add a way to reset a yajl parser without full re-allocation

src/api/yajl_parse.h

@@ -108,6 +108,11 @@ extern "C" {
                                     yajl_alloc_funcs * afs,
                                     void * ctx);
 
+    /** reset a parser handle to a pristine state.  the parser will be minimally
+     *  re-initialized.  This should be faster when parsing multiple documents
+     *  than freeing and re-allocating a YAJL parser.
+     */
+    YAJL_API void yajl_reset(yajl_handle h);
 
     /** configuration parameters for the parser, these may be passed to
      *  yajl_config() along with option specific argument(s).  In general,

src/yajl.c

@@ -68,7 +68,7 @@ yajl_alloc(const yajl_callbacks * callbacks,
 
     hand->callbacks = callbacks;
     hand->ctx = ctx;
-    hand->lexer = NULL; 
+    hand->lexer = NULL;
     hand->bytesConsumed = 0;
     hand->decodeBuf = yajl_buf_alloc(&(hand->alloc));
     hand->flags	    = 0;
@@ -78,6 +78,26 @@ yajl_alloc(const yajl_callbacks * callbacks,
     return hand;
 }
 
+void
+yajl_reset(yajl_handle h)
+{
+    // reset the state stack to start
+    yajl_bs_flush(h->stateStack);
+    yajl_bs_push(h->stateStack, yajl_state_start);
+
+    // reset bytesConsumed
+    h->bytesConsumed = 0;
+
+    // clear decoding buf (note: not strictly neccesary, as
+    // this buffer is cleared on demand and reused)
+    yajl_buf_clear(h->decodeBuf);
+
+    // reset lexer state
+    if (h->lexer != NULL) {
+        yajl_lex_reset(h->lexer);
+    }
+}
+
 int
 yajl_config(yajl_handle h, yajl_option opt, ...)
 {

src/yajl_bytestack.h

@@ -43,10 +43,13 @@ typedef struct yajl_bytestack_t
     }                                           \
 
 
-/* initialize a bytestack */
+/* free dynamically allocated memory inside a byte stack */
 #define yajl_bs_free(obs)                 \
     if ((obs).stack) (obs).yaf->free((obs).yaf->ctx, (obs).stack);
 
+#define yajl_bs_flush(obs)                                         \
+    (obs).used = 0;
+
 #define yajl_bs_current(obs)               \
     (assert((obs).used > 0), (obs).stack[(obs).used - 1])
 

src/yajl_lex.c

@@ -113,6 +113,15 @@ yajl_lex_alloc(yajl_alloc_funcs * alloc,
     return lxr;
 }
 
+void
+yajl_lex_reset(yajl_lexer l) {
+    l->lineOff = 0;
+    l->charOff = 0;
+    l->error = yajl_lex_e_ok;
+    yajl_buf_clear(l->buf);
+    l->bufOff = 0;
+}
+
 void
 yajl_lex_free(yajl_lexer lxr)
 {

src/yajl_lex.h

@@ -51,6 +51,9 @@ yajl_lexer yajl_lex_alloc(yajl_alloc_funcs * alloc,
                           unsigned int allowComments,
                           unsigned int validateUTF8);
 
+void yajl_lex_reset(yajl_lexer l);
+
+
 void yajl_lex_free(yajl_lexer lexer);
 
 /**