Fixed length records
You are encouraged to solve this task according to the task description, using any language you may know.
Fixed length read/write
Before terminals, computers commonly used punch card readers or paper tape input.
A common format before these devices were superseded by terminal technology was based on the Hollerith code, Hollerith code.
These input devices handled 80 columns per card and had a limited character set, encoded by punching holes in one or more rows of the card for each column.
These devices assumed/demanded a fixed line width of 80 characters, newlines were not required (and could not even be encoded in some systems).
- Task
Write a program to read 80 column fixed length records (no newline terminators (but newline characters allowed in the data)) and then write out the reverse of each line as fixed length 80 column records.
Samples here use printable characters, but that is not a given with fixed length data. Filenames used are sample.txt, infile.dat, outfile.dat.
Note: There are no newlines, inputs and outputs are fixed at 80 columns, no more, no less, space padded. Fixed length data is 8 bit complete. NUL bytes of zero are allowed.
These fixed length formats are still in wide use on mainframes, with JCL and with COBOL (which commonly use EBCDIC encoding and not ASCII). Most of the large players in day to day financial transactions know all about fixed length records and the expression logical record length.
- Sample data
To create the sample input file, use an editor that supports fixed length records or use a conversion utility. For instance, most GNU/Linux versions of dd support blocking and unblocking records with a conversion byte size.
Line 1...1.........2.........3.........4.........5.........6.........7.........8
Line 2
Line 3
Line 4
Line 6
Line 7
Indented line 8............................................................
Line 9 RT MARGIN
prompt$ dd if=sample.txt of=infile.dat cbs=80 conv=block
will create a fixed length record file of 80 bytes given newline delimited text input.
prompt$ dd if=infile.dat cbs=80 conv=unblock
will display a file with 80 byte logical record lengths to standard out as standard text with newlines.
- Bonus round
Forth systems often include BLOCK words. A block is 1024 bytes. Source code is stored as 16 lines of 64 characters each (again, no newline character or sequence to mark the end of a line).
Write a program to convert a block file to text (using newlines). Trailing spaces should be excluded from the output.
Also demonstrate how to convert from a normal text file to block form. All lines either truncated or padded to 64 characters with no newline terminators. The last block filled to be exactly 1024 characters by adding blanks if needed. Assume a full range of 8 bit byte values for each character.
The COBOL example uses forth.txt and forth.blk filenames.
Ada
Ada string type is a fixed-length string.
with Ada.Text_IO; use Ada.Text_IO;
procedure Main is
subtype Block is String (1 .. 80);
Infile_Name : String := "infile.dat";
outfile_Name : String := "outfile.dat";
Infile : File_Type;
outfile : File_Type;
Line : Block := (Others => ' ');
begin
Open (File => Infile, Mode => In_File, Name => Infile_Name);
Create (File => outfile, Mode => Out_File, Name => outfile_Name);
Put_Line("Input data:");
New_Line;
while not End_Of_File (Infile) loop
Get (File => Infile, Item => Line);
Put(Line);
New_Line;
for I in reverse Line'Range loop
Put (File => outfile, Item => Line (I));
end loop;
end loop;
Close (Infile);
Close (outfile);
Open(File => infile,
Mode => In_File,
Name => outfile_name);
New_Line;
Put_Line("Output data:");
New_Line;
while not End_Of_File(Infile) loop
Get(File => Infile,
Item => Line);
Put(Line);
New_Line;
end loop;
end Main;
- Output:
Input data:
Line 1...1.........2.........3.........4.........5.........6.........7.........8
Line 2
Line 3
Line 4
Line 6
Line 7
Indented line 8............................................................
Line 9 RT MARGIN
Output data:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
AWK
# syntax: GAWK -f FIXED_LENGTH_RECORDS.AWK
BEGIN {
vlr_fn = "FIXED_LENGTH_RECORDS.TXT"
flr_fn = "FIXED_LENGTH_RECORDS.TMP"
print("bef:")
while (getline rec <vlr_fn > 0) { # read variable length records
printf("%-80.80s",rec) >flr_fn # write fixed length records without CR/LF
printf("%s\n",rec)
}
close(vlr_fn)
close(flr_fn)
print("aft:")
getline rec <flr_fn # read entire file
while (length(rec) > 0) {
printf("%s\n",revstr(substr(rec,1,80),80))
rec = substr(rec,81)
}
exit(0)
}
function revstr(str,start) {
if (start == 0) {
return("")
}
return( substr(str,start,1) revstr(str,start-1) )
}
- Output:
bef:
Line 1...1.........2.........3.........4.........5.........6.........7.........8
Line 2
Line 3
Line 4
Line 6
Line 7
Indented line 8............................................................
Line 9 RT MARGIN
aft:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
C++
#include <algorithm>
#include <cstdlib>
#include <fstream>
#include <iostream>
void reverse(std::istream& in, std::ostream& out) {
constexpr size_t record_length = 80;
char record[record_length];
while (in.read(record, record_length)) {
std::reverse(std::begin(record), std::end(record));
out.write(record, record_length);
}
out.flush();
}
int main(int argc, char** argv) {
std::ifstream in("infile.dat", std::ios_base::binary);
if (!in) {
std::cerr << "Cannot open input file\n";
return EXIT_FAILURE;
}
std::ofstream out("outfile.dat", std::ios_base::binary);
if (!out) {
std::cerr << "Cannot open output file\n";
return EXIT_FAILURE;
}
try {
in.exceptions(std::ios_base::badbit);
out.exceptions(std::ios_base::badbit);
reverse(in, out);
} catch (const std::exception& ex) {
std::cerr << "I/O error: " << ex.what() << '\n';
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
- Output:
After converting with dd:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
COBOL
*> Rosetta Code, fixed length records
*> Tectonics:
*> cobc -xj lrecl80.cob
identification division.
program-id. lrecl80.
environment division.
configuration section.
repository.
function all intrinsic.
input-output section.
file-control.
select infile
assign to infile-name
organization is sequential
file status is infile-status
.
select outfile
assign to outfile-name
organization is sequential
file status is outfile-status
.
data division.
file section.
fd infile.
