path: root/json-glib/json-generator.c

/* json-generator.c - JSON streams generator
 * 
 * This file is part of JSON-GLib
 * Copyright (C) 2007  OpenedHand Ltd.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * Author:
 *   Emmanuele Bassi  <ebassi@openedhand.com>
 */

/**
 * SECTION:json-generator
 * @short_description: Generates JSON data streams
 *
 * #JsonGenerator provides an object for generating a JSON data stream and
 * put it into a buffer or a file.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>
#include <string.h>

#include "json-marshal.h"
#include "json-generator.h"

#define JSON_GENERATOR_GET_PRIVATE(obj) \
        (G_TYPE_INSTANCE_GET_PRIVATE ((obj), JSON_TYPE_GENERATOR, JsonGeneratorPrivate))

struct _JsonGeneratorPrivate
{
  JsonNode *root;

  guint indent;
  gunichar indent_char;

  guint pretty : 1;
};

enum
{
  PROP_0,

  PROP_PRETTY,
  PROP_INDENT,
  PROP_ROOT,
  PROP_INDENT_CHAR
};

static gchar *dump_value  (JsonGenerator *generator,
                           gint           level,
                           const gchar   *name,
                           JsonNode      *node);
static gchar *dump_array  (JsonGenerator *generator,
                           gint           level,
                           const gchar   *name,
                           JsonArray     *array,
                           gsize         *length);
static gchar *dump_object (JsonGenerator *generator,
                           gint           level,
                           const gchar   *name,
                           JsonObject    *object,
                           gsize         *length);

G_DEFINE_TYPE (JsonGenerator, json_generator, G_TYPE_OBJECT);

static void
json_generator_finalize (GObject *gobject)
{
  JsonGeneratorPrivate *priv = JSON_GENERATOR_GET_PRIVATE (gobject);

  if (priv->root)
    json_node_free (priv->root);

  G_OBJECT_CLASS (json_generator_parent_class)->finalize (gobject);
}

static void
json_generator_set_property (GObject      *gobject,
                             guint         prop_id,
                             const GValue *value,
                             GParamSpec   *pspec)
{
  JsonGeneratorPrivate *priv = JSON_GENERATOR_GET_PRIVATE (gobject);

  switch (prop_id)
    {
    case PROP_PRETTY:
      priv->pretty = g_value_get_boolean (value);
      break;
    case PROP_INDENT:
      priv->indent = g_value_get_uint (value);
      break;
    case PROP_INDENT_CHAR:
      priv->indent_char = g_value_get_uint (value);
      break;
    case PROP_ROOT:
      json_generator_set_root (JSON_GENERATOR (gobject),
                               g_value_get_boxed (value));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
      break;
    }
}

static void
json_generator_get_property (GObject    *gobject,
                             guint       prop_id,
                             GValue     *value,
                             GParamSpec *pspec)
{
  JsonGeneratorPrivate *priv = JSON_GENERATOR_GET_PRIVATE (gobject);

  switch (prop_id)
    {
    case PROP_PRETTY:
      g_value_set_boolean (value, priv->pretty);
      break;
    case PROP_INDENT:
      g_value_set_uint (value, priv->indent);
      break;
    case PROP_INDENT_CHAR:
      g_value_set_uint (value, priv->indent_char);
      break;
    case PROP_ROOT:
      g_value_set_boxed (value, priv->root);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
      break;
    }
}

static void
json_generator_class_init (JsonGeneratorClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

  g_type_class_add_private (klass, sizeof (JsonGeneratorPrivate));

  gobject_class->set_property = json_generator_set_property;
  gobject_class->get_property = json_generator_get_property;
  gobject_class->finalize = json_generator_finalize;

