Split lib/xwrap.c from lib/lib.c

3 files changed, 488 insertions, 482 deletions

diff --git a/lib/lib.c b/lib/lib.c
index af347ca5..52c95147 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -1,28 +1,10 @@
-/* lib.c - reusable stuff.
- *
- * Functions with the x prefix are wrappers for library functions.  They either
- * succeed or kill the program with an error message, but never return failure.
- * They usually have the same arguments and return value as the function they
- * wrap.
+/* lib.c - various reusable stuff.
  *
  * Copyright 2006 Rob Landley <rob@landley.net>
  */
 
 #include "toys.h"
 
-// Strcpy with size checking: exit if there's not enough space for the string.
-void xstrncpy(char *dest, char *src, size_t size)
-{
-  if (strlen(src)+1 > size) error_exit("xstrcpy");
-  strcpy(dest, src);
-}
-
-void xexit(void)
-{
-  if (toys.rebound) longjmp(*toys.rebound, 1);
-  else exit(toys.exitval);
-}
-
 void verror_msg(char *msg, int err, va_list va)
 {
   char *s = ": %s";
@@ -67,7 +49,6 @@ void error_exit(char *msg, ...)
   xexit();
 }
 
-
 // Die with an error message and strerror(errno)
 void perror_exit(char *msg, ...)
 {
@@ -80,153 +61,6 @@ void perror_exit(char *msg, ...)
   xexit();
 }
 
-// Die unless we can allocate memory.
-void *xmalloc(size_t size)
-{
-  void *ret = malloc(size);
-  if (!ret) error_exit("xmalloc");
-
-  return ret;
-}
-
-// Die unless we can allocate prezeroed memory.
-void *xzalloc(size_t size)
-{
-  void *ret = xmalloc(size);
-  memset(ret, 0, size);
-  return ret;
-}
-
-// Die unless we can change the size of an existing allocation, possibly
-// moving it.  (Notice different arguments from libc function.)
-void *xrealloc(void *ptr, size_t size)
-{
-  ptr = realloc(ptr, size);
-  if (!ptr) error_exit("xrealloc");
-
-  return ptr;
-}
-
-// Die unless we can allocate a copy of this many bytes of string.
-char *xstrndup(char *s, size_t n)
-{
-  char *ret = xmalloc(++n);
-  strncpy(ret, s, n);
-  ret[--n]=0;
-
-  return ret;
-}
-
-// Die unless we can allocate a copy of this string.
-char *xstrdup(char *s)
-{
-  return xstrndup(s, strlen(s));
-}
-
-// Die unless we can allocate enough space to sprintf() into.
-char *xmsprintf(char *format, ...)
-{
-  va_list va, va2;
-  int len;
-  char *ret;
-
-  va_start(va, format);
-  va_copy(va2, va);
-
-  // How long is it?
-  len = vsnprintf(0, 0, format, va);
-  len++;
-  va_end(va);
-
-  // Allocate and do the sprintf()
-  ret = xmalloc(len);
-  vsnprintf(ret, len, format, va2);
-  va_end(va2);
-
-  return ret;
-}
-
-void xprintf(char *format, ...)
-{
-  va_list va;
-  va_start(va, format);
-
-  vprintf(format, va);
-  if (ferror(stdout)) perror_exit("write");
-}
-
-void xputs(char *s)
-{
-  if (EOF == puts(s) || fflush(stdout)) perror_exit("write");
-}
-
-void xputc(char c)
-{
-  if (EOF == fputc(c, stdout) || fflush(stdout)) perror_exit("write");
-}
-
-void xflush(void)
-{
-  if (fflush(stdout)) perror_exit("write");;
-}
-
-// Die unless we can exec argv[] (or run builtin command).  Note that anything
-// with a path isn't a builtin, so /bin/sh won't match the builtin sh.
-void xexec(char **argv)
-{
-  toy_exec(argv);
-  execvp(argv[0], argv);
-
-  perror_exit("exec %s", argv[0]);
-}
-
-void xaccess(char *path, int flags)
-{
-  if (access(path, flags)) perror_exit("Can't access '%s'", path);
-}
-
-// Die unless we can delete a file.  (File must exist to be deleted.)
-void xunlink(char *path)
-{
-  if (unlink(path)) perror_exit("unlink '%s'", path);
-}
-
-// Die unless we can open/create a file, returning file descriptor.
-int xcreate(char *path, int flags, int mode)
-{
-  int fd = open(path, flags, mode);
-  if (fd == -1) perror_exit("%s", path);
-  return fd;
-}
-
-// Die unless we can open a file, returning file descriptor.
-int xopen(char *path, int flags)
-{
-  return xcreate(path, flags, 0);
-}
-
-void xclose(int fd)
-{
-  if (close(fd)) perror_exit("xclose");
-}
-
-int xdup(int fd)
-{
-  if (fd != -1) {
-    fd = dup(fd);
-    if (fd == -1) perror_exit("xdup");
-  }
-  return fd;
-}
-
-// Die unless we can open/create a file, returning FILE *.
-FILE *xfopen(char *path, char *mode)
-{
-  FILE *f = fopen(path, mode);
-  if (!f) perror_exit("No file %s", path);
-  return f;
-}
-
 // Keep reading until full or EOF
 ssize_t readall(int fd, void *buf, size_t len)
 {
@@ -255,39 +89,6 @@ ssize_t writeall(int fd, void *buf, size_t len)
   return count;
 }
 