01 input-text pic x(80).
fd outfile.
01 output-text pic x(80).
working-storage section.
01 infile-name.
05 value "infile.dat".
01 infile-status pic xx.
88 ok-input value '00'.
88 eof-input value '10'.
01 outfile-name.
05 value "outfile.dat".
01 outfile-status pic xx.
88 ok-output value '00'.
procedure division.
open input infile
if not ok-input then
display "error opening input " infile-name upon syserr
goback
end-if
open output outfile
if not ok-output
display "error opening output " outfile-name upon syserr
goback
end-if
*> read lrecl 80 and write the reverse as lrecl 80
read infile
perform until not ok-input
move function reverse(input-text) to output-text
write output-text
if not ok-output then
display "error writing: " output-text upon syserr
end-if
read infile
end-perform
close infile outfile
*> from fixed length to normal text, outfile is now the input file
open input outfile
if not ok-output then
display "error opening input " outfile-name upon syserr
goback
end-if
read outfile
perform until not ok-output
display function trim(output-text trailing)
read outfile
end-perform
close outfile
goback.
end program lrecl80.
Given a starting file sample.txt of
Line 1...1.........2.........3.........4.........5.........6.........7.........8
Line 2
Line 3
Line 4
Line 6
Line 7
Indented line 8............................................................
Line 9 RT MARGIN
And a setup pass of
prompt$ dd if=sample.txt of=infile.dat cbs=80 conv=block
- Output:
prompt$ cobc -xj fixed-length.cob
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
..............................................................8 enil fo tuO
NIGRAM TR 9 eniL
prompt$ file outfile.dat outfile.dat: ASCII text, with very long lines, with no line terminators
blocks
Demonstrate text to Forth source block form.
*> Rosetta Code fixed length records, text to Forth block
identification division.
program-id. blocking.
environment division.
configuration section.
repository.
function all intrinsic.
input-output section.
file-control.
select infile
assign to infile-name
organization is line sequential
file status is infile-status
.
select outfile
assign to outfile-name
organization is sequential
file status is outfile-status
.
data division.
file section.
fd infile.
01 input-text pic x(64).
fd outfile.
01 output-text pic x(64).
working-storage section.
01 infile-name.
05 value "forth.txt".
01 infile-status pic xx.
88 ok-input value '00'.
88 eof-input value '10'.
01 outfile-name.
05 value "forth.blk".
01 outfile-status pic xx.
88 ok-output value '00'.
procedure division.
*> read a line, padded to or truncated at 64 as defined in FD
open input infile
if not ok-input then
display "error opening input " infile-name upon syserr
goback
end-if
open output outfile
if not ok-output
display "error opening output " outfile-name upon syserr
goback
end-if
move 0 to tally
read infile
perform until not ok-input
move input-text to output-text
write output-text
if not ok-output then
display "error writing: " output-text upon syserr
end-if
add 1 to tally
if tally > 15 then move 0 to tally end-if
read infile
end-perform
*> Output up to next 1024 byte boundary
if tally > 0 then
compute tally = 16 - tally
move spaces to output-text
perform tally times
write output-text
if not ok-output then
display "error writing: " output-text upon syserr
end-if
end-perform
end-if
close infile outfile
goback.
end program blocking.
Demonstrate Forth source block to text form.
*> Rosetta Code fixed length records, Forth blocks to text.
identification division.
program-id. unblocking.
environment division.
configuration section.
repository.
function all intrinsic.
input-output section.
file-control.
select infile
assign to infile-name
organization is sequential
file status is infile-status
.
select outfile
assign to outfile-name
organization is line sequential
file status is outfile-status
.
data division.
file section.
fd infile.
01 input-text pic x(64).
fd outfile.
01 output-text pic x(64).
working-storage section.
01 infile-name.
05 value "forth.blk".
01 infile-status pic xx.
88 ok-input value '00'.
88 eof-input value '10'.
01 outfile-name.
05 value "forth.txt".
01 outfile-status pic xx.
88 ok-output value '00'.
procedure division.
open input infile
if not ok-input then
display "error opening input " trim(infile-name) upon syserr
goback
end-if
open output outfile
if not ok-output
display "error opening write " trim(outfile-name) upon syserr
goback
end-if
*> read a fixed length line, 64 characters
read infile
perform until not ok-input
move trim(input-text) to output-text
write output-text
if not ok-output then
display "error writing: " output-text upon syserr
end-if
read infile
end-perform
close infile outfile
goback.
end program unblocking.
Delphi
See Pascal
DuckDB
DuckDB currently does not seem to have a suitable option for suppressing newlines when generating output, and so in the following, a perl one-liner is used to trim the trailing newline.