  /**
   * JsonGenerator:pretty:
   *
   * Whether the output should be "pretty-printed", with indentation and
   * newlines. The indentation level can be controlled by using the
   * JsonGenerator:indent property
   */
  g_object_class_install_property (gobject_class,
                                   PROP_PRETTY,
                                   g_param_spec_boolean ("pretty",
                                                         "Pretty",
                                                         "Pretty-print the output",
                                                         FALSE,
                                                         G_PARAM_READWRITE));
  /**
   * JsonGenerator:indent:
   *
   * Number of spaces to be used to indent when pretty printing.
   */
  g_object_class_install_property (gobject_class,
                                   PROP_INDENT,
                                   g_param_spec_uint ("indent",
                                                      "Indent",
                                                      "Number of indentation spaces",
                                                      0, G_MAXUINT,
                                                      2,
                                                      G_PARAM_READWRITE));
  /**
   * JsonGenerator:root:
   *
   * The root #JsonNode to be used when constructing a JSON data
   * stream.
   *
   * Since: 0.4
   */
  g_object_class_install_property (gobject_class,
                                   PROP_ROOT,
                                   g_param_spec_boxed ("root",
                                                       "Root",
                                                       "Root of the JSON data tree",
                                                       JSON_TYPE_NODE,
                                                       G_PARAM_READWRITE));
  /**
   * JsonGenerator:indent-char:
   *
   * The character that should be used when indenting in pretty print.
   *
   * Since: 0.6
   */
  g_object_class_install_property (gobject_class,
                                   PROP_INDENT_CHAR,
                                   g_param_spec_unichar ("indent-char",
                                                         "Indent Char",
                                                         "Character that should be used when indenting",
                                                         ' ',
                                                         G_PARAM_READWRITE));
}

static void
json_generator_init (JsonGenerator *generator)
{
  JsonGeneratorPrivate *priv;

  generator->priv = priv = JSON_GENERATOR_GET_PRIVATE (generator);

  priv->pretty = FALSE;
  priv->indent = 2;
  priv->indent_char = ' ';
}

static gchar *
dump_value (JsonGenerator *generator,
            gint           level,
            const gchar   *name,
            JsonNode      *node)
{
  JsonGeneratorPrivate *priv = generator->priv;
  gboolean pretty = priv->pretty;
  guint indent = priv->indent;
  GValue value = { 0, };
  GString *buffer;
  guint i;

  buffer = g_string_new ("");

  if (pretty)
    {
      for (i = 0; i < (level * indent); i++)
        g_string_append_c (buffer, priv->indent_char);
    }

  if (name && name[0] != '\0')
    g_string_append_printf (buffer, "\"%s\" : ", name);

  json_node_get_value (node, &value);

  switch (G_VALUE_TYPE (&value))
    {
    case G_TYPE_INT:
      g_string_append_printf (buffer, "%d", g_value_get_int (&value));
      break;

    case G_TYPE_STRING:
      {
        gchar *tmp;
        gchar *exceptions = g_malloc (128);
        gint chr, i;

        /* non-ascii characters can't be escaped, otherwise utf-8
         * chars will break */
        for (i = 0, chr = 0x7f; chr <= 0xff; chr++, i++)
          exceptions[i] = chr;

        tmp = g_strescape (g_value_get_string (&value), exceptions);
        g_free (exceptions);

        g_string_append_printf (buffer, "\"%s\"", tmp);
        g_free (tmp);
      }
      break;

    case G_TYPE_DOUBLE:
      g_string_append_printf (buffer, "%f", g_value_get_double (&value));
      break;

    case G_TYPE_BOOLEAN:
      g_string_append_printf (buffer, "%s",
                              g_value_get_boolean (&value) ? "true" : "false");
      break;

    default:
      break;
    }

  g_value_unset (&value);

  return g_string_free (buffer, FALSE);
}

static gchar *
dump_array (JsonGenerator *generator,
            gint           level,
            const gchar   *name,
            JsonArray     *array,
            gsize         *length)
{
  JsonGeneratorPrivate *priv = generator->priv;
  guint array_len = json_array_get_length (array);
  guint i;
  GString *buffer;
  gboolean pretty = priv->pretty;
  guint indent = priv->indent;