-// Die if there's an error other than EOF.
-size_t xread(int fd, void *buf, size_t len)
-{
-  ssize_t ret = read(fd, buf, len);
-  if (ret < 0) perror_exit("xread");
-
-  return ret;
-}
-
-void xreadall(int fd, void *buf, size_t len)
-{
-  if (len != readall(fd, buf, len)) perror_exit("xreadall");
-}
-
-// There's no xwriteall(), just xwrite().  When we read, there may or may not
-// be more data waiting.  When we write, there is data and it had better go
-// somewhere.
-
-void xwrite(int fd, void *buf, size_t len)
-{
-  if (len != writeall(fd, buf, len)) perror_exit("xwrite");
-}
-
-// Die if lseek fails, probably due to being called on a pipe.
-
-off_t xlseek(int fd, off_t offset, int whence)
-{
-  offset = lseek(fd, offset, whence);
-  if (offset<0) perror_exit("lseek");
-
-  return offset;
-}
-
 off_t lskip(int fd, off_t offset)
 {
   off_t and = lseek(fd, offset, SEEK_CUR);
@@ -309,19 +110,6 @@ off_t lskip(int fd, off_t offset)
   }
 }
 
-char *xgetcwd(void)
-{
-  char *buf = getcwd(NULL, 0);
-  if (!buf) perror_exit("xgetcwd");
-
-  return buf;
-}
-
-void xstat(char *path, struct stat *st)
-{
-  if(stat(path, st)) perror_exit("Can't stat %s", path);
-}
-
 // Split a path into linked list of components, tracking head and tail of list.
 // Filters out // entries with no contents.
 struct string_list **splitpath(char *path, struct string_list **list)
@@ -347,171 +135,6 @@ struct string_list **splitpath(char *path, struct string_list **list)
   return list;
 }
 