To show that the DuckDB program in conjunction with the perl one-liner does indeed meet the requirements, the result of piping the output to `/bin/dd cbs=80 conv=unblock` is shown. In other words, the output of the following is shown below:
duckdb < program.sql | perl -p -e 'chomp if eof' | /bin/dd cbs=80 conv=unblock
program.sql
.headers off
.mode list
create or replace function reverseBlocks(str) as
regexp_extract_all(str, '.{1,80}') -- {1,80} avoids lossiness
.list_transform(x -> reverse(x))
.array_to_string('') ;
select reverseBlocks(content)
from read_text('rc-infile.dat');
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
1+1 records in
1+1 records out
644 bytes transferred in 0.048590 secs (13254 bytes/sec)
Free Pascal
See Pascal
FreeBASIC
Const As Byte longRegistro = 80
Const archivoEntrada As String = "infile.dat"
Const archivoSalida As String = "outfile.dat"
Dim As String linea
'Abre el archivo origen para lectura
Open archivoEntrada For Input As #1
'Abre el archivo destino para escritura
Open archivoSalida For Output As #2
Print !"Datos de entrada:\n"
Do While Not Eof(1)
Line Input #1, linea 'lee una linea
Print linea 'imprime por pantalla esa linea
For i As Integer = longRegistro To 1 Step -1
Print #2, Chr(Asc(linea, i)); 'escribe el inverso de la linea
Next i
Print #2, Chr(13);
Loop
Close #1, #2
Dim As Integer a
Open archivoSalida For Input As #2
Print !"\nDatos de salida:\n"
Do While Not Eof(2)
Line Input #2, linea
For j As Integer = 0 To Len(linea)-1
Print Chr(linea[j]);
a += 1: If a = longRegistro Then a = 0 : Print Chr(13)
Next j
Loop
Close
Sleep
Go
package main
import (
"fmt"
"log"
"os"
"os/exec"
)
func reverseBytes(bytes []byte) {
for i, j := 0, len(bytes)-1; i < j; i, j = i+1, j-1 {
bytes[i], bytes[j] = bytes[j], bytes[i]
}
}
func check(err error) {
if err != nil {
log.Fatal(err)
}
}
func main() {
in, err := os.Open("infile.dat")
check(err)
defer in.Close()
out, err := os.Create("outfile.dat")
check(err)
record := make([]byte, 80)
empty := make([]byte, 80)
for {
n, err := in.Read(record)
if err != nil {
if n == 0 {
break // EOF reached
} else {
out.Close()
log.Fatal(err)
}
}
reverseBytes(record)
out.Write(record)
copy(record, empty)
}
out.Close()
// Run dd from within program to write output.dat
// to standard output as normal text with newlines.
cmd := exec.Command("dd", "if=outfile.dat", "cbs=80", "conv=unblock")
bytes, err := cmd.Output()
check(err)
fmt.Println(string(bytes))
}
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
Bonus round
package main
import (
"bufio"
"fmt"
"log"
"os"
"strings"
)
func check(err error) {
if err != nil {
log.Fatal(err)
}
}
func block2text(inputFile, outputFile string) {
in, err := os.Open(inputFile)
check(err)
defer in.Close()
out, err := os.Create(outputFile)
check(err)
defer out.Close()
line := make([]byte, 64)
empty := make([]byte, 64)
for {
n, err := in.Read(line)
if err != nil {
if n == 0 {
break // EOF reached
} else {
log.Fatal(err)
}
}
str := string(line)
str = strings.TrimRight(str, " \000")
out.WriteString(str + "\n")
copy(line, empty)
}
}
func text2block(inputFile, outputFile string) {
in, err := os.Open(inputFile)
check(err)
defer in.Close()
out, err := os.Create(outputFile)
check(err)
defer out.Close()
scanner := bufio.NewScanner(in)
count := 0
for scanner.Scan() {
str := scanner.Text()
count++
le := len(str)
if le > 64 {
str = str[0:64]
} else if le < 64 {
str = fmt.Sprintf("%-64s", str)
}
out.WriteString(str)
}
if rem := count % 16; rem > 0 {
str := strings.Repeat(" ", (16-rem)*64)
out.WriteString(str)
}
}
func main() {
block2text("block.dat", "block.txt")
text2block("block.txt", "block2.dat")
}
J
Solution:
Using the 720 byte input file linked to in the Raku entry.
_80 ]\ fread 'flr-infile.dat' NB. reads the file into a n by 80 array
_80 |.\ fread 'flr-infile.dat' NB. as above but reverses each 80 byte chunk
'flr-outfile.dat' fwrite~ , _80 |.\ fread 'flr-infile.dat' NB. as above but writes result to file (720 bytes)
processFixLenFile=: fwrite~ [: , _80 |.\ fread NB. represent operation as a verb/function
Example Usage:
'flr-outfile.dat' processFixLenFile 'flr-infile.dat' NB. returns number of bytes written
720
jq
Also works with gojq and jaq, the Go and Rust implementations of jq
To read the raw input and write out raw strings, the command-line options -R (raw input), -r (raw output) and -j options are necessary:
jq -Rrj -f program.jq infile.dat
where program.jq is shown below.
Currently gojq does not include the `_nwise/1` filter provided by jq, and in any case jq's implementation is suboptimal, so we define `nwise` here so that it can be used for both array and string inputs. Notice that the inner helper function, `n`, has arity 0, allowing jq's tail-call optimization to work.
program.jq
def nwise($n):
def n: if length <= $n then . else .[0:$n] , (.[$n:] | n) end;
n;
nwise(80) | explode | reverse | implodeTo show that this does indeed work, the output of `/bin/dd cbs=80 conv=unblock` is shown:
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
1+1 records in
1+1 records out
644 bytes transferred in 0.030319 secs (21241 bytes/sec)
Julia
The program reads from an "infile.dat" file created with dd, as described in the task instructions.
function processfixedlengthrecords(infname, blocksize, outfname)
inf = open(infname)
outf = open(outfname, "w")
filedata = [ read(inf, blocksize) for _ in 1:10 ]
for line in filedata
s = join([Char(c) for c in line], "")
@assert(length(s) == blocksize)
write(outf, s)
end
end
processfixedlengthrecords("infile.dat", 80, "outfile.dat")
Lua
-- prep: convert given sample text to fixed length "infile.dat"
local sample = [[
Line 1...1.........2.........3.........4.........5.........6.........7.........8
Line 2
Line 3
Line 4
Line 6
Line 7
Indented line 8............................................................
