split: support split -n on larger pipe input

* bootstrap.conf (gnulib_modules): Add free-posix, tmpfile.
* src/split.c (copy_to_tmpfile): New function.
(input_file_size): Use it to split larger files when sizes cannot
easily be determined via fstat or lseek.  See Bug#61386#235.
* tests/split/l-chunk.sh: Mark tests of /dev/zero as
very expensive since they exhaust /tmp.

NEWS

@@ -145,6 +145,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   split now accepts options like '-n SIZE' that exceed machine integer
   range, when they can be implemented as if they were infinity.
 
+  split -n now accepts piped input even when not in round-robin mode,
+  by first copying input to a temporary file to determine its size.
+
   wc now accepts the --total={auto,never,always,only} option
   to give explicit control over when the total is output.
 

bootstrap.conf

@@ -103,6 +103,7 @@ gnulib_modules="
   fnmatch-gnu
   fopen-safer
   fprintftime
+  free-posix
   freopen
   freopen-safer
   fseeko
@@ -270,6 +271,7 @@ gnulib_modules="
   time_rz
   timer-time
   timespec
+  tmpfile
   tzset
   uname
   unicodeio

doc/coreutils.texi

@@ -3409,8 +3409,10 @@ are not split even if they overlap a partition, the files written
 can be larger or smaller than the partition size, and even empty
 if a line/record is so long as to completely overlap the partition.
 
-For @samp{r} mode, the size of @var{input} is irrelevant,
-and so can be a pipe for example.
+When the input is a pipe or some other special file where the size
+cannot easily be determined, there is no trouble for @samp{r} mode
+because the size of the input is irrelevant.  For other modes, such an
+input is first copied to a temporary to determine its size.
 
 @item -a @var{length}
 @itemx --suffix-length=@var{length}

src/split.c

@@ -275,6 +275,39 @@ CHUNKS may be:\n\
   exit (status);
 }
 
+/* Copy the data in FD to a temporary file, then make that file FD.
+   Use BUF, of size BUFSIZE, to copy.  Return the number of
+   bytes copied, or -1 (setting errno) on error.  */
+static off_t
+copy_to_tmpfile (int fd, char *buf, idx_t bufsize)
+{
+  FILE *tmp = tmpfile ();
+  if (!tmp)
+    return -1;
+  off_t copied = 0;
+  off_t r;
+
+  while (0 < (r = read (fd, buf, bufsize)))
+    {
+      if (fwrite (buf, 1, r, tmp) != r)
+        return -1;
+      if (INT_ADD_WRAPV (copied, r, &copied))
+        {
+          errno = EOVERFLOW;
+          return -1;
+        }
+    }
+
+  if (r < 0)
+    return r;
+  r = dup2 (fileno (tmp), fd);
+  if (r < 0)
+    return r;
+  if (fclose (tmp) < 0)
+    return -1;
+  return copied;
+}
+
 /* Return the number of bytes that can be read from FD with status ST.
    Store up to the first BUFSIZE bytes of the file's data into BUF,
    and advance the file position by the number of bytes read.  On
@@ -293,49 +326,35 @@ input_file_size (int fd, struct stat const *st, char *buf, idx_t bufsize)
     }
   while (size < bufsize);
 
-  off_t cur = lseek (fd, 0, SEEK_CUR);
-  if (cur < 0)
+  off_t cur, end;
+  if ((usable_st_size (st) && st->st_size < size)
+      || (cur = lseek (fd, 0, SEEK_CUR)) < 0
+      || cur < size /* E.g., /dev/zero on GNU/Linux.  */
+      || (end = lseek (fd, 0, SEEK_END)) < 0)
     {
-      if (errno == ESPIPE)
-        errno = 0; /* Suppress confusing seek error.  */
-      return cur;
-    }
-
-  off_t end;
-  if (usable_st_size (st))
-    end = st->st_size;
-  else
-    {
-      end = lseek (fd, 0, SEEK_END);
+      char *tmpbuf = xmalloc (bufsize);
+      end = copy_to_tmpfile (fd, tmpbuf, bufsize);
+      free (tmpbuf);
       if (end < 0)
         return end;
-      if (end == OFF_T_MAX)
-        goto overflow;  /* E.g., /dev/zero on GNU/Hurd.  */
-      if (cur < end)
-        {
-          off_t cur1 = lseek (fd, cur, SEEK_SET);
-          if (cur1 < 0)
-            return cur1;
-        }
+      cur = 0;
     }
 
-  /* Report overflow if we filled the buffer from a file with more
-     bytes than stat or lseek reports.  This can happen with mutating
-     (e.g., /proc) files that are larger than the input block size.
-     FIXME: Handle this properly, e.g., by copying the growing file's
-     data into the first output file, and then splitting that output
-     file (which should not grow) into the other output files.  */
-  if (end < size)
-    goto overflow;
+  if (end == OFF_T_MAX /* E.g., /dev/zero on GNU/Hurd.  */
+      || (cur < end && INT_ADD_WRAPV (size, end - cur, &size)))
+    {
+      errno = EOVERFLOW;
+      return -1;
+    }
 
-  if (cur < end && INT_ADD_WRAPV (size, end - cur, &size))
-    goto overflow;
+  if (cur < end)
+    {
+      off_t r = lseek (fd, cur, SEEK_SET);
+      if (r < 0)
+        return r;
+    }
 
   return size;
-
- overflow:
-  errno = EOVERFLOW;
-  return -1;
 }
 
 /* Compute the next sequential output file name and store it into the

tests/split/l-chunk.sh

@@ -37,12 +37,15 @@ rm x??
 
 # 'split' should reject any attempt to create an infinitely
 # long output file.
-returns_ 1 split -n l/2 /dev/zero || fail=1
-rm x??
+# This test is very expensive as it runs out of /tmp space.
+if test "${RUN_VERY_EXPENSIVE_TESTS+set}" = set; then
+  returns_ 1 split -n l/2 /dev/zero || fail=1
+  rm x??
 
-# Repeat the above,  but with 1/2, not l/2:
-returns_ 1 split -n 1/2 /dev/zero || fail=1
-rm x??
+  # Repeat the above,  but with 1/2, not l/2:
+  returns_ 1 split -n 1/2 /dev/zero || fail=1
+  rm x??
+fi
 
 # Ensure --elide-empty-files is honored
 split -e -n l/10 /dev/null || fail=1