Start working on c api

include/weaseljson.h

@@ -1,6 +1,10 @@
 #ifndef WEASELJSON_H
 #define WEASELJSON_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 struct WeaselJsonCallbacks {
   void (*on_begin_object)(void *data);
   void (*on_end_object)(void *data);
@@ -17,4 +21,37 @@ struct WeaselJsonCallbacks {
   void (*on_null_literal)(void *data);
 };
 
+enum WeaselJsonStatus {
+  /** Accept input */
+  WeaselJson_OK,
+  /** Consumed all available input. Call WeaselJsonParser_parse with more data
+     to provide more input, or call with length 0 to indicate end of data*/
+  WeaselJson_AGAIN,
+  /** Invalid json */
+  WeaselJson_REJECT,
+  /** json is too deeply nested */
+  WeaselJson_OVERFLOW,
+};
+
+typedef struct WeaselJsonParser WeaselJsonParser;
+
+/** Increasing stack size increases memory usage but also increases the depth of
+ * nested json accepted. */
+WeaselJsonParser *WeaselJsonParser_create(int stackSize);
+
+/** Restore the parser to its newly-created state */
+void WeaselJsonParser_reset(WeaselJsonParser *parser);
+
+/** Destroy the parser */
+void WeaselJsonParser_destroy(WeaselJsonParser *parser);
+
+/** Incrementally parse `len` more bytes starting at `buf`. `buf` may be
+ * modified. Call with `len` 0 to indicate end of data */
+WeaselJsonStatus WeaselJsonParser_parse(WeaselJsonParser *parser, char *buf,
+                                        int len);
+
+#ifdef __cplusplus
+}
+#endif
+
 #endif