Line 9 RT MARGIN]]
local txtfile = io.open("sample.txt", "w")
txtfile:write(sample)
txtfile:close()
os.execute("dd if=sample.txt of=infile.dat cbs=80 conv=block > /dev/null 2>&1")
-- task: convert fixed length "infile.dat" to fixed length "outfile.dat" (reversed lines)
local infile = io.open("infile.dat", "rb")
local outfile = io.open("outfile.dat", "wb")
while true do
local line = infile:read(80)
if not line then break end
outfile:write(string.reverse(line))
end
infile:close()
outfile:close()
-- output:
os.execute("dd if=outfile.dat cbs=80 conv=unblock")
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL 2 eniL 3 eniL 4 eniL 6 eniL 7 eniL ............................................................8 enil detnednI NIGRAM TR 9 eniL 1+1 records in 1+1 records out
M2000 Interpreter
Fixed length Record
Form Buffer object (hold a memory block) we can read a byte at offset. So Print Eval(Line80,3) return the 4th byte, and Return Line80, 2:=255,5:=0 set two bytes (unsigned, we place any number and interpreter convert it to byte).
Module FixedFile {
Read fixed$
OldLocale=Locale
\\ chr$(string_argument$)
\\ use Locale to convert from Ansi to Utf-16LE
\\ Read Ansi form files also use Locale
Locale 1032
Try ok {
\\ Make the file first
Const Center=2
Font "Courier New"
Bold 0
Italic 0
Def long m, z=1, f
Def text2read$,test3write$
Form 100, 50 ' 100 by 60 characters
Document txt$={Line 1...1.........2.........3.........4.........5.........6.........7.........8
Line 2
Line 3
Line 4
Line 6
Line 7
Indented line 8............................................................
Line 9 RT MARGIN
}
\\ use Help Open in M2000 console for details
\\ Method one
Report Center, "Make file"
\\ for WIDE Random \\ for Utf-16
Open fixed$ for Random Exclusive as #f len=80
m=Paragraph(txt$, 0)
z=1
If forward(txt$, m) then
while m, z<10
text2write$=Paragraph$(txt$,(m))
Print format$("Len:{0}, Data: {1}",Len(text2write$),text2write$)
Put #f, text2write$ , z
\\ record number from 1
\\ if number is total records plus one
\\ we append a record
z++
End while
End If
Print "Press any key"
Push Key$ : Drop
Form 80, 40
Report Center, "Method1"
For z=1 to 9
Get #f, text2read$, z
text2read$=StrRev$(text2read$)
Put #f, text2read$, z
Print text2read$
Next z
Close #f
Report Center, "Method2"
\\ Method2
\\ Buffer Clear Line80 ... \\ to clear memory
\\ here we write all bytes so not needed
Buffer Line80 as byte*80
m=filelen(fixed$)
If m mod 80=0 Then
m=1
\\ now Get/Put read write at byte position
\\ we have to use seek to move to byte position
\\ This way used for Binary files
Open fixed$ for Input as #f1
Open fixed$ for Append as #f2
while not eof(#f1)
seek #f1, m
Rem Print seek(#f)
Get #f1, Line80
Return line80,0:=Str$(StrRev$(Chr$(Eval$(line80,0,80))))
seek #f2, m
Put #f2, Line80
seek #f1, m
Get #f1, Line80
Print Chr$(Eval$(line80,0,80))
m+=80
End While
Close #f1
Close #f2
End if
}
\\ use Close with no parameters for close all files if something happen
If error then Close: Print Error$
Locale OldLocale
}
FixedFile "fixed.random"Forth Blocks
Form 80,50
Print "Forth's Blocks"
\\ Forth Blocks
Structure Line16 {
a`Line as byte*64
}
NewBlock=lambda Line16 -> {
Buffer a`Block as Line16*16
\\ fill spaces
Return a`Block, 0:=str$(string$(" ",1024))
=a`Block
}
\\ Events are value types, but for closures and groups are reference types
Event Doit {
Read something$
}
Header=Doit
DisplayBlock= Lambda NewBlock, Line16, Doit, Header (Blocks`File$,Block`Number, UseLocale=1033)->{
Page1=NewBlock()
Open Blocks`File$ for input as #f
Seek #f, 1024*(Block`Number-1)+1
Get #f,Page1
Close #f
Document NewDoc$
\\ need to convert from Ansi
Call Event Header, "Block:"+Str$(Block`Number)
oldlocale=locale
locale UseLocale
For i=0 to 15
lineAny$=chr$(Eval$(Page1,i, Len(Line16)))
Call Event Doit, format$("{0::-2} {1}",i,chr$(Eval$(Page1,i, Len(Line16))))
Next i
locale oldlocale
}
Document ForthCode$={( Large letter F)
: STAR [CHAR] * EMIT ;
: STARS 0 DO STAR LOOP ;
: MARGIN CR 30 SPACES ;
: BLIP MARGIN STAR ;
: BAR MARGIN 5 STARS ;
: F BAR BLIP BAR BLIP BLIP CR ;
}
\\ Make Document bigger than 16 lines
\\ doc.par(ForthCode$) return paragraphs (here we have no wrap)
\\ actuall lines per layer can be found from Report (the renderer)
\\ using Reportlines. layer can be the printer page.
