Implementing truncate-stream.

* configure: Test for ftruncate and chsize.

* stream.c (unimpl_truncate): New static function.
(fill_stream_ops): Default the truncate operation to unimpl_truncate.
(null_ops): Initialize truncate to unimpl_truncate.
(stdio_truncate): New static function.
(stdio_ops, tail_ops): Initialize truncate to stdio_truncate.
(pipe_ops, dir_ops, string_ops, byte_in_ops, string_out_ops,
strlist_out_ops, cat_stream_ops): Initialize truncate to null,
so it gets defaulted by fill_stream_ops.
(truncate_stream): New function.
(stream_init): Register truncate-stream intrinsic.

* stream.h (struct strm_ops): New member, truncate.
(strm_ops_init): New truncate argument added to macro.
(truncate_stream): Declared.

*syslog.c (syslog_strm_ops): Initialize truncate to null.

* txr.1: Documented.

1 files changed, 34 insertions, 0 deletions

diff --git a/configure b/configure
index 09054bdf..0760afe7 100755
--- a/configure
+++ b/configure
@@ -1953,6 +1953,22 @@ else
   printf "no\n"
 fi
 
+printf "Checking for ftruncate ... "
+cat > conftest.c <<!
+#include <unistd.h>
+
+int main(void)
+{
+  int e = ftruncate(0, 42);
+  return 0;
+}
+!
+if conftest ; then
+  printf "yes\n"
+  printf "#define HAVE_FTRUNCATE 1\n" >> $config_h
+else
+  printf "no\n"
+fi
 
 printf "Checking for _wspawnlp ... "
 
@@ -1975,6 +1991,24 @@ else
   printf "no\n"
 fi
 
+printf "Checking for chsize ... "
+cat > conftest.c <<!
+#include <unistd.h>
+
+int main(void)
+{
+  int e = chsize(0, 42);
+  return 0;
+}
+!
+if conftest ; then
+  printf "yes\n"
+  printf "#define HAVE_CHSIZE 1\n" >> $config_h
+else
+  printf "no\n"
+fi
+
+
 printf "Checking for log2 ... "
 
 cat > conftest.c <<!