[ncl-talk] Writing binary characters while invoking WriteByteOrder

[Dennis Shea]

FYI: A JIRA ticket has been opened: NCL_2462



On Fri, Jul 8, 2016 at 3:10 PM, Dave Allured - NOAA Affiliate <
dave.allured at noaa.gov> wrote:

> Kay and NCL,
>
> I can confirm that fbinrecwrite fails to correctly write an array of
> characters in big endian mode.  I also found the same failure for types
> byte and ubyte.  So I think this is a bug in NCL that needs fixing.
>
> Here is a reduced test case.  Use any of x1, x2, or x3 in the write
> statement.  I get valid little-endian output files when the setfileoption
> statement is commented out.  I get the same good and bad results on both
> Linux and Mac systems; both are little-endian X86 type systems.
>
>   f = "test7.bin"
>   x1 = tochar ("name7")
>   x2 = tobyte (x1)
>   x3 = toubyte (x1)
>   setfileoption ("bin", "WriteByteOrder", "BigEndian")
>   fbinrecwrite (f, 0, x1)
>
> --Dave
>
>
> On Thu, Jul 7, 2016 at 4:31 AM, Kay Shelton <kay.shelton at gmail.com> wrote:
>
>> Hello ncl-talkers,
>>
>> I have a little bit of a conundrum with trying to write a binary file for
>> a colleague that is destined to be used in TELEMAC-2D. The binary file that
>> I am trying to write needs to include characters, integers and floats, and
>> will be used on a machine that is Big Endian. I am creating the file on a
>> Linux machine that is Little Endian, hence when I write the binary file I
>> am using "setfileoption("bin","WriteByteOrder","BigEndian")". This all
>> works fine for integers and floats, but the characters are not correctly
>> represented in the output binary.
>>
>> I have written a short piece of code that demonstrates the problem
>> succinctly:
>>
>> --------------------------------------------------------
>> begin
>>
>> endianness = isbigendian()
>> words = "blah_de_blah_de_blah"
>> words_char = new(strlen(words),character)
>> words_char = tochar(" ")
>> words_char(0:strlen(words)-1) = tochar(words)
>> outfil = "temp.bin"
>>
>> if (.not.endianness) then
>>   print("Endianness is LittleEndian")
>>
>> ; run and look at results, then uncomment the next two lines and re-run
>> ;  setfileoption("bin","ReadByteOrder","BigEndian")
>> ;  setfileoption("bin","WriteByteOrder","BigEndian")
>>
>>   if (fileexists(outfil)) then
>>     system("rm -f "+outfil)
>>   end if
>>   fbinrecwrite (outfil,0, (/ words_char /))
>>   new_words = fbinrecread(outfil, 0, -1, "character")
>>   print("WORDS (original): $$ "+words+" $$")
>>   print("WORDS (original, char to str): $$ "+tostring(words_char)+" $$")
>>   print("NEW_WORDS (char to str): $$ "+tostring(new_words)+" $$")
>> else
>>   print("Already BigEndian")
>> end if
>>
>> end
>> --------------------------------------------------------
>>
>> I have tested this on two completely different Linux machines running NCL
>> 6.3.0 (both 64-bit Ubuntu) and also on one of them using NCL 6.2.1. All
>> give the same result.
>>
>> Running the script first time with the two setfileoption lines commented
>> out (i.e. native LittleEndian binary):
>> (0)     Endianness is LittleEndian
>> (0)     WORDS (original): $$ blah_de_blah_de_blah $$
>> (0)     WORDS (original, char to str): $$ blah_de_blah_de_blah $$
>> (0)     NEW_WORDS (char to str): $$ blah_de_blah_de_blah $$
>>
>> Running with the two setfileoption lines un-commented:
>> (0)     Endianness is LittleEndian
>> (0)     WORDS (original): $$ blah_de_blah_de_blah $$
>> (0)     WORDS (original, char to str): $$ blah_de_blah_de_blah $$
>> (0)     NEW_WORDS (char to str): $$  $$
>>
>> As you can see with the BigEndian option the characters are not correctly
>> written to the file.
>>
>> Is this correct behaviour? Have I missed something I should have included
>> to get this to work? (This is entirely possible and I apologise for wasting
>> your time if this is a simple user-error.)
>>
>> I have searched the ncl-talk archives and have not found this problem
>> encountered by others, so it may well be an issue exclusive to my machines.
>> If it is, I can work around it by wrapping in some fortran to handle the
>> reading and writing of the binary correctly. I would prefer to avoid such a
>> work around as the size of the arrays in the binary files I have to read
>> and write will vary, and I would prefer not to have to hard-code the array
>> sizes when NCL makes calls to the fortran code.
>>
>> [Note: on the machine running NCL 6.2.1 I also get the following warning
>> message on both attempts:
>> warning:fbinrecwrite: end of file reached before record number, writing
>> record as last record in file]
>>
>> Many thanks for your help,
>> Kay
>>
>
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