Fixes https://github.com/simdjson/simdjson/issues/937

include/simdjson/dom/document_stream.h

@@ -15,6 +15,7 @@ namespace dom {
 
 
 #ifdef SIMDJSON_THREADS_ENABLED
+/** @private **/
 struct stage1_worker {
   stage1_worker() noexcept = default;
   stage1_worker(const stage1_worker&) = delete;
@@ -93,7 +94,17 @@ public:
      * @param other the end iterator to compare to.
      */
     really_inline bool operator!=(const iterator &other) const noexcept;
-
+    /**
+     * Gives the current index in the input document in bytes.
+     *
+     *   auto stream = parser.parse_many(json,window);
+     *   auto i = stream.begin();
+     *   for(; i != stream.end(); ++i) {
+     *      auto doc = *i;
+     *      size_t index = i.current_index();
+     *   }
+     */
+     really_inline size_t current_index() noexcept;
   private:
     really_inline iterator(document_stream &s, bool finished) noexcept;
     /** The document_stream we're iterating through. */
@@ -204,6 +215,9 @@ private:
 #endif // SIMDJSON_THREADS_ENABLED
 
   friend class dom::parser;
+
+  size_t doc_index{};
+
 }; // class document_stream
 
 } // namespace dom

include/simdjson/inline/document_stream.h

@@ -143,10 +143,14 @@ inline void document_stream::start() noexcept {
   next();
 }
 
+really_inline size_t document_stream::iterator::current_index() noexcept {
+  return stream.doc_index;
+}
 inline void document_stream::next() noexcept {
   if (error) { return; }
 
   // Load the next document from the batch
+  doc_index = batch_start + parser.implementation->structural_indexes[parser.implementation->next_structural_index];
   error = parser.implementation->stage2_next(parser.doc);
   // If that was the last document in the batch, load another batch (if available)
   while (error == EMPTY) {
@@ -160,6 +164,7 @@ inline void document_stream::next() noexcept {
 #endif
     if (error) { continue; } // If the error was EMPTY, we may want to load another batch.
     // Run stage 2 on the first document in the batch
+    doc_index = batch_start + parser.implementation->structural_indexes[parser.implementation->next_structural_index];
     error = parser.implementation->stage2_next(parser.doc);
   }
 }

tests/basictests.cpp

@@ -371,7 +371,33 @@ namespace document_stream_tests {
       simdjson::padded_string str("{}",2);
       simdjson::dom::document_stream s1 = parse_many_stream_return(parser, str);
   }
-
+  bool test_current_index() {
+    std::cout << "Running " << __func__ << std::endl;
+    std::string base("1         ");// one JSON!
+    std::string json;
+    for(size_t k =  0; k < 1000; k++) {
+      json += base;
+    }
+    simdjson::dom::parser parser;
+    const size_t window = 32; // deliberately small
+    auto stream = parser.parse_many(json,window);
+    auto i = stream.begin();
+    size_t count = 0;
+    for(; i != stream.end(); ++i) {
+      auto doc = *i;
+      if (doc.error()) {
+          std::cerr << doc.error() << std::endl;
+          return false;
+      }
+      if( i.current_index() != count) {
+        std::cout << "index:" << i.current_index() << std::endl;
+        std::cout << "expected index:" << count << std::endl;
+        return false;
+      }
+      count += base.size();
+    }
+    return true;
+  }
   bool small_window() {
     std::cout << "Running " << __func__ << std::endl;
     auto json = R"({"error":[],"result":{"token":"xxx"}}{"error":[],"result":{"token":"xxx"}})"_padded;
@@ -541,7 +567,8 @@ namespace document_stream_tests {
   }
 
   bool run() {
-    return small_window() &&
+    return test_current_index() &&
+           small_window() &&
            large_window() &&
            json_issue467() &&
            document_stream_test() &&