Homebrew [Developer Question] What is the expected read/write speed for the internal SD card (on Ninjhax)?

[d0k3]

A question to the developers here:

What is the expected read/write speed for the internal 3DS SD card? I'm testing with a small program (3DSX, running via Ninjhax, on N3DS) I wrote myself and have CTRUlib and CTRcommon installed, if that matters. And, it is much too slow.


I've read somewhere that O3DS read / write speeds are equivalent to a class 4 SD. That would mean a write speed of 4Mbit / sec, which would be somewhat slow, but still acceptable. However, reading should be quite fast, because otherwise reading installed CIAs of sizes 1GB and above would take ages.


And, related question, what (C/C++ standard) functions would you suggest to use to copy a file from SD to SD?

 

[d0k3]

Oh well, I asked an actual developer question on GBATemp... I'll try to answer it myself, maybe someone can help.

I've seen that CTRUlib comes with it's own function for reading / writing files. They seem to be more low level than fopen / fread / fwrite in C, but they also seem difficult to use. Especially because there are no examples for that and there is virtually no documentation for CTRUlib.

So is it recommended to use these instead of the typical C/C++ functions? Can anyone provide an example?

 

[hippy dave]

I was looking at the blargsnes source (specifically ui_rommenu.c mostly) for example code to read directories using ctrulib's functions. I've plonked those instructions into the code I'm porting and they work fine mixed with the existing fopen/fread etc.

 

[elhobbs]

Oh well, I asked an actual developer question on GBATemp... I'll try to answer it myself, maybe someone can help.

I've seen that CTRUlib comes with it's own function for reading / writing files. They seem to be more low level than fopen / fread / fwrite in C, but they also seem difficult to use. Especially because there are no examples for that and there is virtually no documentation for CTRUlib.

So is it recommended to use these instead of the typical C/C++ functions? Can anyone provide an example?

Ctrulib supports standard C fopen etc. look at the source on github there are examples. Better yet download the source and build and install it. The repository is updated quite frequently with fixes and additional functionality. The installer version does not get updated as frequently.

 

[d0k3]

I was looking at the blargsnes source (specifically ui_rommenu.c mostly) for example code to read directories using ctrulib's functions. I've plonked those instructions into the code I'm porting and they work fine mixed with the existing fopen/fread etc.

Yeah, but the problem is... copying a file via fopen / fread / fwrite seems to be awfully slow (an estimate 100kB / sec). Something seems wrong there.

You may also take a look at my copy function:

bool fsPathCopy(const std::string path, const std::string dest, std::function<bool(u64 pos, u64 totalSize)> onProgress) {
   if(fsIsDirectory(path)) {
        if(mkdir(dest.c_str(), 0777) != 0) return false;
        std::vector<FileInfo> contents = fsGetDirectoryContents(path);
        for (std::vector<FileInfo>::iterator it = contents.begin(); it != contents.end(); it++)
            if (!fsPathCopy((*it).path, dest + "/" + (*it).name)) return false;
        return true;
    } else {
        bool ret = false;
        u8 buffer[BUFSIZ];
        u64 total = fsGetFileSize(path);
        u64 pos = 0;
        u64 size;
        FILE* fp = fopen(path.c_str(), "rb");
        FILE* fd = fopen(dest.c_str(), "wb");
        if ((fp != NULL) && (fd != NULL)) {
            while ((size = fread(buffer, 1, BUFSIZ, fp)) > 0) {
                pos += fwrite(buffer, 1, size, fd);
                if((onProgress != NULL) && !onProgress(pos, total)) break;
            }
            ret = (pos == total);
        }
        if(fp != NULL) fclose(fp);
        if(fd != NULL) fclose(fd);
        return ret;
    }
}

This also uses functions from SteveIce10's CTRcommon library, just so you know.

Ctrulib supports standard C fopen etc. look at the source on github there are examples. Better yet download the source and build and install it. The repository is updated quite frequently with fixes and additional functionality. The installer version does not get updated as frequently.

Yup, I already got the latest version from Github. Compiled and installed from there.

 

[elhobbs]

What does onProgress do? If it is updating the display you may be inadvertently adding a wait for vblank each time through the loop. That will definitely slow things down depending on your buffer size.

 

[d0k3]

What does onProgress do? If it is updating the display you may be inadvertently adding a wait for vblank each time through the loop. That will definitely slow things down depending on your buffer size.

Nope, it's not because of onProgress. OnProgress only updates maximally 101 times per operation (0%...100%), plus I already tried leaving that out completely. I did get a significant speed increase by adjusting the buffer size now, though. Still a bit unhappy. I guess writing to / from SD is just a bit slow on 3DS anyways.