API: Added utilities to operate on blob streams as stdio FILEs

[snej]

This lets you read and write blobs using standard C functions like fread, fseek, fwrite, similarly to the way other CBL platforms let you use the platform's stream classes.

The API is in src/CBLBlob+FILE.h. This is not in the include/cbl directory since it isn't (yet?) official API.

Unfortunately I was unable to find a way to implement this on Windows, since (apparently?) it does not have a function equivalent to funopen or fopencookie for creating a FILE* with custom I/O callbacks. Still, it seems a shame to leave out this feature, especially since the majority of CBL-C clients will probably be Linux-based.

[borrrden]

This looks like it might be helpful -> https://github.com/Snaipe/fmem

[snej]

fmem only provides a FILE that reads/writes a memory buffer. If we used that, the memory usage would be the same as our non-stream-based blob API, since the entire blob would have to exist in memory.

[pasin]

The build is failing now. Should be #include "CBLBlob+FILE.h" instead of "CBLBlob+File.h".

/Users/runner/work/couchbase-lite-C/couchbase-lite-C/test/BlobTest.cc:20:10: warning: non-portable path to file '"CBLBlob+FILE.h"'; specified path differs in case from file name on disk [-Wnonportable-include-path]
#include "CBLBlob+File.h"
         ^~~~~~~~~~~~~~~~
         "CBLBlob+FILE.h"
In file included from /Users/runner/work/couchbase-lite-C/couchbase-lite-C/test/BlobTest.cc:20:
/Users/runner/work/couchbase-lite-C/couchbase-lite-C/test/../src/CBLBlob+File.h:20:10: fatal error: 'CBLBlob.h' file not found
#include "CBLBlob.h"
         ^~~~~~~~~~~
1 warning and 1 error generated.
make[2]: *** [test/CMakeFiles/CBL_C_Tests.dir/BlobTest.cc.o] Error 1
make[1]: *** [test/CMakeFiles/CBL_C_Tests.dir/all] Error 2
make: *** [all] Error 2
Error: Process completed with exit code 2.

[frank-dspeed]

yes keep that work up as the WSL on windows allows that also i guess even cygwin allows that we also use that to binary pipe blobs into chrome on windows via the devtools protocol and this is a nice feat as it will allow my wasm implementation to take browser blobs directly in and out that makes streaming to the couchbase cluster via direct socket api experiment that we currently run much more nice.

Only for your interrest i am building a poc that directly uses current chromium dev the feat is already included to directly connect via the couchbase sdk to a couchbase cluster anyway i also build cblite to wasm and i am using then the binary in and output

it would help me if you could maybe make the fleece api run able more isolated so that i could create cblite with indexdb to run complet in the browser.

[pasin]

@snej Can you check the build failure?

[frank-dspeed]

@pasin please use the latest version and tell me if that happens with that also