[Qemu-devel] [PATCH v2 03/14] qapi: Factor out JSON string escaping

[Eric Blake <eblake@redhat.com>]

Pull out a new qstring_append_json_string() helper, so that all
JSON output producers can use the same output escaping rules.

While it appears that vmstate's use of the simpler qjson.c
formatter is not currently encountering any string that needs
escapes to be valid JSON, it is better to be safe than sorry.

Signed-off-by: Eric Blake <eblake@redhat.com>

---
v2: no change
---
 include/qapi/qmp/qstring.h |  1 +
 qjson.c                    |  9 +++----
 qobject/qobject-json.c     | 58 ++-------------------------------------------
 qobject/qstring.c          | 59 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 62 deletions(-)

diff --git a/include/qapi/qmp/qstring.h b/include/qapi/qmp/qstring.h
index df7df55..1a938f6 100644
--- a/include/qapi/qmp/qstring.h
+++ b/include/qapi/qmp/qstring.h
@@ -31,6 +31,7 @@ const char *qstring_get_str(const QString *qstring);
 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);
 QString *qobject_to_qstring(const QObject *obj);
 void qstring_destroy_obj(QObject *obj);

diff --git a/qjson.c b/qjson.c
index e478802..25afaff 100644
--- a/qjson.c
+++ b/qjson.c
@@ -36,9 +36,8 @@ static void json_emit_element(QJSON *json, const char *name)
     }

     if (name) {
-        qstring_append(json->str, "\"");
-        qstring_append(json->str, name);
-        qstring_append(json->str, "\" : ");
+        qstring_append_json_string(json->str, name);
+        qstring_append(json->str, " : ");
     }
 }

@@ -77,9 +76,7 @@ void json_prop_int(QJSON *json, const char *name, int64_t val)
 void json_prop_str(QJSON *json, const char *name, const char *str)
 {
     json_emit_element(json, name);
-    qstring_append_chr(json->str, '"');
-    qstring_append(json->str, str);
-    qstring_append_chr(json->str, '"');
+    qstring_append_json_string(json->str, str);
 }

 const char *qjson_get_str(QJSON *json)
diff --git a/qobject/qobject-json.c b/qobject/qobject-json.c
index cc96ff6..1557ec6 100644
--- a/qobject/qobject-json.c
+++ b/qobject/qobject-json.c
@@ -79,7 +79,6 @@ static void to_json(const QObject *obj, QString *str, int pretty, int indent);
 static void to_json_dict_iter(const char *key, QObject *obj, void *opaque)
 {
     ToJsonIterState *s = opaque;
-    QString *qkey;
     int j;

     if (s->count) {
@@ -92,9 +91,7 @@ static void to_json_dict_iter(const char *key, QObject *obj, void *opaque)
             qstring_append(s->str, "    ");
     }

-    qkey = qstring_from_str(key);
-    to_json(QOBJECT(qkey), s->str, s->pretty, s->indent);
-    QDECREF(qkey);
+    qstring_append_json_string(s->str, key);

     qstring_append(s->str, ": ");
     to_json(obj, s->str, s->pretty, s->indent);
@@ -136,58 +133,7 @@ static void to_json(const QObject *obj, QString *str, int pretty, int indent)
     }
     case QTYPE_QSTRING: {
         QString *val = qobject_to_qstring(obj);
-        const char *ptr;
-        int cp;
-        char buf[16];
-        char *end;
-
-        ptr = qstring_get_str(val);
-        qstring_append(str, "\"");
-
-        for (; *ptr; ptr = end) {
-            cp = mod_utf8_codepoint(ptr, 6, &end);
-            switch (cp) {
-            case '\"':
-                qstring_append(str, "\\\"");
-                break;
-            case '\\':
-                qstring_append(str, "\\\\");
-                break;
-            case '\b':
-                qstring_append(str, "\\b");
-                break;
-            case '\f':
-                qstring_append(str, "\\f");
-                break;
-            case '\n':
-                qstring_append(str, "\\n");
-                break;
-            case '\r':
-                qstring_append(str, "\\r");
-                break;
-            case '\t':
-                qstring_append(str, "\\t");
-                break;
-            default:
-                if (cp < 0) {
-                    cp = 0xFFFD; /* replacement character */
-                }
-                if (cp > 0xFFFF) {
-                    /* beyond BMP; need a surrogate pair */
-                    snprintf(buf, sizeof(buf), "\\u%04X\\u%04X",
-                             0xD800 + ((cp - 0x10000) >> 10),
-                             0xDC00 + ((cp - 0x10000) & 0x3FF));
-                } else if (cp < 0x20 || cp >= 0x7F) {
-                    snprintf(buf, sizeof(buf), "\\u%04X", cp);
-                } else {
-                    buf[0] = cp;
-                    buf[1] = 0;
-                }
-                qstring_append(str, buf);
-            }
-        };
-
-        qstring_append(str, "\"");
+        qstring_append_json_string(str, qstring_get_str(val));
         break;
     }
     case QTYPE_QDICT: {
diff --git a/qobject/qstring.c b/qobject/qstring.c
index f44c5c4..2882c47 100644
--- a/qobject/qstring.c
+++ b/qobject/qstring.c
@@ -106,6 +106,65 @@ void qstring_append_chr(QString *qstring, int c)
 }

 /**
+ * qstring_append_json_string(): Append a raw string to a QString, while
+ * adding outer "" and JSON escape sequences.
+ */
+void qstring_append_json_string(QString *qstring, const char *raw)
+{
+    const char *ptr = raw;
+    int cp;
+    char buf[16];
+    char *end;
+
+    qstring_append(qstring, "\"");
+
+    for (; *ptr; ptr = end) {
+        cp = mod_utf8_codepoint(ptr, 6, &end);
+        switch (cp) {
+        case '\"':
+            qstring_append(qstring, "\\\"");
+            break;
+        case '\\':
+            qstring_append(qstring, "\\\\");
+            break;
+        case '\b':
+            qstring_append(qstring, "\\b");
+            break;
+        case '\f':
+            qstring_append(qstring, "\\f");
+            break;
+        case '\n':
+            qstring_append(qstring, "\\n");
+            break;
+        case '\r':
+            qstring_append(qstring, "\\r");
+            break;
+        case '\t':
+            qstring_append(qstring, "\\t");
+            break;
+        default:
+            if (cp < 0) {
+                cp = 0xFFFD; /* replacement character */
+            }
+            if (cp > 0xFFFF) {
+                /* beyond BMP; need a surrogate pair */
+                snprintf(buf, sizeof(buf), "\\u%04X\\u%04X",
+                         0xD800 + ((cp - 0x10000) >> 10),
+                         0xDC00 + ((cp - 0x10000) & 0x3FF));
+            } else if (cp < 0x20 || cp >= 0x7F) {
+                snprintf(buf, sizeof(buf), "\\u%04X", cp);
+            } else {
+                buf[0] = cp;
+                buf[1] = 0;
+            }
+            qstring_append(qstring, buf);
+        }
+    };
+
+    qstring_append(qstring, "\"");
+}
+
+/**
  * qobject_to_qstring(): Convert a QObject to a QString
  */
 QString *qobject_to_qstring(const QObject *obj)
-- 
2.4.3