,
baseline: (crate::GLYPH_HEIGHT - 1) as u32,
strikethrough: DecorationDimensions::default_strikethrough(crate::GLYPH_HEIGHT as u32),
underline: DecorationDimensions::default_underline(crate::GLYPH_HEIGHT as u32),
glyph_mapping: &MAPPING,
};
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn strip_size_is_consistent() {
assert_eq!(FONT_DATA.len(), STRIP_BYTES);
assert_eq!(STRIP_BYTES, TOTAL_GLYPHS * 5);
}
#[cfg(feature = "upper")]
#[test]
fn mapping_upper() {
assert_eq!(MAPPING.index('A'), 0);
assert_eq!(MAPPING.index('Z'), 25);
}
#[cfg(all(feature = "upper", feature = "lower"))]
#[test]
fn mapping_lower_offset() {
assert_eq!(MAPPING.index('a'), 26);
assert_eq!(MAPPING.index('z'), 51);
}
#[cfg(all(feature = "upper", feature = "lower", feature = "numbers"))]
#[test]
fn mapping_digit_offset() {
assert_eq!(MAPPING.index('0'), 52);
assert_eq!(MAPPING.index('9'), 61);
}
#[cfg(all(
feature = "upper",
feature = "lower",
feature = "numbers",
feature = "symbols"
))]
#[test]
fn mapping_symbol_offset() {
assert_eq!(MAPPING.index('-'), 62);
assert_eq!(MAPPING.index('\''), 70);
}
#[cfg(feature = "symbols")]
#[test]
fn mapping_unknown_falls_back_to_qmark() {
let qmark = MAPPING.index('?');
assert_eq!(MAPPING.index(' '), qmark);
assert_eq!(MAPPING.index('@'), qmark);
assert_eq!(MAPPING.index('é'), qmark);
}
#[cfg(feature = "upper")]
#[test]
fn strip_starts_with_upper_a() {
assert_eq!(&FONT_DATA[0..5], &crate::UPPER[0]);
}
}
src/lib.rs
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//! Tiny 5×5 monospace pixel font for microcontrollers.
//!
//! Faithful Rust port of Maurycy's `mcufont`
//! (<https://maurycyz.com/projects/mcufont/>), itself based on lcamtuf's
//! `font-inline.h` (<https://lcamtuf.coredump.cx/soft/embedded/font-inline.h>).
//! Covers `A–Z`, `a–z`, `0–9`, and the punctuation set `- + . , ? ! : = '`.
//!
//! # Glyph format
//!
//! Each [`Glyph`] is 5 bytes — one byte per row. Pixels are packed in
//! bits 7..=3 MSB-first (bit 7 = leftmost pixel), bits 2..=0 are zero.
//! This layout matches `embedded_graphics::image::ImageRaw` byte ordering
//! for a 5-pixel-wide row, so the same bytes serve both the raw API and
//! the `embedded-graphics` integration with no transformation.
//!
//! ```text
//! byte = 0b A B C D E _ _ _ → row pixels = A B C D E
//! ```
//!
//! # Features
//!
//! - `upper`, `lower`, `numbers`, `symbols` (default) — include each
//! character category. Drop any you don't need to save flash.
//! - `embedded-graphics` (off by default) — exposes [`eg::MCU_FONT`], a
//! drop-in `MonoFont` for the embedded-graphics ecosystem.
//!
//! # License
//!
//! Currently **CC BY-NC-SA 4.0** — inherited from the upstream font data,
//! which is the only license the source page offers. That means
//! non-commercial use only and share-alike derivatives. See `LICENSE` and
//! the README for the full text and implications.
//!
//! **Pending relicense:** an email is out to the upstream author asking
//! for a permissive software license (MIT / Apache-2.0). If granted, this
//! crate will be relicensed and a new version published. Until then, CC
//! BY-NC-SA 4.0 applies.
#![no_std]
#![forbid(unsafe_code)]
// `0b01110_000` separates the 5 pixel bits from the 3 padding bits — that
// asymmetric grouping is the whole point of this layout.
