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1987-11-25
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FASTBUFF v2.0
Do-It-All Keyboard Enhancer
David Steiner
November 1987
The only thing you really need to know in order to use
FASTBUFF is that to install it you type FASTBUFF and hit the
ENTER key. To see the results just hold down a key and
watch how fast it goes. If you run into problems with a
program that doesn't like FASTBUFF then you may want to look
over this documentation a little closer.
Even if you're not entirely sure you like the idea of such a
keyboard enhancement program, at least give FASTBUFF a trial
run. After all, its a free program. You will quite likely
find it frustrating to go back to the normal repeat rate and
buffer size.
Version 2.0 is a fairly large improvement over version 1.0,
even though this one has been released fairly quickly after
the first. The only bug fix was related to typing in
characters via the numeric keypad. It seems that the repeat
function always ended up set, and wouldn't stop till you hit
another key.
REQUIREMENTS
FASTBUFF was written on an IBM XT compatible computer. It
should work with true IBM PC's just fine. I've also tested
it on AT compatibles, and it seems to work fine. The video
blanking works fine for CGA and monochrome systems, but not
EGA. I doubt it will work for other video cards either.
I'll try to provide support for them at a later date when I
have time. If you don't have a video card that is
supported, it is best to disable this function.
As far as memory is concerned, FASTBUFF only eats up 1500
bytes when its using a 100 character buffer. Even if you
set the buffer as large as it will go (269 characters)
FASTBUFF still only take up about 1800 bytes.
As usual, there are some restrictions on what order you load
FASTBUFF. Although it is a well-behaved resident program
you still get the best results if you load it early. This
has to do with who "hooks" which vectors and will be
discussed below in more detail. Some programs, however, are
very low-level and should be loaded before FASTBUFF. Such
programs include the keyboard drivers supplied with MS-DOS
(KEYxx.COM).
FEATURES
Variable Size Keyboard Buffer:
FASTBUFF takes control of the keystroke interrupt in
order to allow you to set the size of buffer you like.
The default is 100 characters, but may range from 25 to
269 characters.
Increased Key Repeat Rate:
By using the timer interrupt we are able to modify how
fast keys are repeated. When FASTBUFF is activated you
may select between a repeat rate of 18 or 36 characters
per second. Unlike most key quickeners that I've seen,
FASTBUFF has a fairly smooth repeat rate even in its
fast mode. Note that you may also select the normal
repeat rate by turning FASTBUFF off.
Anti-skid Braking:
Given a large buffer and fast repeat rate you could get
way ahead of your application when holding a key down.
FASTBUFF uses a simple but effective method of
preventing this: it doesn't put repeated characters
into the buffer until the application program is ready
(i.e. the buffer is empty).
Screen Blanking:
If you leave your computer unattended for over fifteen
minutes FASTBUFF will automatically blank the video
screen in order to avoid "burning" characters into the
display screen. The screen may be restored by pressing
any key.
Repeat Characters Entered Through the Alt-Keypad:
The IBM will allow you to enter characters by holding
the ALT key down and typing the ASCII character number
on the numeric keypad. When you release the ALT key
the character is inserted at the cursor position.
FASTBUFF also provides a method of repeating the key
entered this way.
Enter Graphics Characters With the Alt-Keypad:
Some of us poor folks with IBM compatibles have a BIOS
that gets confused when entering graphics characters
via the keypad (character numbers over 127). FASTBUFF
takes control of this function and returns these
characters correctly. This fix also pertains to
compatibles that do not return the normal scan code (0)
for these characters.
Disable FASTBUFF:
It is possible that you may need to use a program that
doesn't seem to like FASTBUFF. To account for this
possibility you may turn off the FASTBUFF functions in
order to use these programs. After leaving the
conflicting application, you may re-enable FASTBUFF
again.
RUN-TIME CONTROL KEYS
While FASTBUFF is resident you have several options for the
way it controls your keyboard. First we'll cover the option
for clearing the FASTBUFF keyboard buffer:
ALT-RIGHT SHIFT: Clear the keyboard buffer
You may clear the typeahead buffer by pressing the ALT
and RIGHT SHIFT keys simultaneously. This clears
anything in the buffer, even if you've already hit the
ENTER key. This function is not active when FASTBUFF
is turned off.