  buffer = g_string_new ("");

  if (pretty)
    {
      for (i = 0; i < (level * indent); i++)
        g_string_append_c (buffer, priv->indent_char);
    }

  if (name && name[0] != '\0')
    g_string_append_printf (buffer, "\"%s\" : ", name);

  g_string_append_c (buffer, '[');

  if (pretty)
    g_string_append_c (buffer, '\n');
  else
    g_string_append_c (buffer, ' ');

  for (i = 0; i < array_len; i++)
    {
      JsonNode *cur = json_array_get_element (array, i);
      guint sub_level = level + 1;
      guint j;
      gchar *value; 

      switch (JSON_NODE_TYPE (cur))
        {
        case JSON_NODE_NULL:
          if (pretty)
            {
              for (j = 0; j < (sub_level * indent); j++)
                g_string_append_c (buffer, priv->indent_char);
            }
          g_string_append (buffer, "null");
          break;

        case JSON_NODE_VALUE:
          value = dump_value (generator, sub_level, NULL, cur);
          g_string_append (buffer, value);
          g_free (value);
          break;

        case JSON_NODE_ARRAY:
          value = dump_array (generator, sub_level, NULL, json_node_get_array (cur), NULL);
          g_string_append (buffer, value);
          g_free (value);
          break;

        case JSON_NODE_OBJECT:
          value = dump_object (generator, sub_level, NULL, json_node_get_object (cur), NULL);
          g_string_append (buffer, value);
          g_free (value);
          break;
        }

      if ((i + 1) != array_len)
        g_string_append_c (buffer, ',');

      if (pretty)
        g_string_append_c (buffer, '\n');
      else
        g_string_append_c (buffer, ' ');
    }

  if (pretty)
    {
      for (i = 0; i < (level * indent); i++)
        g_string_append_c (buffer, priv->indent_char);
    }

  g_string_append_c (buffer, ']');

  if (length)
    *length = buffer->len;

  return g_string_free (buffer, FALSE);
}

static gchar *
dump_object (JsonGenerator *generator,
             gint           level,
             const gchar   *name,
             JsonObject    *object,
             gsize         *length)
{
  JsonGeneratorPrivate *priv = generator->priv;
  GList *members, *l;
  GString *buffer;
  gboolean pretty = priv->pretty;
  guint indent = priv->indent;
  guint i;

  buffer = g_string_new ("");

  if (pretty)
    {
      for (i = 0; i < (level * indent); i++)
        g_string_append_c (buffer, priv->indent_char);
    }

  if (name && name[0] != '\0')
    g_string_append_printf (buffer, "\"%s\" : ", name);

  g_string_append_c (buffer, '{');

  if (pretty)
    g_string_append_c (buffer, '\n');
  else
    g_string_append_c (buffer, ' ');

  members = json_object_get_members (object);

  for (l = members; l != NULL; l = l->next)
    {
      const gchar *member_name = l->data;
      JsonNode *cur = json_object_get_member (object, member_name);
      guint sub_level = level + 1;
      guint j;
      gchar *value;

      switch (JSON_NODE_TYPE (cur))
        {
        case JSON_NODE_NULL:
          if (pretty)
            {
              for (j = 0; j < (sub_level * indent); j++)
                g_string_append_c (buffer, priv->indent_char);
            }
          g_string_append_printf (buffer, "\"%s\" : null", member_name);
          break;

        case JSON_NODE_VALUE:
          value = dump_value (generator, sub_level, member_name, cur);
          g_string_append (buffer, value);
          g_free (value);
          break;

        case JSON_NODE_ARRAY:
          value = dump_array (generator, sub_level, member_name,
                              json_node_get_array (cur), NULL);
          g_string_append (buffer, value);
          g_free (value);
          break;

