Fixed length records: Difference between revisions

===Task: fixed length records===

===Bonus: Forth blocks===

<lang Nim>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")</lang>