The rest of the keys are entered by pressing keys while
holding down the FASTBUFF command key. This key has been
chosen to be the "5" key located on your numeric keypad, in
an effort to clash with as few other resident programs as
possible. I will denote this key as [5] from here on out.
You must also note that this key is distinct from the "5"
key located in the top row of the keyboard.
[5]-MINUS: Set repeat rate slow
By pressing the [5] and the "-" key located right next
to it you may set FASTBUFF to use its slower repeat
rate (18 characters per second). Note that this is
still somewhat faster than the normal repeat rate.
Most of the time this mode will also produce a
"smoother" repeat.
[5]-PLUS: Set repeat rate fast
The default setting for FASTBUFF is the fast repeat
rate (36 characters per second). However, this is too
fast for some applications, so you may switch between
the fast and slow modes to suit your needs.
[5]-DEL: Turn off FASTBUFF
This version of FASTBUFF has been rewritten to conflict
with as few other programs as possible. You shouldn't
find too many programs that will require you to turn
FASTBUFF off. On the other hand, you may occasionally
wish to reduce the keyboard buffer and repeat rates to
the normal values and this switch allows you to do just
that.
[5]-INS: Turn FASTBUFF back on
If you've turned off FASTBUFF, you can re-enable it by
pressing these keys simultaneously.
COMMAND LINE SETUP PARAMETERS
I've tried to set the defaults for FASTBUFF the way most
people will like them. However, if there is something you
would like different there are a few startup values you may
change. To do this you may enter setup codes on the command
line after the file name. For example:
FASTBUFF /b255/v0/d9/s <ENTER>
would set the buffer to 255 characters, the video blanking
off, the character repeat delay to about a half second and
the repeat rate to 18 characters per second (FASTBUFF's slow
repeat).
Each parameter consists of a slash "/", the parameter letter
and finally a number, if one is required. These may be
entered in any order, and even repeated. When a parameter
is repeated the rightmost one takes precedence.
FASTBUFF will not be installed if an invalid parameter is
entered, instead you will get a help screen. You may get
this help screen at any time by typing:
FASTBUFF ? <ENTER>
The help screen provides information on both the command
line parameters and the run-time command keys.
PARAMETER DESCRIPTIONS
/Bn : Set buffer size
If you can actually type fast enough to fill the
default buffer you may wish to select a larger one by
using this parameter. Valid sizes are from 25 to 269.
Note that FASTBUFF will accept numbers larger than 269,
but the value actually used will be seemingly random.
/Vn : Set screen blanking delay
The amount of time FASTBUFF will wait for some form of
input or screen I/O before blanking the screen may be
set with this parameter. Valid numbers range from 0 to
60 minutes. Again, larger numbers may be entered, but
will produce delay times ranging from 1 to 60 minutes
anyway. Setting the blanking delay to zero will
disable it.
The video blanking has been tested with CGA, monochrome
(Hercules also) and EGA cards. It works fine with all
except the EGA. If you have this type of video card,
or others not listed, it is suggested that you disable
screen blanking just to be safe. When I get some time
and some more references I'll put together another
version that supports other cards.
/Dn : Set repeat delay
This parameter sets the amount of time (in timer
clicks) a key must be held before it is repeated. The
default setting is 5 clicks, which translates to about
a quarter of a second. I believe the BIOS repeat delay
is somewhere around 9 (a half second) and you may
prefer that delay.
/F : Select fast repeat rate
Actually, there isn't really any reason for this option
since the default setting is fast. I included it
mostly for consistency. The fast repeat rate is 36
characters per second.
/S : Select slow repeat rate
This parameter sets the repeat rate to FASTBUFF's
slower rate, 18 characters per second. The BIOS repeat
rate seems to be about 9 char/second, so FASTBUFF is
still quick, even in its slow mode. Note that setting
the fast or slow repeat rate only affects the startup
mode, the repeat rate may still be switched at any time
by using the run-time commands listed above.
SPECIFICS
Now we will start getting a little more specific about what
each of these functions do. This may (or may not) be
helpful for those of you mucking about in the source code.
