Lazarus
Home
Help
TinyPortal
Search
Login
Register
Lazarus
»
Forum
»
Free Pascal
»
Beginners
(Moderators:
FPK
,
Tomas Hajny
) »
Reading bytes from a specific address in a file
Free Pascal
Website
Downloads
Wiki
Documentation
Bugtracker
Mailing List
Lazarus
Website
Downloads (Laz+FPC)
Packages (OPM)
FAQ
Wiki
Documentation (RTL/FCL/LCL)
Bugtracker
CCR Bugs
IRC channel
GIT
Mailing List
Other languages
Foundation
Website
Useful Wiki Links
Project Roadmap
Getting the Source
Screenshots
How to use the forum
About donations (wiki)
Bookstore
Computer Math and Games in Pascal
(preview)
Lazarus Handbook
Search
Advanced search
Recent
what to do if my target M...
by
nickysn
[
Today
at 04:16:02 pm]
Parameter passing odditie...
by
KodeZwerg
[
Today
at 04:15:23 pm]
trunk compiler bug for mi...
by
nickysn
[
Today
at 04:03:44 pm]
Offical launch of the 1 B...
by
BeniBela
[
Today
at 03:52:05 pm]
compiler error in unit
by
paule32
[
Today
at 03:49:50 pm]
Xcode Command Line Tools ...
by
Martin_fr
[
Today
at 03:45:26 pm]
Compile/Convert Delphi pr...
by
Joseph
[
Today
at 02:43:45 pm]
how to tweek fpmake to co...
by
Key-Real
[
Today
at 02:33:27 pm]
Can function be used for ...
by
VisualLab
[
Today
at 02:15:30 pm]
Multithreading - synchron...
by
mika
[
Today
at 01:48:51 pm]
A fairly simple sound sol...
by
KodeZwerg
[
Today
at 01:48:26 pm]
May be useful to somebody
by
KodeZwerg
[
Today
at 12:38:22 pm]
match automatic highlight...
by
Чебурашка
[
Today
at 11:35:14 am]
Tchart with dual numbers ...
by
wp
[
Today
at 10:48:18 am]
Generics - correct syntax
by
VisualLab
[
Today
at 10:23:16 am]
add new targets to make
by
Key-Real
[
Today
at 09:38:23 am]
Debugger crashes with App...
by
Martin_fr
[
Today
at 09:29:46 am]
Copyrights Q
by
BrassGear
[
Today
at 09:13:14 am]
[SOLVED] how to build the...
by
Key-Real
[
Today
at 09:12:33 am]
Quirky windows
by
tetrastes
[
Today
at 08:59:06 am]
How can I draw a rectangl...
by
Handoko
[
Today
at 07:30:55 am]
Draw a line in the Scroll...
by
Handoko
[
Today
at 07:27:54 am]
web development using pas...
by
Nate897
[
Today
at 02:04:05 am]
questionable function def...
by
440bx
[
Today
at 01:35:28 am]
Why isn't TTIRadioGroup's...
by
jamie
[
Today
at 12:13:45 am]
« previous
next »
Print
Pages: [
1
]
Author
Topic: Reading bytes from a specific address in a file (Read 1716 times)
DumDum
New Member
Posts: 32
Reading bytes from a specific address in a file
«
on:
July 23, 2018, 12:14:49 pm »
Hi,
Wondering if there is a way to display specific bytes on the screen from a predesignated address in a binary file.
C
Logged
taazz
Hero Member
Posts: 5368
Re: Reading bytes from a specific address in a file
«
Reply #1 on:
July 23, 2018, 12:38:55 pm »
In general, yes there are a couple of ways. Here is one example using streams.
Code: Pascal
[Select]
[+]
[-]
function
ReadBytes
(
const
aFilename
:
string
;
aOffset
,
aCount
:
Int64
)
:
TByteArray
;
var
vFile
:
TFileStream
;
begin
vfile
:
=
TFileStream
.
Create
(
aFilename
,
fmOpenReadWrite
or
fmShareExclusive
)
;
try
SetLength
(
Result
,
aCount
)
;
vFile
.
Seek
(
aOffset
,
soFromBeginning
)
;
vFile
.
Read
(
Result
[
0
]
,
aCount
)
;
finally
vFile
.
Free
;
end
;
end
;
here is the same procedure using binary files.
Code: Pascal
[Select]
[+]
[-]
function
ReadBytes
(
const
aFilename
:
string
;
aOffset
,
aCount
:
Int64
)
:
TByteArray
;
var
vFile
:
File
;
begin
AssignFile
(
vFile
,
aFilename
)
;
Reset
(
vFile
,
1
)
;
try
SetLength
(
Result
,
aCount
)
;
Seek
(
vFile
,
aOffset
)
;
BlockRead
(
vFile
,
Result
[
0
]
,
aCount
)
;
finally
CloseFile
(
vFile
)
;
end
;
end
;
Logged
Good judgement is the result of experience … Experience is the result of bad judgement.
OS : Windows 7 64 bit
Laz: Lazarus 1.4.4 FPC 2.6.4 i386-win32-win32/win64
Bart
Hero Member
Posts: 5290
Re: Reading bytes from a specific address in a file
«
Reply #2 on:
July 23, 2018, 01:26:50 pm »
IIRC then blockread can only read chunks of size word (max 65536 bytes)?
At least that was the case in the old days.
Bart
Logged
taazz
Hero Member
Posts: 5368
Re: Reading bytes from a specific address in a file
«
Reply #3 on:
July 23, 2018, 01:31:55 pm »
lazarus 1.4.4 has an overloaded version of blockread with int64 see attachement.
Logged
Good judgement is the result of experience … Experience is the result of bad judgement.
OS : Windows 7 64 bit
Laz: Lazarus 1.4.4 FPC 2.6.4 i386-win32-win32/win64
Thaddy
Hero Member
Posts: 14377
Sensorship about opinions does not belong here.
Re: Reading bytes from a specific address in a file
«
Reply #4 on:
July 23, 2018, 01:54:54 pm »
And when you declare a File of record, you can read any - packed - record by its index.
Logged
Object Pascal programmers should get rid of their "component fetish" especially with the non-visuals.
Print
Pages: [
1
]
« previous
next »
Lazarus
»
Forum
»
Free Pascal
»
Beginners
(Moderators:
FPK
,
Tomas Hajny
) »
Reading bytes from a specific address in a file
TinyPortal
© 2005-2018