commit aa3d7a09ee5d0ee632676fbbabea8fcaf570b83d Author: James Martin Date: Mon Oct 26 18:45:44 2020 -0700 Make PSF code from bootproof into an independent library. diff --git a/.editorconfig b/.editorconfig new file mode 100644 index 0000000..e2139a6 --- /dev/null +++ b/.editorconfig @@ -0,0 +1,11 @@ +root = true + +[*] +charset = utf-8 +indent_style = space +indent_size = 4 +trim_trailing_whitespace = true +insert_final_newline = true + +[*.yml] +indent_size = 2 diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml new file mode 100644 index 0000000..a71c6ef --- /dev/null +++ b/.github/workflows/rust.yml @@ -0,0 +1,20 @@ +name: Rust + +on: [push] + +jobs: + build: + runs-on: ubuntu-latest + steps: + - name: Checkout sources + uses: actions/checkout@v2 + + - name: Install latest stable + uses: actions-rs/toolchain@v1 + with: + profile: minimal + toolchain: stable + override: true + + - name: build + run: cargo build diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..96ef6c0 --- /dev/null +++ b/.gitignore @@ -0,0 +1,2 @@ +/target +Cargo.lock diff --git a/Cargo.toml b/Cargo.toml new file mode 100644 index 0000000..db8e52c --- /dev/null +++ b/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "pc-screen-font" +version = "0.1.0" +authors = ["James Martin "] +edition = "2018" +repository = "https://github.com/jamestmartin/pc-screen-font" +license = "LGPL-3.0+" +publish = false + +[dependencies.num-integer] +version = "0.1.43" +default-features = false diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..0a04128 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,165 @@ + GNU LESSER GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + + This version of the GNU Lesser General Public License incorporates +the terms and conditions of version 3 of the GNU General Public +License, supplemented by the additional permissions listed below. + + 0. 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Combined Libraries. + + You may place library facilities that are a work based on the +Library side by side in a single library together with other library +facilities that are not Applications and are not covered by this +License, and convey such a combined library under terms of your +choice, if you do both of the following: + + a) Accompany the combined library with a copy of the same work based + on the Library, uncombined with any other library facilities, + conveyed under the terms of this License. + + b) Give prominent notice with the combined library that part of it + is a work based on the Library, and explaining where to find the + accompanying uncombined form of the same work. + + 6. Revised Versions of the GNU Lesser General Public License. + + The Free Software Foundation may publish revised and/or new versions +of the GNU Lesser General Public License from time to time. Such new +versions will be similar in spirit to the present version, but may +differ in detail to address new problems or concerns. + + Each version is given a distinguishing version number. If the +Library as you received it specifies that a certain numbered version +of the GNU Lesser General Public License "or any later version" +applies to it, you have the option of following the terms and +conditions either of that published version or of any later version +published by the Free Software Foundation. If the Library as you +received it does not specify a version number of the GNU Lesser +General Public License, you may choose any version of the GNU Lesser +General Public License ever published by the Free Software Foundation. + + If the Library as you received it specifies that a proxy can decide +whether future versions of the GNU Lesser General Public License shall +apply, that proxy's public statement of acceptance of any version is +permanent authorization for you to choose that version for the +Library. diff --git a/README.md b/README.md new file mode 100644 index 0000000..296bd87 --- /dev/null +++ b/README.md @@ -0,0 +1,21 @@ +# PC Screen Font +A Rust library which can parses PSF version 2 fonts from their bytes. +It correctly handles fonts which contain extra pixels in their padding bits. + +This library does not depend on the Rust standard library, +making it suitable for inclusion in bootloaders or kernels, +although it does require a working global allocator. + +This library predates [the PSF crate](https://crates.io/crates/psf). +I have not investigated it at all, but you may wish to investigate using it instead +before choosing to use this library. + +## Maintenance status +This library is only passively maintained, receiving updates as I need them. +I do not intend to publish this library to crates.io, but I will accept pull requests, +and if you wish to publish this library to crates.io and maintain it yourself, +you are welcome to do so. + +## Limitations +Currently, this library does not support multi-codepoint spellings of characters. +Support may be added at some point, but I do not currently have any plans to do so. diff --git a/src/lib.rs b/src/lib.rs new file mode 100644 index 0000000..f3b57ed --- /dev/null +++ b/src/lib.rs @@ -0,0 +1,160 @@ +#![no_std] +extern crate alloc; + +use alloc::vec::Vec; + +pub struct Font { + /// The width in pixels of this font's bounding box. + width: usize, + /// The height in pixels of this font's bounding box. + height: usize, + /// Every single glyph in the font. + glyphs: Vec, + // TODO: Replace this with a proper associative structure. + /// A map between unicode characters and indexes into the glyph vec. + unicode: Vec, +} + +/// Associates a unicode character and a glyph. +struct UnicodeMap { + c: char, + // The index of the glyph. + i: usize, +} + +pub struct Glyph { + /// A set bit indicates that a pixel should be drawn for this glyph. + bitmap: Vec, + /// The number of bytes in the bitmap taken up by each line of pixels in this glyph. + line_size: usize, + /// See the docs for `Glyph::width`. + width: usize, + /// See the docs for `Glyph::height`. + height: usize, +} + +impl Glyph { + /// The width in pixels of this individual glyph. + /// + /// Although each PSF has a nominal width in pixels, + /// the length of each line of pixels stored in bits is actually rounded to the next byte. + /// Some fonts actually use this storage to make glyphs which are slightly wider + /// than the nominal width of the font, because it makes the glyph look better. + /// For example, Cozette does this for the unicode heart glyph. + pub fn width(&self) -> usize { self.width } + /// The height in pixels of this glyph. This will always be the same as the height of the font. + pub fn height(&self) -> usize { self.height } + + /// Check whether an individual pixel of this glyph is set. + /// This will return `None` if `x` or `y` is outside the width or height of this glyph. + pub fn get(&self, x: usize, y: usize) -> Option { + if x > self.width || y > self.height { + return None + } + + let (line_byte_index, bit_index) = num_integer::div_rem(x, 8); + let mask = 0b10000000 >> bit_index; + let byte = self.bitmap[(y * self.line_size + line_byte_index) as usize]; + Some(byte & mask > 0) + } +} + +impl Font { + /// The width in pixels of this font's bounding box. + pub fn width(&self) -> usize { self.width } + /// The height in pixels of this font's bounding box. + pub fn height(&self) -> usize { self.height } + /// The width and height in pixels of this font's bounding box. + pub fn bounding_box(&self) -> (usize, usize) { + (self.width, self.height) + } + + /// Get the glyph associated with a particular unicode character, + /// or `None` if it is not present in this font. + pub fn lookup<'a>(&'a self, c: char) -> Option<&'a Glyph> { + self.index_of(c).map(|i| &self.glyphs[i]) + } + + /// The index of the glyph associated with a particular unicode character. + fn index_of(&self, c: char) -> Option { + for entry in &self.unicode { + if entry.c == c { + return Some(entry.i); + } + } + None + } + + /// Parse a version 2 PC screen font from its bytes. + pub fn parse(font: &[u8]) -> Font { + use core::convert::TryInto; + + // The number of glyphs in this font. + let length = u32::from_le_bytes(font[16..20].try_into().unwrap()) as usize; + // The size in bytes of a single glyph. + let charsize = u32::from_le_bytes(font[20..24].try_into().unwrap()) as usize; + // The height in pixels of this font's bounding box. + let height = u32::from_le_bytes(font[24..28].try_into().unwrap()) as usize; + // The width in pixels of this font's bounding box. + let width = u32::from_le_bytes(font[28..32].try_into().unwrap()) as usize; + // The size in bytes of a single row of pixels in a glyph. + let line_size = num_integer::div_ceil(width, 8); + + let glyphs_offset = 32; // the size of the header + let glyphs_size = length * charsize; + let unicode_offset = glyphs_offset + glyphs_size; + + let mut glyphs = Vec::with_capacity(length); + + for i in 0..length { + let mut bitmap = Vec::with_capacity(charsize); + let bitmap_begin = glyphs_offset + charsize * i; + let bitmap_end = bitmap_begin + charsize; + bitmap.extend_from_slice(&font[bitmap_begin..bitmap_end]); + + glyphs.push(Glyph { + bitmap, + line_size, + // Glyphs may overflow the font's nominal resolution in the padding bytes of the line! + // This trick only works for the width because there is no vertical padding. + // TODO: Pre-compute widths and bounding box offsets of individual glyphs. + width: line_size * 8, + height, + }); + } + + // HACK: This unicode map parser is still a mess. + let mut unicode_map = Vec::new(); + let unicode_info = &font[unicode_offset..]; + let mut glyph = 0; + let mut i = 0; + while i < unicode_info.len() { + let mut nc = unicode_info[i]; + + while nc != 0xFE && nc != 0xFF { + let ch_bytes = nc.leading_ones().max(1) as usize; + let st = core::str::from_utf8(&unicode_info[i..i + ch_bytes]).expect("Invalid character"); + let ch = st.chars().next().unwrap(); + unicode_map.push(UnicodeMap { c: ch, i: glyph }); + i += ch_bytes; + nc = unicode_info[i]; + } + + // TODO: Support multi-codepoint spellings of characters. + while nc != 0xFF { + i += 1; + nc = unicode_info[i]; + } + + i += 1; + glyph += 1; + } + + Font { + width, + height, + glyphs, + unicode: unicode_map, + } + } +}