Dear Mr. Johannes, I am sorry but I think you took me wrong. I never asked you to do things for me. I just wanted few clarifications to proceed further as I was stuck after performing few experiments as below:
For scanning only top-level directory I used the following approach. You can refer to this link for the vvfat original code: http://www.netmite.com/android/mydroid/external/qemu/block-vvfat.c read_directory(.....) { --- while((entry=readdir(dir))) { --- direntry=create_short_and_long_name(s, i, entry->d_name, is_dot || is_dotdot); /* skip sub-directory here */ if(!is_dot && !is_dotdot && (S_ISDIR(st.st_mode))) { free(buffer); s->current_mapping = NULL; break; } ----- } ---- ----- } If I use the above logic I could able to scan only top-level files with empty sub-directories. As follows: # ls -la /mnt/vvfatfs . .. File1.txt File2.txt test1 But there is one problem here if I use the above logic. When I issue "ls" command "vvfat_read" is not getting triggered. So I think there is some problem and I could figure out where to implement the dynamic scanning of sub-directory later. But in the above logic if I scan at least the "dot" and "dotdot" entries for the sub-directories I could get the trigger point in vvfat_read during "ls" command. That is if the output of "ls" is as follows: # ls -la /mnt/vvfatfs . <dot for vvfatfs> .. <dotdot fot vvfatfs> File1.txt File2.txt test1 . <dot for test1> .. <dotdot for test1> I am not sure why this is happening. So I need your help in understanding. Similarly I implemented dynamic creation of mapping for sub-directories in "vvfat_read" by remembering the previous mappings for the sub-directories. And after that I could able to see to get the modified FAT content. But the content itself is not visible (except the dot and dotdot entries) for the sub-directory when we use "ls" command to see them. I will talk about in detail later once you could confirm the top-directory only scanning method. Other comments are in-lined in your mail below. Thanks, Pintu On Sun, Oct 23, 2011 at 12:28 AM, Johannes Schindelin <johannes.schinde...@gmx.de> wrote: > Hi Pintu, > > On Sat, 22 Oct 2011, Pintu Kumar wrote: > >> I already did some work for scanning only top level directory in vvfat. >> Using the following logic in read_directory() >> >> if(parent_index >= 0 & (!dot & !dotdot)) >> { >> free(buffer); >> break; >> } > > Sorry, this is way too deep in the code (and I'd have to guess because you > did not grace me with exact locations), I cannot afford to dive into it > that far. But what I can say is that it is not all that easy; you'll need > to refactor the code. > > You _will_ need to reserve sectors for future directory parsing. You > _will_ need to add code that intercepts reads to those sectors. You _will_ > have to read the directories in question when those sectors are accessed > and thereby commit the sectors to a final state. > > BTW both Kevin and I said that before. > >> Hope this is correct logic for skipping sub-directories content by just >> scanning only dot and dotdot entries inside it. > > It would be, if all you want are empty directories. > >> But as per the recent analysis it was observed that there is some >> problem in skipping sub-directory scanning itself. Because when I issue >> "df" command on VVFAT partition I get read_cluster errors during these >> sector location. > > When you issue "df", you need to commit to which sectors are reserved. By > that, you take almost all the advantage of lazy directory parsing away. > Actually, after using "df" command on the original code itself, it give read cluster error. So, there is something messy here with the original code itself. >> Mr. Johannes, can you clarify on this first. >> >> Then we will look into the dynamic mapping part later. > > I am very sorry, but I do get the impression that the intent is to lure me > into doing all the work, including the investigation what it would take to > turn the code into a version that reads just the top-level first and only > later the subdirectories. > > This will not happen. I have enough projects that I want to tackle myself, > and I am extremely unwilling to do the work for somebody else when that > somebody else is paid to do the work. For the things I _want_ to do I > already have too little time, given that my day job is quite demanding and > asks software design and architecture of me already. > I think you took me wrong. I am sorry but I never asked you to do it for me. I just wanted to get some clarification quickly since you are the author and who else can best explain to me except you. Right now I myself is not fully convinced if some thing like this is completely possible and feasible. I need to perform various experiments and dont want to leave even a single chance before reaching the conclusion that it is not possible. > So: you _will_ have to acquaint yourself with the FAT and then the VFAT > specification. You _will_ have to make a proper plan how the client may be > fooled into believing that there is a fixed filesystem when there is > actually just directories of files. And you _will_ have to write that code > yourself. > Yes, I have already tried implementing it myself and I got some amount of success. But the moment I am stuck, I came to the mailing list for some clarifications and help. > I hope this clarified it? > > Ciao, > Johannes >
