fluidsynth/doc/fluidsynth_sfload_mem.c

/*
 * This is a C99 program that demonstrates how to load a soundfont from memory.
 * 
 * It only gives a brief overview on how to achieve this with fluidsynth's API.
 * Although it should compile, it's highly incomplete, as the details of it's
 * implementation depend on the users needs.
 */

#include <stdio.h>
#include <string.h>
#include <fluidsynth.h>

void * my_open(const char * filename)
{
    void* p;
    if(filename[0] != '&')
    {
        return NULL;
    }
    scanf("&%p", &p);
    return p;
}

int my_read(void *buf, int count, void * handle)
{
    // not yet implemented
    memset(buf, 0, count);
    return FLUID_OK;
}

int my_seek(void * handle, long offset, int origin)
{
    // NYI
    return FLUID_OK;
}

int my_close(void * handle)
{
    // NYI
    return FLUID_OK;
}

long my_tell(void * handle)
{
    // NYI
    return 0;
}

fluid_file_callbacks_t my_cb =
{
    .fopen = my_open,
    .fread = my_read,
    .fseek = my_seek,
    .fclose = my_close,
    .ftell = my_tell
};

int main()
{
    int err = 0;

    fluid_settings_t* settings = new_fluid_settings();
    fluid_synth_t* synth = new_fluid_synth(settings);
    
    fluid_sfloader_t* my_sfloader = new_fluid_defsfloader(settings);
    my_sfloader->file_callbacks = &my_cb;
    fluid_synth_add_sfloader(synth, my_sfloader);
    
    
    char abused_filename[64];
    const void* pointer_to_sf2_in_mem = 0x1234Beef; // some pointer to where the soundfont shall be loaded from
    sprintf(abused_filename, "&%p", pointer_to_sf2_in_mem);
    
    int id = fluid_synth_sfload(synth, abused_filename, 0);
    /* now my_open() will be called with abused_filename and should have opened the memory region */
    
    if(id == FLUID_FAILED)
    {
        puts("oops");
        err = -1;
        goto cleanup;
    }

    /*
     * ~~~ Do your daily business here ~~~
     */
    
cleanup:    
    /* deleting the synth also deletes my_sfloader */
    delete_fluid_synth(synth);
    
    delete_fluid_settings(settings);
    
    return err;
}