StandardFileStream
Last updated at 12:26 pm UTC on 30 October 2019
StandardFileStream subclasses
{CrLfFileStream . MultiByteFileStream}
Consider to use MultiByteFileStream
http://live.exept.de/doc/online/english/overview/basicClasses/streams.html#FILESTREAM
Question: I want to read from data files created by my stock software, and I know it's in binary mode. Exactly, it's written by some C function as Long or Int32. I can't find a suitable filestream class to deal with it. For example I need a nextLong/nextInt32, nextLongPut:, etc.
Question: Vanessa Freudenberg October 10, 2004 Just use the standard file stream. Binary reading is implemented in PositionableStream, which is a superclass of all file streams. You need to be careful about endianness, of course.
In the class FileStreamTest method testReadIntoStartingAtCount you find an example how to deal with a binary stream:
testReadIntoStartingAtCount
| filename file |
filename := 'filestream.tst'.
[ | writeBuffer readBuffer bytesRead |
writeBuffer := (ByteArray new: 2500)
atAllPut: 1 ;
yourself.
(StandardFileStream forceNewFileNamed: filename)
binary ;
nextPutAll: writeBuffer ;
close.
file := StandardFileStream readOnlyFileNamed: filename.
readBuffer := ByteArray new: 400.
bytesRead := file
readInto: readBuffer
startingAt: 10
count: 100.
self assert: bytesRead = 100.
"quick test"
self assert: (readBuffer occurrencesOf: 1) = 100.
"compare test"
1 to: readBuffer size do:
[ : n | self assert:
(readBuffer at: n) = ((n between: 10 and: 10 + 100 - 1)
ifTrue: [ writeBuffer at: n ]
ifFalse: [ 0 ]) ] ]
ensure:
[ file ifNotNil: [ file close ].
FileDirectory default
deleteFileNamed: filename
ifAbsent: [ "ok" ] ]
To read a binary file in one go:
ba := (StandardFileStream readOnlyFileNamed: '../../../myPicture.png') binary contentsOfEntireFile
This will give you a ByteArray so that the following is possible:
(ba at: 1) = 137
true
See http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html
The first eight bytes of a PNG file always contain the following (decimal) values:
137 80 78 71 13 10 26 10
To get back a stream evaluate
ReadStream on: ba
Note
For text files use MultiByteFileStream