HOOKS
If you've had your computer for long, you've probably
already heard too much about hooking vectors and related
quirks of the IBM. Sorry, but FASTBUFF is something of a
"system" program rather than an "application" and hooking is
a requirement (wipe that smirk off your face).
In order to get all of the FASTBUFF features we only had to
hook into three interrupt vectors, although we considered a
few others. Here is a list of the vectors and why we use
(or didn't use) them:
09H : Keystroke
We had to take over this vector in order to steal
characters from the BIOS input buffer and put them into
ours as they were typed. Well, as long as we've taken
over the keystroke interrupt why not make our control
key something that isn't likely to conflict with other
programs (like the five on the numeric keypad).
Hey, we can fix that silly bug with our BIOS that won't
let us enter graphics characters on the keypad too.
(16H : Keyboard I/O)
Well, now we need to be able to get those characters
back out of our new buffer, since we've stolen them
from the BIOS. We could take over this interrupt and
return characters from our buffer whenever the system
asks for keyboard input, but it turns out that this
isn't a good idea.
The problem is that there are just too many programs
that access the BIOS keyboard buffer directly, without
consulting the system. Another, less obvious problem,
is that if we completely take over parts of this
interrupt, we don't pass control on to the next program
that hooked this vector. This is becomes a problem
when such programs are loaded before FASTBUFF.
If you've already seen FASTBUFF v1.0 you know that this
was the original design. Version 2.0 uses the method
described under interrupts 08 and 1C, and is much less
likely to cause problems with other programs.
(08H : Hardware Timer Interrupt)
Lets see... If we don't use interrupt 16 to return
characters, what are we going to do? Well lets try
checking once in a while to see if the normal BIOS
buffer is full and if not insert characters from our
buffer into the BIOS buffer. The only reliable way to
do this is to hook into the timer click interrupt.
This allows us to perform this check 18.2 times per
second (how often this interrupt is generated by the
system).
Well, we have the right notion, but we really shouldn't
use the hardware interrupt for this. The problem is
that the system performs important actions every time
this interrupt is issued, and if we take control first
we will slow down its response. The "proper" method
uses the next interrupt.
1CH : Get Control on Timer Tick
This interrupt was provided by the system to allow
actions of just the type we want. If we're careful we
can insert our code and pass control on to other
programs that hook this vector with no problems.
Now, we already know that we are going to be using this
interrupt to update the BIOS buffer, so as long as
we're here let's add another function that has a
reasonable low overhead.
Lets set up a counter to keep track of how long its
been since the last screen I/O operation was performed.
If the computer sits unattended for too long we can
then blank the screen to avoid damaging the monitor.
To do this right we'll have to reset the counter every
time a key is pressed or something is written to the
screen, which means we'll have to hook one more vector.
10H : Video I/O
To reset our screen blanking cursor when a key is
pressed is no problem, we can just insert a few lines
of code in our interrupt 9 handler. However to detect
if something is written to the screen we must take over
this interrupt. When a program is accessing the video
in the "proper" way it will use this function interrupt
to make changes to the screen. Therefore we should
reset our screen blanking counter whenever this
interrupt is used.
Again, there are some problems. For example, many
programs write to the screen directly and never bother
the system with an interrupt 10 call. For the video
blanking this really isn't very serious since the worst
that could happen is that the screen gets blanked when
there really is some activity. All the user will have
to do is type any key and the screen will be restored
by our interrupt 9 reset function.
Finally, we decide to add one more frill. We'll give
FASTBUFF some way to indicate that it is present if
someone asks nicely. This will enable us to detect if
FASTBUFF is present when the program is executed and
abort the installation in order to avoid having two
copies in memory.
We will add this feature as part of our interrupt 10
handler for two reasons. The reason for choosing an
interrupt to perform this function is that we don't
know where in memory a previous copy of FASTBUFF might
be located, so we need this alternate method for
detecting it. We choose interrupt 10 to perform this
function since it is the only one we have hooked that
normally accepts input parameters and returns output.
Note that in the above list the interrupt vectors listed in
parenthesis are not actually used by FASTBUFF, they are
listed only as alternative considerations.
