[5/8] Introduce QError

diff --git a/Makefile b/Makefile
index 6fcbcaa..2dfaebd 100644
--- a/Makefile
+++ b/Makefile
@@ -135,7 +135,7 @@  obj-y += buffered_file.o migration.o migration-tcp.o qemu-sockets.o
 obj-y += qemu-char.o aio.o savevm.o
 obj-y += msmouse.o ps2.o
 obj-y += qdev.o qdev-properties.o
-obj-y += qint.o qstring.o qdict.o qlist.o qfloat.o qbool.o qjson.o
+obj-y += qint.o qstring.o qdict.o qlist.o qfloat.o qbool.o qjson.o qerror.o
 obj-y += qemu-config.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
diff --git a/qerror.c b/qerror.c
new file mode 100644
index 0000000..7d3137f
--- /dev/null
+++ b/qerror.c
@@ -0,0 +1,235 @@ 
+/*
+ * QError: QEMU Error data-type.
+ *
+ * Copyright (C) 2009 Red Hat Inc.
+ *
+ * Authors:
+ *  Luiz Capitulino <lcapitulino@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+#include "qint.h"
+#include "qjson.h"
+#include "qerror.h"
+#include "qstring.h"
+#include "sysemu.h"
+#include "qemu-common.h"
+
+static void qerror_destroy_obj(QObject *obj);
+
+static const QType qerror_type = {
+    .code = QTYPE_QERROR,
+    .destroy = qerror_destroy_obj,
+};
+
+/**
+ * qerror_new(): Create a new QError
+ *
+ * Return strong reference.
+ */
+QError *qerror_new(void)
+{
+    QError *qerr;
+
+    qerr = qemu_mallocz(sizeof(*qerr));
+    QOBJECT_INIT(qerr, &qerror_type);
+
+    return qerr;
+}
+
+/**
+ * qerror_from_info(): Create a new QError from error information
+ *
+ * The information consists of:
+ *
+ * - name    generic error name
+ * - file    the file name of where the error occurred
+ * - linenr  the line number of where the error occurred
+ * - desc    detailed description (see below)
+ * - fmt     JSON printf-like format for 'specific data'
+ * - va      va_list of all arguments for 'specific data'
+ *
+ * Note that this is a low-level function, it is supposed to be called
+ * by higher-level functions or macros.
+ *
+ * The 'desc' parameter is a printf-like string, the format of the format
+ * string is:
+ *
+ * %(KEY)TYPE
+ *
+ * Where KEY is a QDict key and TYPE is the type of its value, KEY and
+ * its value must be passed to qerror_from_info().
+ *
+ * Valid types are:
+ *
+ * s  (string)
+ * d  (integer)
+ *
+ * Example:
+ *
+ * "foo error on device: %(device)s slot: %(slot_nr)d"
+ *
+ * A single percent sign can be printed if followed by a second one,
+ * for example:
+ *
+ * "running out of foo: %(foo)d%%"
+ *
+ * Return strong reference.
+ */
+QError *qerror_from_info(const char *name, const char *file, int linenr,
+                         const char *desc, const char *fmt, va_list *va)
+{
+    QError *qerr;
+
+    qerr = qerror_new();
+    qerr->name = name;
+    qerr->file = file;
+    qerr->linenr = linenr;
+    qerr->desc = desc;
+    if (fmt) {
+        qerr->data = qobject_from_json_va(fmt, va);
+        assert(qerr->data != NULL);
+    }
+
+    return qerr;
+}
+
+static char *get_substr(const char *start, const char *end)
+{
+    char *str;
+    size_t length;
+
+    length = end - start + 1;
+    str = qemu_malloc(length + 1);
+    memcpy(str, start, length);
+    str[length] = '\0';
+
+    return str;
+}
+
+static void qerror_abort(const QError *qerr)
+{
+    fprintf(stderr, " in '%s' at %s:%d\n", qerr->desc, qerr->file,qerr->linenr);
+    abort();
+}
+
+#define ERROR_PREFIX "\n\nqerror: "
+
+static void type_error(const QError *qerr, int c)
+{
+    fprintf(stderr, ERROR_PREFIX "invalid type '%c'", c);
+    qerror_abort(qerr);
+}
+
+static void key_error(const QError *qerr, const char *key)
+{
+    fprintf(stderr, ERROR_PREFIX "key '%s' not found in QDict ", key);
+    fprintf(stderr, "call at %s:%d\n", qerr->file, qerr->linenr);
+    abort();
+}
+