#![allow(clippy::unusual_byte_groupings)]
#[cfg(feature = "embedded-graphics")]
pub mod eg;
/// Visible glyph width in pixels.
pub const GLYPH_WIDTH: usize = 5;
/// Glyph height in rows.
pub const GLYPH_HEIGHT: usize = 5;
/// Recommended on-screen cell size: 5 px glyph + 1 px gap.
pub const CELL: usize = 6;
/// One glyph: 5 rows, each row one byte. Pixels in bits 7..=3 MSB-first;
/// bits 2..=0 zero.
pub type Glyph = [u8; GLYPH_HEIGHT];
#[cfg(feature = "upper")]
pub static UPPER: [Glyph; 26] = [
[0b01110_000, 0b10001_000, 0b11111_000, 0b10001_000, 0b10001_000], // A
[0b11110_000, 0b10001_000, 0b11110_000, 0b10001_000, 0b11110_000], // B
[0b01111_000, 0b10000_000, 0b10000_000, 0b10000_000, 0b01111_000], // C
[0b11110_000, 0b10001_000, 0b10001_000, 0b10001_000, 0b11110_000], // D
[0b11111_000, 0b10000_000, 0b11100_000, 0b10000_000, 0b11111_000], // E
[0b11111_000, 0b10000_000, 0b11100_000, 0b10000_000, 0b10000_000], // F
[0b01111_000, 0b10000_000, 0b10011_000, 0b10001_000, 0b01111_000], // G
[0b10001_000, 0b10001_000, 0b11111_000, 0b10001_000, 0b10001_000], // H
[0b11111_000, 0b00100_000, 0b00100_000, 0b00100_000, 0b11111_000], // I
[0b11111_000, 0b00010_000, 0b00010_000, 0b10010_000, 0b01100_000], // J
[0b10010_000, 0b10100_000, 0b11000_000, 0b10100_000, 0b10010_000], // K
[0b10000_000, 0b10000_000, 0b10000_000, 0b10000_000, 0b11111_000], // L
[0b11111_000, 0b10101_000, 0b10101_000, 0b10001_000, 0b10001_000], // M
[0b10001_000, 0b11001_000, 0b10101_000, 0b10011_000, 0b10001_000], // N
[0b01110_000, 0b10001_000, 0b10001_000, 0b10001_000, 0b01110_000], // O
[0b11110_000, 0b10001_000, 0b11110_000, 0b10000_000, 0b10000_000], // P
[0b01110_000, 0b10001_000, 0b10001_000, 0b10010_000, 0b01101_000], // Q
[0b11110_000, 0b10001_000, 0b11110_000, 0b10010_000, 0b10001_000], // R
[0b01111_000, 0b10000_000, 0b01110_000, 0b00001_000, 0b11110_000], // S
[0b11111_000, 0b00100_000, 0b00100_000, 0b00100_000, 0b00100_000], // T
[0b10001_000, 0b10001_000, 0b10001_000, 0b10001_000, 0b01110_000], // U
[0b10001_000, 0b10001_000, 0b01010_000, 0b01010_000, 0b00100_000], // V
[0b10001_000, 0b10001_000, 0b10101_000, 0b10101_000, 0b11011_000], // W
[0b10001_000, 0b01010_000, 0b00100_000, 0b01010_000, 0b10001_000], // X
[0b10001_000, 0b01010_000, 0b00100_000, 0b00100_000, 0b00100_000], // Y
[0b11111_000, 0b00010_000, 0b00100_000, 0b01000_000, 0b11111_000], // Z
];
#[cfg(feature = "lower")]
pub static LOWER: [Glyph; 26] = [
[0b00000_000, 0b01111_000, 0b10001_000, 0b10001_000, 0b01111_000], // a
[0b10000_000, 0b11110_000, 0b10001_000, 0b10001_000, 0b11110_000], // b
[0b00000_000, 0b01111_000, 0b10000_000, 0b10000_000, 0b01111_000], // c
[0b00001_000, 0b01111_000, 0b10001_000, 0b10001_000, 0b01111_000], // d
[0b00000_000, 0b01110_000, 0b11111_000, 0b10000_000, 0b01111_000], // e
[0b00000_000, 0b01111_000, 0b10000_000, 0b11110_000, 0b10000_000], // f
[0b00000_000, 0b01110_000, 0b11111_000, 0b00001_000, 0b11110_000], // g
[0b10000_000, 0b10000_000, 0b11110_000, 0b10001_000, 0b10001_000], // h
[0b00100_000, 0b00000_000, 0b01100_000, 0b00100_000, 0b01110_000], // i
[0b00010_000, 0b00000_000, 0b00010_000, 0b10010_000, 0b01100_000], // j
[0b10000_000, 0b10000_000, 0b10110_000, 0b11000_000, 0b10110_000], // k
[0b00000_000, 0b10000_000, 0b10000_000, 0b10000_000, 0b01111_000], // l
[0b00000_000, 0b11110_000, 0b10101_000, 0b10101_000, 0b10001_000], // m
[0b00000_000, 0b11110_000, 0b10001_000, 0b10001_000, 0b10001_000], // n
