LXR toybox/lib/portability.c

   1/* portability.c - code to workaround the deficiencies of various platforms.
   2 *
   3 * Copyright 2012 Rob Landley <rob@landley.net>
   4 * Copyright 2012 Georgi Chorbadzhiyski <gf@unixsol.org>
   5 */
   6
   7#include "toys.h"
   8
   9// We can't fork() on nommu systems, and vfork() requires an exec() or exit()
  10// before resuming the parent (because they share a heap until then). And no,
  11// we can't implement our own clone() call that does the equivalent of fork()
  12// because nommu heaps use physical addresses so if we copy the heap all our
  13// pointers are wrong. (You need an mmu in order to map two heaps to the same
  14// address range without interfering with each other.) In the absence of
  15// a portable way to tell malloc() to start a new heap without freeing the old
  16// one, you pretty much need the exec().)
  17
  18// So we exec ourselves (via /proc/self/exe, if anybody knows a way to
  19// re-exec self without depending on the filesystem, I'm all ears),
  20// and use the arguments to signal reentry.
  21
  22#if CFG_TOYBOX_FORK
  23pid_t xfork(void)
  24{
  25  pid_t pid = fork();
  26
  27  if (pid < 0) perror_exit("fork");
  28
  29  return pid;
  30}
  31#endif
  32
  33#if defined(__APPLE__)
  34ssize_t getdelim(char **linep, size_t *np, int delim, FILE *stream)
  35{
  36  int ch;
  37  size_t new_len;
  38  ssize_t i = 0;
  39  char *line, *new_line;
  40
  41  // Invalid input
  42  if (!linep || !np) {
  43    errno = EINVAL;
  44    return -1;
  45  }
  46
  47  if (*linep == NULL || *np == 0) {
  48    *np = 1024;
  49    *linep = calloc(1, *np);
  50    if (*linep == NULL) return -1;
  51  }
  52  line = *linep;
  53
  54  while ((ch = getc(stream)) != EOF) {
  55    if (i > *np) {
  56      // Need more space
  57      new_len = *np + 1024;
  58      new_line = realloc(*linep, new_len);
  59      if (!new_line) return -1;
  60      *np = new_len;
  61      line = *linep = new_line;
  62    }
  63
  64    line[i++] = ch;
  65    if (ch == delim) break;
  66  }
  67
  68  if (i > *np) {
  69    // Need more space
  70    new_len  = i + 2;
  71    new_line = realloc(*linep, new_len);
  72    if (!new_line) return -1;
  73    *np = new_len;
  74    line = *linep = new_line;
  75  }
  76  line[i] = '\0';
  77
  78  return i > 0 ? i : -1;
  79}
  80
  81ssize_t getline(char **linep, size_t *np, FILE *stream)
  82{
  83  return getdelim(linep, np, '\n', stream);
  84}
  85
  86extern char **environ;
  87
  88int clearenv(void)
  89{
  90  *environ = NULL;
  91  return 0;
  92}
  93#endif
  94