Introduce the new error framework

New error-handling framework that allows for exception-like error
propagation.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Makefile.objs

@@ -59,7 +59,7 @@ fsdev-obj-$(CONFIG_VIRTFS) += $(addprefix fsdev/, $(fsdev-nested-y))
 # system emulation, i.e. a single QEMU executable should support all
 # CPUs and machines.
 
-common-obj-y = $(block-obj-y) blockdev.o
+common-obj-y = $(block-obj-y) blockdev.o error.o
 common-obj-y += $(net-obj-y)
 common-obj-y += $(qobject-obj-y)
 common-obj-$(CONFIG_LINUX) += $(fsdev-obj-$(CONFIG_LINUX))

error.c

@@ -0,0 +1,140 @@
+/*
+ * QEMU Error Objects
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.  See
+ * the COPYING.LIB file in the top-level directory.
+ */
+#include "error.h"
+#include "error_int.h"
+#include "qemu-objects.h"
+#include "qerror.h"
+#include <assert.h>
+
+struct Error
+{
+    QDict *obj;
+    const char *fmt;
+    char *msg;
+};
+
+void error_set(Error **errp, const char *fmt, ...)
+{
+    Error *err;
+    va_list ap;
+
+    if (errp == NULL) {
+        return;
+    }
+
+    err = qemu_mallocz(sizeof(*err));
+
+    va_start(ap, fmt);
+    err->obj = qobject_to_qdict(qobject_from_jsonv(fmt, &ap));
+    va_end(ap);
+    err->fmt = fmt;
+
+    *errp = err;
+}
+
+bool error_is_set(Error **errp)
+{
+    return (errp && *errp);
+}
+
+const char *error_get_pretty(Error *err)
+{
+    if (err->msg == NULL) {
+        QString *str;
+        str = qerror_format(err->fmt, err->obj);
+        err->msg = qemu_strdup(qstring_get_str(str));
+        QDECREF(str);
+    }
+
+    return err->msg;
+}
+
+const char *error_get_field(Error *err, const char *field)
+{
+    if (strcmp(field, "class") == 0) {
+        return qdict_get_str(err->obj, field);
+    } else {
+        QDict *dict = qdict_get_qdict(err->obj, "data");
+        return qdict_get_str(dict, field);
+    }
+}
+
+QDict *error_get_data(Error *err)
+{
+    QDict *data = qdict_get_qdict(err->obj, "data");
+    QINCREF(data);
+    return data;
+}
+
+void error_set_field(Error *err, const char *field, const char *value)
+{
+    QDict *dict = qdict_get_qdict(err->obj, "data");
+    return qdict_put(dict, field, qstring_from_str(value));
+}
+
+void error_free(Error *err)
+{
+    if (err) {
+        QDECREF(err->obj);
+        qemu_free(err->msg);
+        qemu_free(err);
+    }
+}
+
+bool error_is_type(Error *err, const char *fmt)
+{
+    const char *error_class;
+    char *ptr;
+    char *end;
+
+    ptr = strstr(fmt, "'class': '");
+    assert(ptr != NULL);
+    ptr += strlen("'class': '");
+
+    end = strchr(ptr, '\'');
+    assert(end != NULL);
+
+    error_class = error_get_field(err, "class");
+    if (strlen(error_class) != end - ptr) {
+        return false;
+    }
+
+    return strncmp(ptr, error_class, end - ptr) == 0;
+}
+
+void error_propagate(Error **dst_err, Error *local_err)
+{
+    if (dst_err) {
+        *dst_err = local_err;
+    } else if (local_err) {
+        error_free(local_err);
+    }
+}
+
+QObject *error_get_qobject(Error *err)
+{
+    QINCREF(err->obj);
+    return QOBJECT(err->obj);
+}
+
+void error_set_qobject(Error **errp, QObject *obj)
+{
+    Error *err;
+    if (errp == NULL) {
+        return;
+    }
+    err = qemu_mallocz(sizeof(*err));
+    err->obj = qobject_to_qdict(obj);
+    qobject_incref(obj);
+
+    *errp = err;
+}

error.h

@@ -0,0 +1,70 @@
+/*
+ * QEMU Error Objects
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.  See
+ * the COPYING.LIB file in the top-level directory.
+ */
+#ifndef ERROR_H
+#define ERROR_H
+
+#include <stdbool.h>
+
+/**
+ * A class representing internal errors within QEMU.  An error has a string
+ * typename and optionally a set of named string parameters.
+ */
+typedef struct Error Error;
+
+/**
+ * Set an indirect pointer to an error given a printf-style format parameter.
+ * Currently, qerror.h defines these error formats.  This function is not
+ * meant to be used outside of QEMU.
+ */
+void error_set(Error **err, const char *fmt, ...)
+    __attribute__((format(printf, 2, 3)));
+
+/**
+ * Returns true if an indirect pointer to an error is pointing to a valid
+ * error object.
+ */
+bool error_is_set(Error **err);
+
+/**
+ * Get a human readable representation of an error object.
+ */
+const char *error_get_pretty(Error *err);
+
+/**
+ * Get an individual named error field.
+ */
+const char *error_get_field(Error *err, const char *field);
+
+/**
+ * Get an individual named error field.
+ */
+void error_set_field(Error *err, const char *field, const char *value);
+
+/**
+ * Propagate an error to an indirect pointer to an error.  This function will
+ * always transfer ownership of the error reference and handles the case where
+ * dst_err is NULL correctly.
+ */
+void error_propagate(Error **dst_err, Error *local_err);
+
+/**
+ * Free an error object.
+ */
+void error_free(Error *err);
+
+/**
+ * Determine if an error is of a speific type (based on the qerror format).
+ * Non-QEMU users should get the `class' field to identify the error type.
+ */
+bool error_is_type(Error *err, const char *fmt);
+
+#endif

error_int.h

@@ -0,0 +1,29 @@
+/*
+ * QEMU Error Objects
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.  See
+ * the COPYING.LIB file in the top-level directory.
+ */
+#ifndef QEMU_ERROR_INT_H
+#define QEMU_ERROR_INT_H
+
+#include "qemu-common.h"
+#include "qobject.h"
+#include "qdict.h"
+#include "error.h"
+
+/**
+ * Internal QEMU functions for working with Error.
+ *
+ * These are used to convert QErrors to Errors
+ */
+QDict *error_get_data(Error *err);
+QObject *error_get_qobject(Error *err);
+void error_set_qobject(Error **errp, QObject *obj);
+  
+#endif