        case JSON_NODE_OBJECT:
          value = dump_object (generator, sub_level, member_name,
                               json_node_get_object (cur), NULL);
          g_string_append (buffer, value);
          g_free (value);
          break;
        }

      if (l->next != NULL)
        g_string_append_c (buffer, ',');

      if (pretty)
        g_string_append_c (buffer, '\n');
      else
        g_string_append_c (buffer, ' ');
    }

  g_list_free (members);

  if (pretty)
    {
      for (i = 0; i < (level * indent); i++)
        g_string_append_c (buffer, priv->indent_char);
    }

  g_string_append_c (buffer, '}');

  if (length)
    *length = buffer->len;

  return g_string_free (buffer, FALSE);
}

/**
 * json_generator_new:
 * 
 * Creates a new #JsonGenerator. You can use this object to generate a
 * JSON data stream starting from a data object model composed by
 * #JsonNode<!-- -->s.
 *
 * Return value: the newly created #JsonGenerator instance
 */
JsonGenerator *
json_generator_new (void)
{
  return g_object_new (JSON_TYPE_GENERATOR, NULL);
}

/**
 * json_generator_to_data:
 * @generator: a #JsonGenerator
 * @length: return location for the length of the returned buffer, or %NULL
 *
 * Generates a JSON data stream from @generator and returns it as a
 * buffer.
 *
 * Return value: a newly allocated buffer holding a JSON data stream. Use
 *   g_free() to free the allocated resources.
 */
gchar *
json_generator_to_data (JsonGenerator *generator,
                        gsize         *length)
{
  JsonNode *root;
  gchar *retval = NULL;

  g_return_val_if_fail (JSON_IS_GENERATOR (generator), NULL);

  root = generator->priv->root;
  if (!root)
    {
      if (length)
        *length = 0;

      return NULL;
    }

  switch (JSON_NODE_TYPE (root))
    {
    case JSON_NODE_ARRAY:
      retval = dump_array (generator, 0, NULL, json_node_get_array (root), length);
      break;

    case JSON_NODE_OBJECT:
      retval = dump_object (generator, 0, NULL, json_node_get_object (root), length);
      break;

    case JSON_NODE_NULL:
      retval = g_strdup ("null");
      if (length)
        *length = 4;
      break;

    case JSON_NODE_VALUE:
      retval = NULL;
      break;
    }

  return retval;
}

/**
 * json_generator_to_file:
 * @generator: a #JsonGenerator
 * @filename: path to the target file
 * @error: return location for a #GError, or %NULL
 *
 * Creates a JSON data stream and puts it inside @filename, overwriting the
 * current file contents. This operation is atomic.
 *
 * Return value: %TRUE if saving was successful.
 */
gboolean
json_generator_to_file (JsonGenerator  *generator,
                        const gchar    *filename,
                        GError        **error)
{
  gchar *buffer;
  gsize len;
  gboolean retval;

  g_return_val_if_fail (JSON_IS_GENERATOR (generator), FALSE);
  g_return_val_if_fail (filename != NULL, FALSE);

  buffer = json_generator_to_data (generator, &len);
  retval = g_file_set_contents (filename, buffer, len, error);
  g_free (buffer);

  return retval;
}

/**
 * json_generator_set_root:
 * @generator: a #JsonGenerator
 * @node: a #JsonNode
 *
 * Sets @node as the root of the JSON data stream to be serialized by
 * the #JsonGenerator.
 *
 * Note: the node is copied by the generator object, so it can be safely
 * freed after calling this function.
 */
void
json_generator_set_root (JsonGenerator *generator,
                         JsonNode      *node)
{
  g_return_if_fail (JSON_IS_GENERATOR (generator));

  if (generator->priv->root)
    {
      json_node_free (generator->priv->root);
      generator->priv->root = NULL;
    }

  if (node)
    generator->priv->root = json_node_copy (node);
}