ForthCode$=string$(ForthCode$,5)
Print "Make Block"
Page1=NewBlock()
Locale 1033
Blocks`File$="Forth Blocks"
Block`Number=1
\\ Apppend three times same blocks
For Pass=1 to 3
If Doc.Len(ForthCode$)>0 then
For i=1 to Doc.par(ForthCode$)-1
\\ we give order number but Paragraph$ use unique number for paragraphs
\\ if we didn't delete or insert lines, then these two are the same
Print Paragraph$(ForthCode$, Paragraph(ForthCode$,i))
\\ convert to Ansi using Locale
\\ offset from 0, so minus 1
\\ offset 1 is at len(Line16)
\\ Page1(0) is the real address, but here doesn't matter
Return Page1, (i-1) mod 16:=Str$(Paragraph$(ForthCode$, Paragraph(ForthCode$,i)))
if i mod 16=0 then Gosub SaveBlock
Next i
i--
if Not i mod 16=0 then Gosub SaveBlock
End if
Next Pass
\\ now we read from disk
Class DocumentKeeper {
Document Text$
Function AppendLine(aline$) {
\\ right trim$
.Text$<=Mid$(Trim$("*"+aline$),2)+{
}
}
}
Function Disp(aline$) {
Print aline$
}
DocumentKeeper=DocumentKeeper()
Event Doit New Disp()
Event Header New Disp()
For i=1 to Block`Number-1
Call DisplayBlock(Blocks`File$, i)
Print "Press any key"
Push key$ : Drop
Next i
Event Doit Drop Disp()
Event Doit New DocumentKeeper.AppendLine()
Event Header Hold
For i=1 to Block`Number-1
Call DisplayBlock(Blocks`File$, i)
Next i
Report DocumentKeeper.Text$
End
SaveBlock:
Print "Save as Number ";Block`Number
If Exist(Blocks`File$) then
\\ check if there is space for this block
If Not filelen(Blocks`File$) div 1024>=Block`Number-1 Then
Error "Wrong Block Number"
End if
Else
Print "not exist"
Open Blocks`File$ for output as #f
Close #f
Wait 100
\\ or Error "Empty File" if we wish only read
If Block`Number<>1 then Error "Wrong Block Number"
End if
Open Blocks`File$ for append as #f
Seek #f, Block`Number*1024-1023 ' so we seek to first byte
Put #f, Page1
Close #f
Block`Number++
Page1=NewBlock()
ReturnMathematica / Wolfram Language
FixedRecordReverse[inFile_File, outFile_File, length_ : 80] :=
Module[{inStream, outStream, line, byte},
WithCleanup[
inStream = OpenRead[inFile, BinaryFormat -> True];
outStream = OpenWrite[outFile, BinaryFormat -> True];
,
While[True,
line = {};
Do[
byte = BinaryRead[inStream, "Byte"];
AppendTo[line, byte]
,
length
];
If[byte === EndOfFile, Break[]];
line = Reverse[line];
BinaryWrite[outStream, line]
]
,
Close[outStream];
Close[inStream];
];
(* Verify the result *)
RunProcess[{"dd", "if=" <> outFile[[1]], "cbs=" <> ToString[length], "conv=unblock"}, "StandardOutput"]
];
This function will both return the reversed string in the notebook AND write the record to outfile.dat:
- Input:
In[]:= FixedRecordReverse[File["infile.dat"], File["outfile.dat"]]
- Output:
Out[]= "\
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
"
Neko
/**
fixed length records, in Neko
*/
var LRECL = 80
var reverse = function(s) {
var len = $ssize(s)
if len < 2 return s
var reverse = $smake(len)
var pos = 0
while len > 0 $sset(reverse, pos ++= 1, $sget(s, len -= 1))
return reverse
}
var file_open = $loader.loadprim("std@file_open", 2)
var file_read = $loader.loadprim("std@file_read", 4)
var file_write = $loader.loadprim("std@file_write", 4)
var file_close = $loader.loadprim("std@file_close", 1)
var input = file_open("infile.dat", "r")
var output = file_open("outfile.dat", "w")
var len
var pos = 0
var record = $smake(LRECL)
while true {
try {
len = file_read(input, record, pos, LRECL)
if len != LRECL $throw("Invalid read")
len = file_write(output, reverse(record), pos, LRECL)
if len != LRECL $throw("Invalid write")
} catch a break;
}
file_close(input)
file_close(output)
- Output:
prompt$ dd if=infile.txt cbs=80 conv=block status=none of=infile.dat
prompt$ nekoc fixed-length.neko
prompt$ neko fixed-length
prompt$ dd if=outfile.dat cbs=80 conv=unblock status=none
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
Nim
Task: fixed length records
import algorithm
proc reverse(infile, outfile: string) =
let input = infile.open(fmRead)
defer: input.close()
let output = outfile.open(fmWrite)
defer: output.close()
var buffer: array[80, byte]
while not input.endOfFile:
let countRead = input.readBytes(buffer, 0, 80)
if countRead < 80:
raise newException(IOError, "truncated data when reading")
buffer.reverse()
let countWrite = output.writeBytes(buffer, 0, 80)
if countWrite < 80:
raise newException(IOError, "truncated data when writing")
reverse("infile.dat", "outfile.dat")
- Output:
Contents of file “result.txt" created by command dd if=outfile.dat of=result.txt cbs=80 conv=unblock:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
Bonus: Forth blocks
import strutils
const EmptyRecord = repeat(' ', 64)
#---------------------------------------------------------------------------------------------------
proc textToBlock(infile, outfile: string) =
## Read lines of a text file and write them as 64 bytes records.
let input = infile.open(fmRead)
defer: input.close()
let output = outfile.open(fmWrite)
defer: output.close()
var count = 0
while not input.endOfFile:
var record = input.readLine()
if record.len > 64:
record.setLen(64) # Truncate to 64 bytes.
