migration/qjson.c

   1 /*
   2  * A simple JSON writer
   3  *
   4  * Copyright Alexander Graf
   5  *
   6  * Authors:
   7  *  Alexander Graf <agraf@suse.de>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 /*
  15  * Type QJSON lets you build JSON text.  Its interface mirrors (a
  16  * subset of) abstract JSON syntax.
  17  *
  18  * It does *not* detect incorrect use.  It happily produces invalid
  19  * JSON then.  This is what migration wants.
  20  *
  21  * QAPI output visitors also produce JSON text.  However, they do
  22  * assert their preconditions and invariants, and therefore abort on
  23  * incorrect use.
  24  */
  25
  26 #include "qemu/osdep.h"
  27 #include "qapi/qmp/qstring.h"
  28 #include "migration/qjson.h"
  29
  30 struct QJSON {
  31     QString *str;
  32     bool omit_comma;
  33 };
  34
  35 static void json_emit_element(QJSON *json, const char *name)
  36 {
  37     /* Check whether we need to print a , before an element */
  38     if (json->omit_comma) {
  39         json->omit_comma = false;
  40     } else {
  41         qstring_append(json->str, ", ");
  42     }
  43
  44     if (name) {
  45         qstring_append(json->str, "\"");
  46         qstring_append(json->str, name);
  47         qstring_append(json->str, "\" : ");
  48     }
  49 }
  50
  51 void json_start_object(QJSON *json, const char *name)
  52 {
  53     json_emit_element(json, name);
  54     qstring_append(json->str, "{ ");
  55     json->omit_comma = true;
  56 }
  57
  58 void json_end_object(QJSON *json)
  59 {
  60     qstring_append(json->str, " }");
  61     json->omit_comma = false;
  62 }
  63
  64 void json_start_array(QJSON *json, const char *name)
  65 {
  66     json_emit_element(json, name);
  67     qstring_append(json->str, "[ ");
  68     json->omit_comma = true;
  69 }
  70
  71 void json_end_array(QJSON *json)
  72 {
  73     qstring_append(json->str, " ]");
  74     json->omit_comma = false;
  75 }
  76
  77 void json_prop_int(QJSON *json, const char *name, int64_t val)
  78 {
  79     json_emit_element(json, name);
  80     qstring_append_int(json->str, val);
  81 }
  82
  83 void json_prop_str(QJSON *json, const char *name, const char *str)
  84 {
  85     json_emit_element(json, name);
  86     qstring_append_chr(json->str, '"');
  87     qstring_append(json->str, str);
  88     qstring_append_chr(json->str, '"');
  89 }
  90
  91 const char *qjson_get_str(QJSON *json)
  92 {
  93     return qstring_get_str(json->str);
  94 }
  95
  96 QJSON *qjson_new(void)
  97 {
  98     QJSON *json = g_new0(QJSON, 1);
  99
 100     json->str = qstring_from_str("{ ");
 101     json->omit_comma = true;
 102     return json;
 103 }
 104
 105 void qjson_finish(QJSON *json)
 106 {
 107     json_end_object(json);
 108 }
 109
 110 void qjson_destroy(QJSON *json)
 111 {
 112     QDECREF(json->str);
 113     g_free(json);
 114 }