This allows the users to disable threading. (#1122)

* This allows the users to disable threading.

* This would disable bash scripts under FreeBSD. (#1118)

* This would disable bash scripts under FreeBSD.

* Let us also disable GIT.

* Let us try to just disable GIT

* Nope. We must have both bash and git disabled.

* This allows the users to disable threading.

include/simdjson/dom/document_stream.h

@@ -169,6 +169,11 @@ private:
   /**
    * Construct a document_stream. Does not allocate or parse anything until the iterator is
    * used.
+   * 
+   * @param parser is a reference to the parser instance used to generate this document_stream
+   * @param buf is the raw byte buffer we need to process
+   * @param len is the length of the raw byte buffer in bytes
+   * @param batch_size is the size of the windows (must be strictly greater or equal to the largest JSON document)
    */
   really_inline document_stream(
     dom::parser &parser,
@@ -231,6 +236,9 @@ private:
   size_t doc_index{};
 
 #ifdef SIMDJSON_THREADS_ENABLED
+  /** Indicates whether we use threads. Note that this needs to be a constant during the execution of the parsing. */
+  bool use_thread; 
+
   inline void load_from_stage1_thread() noexcept;
 
   /** Start a thread to run stage 1 on the next batch. */

include/simdjson/dom/parser.h

@@ -342,6 +342,14 @@ public:
    */
   really_inline void set_max_capacity(size_t max_capacity) noexcept;
 
+#ifdef SIMDJSON_THREADS_ENABLED
+  /**
+   * The parser instance can use threads when they are available to speed up some
+   * operations. It is enabled by default. Changing this attribute will change the
+   * behavior of the parser for future operations.
+   */
+  bool threaded{true};
+#endif
   /** @private Use the new DOM API instead */
   class Iterator;
   /** @private Use simdjson_error instead */
@@ -380,6 +388,7 @@ public:
   /** @private Private and deprecated: use `parser.parse(...).doc.dump_raw_tape()` instead */
   inline bool dump_raw_tape(std::ostream &os) const noexcept;
 
+
 private:
   /**
    * The maximum document length this parser will automatically support.
@@ -421,6 +430,8 @@ private:
 
   friend class parser::Iterator;
   friend class document_stream;
+
+
 }; // class parser
 
 } // namespace dom

include/simdjson/inline/document_stream.h

@@ -75,6 +75,9 @@ really_inline document_stream::document_stream(
     len{_len},
     batch_size{_batch_size},
     error{SUCCESS}
+#ifdef SIMDJSON_THREADS_ENABLED
+    , use_thread(_parser.threaded) // we need to make a copy because _parser.threaded can change
+#endif
 {
 #ifdef SIMDJSON_THREADS_ENABLED
   if(worker.get() == nullptr) {
@@ -88,7 +91,11 @@ really_inline document_stream::document_stream() noexcept
     buf{nullptr},
     len{0},
     batch_size{0},
-    error{UNINITIALIZED} {
+    error{UNINITIALIZED}
+#ifdef SIMDJSON_THREADS_ENABLED
+    , use_thread(false)
+#endif 
+{
 }
 
 really_inline document_stream::~document_stream() noexcept {
@@ -137,7 +144,7 @@ inline void document_stream::start() noexcept {
   if (error) { return; }
 
 #ifdef SIMDJSON_THREADS_ENABLED
-  if (next_batch_start() < len) {
+  if (use_thread && next_batch_start() < len) {
     // Kick off the first thread if needed
     error = stage1_thread_parser.ensure_capacity(batch_size);
     if (error) { return; }
@@ -172,7 +179,11 @@ inline void document_stream::next() noexcept {
     if (batch_start >= len) { break; }
 
 #ifdef SIMDJSON_THREADS_ENABLED
-    load_from_stage1_thread();
+    if(use_thread) {
+      load_from_stage1_thread();
+    } else {
+      error = run_stage1(*parser, batch_start);
+    }
 #else
     error = run_stage1(*parser, batch_start);
 #endif

tests/document_stream_tests.cpp

@@ -69,6 +69,7 @@ namespace document_stream_tests {
     }
     return true;
   }
+
   bool small_window() {
     std::cout << "Running " << __func__ << std::endl;
     auto json = R"({"error":[],"result":{"token":"xxx"}}{"error":[],"result":{"token":"xxx"}})"_padded;
@@ -91,6 +92,31 @@ namespace document_stream_tests {
     return true;
   }
 
+#ifdef SIMDJSON_THREADS_ENABLED
+  bool threaded_disabled() {
+    std::cout << "Running " << __func__ << std::endl;
+    auto json = R"({"error":[],"result":{"token":"xxx"}}{"error":[],"result":{"token":"xxx"}})"_padded;
+    simdjson::dom::parser parser;
+    parser.threaded = false;
+    size_t count = 0;
+    size_t window_size = 10; // deliberately too small
+    simdjson::dom::document_stream stream;
+    ASSERT_SUCCESS( parser.parse_many(json, window_size).get(stream) );
+    for (auto doc : stream) {
+      if (!doc.error()) {
+          std::cerr << "Expected a capacity error " << doc.error() << std::endl;
+          return false;
+      }
+      count++;
+    }
+    if(count == 2) {
+      std::cerr << "Expected a capacity error " << std::endl;
+      return false;
+    }
+    return true;
+  }
+#endif 
+
   bool large_window() {
     std::cout << "Running " << __func__ << std::endl;
 #if SIZE_MAX > 17179869184
@@ -222,6 +248,9 @@ namespace document_stream_tests {
 
   bool run() {
     return test_current_index() &&
+#ifdef SIMDJSON_THREADS_ENABLED
+           threaded_disabled() &&
+#endif
            small_window() &&
            large_window() &&
            json_issue467() &&