[0b00000_000, 0b01110_000, 0b10001_000, 0b10001_000, 0b01110_000], // o
[0b00000_000, 0b11110_000, 0b10001_000, 0b11110_000, 0b10000_000], // p
[0b00000_000, 0b01111_000, 0b10001_000, 0b01111_000, 0b00001_000], // q
[0b00000_000, 0b01110_000, 0b10000_000, 0b10000_000, 0b10000_000], // r
[0b00000_000, 0b01110_000, 0b11000_000, 0b00110_000, 0b11100_000], // s
[0b00000_000, 0b11111_000, 0b00100_000, 0b00100_000, 0b00100_000], // t
[0b00000_000, 0b10001_000, 0b10001_000, 0b10001_000, 0b01110_000], // u
[0b00000_000, 0b10001_000, 0b10001_000, 0b01010_000, 0b00100_000], // v
[0b00000_000, 0b10001_000, 0b10101_000, 0b10101_000, 0b01110_000], // w
[0b00000_000, 0b10010_000, 0b01100_000, 0b01100_000, 0b10010_000], // x
[0b00000_000, 0b10010_000, 0b01110_000, 0b00010_000, 0b01100_000], // y
[0b00000_000, 0b11110_000, 0b00100_000, 0b01000_000, 0b11110_000], // z
];
#[cfg(feature = "numbers")]
pub static DIGITS: [Glyph; 10] = [
[0b01110_000, 0b10001_000, 0b10101_000, 0b10001_000, 0b01110_000], // 0
[0b01100_000, 0b10100_000, 0b00100_000, 0b00100_000, 0b11111_000], // 1
[0b01110_000, 0b10001_000, 0b00110_000, 0b01000_000, 0b11111_000], // 2
[0b11111_000, 0b00001_000, 0b01110_000, 0b00001_000, 0b11110_000], // 3
[0b10010_000, 0b10010_000, 0b11111_000, 0b00010_000, 0b00010_000], // 4
[0b11111_000, 0b10000_000, 0b01110_000, 0b00001_000, 0b11110_000], // 5
[0b01110_000, 0b10000_000, 0b11110_000, 0b10001_000, 0b01110_000], // 6
[0b11111_000, 0b00010_000, 0b00100_000, 0b01000_000, 0b01000_000], // 7
[0b01110_000, 0b10001_000, 0b01110_000, 0b10001_000, 0b01110_000], // 8
[0b11111_000, 0b10001_000, 0b11111_000, 0b00001_000, 0b00001_000], // 9
];
/// Index of `'-'` (minus) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_MINUS: usize = 0;
/// Index of `'+'` (plus) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_PLUS: usize = 1;
/// Index of `'.'` (dot) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_DOT: usize = 2;
/// Index of `','` (comma) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_COMMA: usize = 3;
/// Index of `'?'` (question mark) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_QMARK: usize = 4;
/// Index of `'!'` (exclamation mark) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_EXMARK: usize = 5;
/// Index of `':'` (colon) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_COLON: usize = 6;
/// Index of `'='` (equals) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_EQ: usize = 7;
/// Index of `'\''` (apostrophe) in [`SYMBOLS`].
#[cfg(feature = "symbols")]
pub const SYM_TICK: usize = 8;
#[cfg(feature = "symbols")]
pub static SYMBOLS: [Glyph; 9] = [
[0b00000_000, 0b00000_000, 0b01110_000, 0b00000_000, 0b00000_000], // -
[0b00000_000, 0b00100_000, 0b01110_000, 0b00100_000, 0b00000_000], // +
[0b00000_000, 0b00000_000, 0b00000_000, 0b00000_000, 0b01000_000], // .
[0b00000_000, 0b00000_000, 0b00000_000, 0b00100_000, 0b01000_000], // ,
[0b01110_000, 0b10001_000, 0b00110_000, 0b00000_000, 0b00100_000], // ?
[0b00100_000, 0b00100_000, 0b00100_000, 0b00000_000, 0b00100_000], // !
[0b00000_000, 0b01000_000, 0b00000_000, 0b01000_000, 0b00000_000], // :
[0b00000_000, 0b01110_000, 0b00000_000, 0b01110_000, 0b00000_000], // =
[0b00100_000, 0b00100_000, 0b00000_000, 0b00000_000, 0b00000_000], // '
];
/// Look up the glyph for an ASCII character. Returns `None` if the
/// character isn't in the supported set (or if its category feature
/// is disabled).