elif record.len < 64:
record &= repeat(' ', 64 - record.len) # Pad to 64 bytes.
if output.writeChars(record, 0, 64) != 64:
raise newException(IOError, "error while writing block file")
inc count
# Complete block with empty records.
let rem = count mod 16
if rem != 0:
for _ in 1..(16 - rem):
if output.writeChars(EmptyRecord, 0, 64) != 64:
raise newException(IOError, "error while writing block file")
#---------------------------------------------------------------------------------------------------
proc blockToText(infile, outfile: string) =
## Read 64 bytes records and write them as lines trimming spaces.
let input = infile.open(fmRead)
defer: input.close()
let output = outfile.open(fmWrite)
defer: output.close()
var line: string
while not input.endOfFile:
line.setLen(64) # Allocate space for the 64 bytes to read.
if input.readChars(line, 0, 64) != 64:
raise newException(IOError, "error while reading block file")
line = line.strip(leading = false, trailing = true) & '\n'
output.write(line)
#———————————————————————————————————————————————————————————————————————————————————————————————————
when isMainModule:
textToBlock("block1.txt", "block.dat")
blockToText("block.dat", "block2.txt")
Pascal
program reverseFixedLines(input, output, stdErr);
const
lineLength = 80;
var
// in Pascal, `string[n]` is virtually an alias for `array[1..n] of char`
line: string[lineLength];
i: integer;
begin
while not eof() do
begin
for i := 1 to lineLength do
begin
read(line[i]);
end;
for i := lineLength downto 1 do
begin
write(line[i]);
end;
writeLn();
end;
end.
Perl
open $in, '<', 'flr-infile.dat';
open $out, '>', 'flr-outfile.dat';
while ($n=sysread($in, $record, 80)) { # read in fixed sized binary chunks
syswrite $out, reverse $record; # write reversed records to file
print reverse($record)."\n" # display reversed records, line-by-line
}
close $out;
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
There Is More Than One Way To Do It
Read with standard <> using $/ set to a ref-to-int to read a fixed block size.
{
local ($/, @ARGV) = (\80, 'infile.dat');
open my $out, '>', 'outfile.dat' or die $!;
print $out scalar reverse while <>; # can read fixed length too :)
close $out;
}
Slurp and reverse each line in place.
use Path::Tiny;
path('outfile.dat')->spew(path('infile.dat')->slurp =~ s/.{80}/reverse $&/gesr);
Double reverse.
use Path::Tiny;
path('outfile.dat')->spew(reverse unpack '(a80)*', reverse path('infile.dat')->slurp);
Bonus round: convert the sample file to Forth Block format.
use Path::Tiny;
path('outfile.dat')->spew(pack '(A64)16', split /\n/, path('sample.txt')->slurp);
Bonus Round: convert Forth Block format to plain text format.
use Path::Tiny;
path('sample2.txt')->spew(map "$_\n", unpack '(A64)16', path('outfile.dat')->slurp);
Phix
You might want to investigate using builtins such as get_text() and read_lines(), but they were never really designed for fixed length record handling and for me, for this task, their limits outweight any advantages. To simplify matters, this creates any files needed on the fly.
without js -- file i/o constant sample_text = """ Line 1...1.........2.........3.........4.........5.........6.........7.........8 Line 2 Line 3 Line 4 Line 6 Line 7 Indented line 8............................................................ Line 9 RT MARGIN""" constant indat = "infile.dat", outdat = "outfile.dat" if not file_exists(indat) then object text = get_text("sample.txt") if text=-1 then text = sample_text end if sequence s = split(text,'\n') integer fn = open(indat,"wb") for i=1 to length(s) do puts(fn,s[i]&repeat(' ',80-length(s[i]))) end for close(fn) printf(1,"%s created (%d bytes)\n",{indat,get_file_size(indat)}) end if function get_block(integer fn, size) string res = "" for i=1 to size do res &= getc(fn) end for return res end function integer fn = open(indat,"rb"), isize = get_file_size(indat) puts(1,"reversed:\n") for i=1 to isize by 80 do ?reverse(get_block(fn,80)) end for close(fn) -- Bonus part, 16*64 (=1024) block handling: procedure put_block(integer fn, sequence lines) lines &= repeat("",16-length(lines)) for i=1 to length(lines) do string li = lines[i] if length(li)>64 then li = li[1..64] else li &= repeat(' ',64-length(li)) end if puts(fn,li) end for end procedure fn = open(outdat,"wb") put_block(fn,split(sample_text,'\n')) close(fn) integer osize = get_file_size(outdat) printf(1,"\n%s created (%d bytes):\n",{outdat,osize}) fn = open(outdat,"rb") sequence lines = {} for i=1 to osize by 64 do string line = get_block(fn,64) ?line lines = append(lines,trim_tail(line,' ')) end for lines = trim_tail(lines,{""}) puts(1,"\ntrimmed:\n") pp(lines,{pp_Nest,1}) {} = delete_file(indat) -- (for consistent 2nd run)
- Output:
infile.dat created (720 bytes)
reversed:
"8.........7.........6.........5.........4.........3.........2.........1...1 eniL"
" 2 eniL"
" 3 eniL"
" 4 eniL"
" "
" 6 eniL"
" 7 eniL"
"............................................................8 enil detnednI "
"NIGRAM TR 9 eniL"
outfile.dat created (1024 bytes):
"Line 1...1.........2.........3.........4.........5.........6...."