-// Cannonicalize path, even to file with one or more missing components at end.
-// if exact, require last path component to exist
-char *xabspath(char *path, int exact) 
-{
-  struct string_list *todo, *done = 0;
-  int try = 9999, dirfd = open("/", 0);;
-  char buf[4096], *ret;
-
-  // If this isn't an absolute path, start with cwd.
-  if (*path != '/') {
-    char *temp = xgetcwd();
-
-    splitpath(path, splitpath(temp, &todo));
-    free(temp);
-  } else splitpath(path, &todo);
-
-  // Iterate through path components
-  while (todo) {
-    struct string_list *new = llist_pop(&todo), **tail;
-    ssize_t len;
-
-    if (!try--) {
-      errno = ELOOP;
-      goto error;
-    }
-
-    // Removable path componenents.
-    if (!strcmp(new->str, ".") || !strcmp(new->str, "..")) {
-      int x = new->str[1];
-
-      free(new);
-      if (x) {
-        if (done) free(llist_pop(&done));
-        len = 0;
-      } else continue;
-
-    // Is this a symlink?
-    } else len=readlinkat(dirfd, new->str, buf, 4096);
-
-    if (len>4095) goto error;
-    if (len<1) {
-      int fd;
-      char *s = "..";
-
-      // For .. just move dirfd
-      if (len) {
-        // Not a symlink: add to linked list, move dirfd, fail if error
-        if ((exact || todo) && errno != EINVAL) goto error;
-        new->next = done;
-        done = new;
-        if (errno == EINVAL && !todo) break;
-        s = new->str;
-      }
-      fd = openat(dirfd, s, 0);
-      if (fd == -1 && (exact || todo || errno != ENOENT)) goto error;
-      close(dirfd);
-      dirfd = fd;
-      continue;
-    }
-
-    // If this symlink is to an absolute path, discard existing resolved path
-    buf[len] = 0;
-    if (*buf == '/') {
-      llist_traverse(done, free);
-      done=0;
-      close(dirfd);
-      dirfd = open("/", 0);
-    }
-    free(new);
-
-    // prepend components of new path. Note symlink to "/" will leave new NULL
-    tail = splitpath(buf, &new);
-
-    // symlink to "/" will return null and leave tail alone
-    if (new) {
-      *tail = todo;
-      todo = new;
-    }
-  }
-  close(dirfd);
-
-  // At this point done has the path, in reverse order. Reverse list while
-  // calculating buffer length.
-
-  try = 2;
-  while (done) {
-    struct string_list *temp = llist_pop(&done);;
-
-    if (todo) try++;
-    try += strlen(temp->str);
-    temp->next = todo;
-    todo = temp;
-  }
-
-  // Assemble return buffer
-
-  ret = xmalloc(try);
-  *ret = '/';
-  ret [try = 1] = 0;
-  while (todo) {
-    if (try>1) ret[try++] = '/';
-    try = stpcpy(ret+try, todo->str) - ret;
-    free(llist_pop(&todo));
-  }
-
-  return ret;
-
-error:
-  close(dirfd);
-  llist_traverse(todo, free);
-  llist_traverse(done, free);
-
-  return NULL;
-}
-
-// Resolve all symlinks, returning malloc() memory.
-char *xrealpath(char *path)
-{
-  char *new = realpath(path, NULL);
-  if (!new) perror_exit("realpath '%s'", path);
-  return new;
-}
-
-void xchdir(char *path)
-{
-  if (chdir(path)) error_exit("chdir '%s'", path);
-}
-
-// Ensure entire path exists.
-// If mode != -1 set permissions on newly created dirs.
-// Requires that path string be writable (for temporary null terminators).
-void xmkpath(char *path, int mode)
-{
-  char *p, old;
-  mode_t mask;
-  int rc;
-  struct stat st;
-
-  for (p = path; ; p++) {
-    if (!*p || *p == '/') {
-      old = *p;
-      *p = rc = 0;
-      if (stat(path, &st) || !S_ISDIR(st.st_mode)) {
-        if (mode != -1) {
-          mask=umask(0);
-          rc = mkdir(path, mode);
-          umask(mask);
-        } else rc = mkdir(path, 0777);
-      }
-      *p = old;
-      if(rc) perror_exit("mkpath '%s'", path);
-    }
-    if (!*p) break;
-  }
-}
-
-// setuid() can fail (for example, too many processes belonging to that user),
-// which opens a security hole if the process continues as the original user.
-
-void xsetuid(uid_t uid)
-{
-  if (setuid(uid)) perror_exit("xsetuid");
-}
-
-
 // Find all file in a colon-separated path with access type "type" (generally
 // X_OK or R_OK).  Returns a list of absolute paths to each file found, in
 // order.
@@ -692,30 +315,6 @@ off_t fdlength(int fd)
   return pos + 1;
 }
 
