Powered by ViewCVS 1.0-dev
| 1 : | dvdkhlng | 1.1 | \ Rewritten and improved bitmask code |
| 2 : | |||
| 3 : | \ Author: David Kühling <dvdkhlng AT gmx DOT de> | ||
| 4 : | \ Created: May 2010 | ||
| 5 : | |||
| 6 : | \ Copyright (C) 2010 Free Software Foundation, Inc. | ||
| 7 : | |||
| 8 : | \ This file is part of Gforth. | ||
| 9 : | |||
| 10 : | \ Gforth is free software; you can redistribute it and/or | ||
| 11 : | \ modify it under the terms of the GNU General Public License | ||
| 12 : | \ as published by the Free Software Foundation, either version 3 | ||
| 13 : | \ of the License, or (at your option) any later version. | ||
| 14 : | |||
| 15 : | \ This program is distributed in the hope that it will be useful, | ||
| 16 : | \ but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 17 : | \ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| 18 : | \ GNU General Public License for more details. | ||
| 19 : | |||
| 20 : | \ You should have received a copy of the GNU General Public License | ||
| 21 : | \ along with this program. If not, see http://www.gnu.org/licenses/. | ||
| 22 : | |||
| 23 : | : bitset? ( x #bit -- flag ) \ get value of single bit in cell x | ||
| 24 : | rshift 1 and ; | ||
| 25 : | : setbit ( x1 0|1 #bit -- x2 ) \ set value of single bit in cell x | ||
| 26 : | 1 over lshift invert -rot \ mask for deleting bit | ||
| 27 : | lshift \ mask for optionally setting bit | ||
| 28 : | -rot and or ; \ first delete then optionally set bit | ||
| 29 : | : (bits/cell) ( -- +n ) \ measure number of bits per cell | ||
| 30 : | 1 1 begin 1 lshift dup while | ||
| 31 : | swap 1+ swap | ||
| 32 : | repeat drop ; | ||
| 33 : | (bits/cell) CONSTANT bits/cell | ||
| 34 : | |||
| 35 : | : dispense ( x1-val x2-mask -- x3-masked ) | ||
| 36 : | \ encode val into the bits given by mask. bits in mask can be spread out | ||
| 37 : | \ as much as you like. for signed values 'val', first apply 'narrow' below | ||
| 38 : | bits/cell 0 do \ iterate over bits in mask | ||
| 39 : | dup i bitset? if \ if mask bit set: | ||
| 40 : | over 1 and i setbit \ replace bit in mask by val's bit | ||
| 41 : | swap 1 rshift swap \ and remove bit from val | ||
| 42 : | then | ||
| 43 : | loop | ||
| 44 : | swap 0<> ABORT" dispense: value does not fit into masked bits" ; | ||
| 45 : | : embed ( x1-accu x2-val x3-mask -- x4-result ) | ||
| 46 : | \ encode 'val' into bits set given by mask, replacing corresponding bits in | ||
| 47 : | \ 'accu' | ||
| 48 : | dup >r dispense \ dispense value over masked bits | ||
| 49 : | swap r> invert and \ delete corresponding bits in accu | ||
| 50 : | or ; \ and add dispensed bits | ||
| 51 : | |||
| 52 : | : mask ( +n -- mask ) \ get bitmask for lowest #n bits | ||
| 53 : | 0 invert swap lshift invert ; | ||
| 54 : | : narrow ( n1 n2 -- x ) \ limit signed value to n2 bits | ||
| 55 : | \ note: assumes 2-complement number n1 and 2-complement host | ||
| 56 : | 2dup mask and -rot \ compute masked value, | ||
| 57 : | 1- \ but before returning, check whether no bits lost | ||
| 58 : | -1 over lshift ( lower bund) | ||
| 59 : | 1 rot lshift ( upper bound) | ||
| 60 : | within 0= ABORT" narrow: signed value out of range" ; | ||
| 61 : | |||
| 62 : | : maskinto ( "x-mask" -- runtime: x1-val x1-accu -- x2-masked ) | ||
| 63 : | \ for backwards compatability with old bitmask code | ||
| 64 : | ]] swap [[ parse-word s>number drop ]]L embed [[ ; IMMEDIATE |
|
CVS Admin Powered by ViewCVS 1.0-dev |
ViewCVS and CVS Help |