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The PSF file-format
(C) 1997 Yann Dirson <dirson@debian.org>
This file documents the PSF font-file-format, as understood by version 0.94
and above of the Linux console utilities ('kbd'). This file makes obsolete
the old `psffile.doc'.
This file has revision number 1.1, and is dated 1998/04/20.
Any useful additionnal information on PSF files would be great.
0. Changes:
1998/08/20: updated author's e-mail.
1998/08/20: History of the format from hpa himself.
1998/08/20: Fixed `filemode' description from hpa's input.
1. Summary
PSF stands for PC Screen Font.
A PSF file basically contains one character-font, whose width is 8 pixels,
ie. each scanline in a character occupies 1 byte.
It may contain characters of any height between 0 and 255, though character
heights lower than 8 or greater than 32 are not attested to exist or even be
useful [more info needed on this].
Fonts can contain either 256 or 512 characters.
The file can optionnally contain a unicode mapping-table, telling, for each
character in the font, which UCS2 characters it can be used to display.
The "file mode" byte controls font size (256/512) and whether file contains
a unicode mapping table.
2. History
The PSF file format was designed by H. Peter Anvin
<hpa@transmeta.com> in 1989 or so for his DOS screen font editor,
FONTEDIT.EXE. When he became involved with Linux, he used it for the
Linux font stuff he worked with, released a binary of FONTEDIT.EXE for
free distribution, and added the Unicode table to the spec.
3. Known programs understanding this file-format.
The following program in the Linux console utilities can read and/or write
PSF files:
setfont (R/W)
psfaddtable (R/W)
psfstriptable (R/W)
psfgettable (R)
4. Technical data
The file format is described here in sort-of EBNF notation. Upper-case
WORDS represent terminal symbols, ie. C types; lower-case words represent
non-terminal symbols, ie. symbols defined in terms of other symbols.
[sym] is an optional symbol
{sym} is a symbol that can be repeated 0 or more times
{sym}*N is a symbol that must be repeated N times
Comments are introduced with a # sign.
# The data (U_SHORT's) are stored in LITTLE_ENDIAN byte order.
psf_file = psf_header
raw_fontdata
[unicode_data]
psf_header = CHAR = 0x36 CHAR = 0x04 # magic number
filemode
fontheight
fontheight = CHAR # measured in scan lines
filemode = CHAR # 0 : 256 characters, no unicode_data
# 1 : 512 characters, no unicode_data
# 2 : 256 characters, with unicode_data
# 3 : 512 characters, with unicode_data
#
raw_fontdata = {char_data}*<fontsize>
char_data = {BYTE}*<fontheight>
#
unicode_data = { unicode_array psf_separator }*<fontsize>
unicode_array = { unicode } # any necessary number of times
unicode = U_SHORT # UCS2 code
psf_separator = unicode = 0xFFFF