"Line 2 "
"Line 3 "
"Line 4 "
" "
"Line 6 "
"Line 7 "
" Indented line 8............................................"
"Line 9 "
" "
" "
" "
" "
" "
" "
" "
trimmed:
{"Line 1...1.........2.........3.........4.........5.........6....",
"Line 2",
"Line 3",
"Line 4",
{},
"Line 6",
"Line 7",
" Indented line 8............................................",
"Line 9"}
Python
infile = open('infile.dat', 'rb')
outfile = open('outfile.dat', 'wb')
while True:
onerecord = infile.read(80)
if len(onerecord) < 80:
break
onerecordreversed = bytes(reversed(onerecord))
outfile.write(onerecordreversed)
infile.close()
outfile.close()
Output:
dd if=outfile.dat cbs=80 conv=unblock 8.........7.........6.........5.........4.........3.........2.........1...1 eniL 2 eniL 3 eniL 4 eniL 6 eniL 7 eniL ............................................................8 enil detnednI NIGRAM TR 9 eniL 1+1 records in 1+1 records out
Raku
(formerly Perl 6) Link to a copy of the input file used: flr-infile.dat
Essentially the same as task Selective_File_Copy except more boring.
$*OUT = './flr-outfile.dat'.IO.open(:w, :bin) orelse .die; # open a file in binary mode for writing
while my $record = $*IN.read(80) { # read in fixed sized binary chunks
$*OUT.write: $record.=reverse; # write reversed records out to $outfile
$*ERR.say: $record.decode('ASCII'); # display decoded records on STDERR
}
close $*OUT;
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
REBOL
inp: open %infile.dat
out: open/new %outfile.dat
while [ not empty? line: copy/part inp 80 ][ write out reverse line ]
close inp
close out
REXX
/*REXX pgm reads fixed─length 80 byte records; reverses each record, displays to term. */
iFID= 'FIXEDLEN.TXT' /*the file's filename (used for input).*/
call charin iFID, 1, 0 /*open the file, point rec pointer to 1*/
/* [+] just to be safe, position file.*/
do j=1 while chars(iFID) >= 80 /*read data records of LRECL ≡ eighty. */
@.j= charin(iFID, , 80) /*read a data record of eighty bytes. */
end /*j*/
#= j - 1 /*adjust # of records (J is 1 too high)*/
do k=1 for # /* [↓] process all the records read. */
say reverse(@.k) /* reverse a record and write to term. */
end /*k*/ /*stick a fork in it, we're all done. */
- output when using the default input file:
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
Ruby
open("outfile.dat", "w") do |out_f|
open("infile.dat") do |in_f|
while record = in_f.read(80)
out_f << record.reverse
end
end
end # both files automatically closed
Rust
use std::fs::File;
use std::io::prelude::*;
use std::io::{BufReader, BufWriter};
fn reverse_file(
input_filename: &str,
output_filename: &str,
record_len: usize,
) -> std::io::Result<()> {
let mut input = BufReader::new(File::open(input_filename)?);
let mut output = BufWriter::new(File::create(output_filename)?);
let mut buffer = vec![0; record_len];
while input.read(&mut buffer)? == record_len {
buffer.reverse();
output.write_all(&buffer)?;
}
output.flush()?;
Ok(())
}
fn main() {
match reverse_file("infile.dat", "outfile.dat", 80) {
Ok(()) => {}
Err(error) => eprintln!("I/O error: {}", error),
}
}
- Output:
After converting with dd:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
Tcl
chan configure stdin -translation binary
chan configure stdout -translation binary
set lines [regexp -inline -all {.{80}} [read stdin]]
puts -nonewline [join [lmap line $lines {string reverse $line}] ""]
# More "traditional" way
# while {[set line [read stdin 80]] ne ""} {
# puts -nonewline [string reverse $line]
# }
- Output:
$ exec 2>/dev/null
$ dd if=sample.txt cbs=80 conv=block | tclsh flr.tcl | dd cbs=80 conv=unblock
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
TXR
80 Column Task
At the shell prompt:
$ txr -e '(let ((buf (make-buf 80))
(nread 80))
(while (eql nread 80)
(set nread (fill-buf-adjust buf))
(buf-set-length buf 80)
(put-buf (nreverse buf))))' < infile80.bin > outfile80.bin
$ dd if=outfile80.bin cbs=80 conv=unblock
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
1+1 records in
1+1 records out
725 bytes copied, 8.658e-05 s, 8.4 MB/s
This handles a final bit that is shorter than 80. When buf-set-length sets the buffer size back to 80, zero padding is applied. The zero-padded record is reversed.