+static void parse_error(const QError *qerror, int c)
+{
+    fprintf(stderr, ERROR_PREFIX "expected '%c'", c);
+    qerror_abort(qerror);
+}
+
+static const char *append_field(QString *qstring, const QError *qerror,
+                                const char *start)
+{
+    int type;
+    char *name;
+    QDict *qdict;
+    const char *end;
+
+    if (*start != '%')
+        parse_error(qerror, '%');
+    start++;
+    if (*start != '(')
+        parse_error(qerror, '(');
+    start++;
+
+    end = strchr(start, ')');
+    if (!end)
+        parse_error(qerror, ')');
+
+    name = get_substr(start, end - 1);
+    qdict = qobject_to_qdict(qerror->data);
+
+    if (!qdict_haskey(qdict, name)) {
+        key_error(qerror, name);
+    }
+
+    type = *++end;
+    switch (type) {
+        case 's':
+            qstring_append(qstring, qdict_get_str(qdict, name));
+            break;
+        case 'd':
+            qstring_append_int(qstring, qdict_get_int(qdict, name));
+            break;
+        default:
+            type_error(qerror, type);
+    }
+
+    qemu_free(name);
+    return ++end;
+}
+
+/**
+ * qerror_print(): Print QError data
+ *
+ * This function will print the member 'desc' of the specified QError object,
+ * it uses qemu_error() for this, so that the output is routed to the right
+ * place (ie. stderr ou Monitor's device).
+ */
+void qerror_print(const QError *qerror)
+{
+    const char *p;
+    QString *qstring;
+
+    assert(qerror->desc != NULL);
+
+    qstring = qstring_new();
+
+    for (p = qerror->desc; *p != '\0';) {
+        if (*p != '%') {
+            qstring_append_chr(qstring, *p++);
+        } else if (*(p + 1) == '%') {
+            qstring_append_chr(qstring, '%');
+            p += 2;
+        } else {
+            p = append_field(qstring, qerror, p);
+        }
+    }
+
+    qemu_error("%s\n", qstring_get_str(qstring));
+    QDECREF(qstring);
+}
+
+/**
+ * qobject_to_qerror(): Convert a QObject into a QError
+ */
+QError *qobject_to_qerror(const QObject *obj)
+{
+    if (qobject_type(obj) != QTYPE_QERROR) {
+        return NULL;
+    }
+
+    return container_of(obj, QError, base);
+}
+
+/**
+ * qerror_destroy_obj(): Free all memory allocated by a QError
+ */
+static void qerror_destroy_obj(QObject *obj)
+{
+    QError *qerr;
+
+    assert(obj != NULL);
+    qerr = qobject_to_qerror(obj);
+
+    qobject_decref(qerr->data);
+    qemu_free(qerr);
+}
diff --git a/qerror.h b/qerror.h
new file mode 100644
index 0000000..dc39dec
--- /dev/null
+++ b/qerror.h
@@ -0,0 +1,39 @@ 
+/*
+ * QError header file.
+ *
+ * Copyright (C) 2009 Red Hat Inc.
+ *
+ * Authors:
+ *  Luiz Capitulino <lcapitulino@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+#ifndef QERROR_H
+#define QERROR_H
+
+#include <stdarg.h>
+#include "qobject.h"
+
+typedef struct QError {
+    QObject_HEAD;
+    const char *name;   /* generic name */
+    const char *desc;   /* description */
+    int linenr;         /* line number */
+    const char *file;   /* file name */
+    QObject *data;      /* run-time data */
+} QError;
+
+QError *qerror_new(void);
+QError *qerror_from_info(const char *name, const char *file, int linenr,
+                         const char *desc, const char *fmt, va_list *va);
+void qerror_print(const QError *qerror);
+QError *qobject_to_qerror(const QObject *obj);
+
+/*
+ * Common error names
+ */
+#define QERR_DEV_NFOUND "DeviceNotFound"
+#define QERR_SER_UNAV   "ServiceUnavailable"
+
+#endif /* QERROR_H */
diff --git a/qobject.h b/qobject.h
index 167b607..838dddc 100644
--- a/qobject.h
+++ b/qobject.h
@@ -43,6 +43,7 @@  typedef enum {
     QTYPE_QLIST,
     QTYPE_QFLOAT,
     QTYPE_QBOOL,
+    QTYPE_QERROR,
 } qtype_code;
 
 struct QObject;