-// This can return null (meaning file not found).  It just won't return null
-// for memory allocation reasons.
-char *xreadlink(char *name)
-{
-  int len, size = 0;
-  char *buf = 0;
-
-  // Grow by 64 byte chunks until it's big enough.
-  for(;;) {
-    size +=64;
-    buf = xrealloc(buf, size);
-    len = readlink(name, buf, size);
-
-    if (len<0) {
-      free(buf);
-      return 0;
-    }
-    if (len<size) {
-      buf[len]=0;
-      return buf;
-    }
-  }
-}
-
 // Read contents of file as a single freshly allocated nul-terminated string.
 char *readfile(char *name)
 {
@@ -732,13 +331,6 @@ char *readfile(char *name)
   return buf;
 }
 
-char *xreadfile(char *name)
-{
-  char *buf = readfile(name);
-  if (!buf) perror_exit("xreadfile %s", name);
-  return buf;
-}
-
 // Sleep for this many thousandths of a second
 void msleep(long miliseconds)
 {
@@ -749,17 +341,6 @@ void msleep(long miliseconds)
   nanosleep(&ts, &ts);
 }
 
-int xioctl(int fd, int request, void *data)
-{
-  int rc;
-
-  errno = 0;
-  rc = ioctl(fd, request, data);
-  if (rc == -1 && errno) perror_exit("ioctl %x", request);
-
-  return rc;
-}
-
 int64_t peek(void *ptr, int size)
 {
   if (size & 8) {
@@ -794,39 +375,6 @@ void poke(void *ptr, uint64_t val, int size)
   }
 }
 
-// Open a /var/run/NAME.pid file, dying if we can't write it or if it currently
-// exists and is this executable.
-void xpidfile(char *name)
-{
-  char pidfile[256], spid[32];
-  int i, fd;
-  pid_t pid;
-
-  sprintf(pidfile, "/var/run/%s.pid", name);
-  // Try three times to open the sucker.
-  for (i=0; i<3; i++) {
-    fd = open(pidfile, O_CREAT|O_EXCL, 0644);
-    if (fd != -1) break;
-
-    // If it already existed, read it.  Loop for race condition.
-    fd = open(pidfile, O_RDONLY);
-    if (fd == -1) continue;
-
-    // Is the old program still there?
-    spid[xread(fd, spid, sizeof(spid)-1)] = 0;
-    close(fd);
-    pid = atoi(spid);
-    if (pid < 1 || kill(pid, 0) == ESRCH) unlink(pidfile);
-
-    // An else with more sanity checking might be nice here.
-  }
-
-  if (i == 3) error_exit("xpidfile %s", name);
-
-  xwrite(fd, spid, sprintf(spid, "%ld\n", (long)getpid()));
-  close(fd);
-}
-
 // Iterate through an array of files, opening each one and calling a function
 // on that filehandle and name.  The special filename "-" means stdin if
 // flags is O_RDONLY, stdout otherwise.  An empty argument list calls
@@ -890,21 +438,6 @@ char *get_line(int fd)
   return buf;
 }
 
-// Copy the rest of in to out and close both files.
-
-void xsendfile(int in, int out)
-{
-  long len;
-  char buf[4096];
-
-  if (in<0) return;
-  for (;;) {
-    len = xread(in, buf, 4096);
-    if (len<1) break;
-    xwrite(out, buf, len);
-  }
-}
-
 int wfchmodat(int fd, char *name, mode_t mode)
 {
   int rc = fchmodat(fd, name, mode, 0);
diff --git a/lib/lib.h b/lib/lib.h
index 2b65495a..907d96eb 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -85,14 +85,9 @@ struct dirtree *dirtree_read(char *path, int (*callback)(struct dirtree *node));
 
 void show_help(void);
 
