Introducing persistent error state on streams.

* lib.c (cobj_ops): New function.

* lib.h (cobj_ops): Declared.

* stream.c (null_ops): Initializer updated.
(struct stdio_handle): New member, err.
(stdio_stream_mark): Mark the err member.
(errno_to_string): New static function.
(stdio_maybe_read_error, stdio_maybe_error): Set persistent error
state. Use errno_to_string_function.
(stdio_put_string, stdio_put_char, stdio_put_byte, stdio_seek,
stdio_get_line): Set errno to zero, so that if the underlying
operations do not set errno on err, we don't misinterpret some pervious
errno value as pertaining to the failed stream operation.
(stdio_get_error, stdio_get_error_str, stdio_clear_error): New static
functions.
(stdio_ops, tail_ops, pipe_ops): Update initializer with new functions.
(string_in_get_error, string_in_get_error_str): New static functions.
(string_in_ops): Update initializer with new functions.
(byte_in_get_error, byte_in_get_error_str): New static functions.
(byte_in_ops): Update initializer with new functions.
(string_out_ops, strlist_out_ops): Update initializer with null
pointers for new functions.
(struct dir_handle): New struct type.
(dir_destroy, dir_mark): New functions.
(dir_get_line): Refactor for struct dir_handle context rather than DIR.
Persist error state.
(dir_close): Refactor for struct dir_handle.
(dir_get_error, dir_get_error_str, dir_clear_error): New static functions.
(dir_ops): Update initializer with new functions.
(make_stdio_stream_common): Initialize new err member.
(make_dir_stream): Refactor for struct dir_handle.
(get_error, get_error_str, clear_error): New functions.
(cat_get_error, cat_get_error_str, cat_clear_error): New static
functions.
(cat_stream_ops): Update initializer with new functions.
(stream_init): Register get-error, get-error-str, clear-error intrinsics.

* stream.h (struct strm_ops): New function pointer members, get_error,
get_error_str and clear_error.
(strm_ops_init): Macro extended with new arguments for new function pointers.
(get_error, get_error_str, clear_error): Declared.

* syslog.c (syslog_strm_ops): Update initializer with null
pointers for new functions.

* txr.1: Documented get-error, get-error-str and clear-error.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 17728fc3..8fd4034d 100644
--- a/lib.c
+++ b/lib.c
@@ -5356,6 +5356,12 @@ mem_t *cobj_handle(val cobj, val cls_sym)
   return cobj->co.handle;
 }
 
+struct cobj_ops *cobj_ops(val cobj, val cls_sym)
+{
+  class_check(cobj, cls_sym);
+  return cobj->co.ops;
+}
+
 void cobj_print_op(val obj, val out)
 {
   put_string(lit("#<"), out);