Well that list should give you a feel for how FASTBUFF
works. Of course, I didn't actually design it in that
manner, I used a much more professional approach (I wrote
version 1.0 and started discovering bugs a couple of days
later).
THE SOURCE CODE
In this section I'll go over what each interrupt handler in
the source code does, in a general manner. I won't cover
the initialization code, other than detecting if FASTBUFF is
installed, since that stuff is small potatoes.
If you don't fully understand interrupt vectors yet, there
isn't much I can help you with here. There are entire books
written on the subject.
INT 9 - KEYSTROKE
The first thing I should note here is how and when this
interrupt is called. This interrupt is issued every time a
key is pressed or released. The keyboard returns the scan
code (a byte) through one of the input ports to let the
computer know which key it was.
The scan codes that have meaning to us are defined in the
equates set in the first section of the source code. These
codes are for the "make" signals, or when the key is
depressed. The "break" code, or when the key is released,
can be calculated by setting the high bit of the make code
(code+80H).
Another note is that FASTBUFF keeps all of its status
information in a single byte. We use the bits in this byte
(switches) to indicate certain conditions in FASTBUFF. The
bits will be accessed by anding and oring the status byte
with masks that we set in the equates section of the code.
Setup:
When we enter this interrupt there are a few things we
must do along the lines of resetting FASTBUFF. The
first such item is turning off our repeat switch bit
(repmask). This is done so FASTBUFF won't continue to
repeat a character after another key is pressed.
Next we set the ES register so we can use it to access
the BIOS data used by the rest of the system. After
doing this we reset the BIOS break detection bit. We
do this so we can test it again after the old interrupt
9 call in order to see if we need to clear our buffers.
Video counter:
The next item we should take care of is resetting our
video blanking counter. If this interrupt is called
the user must have typed some key, so we should start
the blanking countdown again.
A related check is to see if the video is currently
shut off. If the user was gone for a while and the
screen was shut off we now need to turn it back on
since they are obviously back.
Command Key Check:
Next we need to see if the command key is currently
pressed. We keep track of this by setting a bit
(ctrlmodemask) in our FASTBUFF status byte when the [5]
key is pressed. We leave this bit set until we receive
the scan code indicating that the [5] key was released.
If the command mode bit is set we then need to see if
second key in a control key combination was pressed.
If one of the two combinations were pressed for turning
FASTBUFF on or off then we need to set the appropriate
bit in our status byte (fbmask). If FASTBUFF is turned
on or off we need to clear our keyboard buffer just to
be certain there aren't any problems caused by the
switch.
Note that even when we intercept these command keys
that we still pass control on to the old interrupt
handler, even though we ignore any characters it may
have tried to put in the BIOS buffer. This pass is
done to minimize the possibility of FASTBUFF clobbering
another resident program.
Next, if FASTBUFF is on, we need to check for the key
combinations that are used to set the key repeat speed.
We don't perform this check when FASTBUFF is off, again
to minimize clashing with other resident utilities.
FASTBUFF on/off:
At this point we have taken care of all the required
resettings and checks so we may finally check if
FASTBUFF is active. If FASTBUFF is currently turned
off we may safely make the call to the old interrupt 9
handler and exit the interrupt call.
First Alt-Key Break Check:
One of the things FASTBUFF is supposed to do is take
care of the Alt-keypad entries and make sure they are
returned in the standard IBM BIOS format. The first
step in this direction is to watch for the scan code
that indicates that the ALT key was released.
If this code is detected we will steal a copy of the
character number created by the BIOS. This character
is stored in a byte in the BIOS data area
(BIOSaltbuff). We need to store it now since it will
be zeroed when the call to the old interrupt 9 handler.
Check for Clear Key Combination:
Another control-type key we need to check for is the
CTRL-RIGHT SHIFT clear buffer combination. If this key
is detected (while FASTBUFF is active) we need to clear
out the buffer.
Call Old Interrupt Handler:
If we make it this far without encountering a control
key we finally call the old keystroke interrupt
handler. We are doing this for two reasons: its a good
idea to pass control on to the old one and there is no
reason to duplicate the BIOS code that translates the
keyboard scan codes into ASCII characters.
