Add `library_jansson` for JSON parsing.

Jansson is a C library for encoding, decoding and manipulating JSON data [1]. `library_jansson` mimics this interface (currently only for decoding) to perform JSON parsing in Javascript.

[1] https://github.com/akheron/jansson

1 files changed, 225 insertions, 0 deletions

diff --git a/src/library_jansson.js b/src/library_jansson.js
new file mode 100644
index 00000000..8ecb535b
--- /dev/null
+++ b/src/library_jansson.js
@@ -0,0 +1,225 @@
+/*
+ * Javascript implementation for the Jansson JSON parser.
+ * Source: https://github.com/akheron/jansson
+ *
+ * Implemented and tested with:
+ * https://github.com/akheron/jansson/commit/cf1074e70ea42a1dea4d6e57b2b29532049bcd28
+ */
+
+var LibraryJansson = {
+
+    $JANSSON: {
+
+      load: function(string, flags, error) {
+        var json_obj = eval('(' + string + ')');
+
+        if (json_obj != null) {
+          // Create the root node with the nodeID `1`
+          g_json_context = [null, {"name" : "root", "node" : json_obj}];
+          return 1;
+        } else {
+          g_json_context = null;
+          return null;
+        }
+      },
+
+      type: function(nodeID) {
+        if (!g_json_context)
+          return null;
+
+        var node = g_json_context[nodeID].node;
+        if (typeof(node) === 'object' && (node instanceof Array))
+          return 'array'
+        else
+          return typeof(node);
+      },
+
+      getNode: function(parentNodeID) {
+        if (!g_json_context)
+          return null;
+
+        var parentNode = g_json_context[parentNodeID];
+    
+        if (!parentNode) {
+          console.log("Jansson: Node with ID `" + parentNodeID + "` not found.");
+          return null;
+        }
+
+        // Add all child nodes of the parent node to the context.
+        // Consequently we can access these child nodes with an ID (pointer)
+        // TODO: Here is room for performance improvements
+        if (!parentNode.begin) {
+          var childNodeID = g_json_context.length;
+          for(var childNode in parentNode.node) {
+            var childNodeID = g_json_context.length;
+            g_json_context[childNodeID] = {"name" : childNode, "node" : parentNode.node[childNode]};
+            if (!parentNode.begin) parentNode.begin = childNodeID;
+          };
+          parentNode.end = childNodeID;
+        }
+
+        return parentNode;
+      }
+
+    },
+
+    json_loads: function(string, flags, error) {
+     return JANSSON.load(Pointer_stringify(string), flags, error);
+    },
+
+    json_loadb: function(buffer, buflen, flags, error) {
+      return JANSSON.load(Pointer_stringify(buffer).substr(0, buflen), flags, error);
+    },
+
+    json_is_object: function(nodeID) {
+      return (JANSSON.type(nodeID) === 'object');
+    },
+
+    json_is_array: function(nodeID) {
+      return (JANSSON.type(nodeID) === 'array');
+    },
+
+    json_is_string: function(nodeID) {
+      return (JANSSON.type(nodeID) === 'string');
+    },
+
+    json_is_integer: function(nodeID) {
+      return (JANSSON.type(nodeID) === 'number');
+    },
+
+    json_is_real: function(nodeID) {
+      return (JANSSON.type(nodeID) === 'number');
+    },
+
+    json_is_number: function(nodeID) {
+      return (JANSSON.type(nodeID) === 'number');
+    },
+
+    json_is_null: function(nodeID) {
+      var nodeType = JANSSON.type(nodeID);
+      return (nodeType === 'undefined' || nodeType === 'null');
+    },
+
+    json_object_get: function(parentNodeID, key) {
+      var key = Pointer_stringify(key);
+      var parentNode = JANSSON.getNode(parentNodeID);
+
+      if (!parentNode)
+        return null;
+
+      // Find the ID (pointer) of the requested child node
+      for (var i=parentNode.begin; i<=parentNode.end; i++) {
+        if (g_json_context[i].name == key) return i; 
+      }
+      
+      return null;
+    },
+
+    json_object_iter: function(parentNodeID) {
+      var parentNode = JANSSON.getNode(parentNodeID);
+
+      if (!parentNode)
+        return null;
+
+      return parentNode.begin;
+    },
+
+    json_object_iter_next: function(parentNodeID, childNodeID) {
+      var parentNode = JANSSON.getNode(parentNodeID);
+
+      if (!parentNode)
+        return null;
+
+      if (childNodeID < parentNode.begin || childNodeID >= parentNode.end)
+        return null;
+      else
+        return childNodeID+1;
+    },
+
+    json_array_size: function(parentNodeID, index) {
+      var parentNode = JANSSON.getNode(parentNodeID);
+
+      if (!parentNode)
+        return 0;
+
+      var size = parentNode.end - parentNode.begin + 1;
+
+      if (size < 0)
+       size = 0;
+
+      return size;
+    },
+
+    json_array_get: function(parentNodeID, index) {
+      var parentNode = JANSSON.getNode(parentNodeID);
+      var position = parentNode.begin + index;
+
+      if (position < parentNode.begin || position > parentNode.end)
+        return null;
+      else
+        return position;
+    },
+
+    json_object_iter_key: function(nodeID) {
+      var node = g_json_context[nodeID];
+
+      if (!node)
+        return null;
+
+      return allocate(intArrayFromString(node.name), 'i8', ALLOC_NORMAL);
+    },
+
+    json_object_iter_value: function(nodeID) {
+      return nodeID;
+    },
+
+    json_string_value: function(nodeID) {
+      var node = g_json_context[nodeID];
+
+      if (!node)
+        return null;
+
+      return allocate(intArrayFromString(node.node), 'i8', ALLOC_NORMAL);
+    },
+
+    json_integer_value: function(nodeID) {
+      var node = g_json_context[nodeID];
+
+      if (!node)
+        return null;
+
+      // Convert JSON number to an integer
+      // c.f. http://stackoverflow.com/questions/596467/how-do-i-convert-a-float-to-an-int-in-javascript
+      if (node.node<0)
+        return Math.ceil(node.node);
+      else
+        return Math.floor(node.node);
+    },
+
+    json_real_value: function(nodeID) {
+      var node = g_json_context[nodeID];
+
+      if (!node)
+        return null;
+
+      return node.node;
+    },
+
+    json_number_value: function(nodeID) {
+      var node = g_json_context[nodeID];
+
+      if (!node)
+        return null;
+
+      return node.node;
+    },
+
+    json_delete: function(nodeID) {
+      // We assume, if the root node's reference count is decreased, we can forget the context.
+      if (nodeID == 1)
+        g_json_context = null;
+    }
+};
+
+autoAddDeps(LibraryJansson, '$JANSSON');
+mergeInto(LibraryManager.library, LibraryJansson);