Permissive stream open mode strings.

There is more to this patch than just more permissive
mode strings. Now if a socket can be opened with mode
"l2" for instance, and these options are effectively applied
to the socket-specific "r+b" default, not to "r".

* stream.c (parse_mode): New argument specifying a default
mode. The syntax is relaxed, allowing previously required
elements to be omitted.
(normalize_mode): New argument specifying a default mode.
Format mode is always called now, because an input string
is no longer necessarily a valid fopen string even in cases
when it doesn't specify any extensions.
(open_file, open_fileno, open_tail, open_command,
open_process): Use new normalize_mode argument for defaulting;
normalize_mode no longer defaults to "r".

* stream.h (stdio_mode_init_trivial): Macro removed.
(stdio_mode_init_blank, stdio_mode_init_r,
stdio_mode_init_rpb): New initializer macros.
(parse_mode, normalize_mode): Declarations updated.

* socket.c (sock_accept): In datagram socket case, use new
parse_mode argument for defaulting using stdio_mode_init_rpb,
rather than overriding a missing string with "r+b".
(open_sockfd): Likewise, and use new normalize_mode
argument similarly for defaulting the mode on a stream socket.

* txr.1: Documented mode string permissiveness.

1 files changed, 5 insertions, 3 deletions

diff --git a/stream.h b/stream.h
index abb0bec0..c1699c05 100644
--- a/stream.h
+++ b/stream.h
@@ -95,7 +95,9 @@ struct stdio_mode {
   int buforder : 5;
 };
 
-#define stdio_mode_init_trivial(read) { 0, read, 0, 0, 0, 0, 0, 0, 0, -1 }
+#define stdio_mode_init_blank { 0, 0, 0, 0, 0, 0, 0, 0, 0, -1 }
+#define stdio_mode_init_r     { 0, 1, 0, 0, 0, 0, 0, 0, 0, -1 }
+#define stdio_mode_init_rpb   { 0, 1, 1, 0, 0, 1, 0, 0, 0, -1 }
 
 #define std_input (deref(lookup_var_l(nil, stdin_s)))
 #define std_output (deref(lookup_var_l(nil, stdout_s)))
@@ -126,8 +128,8 @@ void fill_stream_ops(struct strm_ops *ops);
 void stream_print_op(val stream, val out, val pretty);
 void stream_mark_op(val stream);
 void stream_destroy_op(val stream);
-struct stdio_mode parse_mode(val mode_str);
-val normalize_mode(struct stdio_mode *m, val mode_str);
+struct stdio_mode parse_mode(val mode_str, struct stdio_mode m_dfl);
+val normalize_mode(struct stdio_mode *m, val mode_str, struct stdio_mode m_dfl);
 val set_mode_props(const struct stdio_mode m, val stream);
 val generic_get_line(val stream);
 val errno_to_string(val err);