Something that I'll cover in more detail later is the
reason for setting a bit in our status byte that
indicates we are calling the old interrupt 9 handler.
After calling the old BIOS handler we can tell if a
character was entered by whether or not the BIOS tail
pointer has moved. After storing this character and
checking for a new character we restore the old value
of the BIOS tail pointer. This effectively removes the
character from the BIOS buffer.
CTRL-BREAK Check:
We now need to check the CTRL-BREAK bit again to see if
that key combination was pressed. If so we have to
clear the buffers and output a dummy character. The
dummy character is done to emulate the way the normal
BIOS returns a CTRL-BREAK sequence.
New Character Detected:
If a new character was input we need to remove it from
the BIOS keyboard buffer and insert into ours. Before
we insert the character we want to check again to see
if it was entered via the keypad. If so we must first
fix the character code to be inserted.
The fix for these characters simply consists of
retrieving the character we saved earlier and forcing
it into the standard format. The standard format is
just the ASCII code in the low byte and a zero in the
high byte. If your system already does this correctly,
then the fix doesn't hurt anything anyway.
The actual insertion of the character into our buffer
will be covered in the next section.
PUT CHARACTER INTO OUR BUFFER
Last Character:
This check is done to make sure that the character just
just entered did not come from the standard BIOS repeat
function. If the character input matches the last one
typed it may be assumed that the scan code came from
the standard repeat and we will ignore it. The
character is ignored in order to avoid a repeat speed
that looks jerky.
Note that we may assume that a character that matches
the lastchar value is from the standard repeat since we
would see the break scan code if the key was released.
Repeat Delay:
There are two variables that must be set for use later
by the repeat function. The first is the one mentioned
above. We need to keep track of the last character
entered for use by the repeat function. Since this is
a new character we set the counter for the repeat delay
to its starting value.
Increment Tail Pointer:
The next step is to increment the tail pointer on our
buffer. If this incremented value matches the head
pointer then the buffer is full and we need to beep to
tell the user.
Turn the repeat function on:
Since we detected a new typeable character we need to
turn the repeat function back on. This tells the
interrupt 1C handler to repeat the character when it is
called later.
There is another modification that FASTBUFF makes to
the character repeat function. If the character was
entered through the keypad its scan code will be zero.
If this is true and the user is currently holding down
the LEFT SHIFT key we will allow the character to
repeat until the LEFT SHIFT is released.
INT 10 - VIDEO I/O
Reset Blanking Counter:
The first thing to do is reset the screen blanking
cursor. If the program performs any video output then
we assume that the counter should be reset.
Check if Video Disabled:
After resetting the counter we still need to make sure
the video is still on. If it was disabled earlier the
video active bit will have been cleared to let us know
that we need to restore it.
Function FAH:
A final addition to this interrupt will be a way for
FASTBUFF to indicate that it is resident. This will
allow us to avoid loading two copies of FASTBUFF.
All we need to do to implement this is to check if the
AH register contains FAH. If it does we will return
00FAH in the entire AX register to let the calling
program know we're resident.
Unless there is some other application resident that
doesn't behave properly this shouldn't cause a problem.
The BIOS will normally ignore any function request it
doesn't recognize. The likelihood of some other
resident program using function request FAH is pretty
low.
INT 1C - TIMER TICK
Check if FASTBUFF is on:
The first thing for this interrupt handler is to make
sure FASTBUFF is currently active. If it isn't active
then we aren't supposed to be doing anything here.
Decrement Blanking Counter:
If the program is active then we need to decrement the
counter that lets us know when the screen is to be
blanked.
Video Blanking Check:
When the counter reaches zero we still have to make
sure that the video blanking option is enabled. If the
screen is supposed to be blanked then we call the
routine that does this and clear the bit that indicates
the screen is active.
Update BIOS Buffer:
As mentioned earlier we aren't using the keyboard i/o
interrupt to return characters to the system. We chose
this method to improve compatibility with other
programs.
The updateBIOS procedure will be covered in the next
section, but for now we should note the check with the
oldint9mask. This check is done to make sure we aren't
currently making a call to the old interrupt 9 handler.
