Pull out a new qstring_append_json_number() helper, so that all
JSON output producers can use a consistent style for printing
floating point without duplicating code (since we are doing more
data massaging than a simple printf format can handle).
Address one FIXME by adding an Error parameter and warning the
caller if the requested number cannot be represented in JSON;
but add another FIXME in its place because we have no way to
report the problem higher up the stack.
Signed-off-by: Eric Blake <ebl...@redhat.com>
Reviewed-by: Fam Zheng <f...@redhat.com>
---
v3: rebase to latest; even though the patch differs quite a bit
from v2, the changes are due to prior comment changes that are
just moving between files, so R-b kept
v2: minor wording tweaks
---
include/qapi/qmp/qstring.h | 4 +++-
qobject/qobject-json.c | 27 +++------------------------
qobject/qstring.c | 42 +++++++++++++++++++++++++++++++++++++++++-
3 files changed, 47 insertions(+), 26 deletions(-)
diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h
index a254ee3..f00e3df 100644
--- a/include/qapi/qmp/qstring.h
+++ b/include/qapi/qmp/qstring.h
@@ -1,7 +1,7 @@
/*
* QString Module
*
- * Copyright (C) 2009 Red Hat Inc.
+ * Copyright (C) 2009, 2015 Red Hat Inc.
*
* Authors:
* Luiz Capitulino <lcapitul...@redhat.com>
@@ -14,6 +14,7 @@
#define QSTRING_H
#include "qapi/qmp/qobject.h"
+#include "qapi/error.h"
typedef struct QString {
QObject base;
@@ -31,6 +32,7 @@ void qstring_append_int(QString *qstring, int64_t value);
void qstring_append(QString *qstring, const char *str);
void qstring_append_chr(QString *qstring, int c);
void qstring_append_json_string(QString *qstring, const char *raw);
+void qstring_append_json_number(QString *qstring, double number, Error **errp);
QString *qobject_to_qstring(const QObject *obj);
void qstring_destroy_obj(QObject *obj);
diff --git a/qobject/qobject-json.c b/qobject/qobject-json.c
index 6fed1ee..97bccb7 100644
--- a/qobject/qobject-json.c
+++ b/qobject/qobject-json.c
@@ -177,30 +177,9 @@ static void to_json(const QObject *obj, QString *str, int
pretty, int indent)
}
case QTYPE_QFLOAT: {
QFloat *val = qobject_to_qfloat(obj);
- char buffer[1024];
- int len;
-
- /* FIXME: snprintf() is locale dependent; but JSON requires
- * numbers to be formatted as if in the C locale. Dependence
- * on C locale is a pervasive issue in QEMU. */
- /* FIXME: This risks printing Inf or NaN, which are not valid
- * JSON values. */
- /* FIXME: the default precision of 6 for %f often causes
- * rounding errors; we should be using DBL_DECIMAL_DIG (17),
- * and only rounding to a shorter number if the result would
- * still produce the same floating point value. */
- len = snprintf(buffer, sizeof(buffer), "%f", qfloat_get_double(val));
- while (len > 0 && buffer[len - 1] == '0') {
- len--;
- }
-
- if (len && buffer[len - 1] == '.') {
- buffer[len - 1] = 0;
- } else {
- buffer[len] = 0;
- }
-
- qstring_append(str, buffer);
+ /* FIXME: no way to report invalid JSON to caller, so for now
+ * we just ignore it */
+ qstring_append_json_number(str, qfloat_get_double(val), NULL);
break;
}
case QTYPE_QBOOL: {
diff --git a/qobject/qstring.c b/qobject/qstring.c
index 9f0df5b..618dd8f 100644
--- a/qobject/qstring.c
+++ b/qobject/qstring.c
@@ -1,7 +1,7 @@
/*
* QString Module
*
- * Copyright (C) 2009 Red Hat Inc.
+ * Copyright (C) 2009, 2015-2016 Red Hat Inc.
*
* Authors:
* Luiz Capitulino <lcapitul...@redhat.com>
@@ -15,6 +15,7 @@
#include "qapi/qmp/qstring.h"
#include "qemu-common.h"
#include "qemu/unicode.h"
+#include <math.h>
/**
* qstring_new(): Create a new empty QString
@@ -167,6 +168,45 @@ void qstring_append_json_string(QString *qstring, const
char *raw)
}
/**
+ * qstring_append_json_number(): Append a JSON number to a QString.
+ * Set @errp if the number is not representable in JSON, but append the
+ * output anyway (callers can then choose to ignore the warning).
+ */
+void qstring_append_json_number(QString *qstring, double number, Error **errp)
+{
+ char buffer[1024];
+ int len;
+
+ /* JSON does not allow Inf or NaN; append it but set errp */
+ if (!isfinite(number)) {
+ error_setg(errp, "Non-finite number %f is not valid JSON", number);
+ }
+
+ /* FIXME: snprintf() is locale dependent; but JSON requires
+ * numbers to be formatted as if in the C locale. Dependence
+ * on C locale is a pervasive issue in QEMU. */
+ /* FIXME: This risks printing Inf or NaN, which are not valid
+ * JSON values. */
+ /* FIXME: the default precision of 6 for %f often causes
+ * rounding errors; we should be using DBL_DECIMAL_DIG (17),
+ * and only rounding to a shorter number if the result would
+ * still produce the same floating point value. */
+ len = snprintf(buffer, sizeof(buffer), "%f", number);
+ assert(len > 0 && len < sizeof(buffer));
+ while (len > 0 && buffer[len - 1] == '0') {
+ len--;
+ }
+
+ if (len && buffer[len - 1] == '.') {
+ buffer[len - 1] = 0;
+ } else {
+ buffer[len] = 0;
+ }
+
+ qstring_append(qstring, buffer);
+}
+
+/**
* qobject_to_qstring(): Convert a QObject to a QString
*/
QString *qobject_to_qstring(const QObject *obj)
--
2.5.5