-// lib.c
+// xfuncs.c
 void xstrncpy(char *dest, char *src, size_t size);
 void xexit(void) noreturn;
-void verror_msg(char *msg, int err, va_list va);
-void error_msg(char *msg, ...);
-void perror_msg(char *msg, ...);
-void error_exit(char *msg, ...) noreturn;
-void perror_exit(char *msg, ...) noreturn;
 void *xmalloc(size_t size);
 void *xzalloc(size_t size);
 void *xrealloc(void *ptr, size_t size);
@@ -111,19 +106,12 @@ int xopen(char *path, int flags);
 void xclose(int fd);
 int xdup(int fd);
 FILE *xfopen(char *path, char *mode);
-ssize_t readall(int fd, void *buf, size_t len);
-ssize_t writeall(int fd, void *buf, size_t len);
 size_t xread(int fd, void *buf, size_t len);
 void xreadall(int fd, void *buf, size_t len);
 void xwrite(int fd, void *buf, size_t len);
 off_t xlseek(int fd, off_t offset, int whence);
-off_t lskip(int fd, off_t offset);
-char *readfile(char *name);
 char *xreadfile(char *name);
-void msleep(long miliseconds);
 int xioctl(int fd, int request, void *data);
-int64_t peek(void *ptr, int size);
-void poke(void *ptr, uint64_t val, int size);
 char *xgetcwd(void);
 void xstat(char *path, struct stat *st);
 char *xabspath(char *path, int exact);
@@ -131,6 +119,22 @@ char *xrealpath(char *path);
 void xchdir(char *path);
 void xmkpath(char *path, int mode);
 void xsetuid(uid_t uid);
+char *xreadlink(char *name);
+
+// lib.c
+void verror_msg(char *msg, int err, va_list va);
+void error_msg(char *msg, ...);
+void perror_msg(char *msg, ...);
+void error_exit(char *msg, ...) noreturn;
+void perror_exit(char *msg, ...) noreturn;
+ssize_t readall(int fd, void *buf, size_t len);
+ssize_t writeall(int fd, void *buf, size_t len);
+off_t lskip(int fd, off_t offset);
+struct string_list **splitpath(char *path, struct string_list **list);
+char *readfile(char *name);
+void msleep(long miliseconds);
+int64_t peek(void *ptr, int size);
+void poke(void *ptr, uint64_t val, int size);
 struct string_list *find_in_path(char *path, char *filename);
 void utoa_to_buf(unsigned n, char *buf, unsigned buflen);
 void itoa_to_buf(int n, char *buf, unsigned buflen);
@@ -140,7 +144,6 @@ long atolx(char *c);
 int numlen(long l);
 int stridx(char *haystack, char needle);
 off_t fdlength(int fd);
-char *xreadlink(char *name);
 void loopfiles_rw(char **argv, int flags, int permissions, int failok,
   void (*function)(int fd, char *name));
 void loopfiles(char **argv, void (*function)(int fd, char *name));
diff --git a/lib/xwrap.c b/lib/xwrap.c
new file mode 100644
index 00000000..b0029eef
--- /dev/null
+++ b/lib/xwrap.c
@@ -0,0 +1,470 @@
+/* xwrap.c - wrappers around existing library functions.
+ *
+ * Functions with the x prefix are wrappers that either succeed or kill the
+ * program with an error message, but never return failure. They usually have
+ * the same arguments and return value as the function they wrap.
+ *
+ * Copyright 2006 Rob Landley <rob@landley.net>
+ */
+
+#include "toys.h"
+
+// Strcpy with size checking: exit if there's not enough space for the string.
+void xstrncpy(char *dest, char *src, size_t size)
+{
+  if (strlen(src)+1 > size) error_exit("xstrcpy");
+  strcpy(dest, src);
+}
+
+void xexit(void)
+{
+  if (toys.rebound) longjmp(*toys.rebound, 1);
+  else exit(toys.exitval);
+}
+
+// Die unless we can allocate memory.