Forth Blocks Task
Encoding
The following program is called forth-enblock.tl:
(typedef forth-line (array 64 bchar))
(let ((lno 0)
(blanks (make-buf 64 #\space)))
(whilet ((line (get-line)))
(put-obj (fmt "~-64,64a" line) (ffi forth-line))
(inc lno))
(while (plusp (mod (pinc lno) 16))
(put-buf blanks)))- Output:
$ txr forth-enblock.tl < forth-enblock.tl > forth-enblock.blk $ xxd forth-enblock.blk 00000000: 2874 7970 6564 6566 2066 6f72 7468 2d6c (typedef forth-l 00000010: 696e 6520 2861 7272 6179 2036 3420 6263 ine (array 64 bc 00000020: 6861 7229 2920 2020 2020 2020 2020 2020 har)) 00000030: 2020 2020 2020 2020 2020 2020 2020 2020 00000040: 2020 2020 2020 2020 2020 2020 2020 2020 00000050: 2020 2020 2020 2020 2020 2020 2020 2020 00000060: 2020 2020 2020 2020 2020 2020 2020 2020 00000070: 2020 2020 2020 2020 2020 2020 2020 2020 00000080: 286c 6574 2028 286c 6e6f 2030 2920 2020 (let ((lno 0) [... snip ...] 000003e0: 2020 2020 2020 2020 2020 2020 2020 2020 000003f0: 2020 2020 2020 2020 2020 2020 2020 2020
Decoding
This is forth-deblock.tl
(typedef forth-block (array 16 (array 64 bchar)))
(defsymacro fbsz (sizeof forth-block))
(let* ((buf (make-buf fbsz))
(block-view (carray-buf buf (ffi forth-block)))
(nread fbsz))
(while (eql fbsz nread)
(set nread (fill-buf-adjust buf))
(when (plusp nread)
(buf-set-length buf fbsz #\space)
(each ((row [block-view 0]))
(put-line (trim-right #/ +/ row))))))- Output:
$ txr forth-deblock.tl < forth-enblock.blk
(typedef forth-line (array 64 bchar))
(let ((lno 0)
(blanks (make-buf 64 #\space)))
(whilet ((line (get-line)))
(put-obj (fmt "~-64,64a" line) (ffi forth-line))
(inc lno))
(while (plusp (mod (pinc lno) 16))
(put-buf blanks)))
Wren
import "io" for File
import "./str" for Str
var records = File.read("infile.dat")
File.create("outfile.dat") { |f|
for (record in Str.chunks(records, 80)) {
record = record[-1..0]
f.writeBytes(record)
}
}
records = File.read("outfile.dat")
for (record in Str.chunks(records, 80)) System.print(record)
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
Bonus round
import "./ioutil" for File, FileUtil
import "./str" for Str
var blockToText = Fn.new { |blockFileName, textFileName|
var block = File.read(blockFileName)
var lb = FileUtil.lineBreak
File.create(textFileName) { |f|
for (chunk in Str.chunks(block, 64)) {
f.writeBytes(chunk.trimEnd() + lb)
}
}
}
var textToBlock = Fn.new { |textFileName, blockFileName|
var lines = FileUtil.readLines(textFileName).where { |l| l != "" }.toList
var text = lines.map { |l| (l.count < 64) ? l + (" " * (64-l.count)) : l[0..63] }.join()
var rem = text.count % 1024
if (rem > 0) text = text + (" " * (1024 - rem))
File.create(blockFileName) { |f| f.writeBytes(text) }
}
// create a block file
File.create("data.blk") { |f|
f.writeBytes("a" * 1024)
f.writeBytes("b" * 1024)
f.writeBytes("c" * 1024)
f.writeBytes("d" * 1024)
}
blockToText.call("data.blk", "data.txt")
textToBlock.call("data.txt", "data2.blk")
System.print(FileUtil.areDuplicates("data.blk", "data2.blk"))
- Output:
true
XPL0
include xpllib;
int N, I;
char A(80);
[OpenInFile("infile.dat");
OpenOutFile("outfile.dat");
for N:= 1 to 9 do
[for I:= 0 to 80-1 do A(I):= ChIn(3);
for I:= 80-1 downto 0 do ChOut(3, A(I));
];
OpenInFile("outfile.dat");
for N:= 1 to 9 do
[for I:= 0 to 80-1 do ChOut(0, ChIn(3)); CrLf(0)];
]- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
zkl
Reading from the dd formatted file, which is 720 characters:
Line 1...1.........2.........3.........4.........5.........6.........7.........8Line 2 Line 3 Line 4 Line 6 Line 7 Indented line 8............................................................Line 9 RT MARGIN
File("infile.dat","rb") // could contain nulls and newlines
// Since we are writing to a ASCII terminal, ignore nulls
.walker(3).chunk(80,String).pump(Console.println,"reverse"); // 3-->read chars- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL
2 eniL
3 eniL
4 eniL
6 eniL
7 eniL
............................................................8 enil detnednI
NIGRAM TR 9 eniL
To write to a file (as one big line), preserving nulls:
in,out := File("infile.dat","rb"), File("outfile.dat","wb");
in.walker(0).chunk(80).pump(out,"reverse"); // may contain nulls and newlines
// 0-->read bytes, chunk to list of bytes, reverse and write the bytes
in.close(); out.close();outfile.dat:
- Output:
8.........7.........6.........5.........4.........3.........2.........1...1 eniL 2 eniL 3 eniL 4 eniL 6 eniL 7 eniL............................................................8 enil detnednI NIGRAM TR 9 eniL
Bonus Round
// read block file (as in read a file of blocks) to text
fcn readFourthBlock(inFileNm){
out,f,buf := Sink(String), File(inFileNm,"rb"), Data(1024);
while(f.read(1024,buf,False)){
// read 64 chars from buf, strip ws from right side, repeat
buf.walker(3).chunk(64,String).pump(out,T("strip",1),'+("\n"));
}
f.close(); out.close();
}// read text file and write as block to file
fcn formatToFourthBlock(inFileNm,outFileNm){
n,blk,in,out := 0, Data(), File(inFileNm,"r"), File(outFileNm,"wb");
foreach line in (in.walker(11)){ // right side stripped
if(not line) blk.write(" "*64);
else blk.write(line.walker().chunk(64,String).pump(String,"%-64s".fmt));
if(blk.len()==1024){ out.write(blk); blk.clear(); }
}
if(blk) out.write(blk, " "*(1024 - blk.len()));
f.close(); out.close();
}