If we were to try to add characters while BIOS is
trying to take them out we will occasionally lose a
character or two. We set our own flag for this because
the interrupt flag will be reset from within the old
int 9 handler if we try to use the CLI instruction.
Repeating Keys:
If the repeat bit is still set from the interrupt 9
call above then we need to repeat the character stored
as the lastchar. This procedure will be described
below.
UPDATEBIOS
This method is used to increase compatibility with other
programs that may do low-level keyboard i/o. Using this
method we are always transferring characters into the BIOS
buffer and letting the system to the retrieval for us. This
also allows other programs to access the BIOS buffer
directly in order to get input.
Check FASTBUFF Buffer:
Of course the first step in copying characters from our
buffer to the BIOS buffer is to make sure we have
something to insert.
Transfer to BIOS:
If there are characters to copy then we move as many as
we can into the BIOS buffer. We must, however, keep in
mind that the old BIOS keystroke handler expects to put
input characters into its buffer. For this reason we
must keep an extra space open for its use when we do
the update, otherwise the BIOS routine will just beep
at us when we call it.
Minimum Buffer Size:
Now that you know how this works I can explain why the
minimum buffer size is set at 25. In order to avoid a
lot of special cases we need to make the minimum at
least 15 (14 from the BIOS and 1 in our buffer).
However, since we need to occasionally expand our
buffer before the BIOS update this is not a good idea,
FASTBUFF would then beep if only two characters were
received in quick succession.
The minimum of 25 allows 14 characters of BIOS storage
and 16 in ours. It is nearly impossible to type
characters fast enough to fill our buffer before we get
a chance to transfer some of them to the BIOS buffer.
REPEATING KEYS
Set Repeat Rate:
The first thing that must be done after we deciding to
repeat a key is to reset the repeat count to 1. This
allows us to check for a repeat on the next tick again.
Back in the character input routines we set the repeat
count to the starting delay, which defaults to 5
clicks.
Anti-Skid Check:
FASTBUFF uses a very simple check to make sure it is
not going too fast for the application being used. It
just checks the BIOS buffer, and if its empty then we
repeat the character, if not we can just wait till the
next click and check again.
Since we just checked to make sure the buffer was
empty, and the minimum buffer size is 25 we know there
won't be any problems with filling the buffer either.
This allows us to repeat the character without
bothering to check if the buffer overflows.
Repeating the Key:
Next we retrieve the character to be repeated and put 1
(slow repeat) or 2 (fast) copies of it into the BIOS
buffer. Note that we must insert more than one
character per click to achieve repeat rates faster than
18 characters per second.
INITIALIZATION
As mentioned above, all I am going to cover here is the
check to see if FASTBUFF is already installed. The method
was described above anyway, but I'll mention it again just
for the heck of it.
Since we don't know where in memory FASTBUFF will be
installed we need some way other than just looking for a
certain string we may have placed in the code. One approach
using this method would be to use the DOS call to get the
interrupt address for one of the vectors FASTBUFF hooks and
then look for such a search string assuming that was the
code segment for a previously installed FASTBUFF. The
problem with this is that there may be another application
installed later that that hooks that vector also.
Instead we will allow our interrupt 10 handler an extra
function. When we send an function FAH request, FASTBUFF
will send back 00FAH in the AX register. If we don't get
this code we should be able to assume that FASTBUFF is not
already present on the system.
Another note on the initialization process is that we don't
enable FASTBUFF until well after we have initialized its
variables and hooked all the required vectors. This is done
to prevent someone from typing ahead during the FASTBUFF
initialization and only having part of the required routines
to handle the input.
Finally we print the initialization message well before
hooking any vectors or enabling FASTBUFF. This is because
we are using a DOS call to write out output to the screen
and the user can hit CTRL-BREAK during this message and halt
the program. If this were done after the vectors are hooked
and before FASTBUFF terminates and remains resident the
system will hang as soon as the next program is run, since
the interrupt handlers will be overwritten at that time.
BYE
Well I hope someone finds this program useful. Sorry I get
write such long documentation, but I get started and then
hate to leave anything out.
If you find any bugs, or have any additional information you
think I'll find useful please let me know:
David Steiner
[D.STEINER] on GEnie
2035 J Apt.6
Lincoln, NE 68510