+void *xmalloc(size_t size)
+{
+  void *ret = malloc(size);
+  if (!ret) error_exit("xmalloc");
+
+  return ret;
+}
+
+// Die unless we can allocate prezeroed memory.
+void *xzalloc(size_t size)
+{
+  void *ret = xmalloc(size);
+  memset(ret, 0, size);
+  return ret;
+}
+
+// Die unless we can change the size of an existing allocation, possibly
+// moving it.  (Notice different arguments from libc function.)
+void *xrealloc(void *ptr, size_t size)
+{
+  ptr = realloc(ptr, size);
+  if (!ptr) error_exit("xrealloc");
+
+  return ptr;
+}
+
+// Die unless we can allocate a copy of this many bytes of string.
+char *xstrndup(char *s, size_t n)
+{
+  char *ret = xmalloc(++n);
+  strncpy(ret, s, n);
+  ret[--n]=0;
+
+  return ret;
+}
+
+// Die unless we can allocate a copy of this string.
+char *xstrdup(char *s)
+{
+  return xstrndup(s, strlen(s));
+}
+
+// Die unless we can allocate enough space to sprintf() into.
+char *xmsprintf(char *format, ...)
+{
+  va_list va, va2;
+  int len;
+  char *ret;
+
+  va_start(va, format);
+  va_copy(va2, va);
+
+  // How long is it?
+  len = vsnprintf(0, 0, format, va);
+  len++;
+  va_end(va);
+
+  // Allocate and do the sprintf()
+  ret = xmalloc(len);
+  vsnprintf(ret, len, format, va2);
+  va_end(va2);
+
+  return ret;
+}
+
+void xprintf(char *format, ...)
+{
+  va_list va;
+  va_start(va, format);
+
+  vprintf(format, va);
+  if (ferror(stdout)) perror_exit("write");
+}
+
+void xputs(char *s)
+{
+  if (EOF == puts(s) || fflush(stdout)) perror_exit("write");
+}
+
+void xputc(char c)
+{
+  if (EOF == fputc(c, stdout) || fflush(stdout)) perror_exit("write");
+}
+
+void xflush(void)
+{
+  if (fflush(stdout)) perror_exit("write");;
+}
+
+// Die unless we can exec argv[] (or run builtin command).  Note that anything
+// with a path isn't a builtin, so /bin/sh won't match the builtin sh.
+void xexec(char **argv)
+{
+  toy_exec(argv);
+  execvp(argv[0], argv);
+
+  perror_exit("exec %s", argv[0]);
+}
+
+void xaccess(char *path, int flags)
+{
+  if (access(path, flags)) perror_exit("Can't access '%s'", path);
+}
+
+// Die unless we can delete a file.  (File must exist to be deleted.)
+void xunlink(char *path)
+{
+  if (unlink(path)) perror_exit("unlink '%s'", path);
+}
+
+// Die unless we can open/create a file, returning file descriptor.
+int xcreate(char *path, int flags, int mode)
+{
+  int fd = open(path, flags, mode);
+  if (fd == -1) perror_exit("%s", path);
+  return fd;
+}
+
+// Die unless we can open a file, returning file descriptor.
+int xopen(char *path, int flags)
+{
+  return xcreate(path, flags, 0);
+}
+
+void xclose(int fd)
+{
+  if (close(fd)) perror_exit("xclose");
+}
+
+int xdup(int fd)
+{
+  if (fd != -1) {
+    fd = dup(fd);
+    if (fd == -1) perror_exit("xdup");
+  }
+  return fd;
+}
+
+// Die unless we can open/create a file, returning FILE *.
+FILE *xfopen(char *path, char *mode)
+{
+  FILE *f = fopen(path, mode);
+  if (!f) perror_exit("No file %s", path);
+  return f;
+}
+
+// Die if there's an error other than EOF.
+size_t xread(int fd, void *buf, size_t len)
+{
+  ssize_t ret = read(fd, buf, len);
+  if (ret < 0) perror_exit("xread");
+
+  return ret;
+}
+
+void xreadall(int fd, void *buf, size_t len)
+{
+  if (len != readall(fd, buf, len)) perror_exit("xreadall");
+}
+
