The fopen, fread, fwrite et all functions are common and a standard "idiom" in many C programs.
By providing fcurl* functions with the same general behavior as the file based versions, but instead allowing URLs where file names are otherwise used, this is an attempt to allow existing file-based applications to switch over to read and write files over common internet protocols instead.
Maybe something like this?
FCURL *fcurl_open(const char *path, const char *mode);
size_t fcurl_read(void *ptr, size_t size, size_t nmemb, FCURL *stream);
size_t fcurl_write(const void *ptr, size_t size, size_t nmemb,
FCURL *stream);
int fcurl_flush(FCURL *stream);
int fcurl_close(FCURL *stream);
int fcurl_getc(FCURL *stream);
char *fcurl_gets(char *s, int size, FCURL *stream);
int fcurl_ungetc(int c, FCURL *stream);
int fcurl_seek(FCURL *stream, long offset, int whence);
long fcurl_tell(FCURL *stream);
void fcurl_rewind(FCURL *stream);
int fcurl_getpos(FCURL *stream, fpos_t *pos);
int fcurl_setpos(FCURL *stream, const fpos_t *pos);