The RobinHood library

The RobinHood library is the heart of the RobinHood project (since version 4). It provides an efficient C-API to store and query any filesystem's metadata.

A broad description of its internals is available here.

Installation

Download the sources:

git clone https://github.com/cea-hpc/librobinhood.git
cd librobinhood

Build and install with meson and ninja:

meson builddir
ninja -C builddir
sudo ninja -C builddir install

Documentation

To build the API documentation, use doxygen:

# Generate a template configuration file for doxygen (Doxyfile)
doxygen -g

# Change some of the default parameters:
doxyconfig() {
    sed -i "s|\($1\s*\)=.*$|\1= ${*:2}|" Doxyfile
}
doxyconfig PROJECT_NAME      librobinhood
doxyconfig INPUT             include/robinhood
doxyconfig RECURSIVE         YES
doxyconfig FILE_PATTERNS     "*.h" "*.h.in"
doxyconfig EXTENSION_MAPPING in=C
doxyconfig EXTRACT_ALL       YES
doxyconfig EXTRACT_STATIC    YES
doxyconfig ALIASES           error=@exception

# Run doxygen
doxygen

Usage

The following program, linked with the RobinHood library, will print the name of every entry under the current directory and exit:

#include <errno.h>
#include <error.h>
#include <stdio.h>
#include <stdlib.h>

#include <robinhood.h>
#include <robinhood/utils.h>

static const char *uri = "rbh:posix:.";

int
main()
{
    struct rbh_filter_options options = {
        .projection = {
            .fsentry_mask = RBH_FP_NAME,
        }
    };
    struct rbh_mut_iterator *fsentries;
    struct rbh_backend *backend;

    /* Build a backend from a URI */
    backend = rbh_backend_from_uri(uri);

    /* Fetch every fsentry */
    fsentries = rbh_backend_filter(backend, NULL, &options);

    /* Iterate over each fsentry and print its name (if it is set) */
    while (1) {
        struct rbh_fsentry *fsentry;

        errno = 0;
        fsentry = rbh_mut_iter_next(fsentries);
        if (fsentry == NULL)
            break;

        /* Some fsentries may not have a name in the backend */
        if (fsentry->mask & RBH_FP_NAME)
            printf("%s\n", fsentry->name);
    }

    if (errno != ENODATA)
        error(EXIT_FAILURE, errno, "while iterating over %s", uri);

    rbh_mut_iter_destroy(fsentries);
    rbh_backend_destroy(backend);

    return EXIT_SUCCESS;
}

For more advanced use cases, check out the following applications built on top of librobinhood:

• rbh-sync to synchronize two backends
• rbh-fsevents to update a backend with changelog events
• rbh-find to query a backend and filter entries