| /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
| |
| /*** |
| This file is part of systemd. |
| |
| Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com> |
| |
| systemd is free software; you can redistribute it and/or modify it |
| under the terms of the GNU Lesser General Public License as published by |
| the Free Software Foundation; either version 2.1 of the License, or |
| (at your option) any later version. |
| |
| systemd is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with systemd; If not, see <http://www.gnu.org/licenses/>. |
| ***/ |
| |
| #pragma once |
| |
| #include <stdbool.h> |
| #include <stdint.h> |
| #include <stdlib.h> |
| #include "sparse-endian.h" |
| #include "util.h" |
| |
| typedef struct unifont_header unifont_header; |
| typedef struct unifont_glyph_header unifont_glyph_header; |
| |
| /* |
| * Unifont: On-disk data |
| * Conventional font-formats have the problem that you have to pre-render each |
| * glyph before you can use it. If you just need one glyph, you have to parse |
| * the font-file until you found that glyph. |
| * GNU-Unifont is a bitmap font with very good Unicode coverage. All glyphs are |
| * (n*8)x16 bitmaps. Our on-disk data stores all those glyphs pre-compiled with |
| * fixed offsets. Therefore, the font-file can be mmap()ed and all glyphs can |
| * be accessed in O(1) (because all glyphs have the same size and thus their |
| * offsets can be easily computed). This guarantees, that the kernel only loads |
| * the pages that are really accessed. Thus, we have a far lower overhead than |
| * traditional font-formats like BDF. Furthermore, the backing file is read-only |
| * and can be shared in memory between multiple users. |
| * |
| * The binary-format starts with a fixed header: |
| * |
| * | 2bytes | 2bytes | 2bytes | 2bytes | |
| * |
| * +-----------------------------------+ |
| * | SIGNATURE | 8 bytes |
| * +-----------------+-----------------+ |
| * | COMPAT FLAGS | INCOMPAT FLAGS | 8 bytes |
| * +-----------------+--------+--------+ |
| * | HEADER SIZE |GH-SIZE |G-STRIDE| 8 bytes |
| * +-----------------+--------+--------+ |
| * | GLYPH BODY SIZE | 8 bytes |
| * +-----------------------------------+ |
| * |
| * * The 8 bytes signature must be set to the ASCII string "DVDHRMUF". |
| * * The 4 bytes compatible-flags field contains flags for new features that |
| * might be added in the future and which are compatible to older parsers. |
| * * The 4 bytes incompatible-flags field contains flags for new features that |
| * might be added in the future and which are incompatible to old parses. |
| * Thus, if you encounter an unknown bit set, you must abort! |
| * * The 4 bytes header-size field contains the size of the header in bytes. It |
| * must be at least 32 (the size of this fixed header). If new features are |
| * added, it might be increased. It can also be used to add padding to the |
| * end of the header. |
| * * The 2 bytes glyph-header-size field specifies the size of each glyph |
| * header in bytes (see below). |
| * * The 2 bytes glyph-stride field specifies the stride of each line of glyph |
| * data in "bytes per line". |
| * * The 8 byte glyph-body-size field defines the size of each glyph body in |
| * bytes. |
| * |
| * After the header, the file can contain padding bytes, depending on the |
| * header-size field. Everything beyond the header+padding is treated as a big |
| * array of glyphs. Each glyph looks like this: |
| * |
| * | 1 byte | |
| * |
| * +-----------------------------------+ |
| * | WIDTH | 1 byte |
| * +-----------------------------------+ |
| * ~ PADDING ~ |
| * +-----------------------------------+ |
| * ~ ~ |
| * ~ ~ |
| * ~ DATA ~ |
| * ~ ~ |
| * ~ ~ |
| * +-----------------------------------+ |
| * |
| * * The first byte specifies the width of the glyph. If it is 0, the glyph |
| * must be treated as non-existant. |
| * All glyphs are "8*n" pixels wide and "16" pixels high. The width-field |
| * specifies the width multiplier "n". |
| * * After the width field padding might be added. This depends on the global |
| * glyph-header-size field. It defines the total size of each glyph-header. |
| * After the glyph-header+padding, the data-field starts. |
| * * The data-field contains a byte-array of bitmap data. The array is always |
| * as big as specified in the global glyph-body-size header field. This might |
| * include padding. |
| * The array contains all 16 lines of bitmap information for that glyph. The |
| * stride is given in the global glyph-stride header field. This can be used |
| * to add padding after each line. |
| * Each line is encoded as 1 bit per pixel bitmap. That is, each byte encodes |
| * data for 8 pixels (left most pixel is encoded in the LSB, right most pixel |
| * in the MSB). The width field defines the number of bytes valid per line. |
| * For width==1, you need 1 byte to encode the 8 pixels. The stride defines |
| * where the encoding of the next line starts. |
| * Any data beyond the 16th line is padding and must be ignored. |
| */ |
| |
| /* path to binary file */ |
| #define UNIFONT_PATH "/usr/share/systemd/unifont-glyph-array.bin" |
| |
| /* header-size of version 1 */ |
| #define UNIFONT_HEADER_SIZE_MIN 32 |
| |
| struct unifont_header { |
| /* fields available in version 1 */ |
| uint8_t signature[8]; |
| le32_t compatible_flags; |
| le32_t incompatible_flags; |
| le32_t header_size; |
| le16_t glyph_header_size; |
| le16_t glyph_stride; |
| le64_t glyph_body_size; |
| } _packed_; |
| |
| struct unifont_glyph_header { |
| /* fields available in version 1 */ |
| uint8_t width; |
| } _packed_; |