Provide marshalling mechanism for json

This introduces qobject_to_json which will convert a QObject to a JSON string
representation.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

qjson.c

@@ -15,6 +15,11 @@
 #include "json-parser.h"
 #include "json-streamer.h"
 #include "qjson.h"
+#include "qint.h"
+#include "qlist.h"
+#include "qbool.h"
+#include "qfloat.h"
+#include "qdict.h"
 
 typedef struct JSONParsingState
 {
@@ -58,3 +63,176 @@ QObject *qobject_from_jsonf(const char *string, ...)
 
     return state.result;
 }
+
+typedef struct ToJsonIterState
+{
+    int count;
+    QString *str;
+} ToJsonIterState;
+
+static void to_json(const QObject *obj, QString *str);
+
+static void to_json_dict_iter(const char *key, QObject *obj, void *opaque)
+{
+    ToJsonIterState *s = opaque;
+    QString *qkey;
+
+    if (s->count) {
+        qstring_append(s->str, ", ");
+    }
+
+    qkey = qstring_from_str(key);
+    to_json(QOBJECT(qkey), s->str);
+    QDECREF(qkey);
+
+    qstring_append(s->str, ": ");
+    to_json(obj, s->str);
+    s->count++;
+}
+
+static void to_json_list_iter(QObject *obj, void *opaque)
+{
+    ToJsonIterState *s = opaque;
+
+    if (s->count) {
+        qstring_append(s->str, ", ");
+    }
+
+    to_json(obj, s->str);
+    s->count++;
+}
+
+static void to_json(const QObject *obj, QString *str)
+{
+    switch (qobject_type(obj)) {
+    case QTYPE_QINT: {
+        QInt *val = qobject_to_qint(obj);
+        char buffer[1024];
+
+        snprintf(buffer, sizeof(buffer), "%" PRId64, qint_get_int(val));
+        qstring_append(str, buffer);
+        break;
+    }
+    case QTYPE_QSTRING: {
+        QString *val = qobject_to_qstring(obj);
+        const char *ptr;
+
+        ptr = qstring_get_str(val);
+        qstring_append(str, "\"");
+        while (*ptr) {
+            if ((ptr[0] & 0xE0) == 0xE0 &&
+                (ptr[1] & 0x80) && (ptr[2] & 0x80)) {
+                uint16_t wchar;
+                char escape[7];
+
+                wchar  = (ptr[0] & 0x0F) << 12;
+                wchar |= (ptr[1] & 0x3F) << 6;
+                wchar |= (ptr[2] & 0x3F);
+                ptr += 2;
+
+                snprintf(escape, sizeof(escape), "\\u%04X", wchar);
+                qstring_append(str, escape);
+            } else if ((ptr[0] & 0xE0) == 0xC0 && (ptr[1] & 0x80)) {
+                uint16_t wchar;
+                char escape[7];
+
+                wchar  = (ptr[0] & 0x1F) << 6;
+                wchar |= (ptr[1] & 0x3F);
+                ptr++;
+
+                snprintf(escape, sizeof(escape), "\\u%04X", wchar);
+                qstring_append(str, escape);
+            } else switch (ptr[0]) {
+                case '\"':
+                    qstring_append(str, "\\\"");
+                    break;
+                case '\\':
+                    qstring_append(str, "\\\\");
+                    break;
+                case '\b':
+                    qstring_append(str, "\\b");
+                    break;
+                case '\n':
+                    qstring_append(str, "\\n");
+                    break;
+                case '\r':
+                    qstring_append(str, "\\r");
+                    break;
+                case '\t':
+                    qstring_append(str, "\\t");
+                    break;
+                default: {
+                    char buf[2] = { ptr[0], 0 };
+                    qstring_append(str, buf);
+                    break;
+                }
+                }
+            ptr++;
+        }
+        qstring_append(str, "\"");
+        break;
+    }
+    case QTYPE_QDICT: {
+        ToJsonIterState s;
+        QDict *val = qobject_to_qdict(obj);
+
+        s.count = 0;
+        s.str = str;
+        qstring_append(str, "{");
+        qdict_iter(val, to_json_dict_iter, &s);
+        qstring_append(str, "}");
+        break;
+    }
+    case QTYPE_QLIST: {
+        ToJsonIterState s;
+        QList *val = qobject_to_qlist(obj);
+
+        s.count = 0;
+        s.str = str;
+        qstring_append(str, "[");
+        qlist_iter(val, (void *)to_json_list_iter, &s);
+        qstring_append(str, "]");
+        break;
+    }
+    case QTYPE_QFLOAT: {
+        QFloat *val = qobject_to_qfloat(obj);
+        char buffer[1024];
+        int len;
+
+        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);
+        break;
+    }
+    case QTYPE_QBOOL: {
+        QBool *val = qobject_to_qbool(obj);
+
+        if (qbool_get_int(val)) {
+            qstring_append(str, "true");
+        } else {
+            qstring_append(str, "false");
+        }
+        break;
+    }
+    case QTYPE_NONE:
+        break;
+    }
+}
+
+QString *qobject_to_json(const QObject *obj)
+{
+    QString *str = qstring_new();
+
+    to_json(obj, str);
+
+    return str;
+}

qjson.h

@@ -15,9 +15,12 @@
 #define QJSON_H
 
 #include "qobject.h"
+#include "qstring.h"
 
 QObject *qobject_from_json(const char *string);
 QObject *qobject_from_jsonf(const char *string, ...)
     __attribute__((__format__ (__printf__, 1, 2)));
 
+QString *qobject_to_json(const QObject *obj);
+
 #endif /* QJSON_H */