libdpkg: Add new error module

This new module provides error reporting infrastructure, which will
be used to report back error information from inner functions that
are not supposed to ohshit() directly, the caller should be
responsible for the outcome, including just forwarding the error
to its own caller.

lib/dpkg/Makefile.am

@@ -35,6 +35,7 @@ libdpkg_a_SOURCES = \
 	dir.c \
 	dump.c \
 	ehandle.c \
+	error.c \
 	fdio.c \
 	file.c \
 	fields.c \
@@ -81,6 +82,7 @@ pkginclude_HEADERS = \
 	dpkg.h \
 	dpkg-db.h \
 	ehandle.h \
+	error.h \
 	fdio.h \
 	file.h \
 	glob.h \

lib/dpkg/error.c

@@ -0,0 +1,93 @@
+/*
+ * libdpkg - Debian packaging suite library routines
+ * error.c - error message reporting
+ *
+ * Copyright © 2011 Guillem Jover <guillem@debian.org>
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <compat.h>
+
+#include <errno.h>
+#include <stdlib.h>
+
+#include <dpkg/dpkg.h>
+#include <dpkg/varbuf.h>
+#include <dpkg/error.h>
+
+static void DPKG_ATTR_VPRINTF(3)
+dpkg_error_set(struct dpkg_error *err, int type, const char *fmt, va_list args)
+{
+	struct varbuf str = VARBUF_INIT;
+
+	if (err == NULL)
+		return;
+
+	err->type = type;
+
+	varbuf_vprintf(&str, fmt, args);
+	err->str = str.buf;
+}
+
+int
+dpkg_put_warn(struct dpkg_error *err, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	dpkg_error_set(err, DPKG_MSG_WARN, fmt, args);
+	va_end(args);
+
+	return -1;
+}
+
+int
+dpkg_put_error(struct dpkg_error *err, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	dpkg_error_set(err, DPKG_MSG_ERROR, fmt, args);
+	va_end(args);
+
+	return -1;
+}
+
+int
+dpkg_put_errno(struct dpkg_error *err, const char *fmt, ...)
+{
+	va_list args;
+	char *new_fmt;
+	int errno_saved = errno;
+
+	va_start(args, fmt);
+	m_asprintf(&new_fmt, "%s (%s)", fmt, strerror(errno_saved));
+	va_end(args);
+
+	dpkg_error_set(err, DPKG_MSG_ERROR, new_fmt, args);
+
+	free(new_fmt);
+
+	return -1;
+}
+
+void
+dpkg_error_destroy(struct dpkg_error *err)
+{
+	err->type = DPKG_MSG_NONE;
+	free(err->str);
+	err->str = NULL;
+}

lib/dpkg/error.h

@@ -0,0 +1,49 @@
+/*
+ * libdpkg - Debian packaging suite library routines
+ * error.h - error message reporting
+ *
+ * Copyright © 2011 Guillem Jover <guillem@debian.org>
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef LIBDPKG_ERROR_H
+#define LIBDPKG_ERROR_H
+
+#include <dpkg/macros.h>
+
+DPKG_BEGIN_DECLS
+
+struct dpkg_error {
+	enum dpkg_msg_type {
+		DPKG_MSG_NONE,
+		DPKG_MSG_WARN,
+		DPKG_MSG_ERROR,
+	} type;
+
+	char *str;
+};
+
+int dpkg_put_warn(struct dpkg_error *err, const char *fmt, ...)
+	DPKG_ATTR_PRINTF(2);
+int dpkg_put_error(struct dpkg_error *err, const char *fmt, ...)
+	DPKG_ATTR_PRINTF(2);
+int dpkg_put_errno(struct dpkg_error *err, const char *fmt, ...)
+	DPKG_ATTR_PRINTF(2);
+
+void dpkg_error_destroy(struct dpkg_error *err);
+
+DPKG_END_DECLS
+
+#endif /* LIBDPKG_ERROR_H */