+// There's no xwriteall(), just xwrite().  When we read, there may or may not
+// be more data waiting.  When we write, there is data and it had better go
+// somewhere.
+
+void xwrite(int fd, void *buf, size_t len)
+{
+  if (len != writeall(fd, buf, len)) perror_exit("xwrite");
+}
+
+// Die if lseek fails, probably due to being called on a pipe.
+
+off_t xlseek(int fd, off_t offset, int whence)
+{
+  offset = lseek(fd, offset, whence);
+  if (offset<0) perror_exit("lseek");
+
+  return offset;
+}
+
+char *xgetcwd(void)
+{
+  char *buf = getcwd(NULL, 0);
+  if (!buf) perror_exit("xgetcwd");
+
+  return buf;
+}
+
+void xstat(char *path, struct stat *st)
+{
+  if(stat(path, st)) perror_exit("Can't stat %s", path);
+}
+
+// Cannonicalize path, even to file with one or more missing components at end.
+// if exact, require last path component to exist
+char *xabspath(char *path, int exact) 
+{
+  struct string_list *todo, *done = 0;
+  int try = 9999, dirfd = open("/", 0);;
+  char buf[4096], *ret;
+
+  // If this isn't an absolute path, start with cwd.
+  if (*path != '/') {
+    char *temp = xgetcwd();
+
+    splitpath(path, splitpath(temp, &todo));
+    free(temp);
+  } else splitpath(path, &todo);
+
+  // Iterate through path components
+  while (todo) {
+    struct string_list *new = llist_pop(&todo), **tail;
+    ssize_t len;
+
+    if (!try--) {
+      errno = ELOOP;
+      goto error;
+    }
+
+    // Removable path componenents.
+    if (!strcmp(new->str, ".") || !strcmp(new->str, "..")) {
+      int x = new->str[1];
+
+      free(new);
+      if (x) {
+        if (done) free(llist_pop(&done));
+        len = 0;
+      } else continue;
+
+    // Is this a symlink?
+    } else len=readlinkat(dirfd, new->str, buf, 4096);
+
+    if (len>4095) goto error;
+    if (len<1) {
+      int fd;
+      char *s = "..";
+
+      // For .. just move dirfd
+      if (len) {
+        // Not a symlink: add to linked list, move dirfd, fail if error
+        if ((exact || todo) && errno != EINVAL) goto error;
+        new->next = done;
+        done = new;
+        if (errno == EINVAL && !todo) break;
+        s = new->str;
+      }
+      fd = openat(dirfd, s, 0);
+      if (fd == -1 && (exact || todo || errno != ENOENT)) goto error;
+      close(dirfd);
+      dirfd = fd;
+      continue;
+    }
+
+    // If this symlink is to an absolute path, discard existing resolved path
+    buf[len] = 0;
+    if (*buf == '/') {
+      llist_traverse(done, free);
+      done=0;
+      close(dirfd);
+      dirfd = open("/", 0);
+    }
+    free(new);
+
+    // prepend components of new path. Note symlink to "/" will leave new NULL
+    tail = splitpath(buf, &new);
+
+    // symlink to "/" will return null and leave tail alone
+    if (new) {
+      *tail = todo;
+      todo = new;
+    }
+  }
+  close(dirfd);
+
+  // At this point done has the path, in reverse order. Reverse list while
+  // calculating buffer length.
+
+  try = 2;
+  while (done) {
+    struct string_list *temp = llist_pop(&done);;
+
+    if (todo) try++;
+    try += strlen(temp->str);
+    temp->next = todo;
+    todo = temp;
+  }
+
+  // Assemble return buffer
+
+  ret = xmalloc(try);
+  *ret = '/';
+  ret [try = 1] = 0;
+  while (todo) {
+    if (try>1) ret[try++] = '/';
+    try = stpcpy(ret+try, todo->str) - ret;
+    free(llist_pop(&todo));
