libssh2_session_set_last_error: Add function

Net::SSH2, the Perl wrapping module for libssh2 implements several features*
on top of libssh2 that can fail and so need some mechanism to report the error
condition to the user.

Until now, besides the error state maintained internally by libssh2, another
error state was maintained at the Perl level for every session object and then
additional logic was used to merge both error states. That is a maintenance
nighmare, and actually there is no way to do it correctly and consistently.

In order to allow the high level language to add new features to the library
but still rely in its error reporting features the new function
libssh2_session_set_last_error (that just exposses _libssh2_error_flags) is
introduced.

*) For instance, connecting to a remote SSH service giving the hostname and
port.

Signed-off-by: Salvador Fandino <sfandino@yahoo.com>
Signed-off-by: Salvador Fandiño <sfandino@yahoo.com>

docs/CMakeLists.txt

@@ -139,6 +139,7 @@ set(MAN_PAGES
   libssh2_session_init_ex.3
   libssh2_session_last_errno.3
   libssh2_session_last_error.3
+  libssh2_session_set_last_error.3
   libssh2_session_method_pref.3
   libssh2_session_methods.3
   libssh2_session_set_blocking.3

docs/Makefile.am

@@ -110,6 +110,7 @@ dist_man_MANS = \
 	libssh2_session_init_ex.3 \
 	libssh2_session_last_errno.3 \
 	libssh2_session_last_error.3 \
+	libssh2_session_set_last_error.3 \
 	libssh2_session_method_pref.3 \
 	libssh2_session_methods.3 \
 	libssh2_session_set_blocking.3 \

docs/libssh2_session_last_errno.3

@@ -18,3 +18,4 @@ Numeric error code corresponding to the the Error Code constants.
 
 .SH SEE ALSO
 .BR libssh2_session_last_error(3)
+.BR libssh2_session_set_last_error(3)

docs/libssh2_session_last_error.3

@@ -29,3 +29,4 @@ Numeric error code corresponding to the the Error Code constants.
 
 .SH SEE ALSO
 .BR libssh2_session_last_errno(3)
+.BR libssh2_session_set_last_error(3)

docs/libssh2_session_set_last_error.3

@@ -0,0 +1,33 @@
+.TH libssh2_session_set_last_error 3 "26 Oct 2015" "libssh2 1.6.1" "libssh2 manual"
+.SH NAME
+libssh2_session_set_last_error - sets the internal error state
+.SH SYNOPSIS
+#include <libssh2.h>
+
+int
+libssh2_session_set_last_error(LIBSSH2_SESSION *session, int errcode, const char *errmsg)
+
+.SH DESCRIPTION
+\fIsession\fP - Session instance as returned by
+.BR libssh2_session_init_ex(3)
+
+\fIerrcode\fP - One of the error codes as defined in the public
+libssh2 header file.
+
+\fIerrmsg\fP - If not NULL, a copy of the given string is stored
+inside the session object as the error message.
+
+This function is provided for high level language wrappers
+(i.e. Python or Perl) and other libraries that may extend libssh2 with
+additional features while still relying on its error reporting
+mechanism.
+
+.SH RETURN VALUE
+Numeric error code corresponding to the the Error Code constants.
+
+.SH AVAILABILITY
+Added in 1.6.1
+
+.SH SEE ALSO
+.BR libssh2_session_last_error(3)
+.BR libssh2_session_last_errno(3)

include/libssh2.h

@@ -567,6 +567,9 @@ LIBSSH2_API int libssh2_session_last_error(LIBSSH2_SESSION *session,
                                            char **errmsg,
                                            int *errmsg_len, int want_buf);
 LIBSSH2_API int libssh2_session_last_errno(LIBSSH2_SESSION *session);
+LIBSSH2_API int libssh2_session_set_last_error(LIBSSH2_SESSION* session,
+                                               int errcode,
+                                               const char* errmsg);
 LIBSSH2_API int libssh2_session_block_directions(LIBSSH2_SESSION *session);
 
 LIBSSH2_API int libssh2_session_flag(LIBSSH2_SESSION *session, int flag,

src/session.c

@@ -1290,7 +1290,24 @@ libssh2_session_last_errno(LIBSSH2_SESSION * session)
     return session->err_code;
 }
 
-/* libssh2_session_flag
+/* libssh2_session_set_last_error
+ *
+ * Sets the internal error code for the session.
+ *
+ * This function is available specifically to be used by high level
+ * language wrappers (i.e. Python or Perl) that may extend the library
+ * features while still relying on its error reporting mechanism.
+ */
+LIBSSH2_API int
+libssh2_session_set_last_error(LIBSSH2_SESSION* session,
+                               int errcode,
+                               const char* errmsg)
+{
+    return _libssh2_error_flags(session, errcode, errmsg,
+                                LIBSSH2_ERR_FLAG_DUP);
+}
+
+/* Libssh2_session_flag
  *
  * Set/Get session flags
  *