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Re: Simple filesystem for embedded platform

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On 01/02/18 12:04, pozz wrote:
> Il 01/02/2018 10:00, David Brown ha scritto:
>> On 01/02/18 09:39, pozz wrote:
>>> I'm using lwip that runs httpd over LPC1769 MCU.  Now the filesystem for
>>> httpd can't fit the internal Flash memory anymore.  So I'm going to use
>>> an external SPI Flash memory.
>>>
>>> I need some suggestions about a filesystem to use.  I need:
>>>
>>> - a tool that creates a binary (or Intel HEX) image from a folder on my
>>>    Windows development machine (the image will be downloaded to Flash);
>>> - file management functions (open, close, read);
>>> - simple integration with lwip httpd;
>>>
>>> I don't need to change the filesystem, so a read-only filesystem is
>>> enough.
>>
>> Do you really need open, close and read functions?  All you actually
>> need is to copy a block of SPI memory into ram.  That might simplify
>> things a bit.
> 
> Yes, you're right. open/close here can be avoided.  read is a must (your
> copy from SPI to memory RAM is a *read*).
> 
> 
>> Does your filesystem need to be independent of the main program?  Your
>> filesystem tool could read through the files in a directory, concatenate
>> them together into a single binary file, and generate a C header with
>> something like:
>>
>> enum {
>>     start_index_html = 0, length_index_html = 4040,
>>     start_favicon_ico = 4040, length_favicon_ico = 840,
>>     start_node_js = 4880, length_node_js = 10391,
>>     ...
>> };
>>
>> If that is enough, then your "tool" could be done as a bash script if
>> you wanted (I'd use Python myself).
> 
> I can't understand. Suppose you need to open the URI "/index.html". How
> to search for this filename in your enum list?

First ask yourself, /do/ you need to search for this URI in a list?  An
embedded web server will often have just one web page - it might not
even have any other files or URI's at all.  Then you don't need to parse
the incoming URI in any way - you return the same "file" each time.  For
the web server in an application I have, I have 4 files - index.html,
favicon.ico, 404.html, and a jquery.js file.  The searching can be done
be a set of "if (strcmp....)" checks that are fixed in the code.  (My
server is a little bit beyond that, but not much.)

You are not trying to re-create Apache here - there is no need to make
things more complex than they have to be for the task in hand.  I don't
know what features you need here, and whether such a method for
"searching" is enough - but it is possible.

> 
> 
>> It will be a little more work if you want to track filenames as well,
>> rather than having them fixed in the code, but you could generate a
>> table of indexes, lengths, and names.  It is easier if that part can be
>> linked directly in the C code, but it would be possible to have it at
>> the start of the binary blob for the SPI.
> 
> I know I can write something from zero, but I'm sure something already
> written that can be reused.

My script for reading a bunch of files and putting them in a static data
structures linked directly with my C code (I guess my microcontroller
has more flash than yours!) is about 130 lines of Python.  Half of that
is static text copied directly to the generated header and C file.  I
wrote that myself, along with the httpd daemon in C, because I found it
easier to get the features I wanted than to use the demo server and code
from the LWIP httpd server.  The "filesystem" bit was easy.  Perhaps
writing it from zero is not as hard as you think it might be - while
finding and adapting existing solutions may be more effort.  (Of course
I cannot give you an answer here, I am just giving ideas for consideration.)

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Thread

Simple filesystem for embedded platform pozz <pozzugno@gmail.com> - 2018-02-01 09:39 +0100
  Re: Simple filesystem for embedded platform David Brown <david.brown@hesbynett.no> - 2018-02-01 10:00 +0100
    Re: Simple filesystem for embedded platform pozz <pozzugno@gmail.com> - 2018-02-01 12:04 +0100
      Re: Simple filesystem for embedded platform David Brown <david.brown@hesbynett.no> - 2018-02-01 12:21 +0100
        Re: Simple filesystem for embedded platform pozz <pozzugno@gmail.com> - 2018-02-02 13:22 +0100
          Re: Simple filesystem for embedded platform David Brown <david.brown@hesbynett.no> - 2018-02-02 14:43 +0100
          Re: Simple filesystem for embedded platform Stefan Reuther <stefan.news@arcor.de> - 2018-02-02 19:08 +0100
  Re: Simple filesystem for embedded platform pippo2@disney.com (Jack) - 2018-02-01 21:58 +0100
    Re: Simple filesystem for embedded platform Dave Nadler <drn@nadler.com> - 2018-02-01 18:18 -0800
  Re: Simple filesystem for embedded platform Joe Chisolm <jchisolm6@earthlink.net> - 2018-02-01 17:25 -0600

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