+  }
+
+  return ret;
+
+error:
+  close(dirfd);
+  llist_traverse(todo, free);
+  llist_traverse(done, free);
+
+  return NULL;
+}
+
+// Resolve all symlinks, returning malloc() memory.
+char *xrealpath(char *path)
+{
+  char *new = realpath(path, NULL);
+  if (!new) perror_exit("realpath '%s'", path);
+  return new;
+}
+
+void xchdir(char *path)
+{
+  if (chdir(path)) error_exit("chdir '%s'", path);
+}
+
+// Ensure entire path exists.
+// If mode != -1 set permissions on newly created dirs.
+// Requires that path string be writable (for temporary null terminators).
+void xmkpath(char *path, int mode)
+{
+  char *p, old;
+  mode_t mask;
+  int rc;
+  struct stat st;
+
+  for (p = path; ; p++) {
+    if (!*p || *p == '/') {
+      old = *p;
+      *p = rc = 0;
+      if (stat(path, &st) || !S_ISDIR(st.st_mode)) {
+        if (mode != -1) {
+          mask=umask(0);
+          rc = mkdir(path, mode);
+          umask(mask);
+        } else rc = mkdir(path, 0777);
+      }
+      *p = old;
+      if(rc) perror_exit("mkpath '%s'", path);
+    }
+    if (!*p) break;
+  }
+}
+
+// setuid() can fail (for example, too many processes belonging to that user),
+// which opens a security hole if the process continues as the original user.
+
+void xsetuid(uid_t uid)
+{
+  if (setuid(uid)) perror_exit("xsetuid");
+}
+
+// This can return null (meaning file not found).  It just won't return null
+// for memory allocation reasons.
+char *xreadlink(char *name)
+{
+  int len, size = 0;
+  char *buf = 0;
+
+  // Grow by 64 byte chunks until it's big enough.
+  for(;;) {
+    size +=64;
+    buf = xrealloc(buf, size);
+    len = readlink(name, buf, size);
+
+    if (len<0) {
+      free(buf);
+      return 0;
+    }
+    if (len<size) {
+      buf[len]=0;
+      return buf;
+    }
+  }
+}
+
+char *xreadfile(char *name)
+{
+  char *buf = readfile(name);
+  if (!buf) perror_exit("xreadfile %s", name);
+  return buf;
+}
+
+int xioctl(int fd, int request, void *data)
+{
+  int rc;
+
+  errno = 0;
+  rc = ioctl(fd, request, data);
+  if (rc == -1 && errno) perror_exit("ioctl %x", request);
+
+  return rc;
+}
+
+// Open a /var/run/NAME.pid file, dying if we can't write it or if it currently
+// exists and is this executable.
+void xpidfile(char *name)
+{
+  char pidfile[256], spid[32];
+  int i, fd;
+  pid_t pid;
+
+  sprintf(pidfile, "/var/run/%s.pid", name);
+  // Try three times to open the sucker.
+  for (i=0; i<3; i++) {
+    fd = open(pidfile, O_CREAT|O_EXCL, 0644);
+    if (fd != -1) break;
+
+    // If it already existed, read it.  Loop for race condition.
+    fd = open(pidfile, O_RDONLY);
+    if (fd == -1) continue;
+
+    // Is the old program still there?
+    spid[xread(fd, spid, sizeof(spid)-1)] = 0;
+    close(fd);
+    pid = atoi(spid);
+    if (pid < 1 || kill(pid, 0) == ESRCH) unlink(pidfile);
+
+    // An else with more sanity checking might be nice here.
+  }
+
+  if (i == 3) error_exit("xpidfile %s", name);
+
+  xwrite(fd, spid, sprintf(spid, "%ld\n", (long)getpid()));
+  close(fd);
+}
+
+// Copy the rest of in to out and close both files.
+
+void xsendfile(int in, int out)
+{
+  long len;
+  char buf[4096];
+
+  if (in<0) return;
+  for (;;) {
+    len = xread(in, buf, 4096);
+    if (len<1) break;
+    xwrite(out, buf, len);
+  }
+}