Re: [PATCH 2/3] Introduce scoped_mmapped_file

[Tom Tromey <tom@tromey.com>]

>>>>> "Simon" == Simon Marchi <simon.marchi@ericsson.com> writes:

Simon> We already have scoped_mmap, which can is a thin RAII layer over mmap.
Simon> If one simply wants to mmap an entire file for reading, it takes a bit
Simon> of boilerplate.  This patch introduces the scoped_mmapped_file class to
Simon> make this easier.

Simon> +  /* Map FILENAME in memory.  Throw an error if anything goes wrong.  */
Simon> +  scoped_mmapped_file (const char *filename)
Simon> +  {
Simon> +    m_fd.reset (open (filename, O_RDONLY));
Simon> +    if (m_fd.get () < 0)
Simon> +      perror_with_name ("open");
Simon> +
Simon> +    off_t size = lseek (m_fd.get (), 0, SEEK_END);
Simon> +    if (size < 0)
Simon> +      perror_with_name ("lseek");
Simon> +
Simon> +    /* We can't map an empty file.  */
Simon> +    if (size == 0)
Simon> +      error (_("file to mmap is empty"));
Simon> +
Simon> +    m_mmap.reset (nullptr, size, PROT_READ, MAP_PRIVATE, m_fd.get (), 0);
Simon> +    if (m_mmap.get () == MAP_FAILED)
Simon> +      perror_with_name ("mmap");

It seems to me that there's no need to keep the fd open after the mmap,
so this could be done by just having the scoped_fd as a local variable,
and then I suppose the scoped_fd changes wouldn't be needed either.

Tom