// examples/utils.c

#include <stddef.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>

#include "utils.h"

struct cmmm__sv
mmap_whole (int fd)
{
  struct cmmm__sv sv;

  struct stat st;
  int ret = fstat (fd, &st);
  UNUSED (ret);
  ASSERT_MSG (ret != -1, "fstat: %s", strerror (errno));
  ASSERT (S_ISREG (st.st_mode));

  posix_fadvise (fd, 0, st.st_size, POSIX_FADV_SEQUENTIAL |
                                    POSIX_FADV_WILLNEED |
                                    POSIX_FADV_NOREUSE);

  sv.begin = mmap (NULL, st.st_size, PROT_READ, MAP_PRIVATE |
                                                MAP_POPULATE |
                                                MAP_NONBLOCK, fd, 0);
  ASSERT_MSG (sv.begin != MAP_FAILED, "mmap: %s", strerror (errno));
  posix_madvise ((void *) sv.begin, st.st_size, MADV_HUGEPAGE | MADV_WILLNEED);

  sv.end = sv.begin + st.st_size;

  return sv;
}

struct cmmm__sv
read_until_eof (ARENA arena, int fd)
{
  struct arena__checkpoint checkpoint = arena__checkpoint (arena);
  size_t reserve = 4096;

  size_t read_total = 0;
  for (;;) {
    arena__reserve (arena, reserve, 1);
    ssize_t bytes_read = read (fd,
                               arena__next_free (arena, 1),
                               arena__room      (arena, 1));

    if (bytes_read < 0) {
      DEBUG ("fstat: %s", strerror (errno));
      arena__rollback_to (arena, checkpoint);
      return (struct cmmm__sv) {0};
    }

    if (bytes_read == 0)
      break;

    read_total += bytes_read;

    arena__allocate_fast (arena, bytes_read, 1);
    reserve *= 2;
  }

  if (arena->tail->free == checkpoint.free)
    return (struct cmmm__sv) {0};

  char *ptr = arena__coalesce_from_fast (arena, checkpoint, read_total);
  return (struct cmmm__sv) {
    .begin = ptr,
    .end   = ptr + read_total,
  };
}

// examples/utils.c ends here