Further to my old question, We are generating XML using following code:
download_xml('GET', [])->
Xml =generateXML(123445),
%% generated Xml data in string without any values 400,.etc
Filename = export_xml:get_file_name(?SESSION_ID1, ?SESSION_ID2),
Filepath = "./priv/static/" ++ Filename,
TotalSize = filelib:file_size(Filepath),
{ok, FP} = file:open(Filepath, [read]),
Generator = fun(FH) ->
case file:read(FH, 1024) of %% But this line is causing something that we never wanted.
eof -> file:close(FH),
done;
{ok, Data} ->
{output, Data, FH}
end
end,
{stream, Generator, FP, [
{"Content-Type", "application/force-download"},
{"Content-Disposition", "attachment; filename=" ++ Filename},
{"Content-length", TotalSize}
]}.
We are reading files in chunks using file:read(FH, 1024) by this line. But this line is also appending some numbers 400, 400, 3b2 in each chunk. We have observed that those codes are nothing but the Hexadecimal values for each chunk.
Here is the sample XML :
sample.xml
400
<?xml version="1.0" encoding="UTF-8"?>.....</info><inf
400
tel>4444</tel>...<address></address>
3b2
<name> Abc</name><surname>EFg</surname><city>XYZ</city>....
</DATA>
0
Since, on changing the chunk size to 2048 from 1024 (i.e file:read(FH, 2048)) values also get changed to 808, 365, 0.
What we're not understanding is: - While streaming the file contents in chunks, each chunk is appending, it's (chunk's) size in the XML and then actual chunk is inserted.
Here is small XML wanted to generate has size (93 Bytes):
<?xml version="1.0">
<info>
<name> Abc</name>
<surname>EFg</surname>
<city>XYZ</city>
</info>
After generating we get the output as:
5d
<?xml version="1.0">
<info>
<name> Abc</name>
<surname>EFg</surname>
<city>XYZ</city>
</info>
0
5d = 93 (Chunk size) In this case file size.
The Question is:
- Why chunk is appending size before each chunk while streaming the file with Generator?
NOTE - We also tried removing header list {"Content-length", TotalSize} from the code, but did not work :(