pub fn glyph(c: char) -> Option<&'static Glyph> {
#[cfg(feature = "upper")]
if c.is_ascii_uppercase() {
return Some(&UPPER[c as usize - 'A' as usize]);
}
#[cfg(feature = "lower")]
if c.is_ascii_lowercase() {
return Some(&LOWER[c as usize - 'a' as usize]);
}
#[cfg(feature = "numbers")]
if c.is_ascii_digit() {
return Some(&DIGITS[c as usize - '0' as usize]);
}
#[cfg(feature = "symbols")]
match c {
'-' => return Some(&SYMBOLS[SYM_MINUS]),
'+' => return Some(&SYMBOLS[SYM_PLUS]),
'.' => return Some(&SYMBOLS[SYM_DOT]),
',' => return Some(&SYMBOLS[SYM_COMMA]),
'?' => return Some(&SYMBOLS[SYM_QMARK]),
'!' => return Some(&SYMBOLS[SYM_EXMARK]),
':' => return Some(&SYMBOLS[SYM_COLON]),
'=' => return Some(&SYMBOLS[SYM_EQ]),
'\'' => return Some(&SYMBOLS[SYM_TICK]),
_ => {}
}
let _ = c;
None
}
#[cfg(test)]
mod tests {
use super::*;
#[cfg(feature = "upper")]
#[test]
fn upper_lookup() {
assert_eq!(glyph('A'), Some(&UPPER[0]));
assert_eq!(glyph('M'), Some(&UPPER[12]));
assert_eq!(glyph('Z'), Some(&UPPER[25]));
}
#[cfg(feature = "lower")]
#[test]
fn lower_lookup() {
assert_eq!(glyph('a'), Some(&LOWER[0]));
assert_eq!(glyph('m'), Some(&LOWER[12]));
assert_eq!(glyph('z'), Some(&LOWER[25]));
}
#[cfg(feature = "numbers")]
#[test]
fn digit_lookup() {
assert_eq!(glyph('0'), Some(&DIGITS[0]));
assert_eq!(glyph('5'), Some(&DIGITS[5]));
assert_eq!(glyph('9'), Some(&DIGITS[9]));
}
#[cfg(feature = "symbols")]
#[test]
fn symbol_lookup() {
assert_eq!(glyph('-'), Some(&SYMBOLS[SYM_MINUS]));
assert_eq!(glyph('+'), Some(&SYMBOLS[SYM_PLUS]));
assert_eq!(glyph('.'), Some(&SYMBOLS[SYM_DOT]));
assert_eq!(glyph(','), Some(&SYMBOLS[SYM_COMMA]));
assert_eq!(glyph('?'), Some(&SYMBOLS[SYM_QMARK]));
assert_eq!(glyph('!'), Some(&SYMBOLS[SYM_EXMARK]));
assert_eq!(glyph(':'), Some(&SYMBOLS[SYM_COLON]));
assert_eq!(glyph('='), Some(&SYMBOLS[SYM_EQ]));
assert_eq!(glyph('\''), Some(&SYMBOLS[SYM_TICK]));
}
#[test]
fn unsupported_returns_none() {
assert_eq!(glyph(' '), None);
assert_eq!(glyph('@'), None);
assert_eq!(glyph('é'), None);
assert_eq!(glyph('~'), None);
assert_eq!(glyph('/'), None);
assert_eq!(glyph('['), None);
}
/// Every byte in every table must have its low 3 bits clear; the
/// pixel data lives in bits 7..=3.
#[test]
fn padding_bits_are_zero() {
let check = |g: &Glyph| g.iter().all(|b| b & 0b0000_0111 == 0);
#[cfg(feature = "upper")]
assert!(UPPER.iter().all(check));
#[cfg(feature = "lower")]
assert!(LOWER.iter().all(check));
#[cfg(feature = "numbers")]
assert!(DIGITS.iter().all(check));
#[cfg(feature = "symbols")]
assert!(SYMBOLS.iter().all(check));
}
/// Spot-check transcription against the C source: each row in C is
/// in bits 4..=0; ours is in bits 7..=3. Verify a handful of glyphs.
#[cfg(feature = "upper")]
#[test]
fn matches_c_source_upper() {
// 'A': 0b01110, 0b10001, 0b11111, 0b10001, 0b10001
assert_eq!(
UPPER[0],
[
0b01110 << 3,
0b10001 << 3,
0b11111 << 3,
0b10001 << 3,
0b10001 << 3,
]
);
// 'M': 0b11111, 0b10101, 0b10101, 0b10001, 0b10001
assert_eq!(
UPPER[12],
[
0b11111 << 3,
0b10101 << 3,
0b10101 << 3,
0b10001 << 3,
0b10001 << 3,
]
);
}
#[cfg(feature = "numbers")]
#[test]
fn matches_c_source_zero() {
// '0': 0b01110, 0b10001, 0b10101, 0b10001, 0b01110
assert_eq!(
DIGITS[0],
[
0b01110 << 3,
0b10001 << 3,
0b10101 << 3,
0b10001 << 3,
0b01110 << 3,
]
);
}
}