From 06349583297b7a31daaca462dcdbb93b1db63120 Mon Sep 17 00:00:00 2001
From: John Keiser <john@johnkeiser.com>
Date: Sun, 21 Feb 2021 11:42:27 -0800
Subject: [PATCH] Don't emit out of order iteration error for empty array

---
 include/simdjson/generic/ondemand/array-inl.h          | 2 +-
 include/simdjson/generic/ondemand/object-inl.h         | 2 +-
 include/simdjson/generic/ondemand/value_iterator-inl.h | 6 +++++-
 include/simdjson/generic/ondemand/value_iterator.h     | 1 +
 4 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/simdjson/generic/ondemand/array-inl.h b/include/simdjson/generic/ondemand/array-inl.h
index ca4ea43e..1018e9ac 100644
--- a/include/simdjson/generic/ondemand/array-inl.h
+++ b/include/simdjson/generic/ondemand/array-inl.h
@@ -57,7 +57,7 @@ simdjson_really_inline array array::started(value_iterator &iter) noexcept {
 
 simdjson_really_inline simdjson_result<array_iterator> array::begin() noexcept {
 #ifdef SIMDJSON_DEVELOPMENT_CHECKS
-  if (!iter.is_at_container_start()) { return OUT_OF_ORDER_ITERATION; }
+  if (!iter.is_at_iterator_start()) { return OUT_OF_ORDER_ITERATION; }
 #endif
   return array_iterator(iter);
 }
diff --git a/include/simdjson/generic/ondemand/object-inl.h b/include/simdjson/generic/ondemand/object-inl.h
index 6b973694..b1d8620c 100644
--- a/include/simdjson/generic/ondemand/object-inl.h
+++ b/include/simdjson/generic/ondemand/object-inl.h
@@ -53,7 +53,7 @@ simdjson_really_inline object::object(const value_iterator &_iter) noexcept
 
 simdjson_really_inline simdjson_result<object_iterator> object::begin() noexcept {
 #ifdef SIMDJSON_DEVELOPMENT_CHECKS
-  if (!iter.is_at_container_start()) { return OUT_OF_ORDER_ITERATION; }
+  if (!iter.is_at_iterator_start()) { return OUT_OF_ORDER_ITERATION; }
 #endif
   return object_iterator(iter);
 }
diff --git a/include/simdjson/generic/ondemand/value_iterator-inl.h b/include/simdjson/generic/ondemand/value_iterator-inl.h
index b6dc3972..af2eb539 100644
--- a/include/simdjson/generic/ondemand/value_iterator-inl.h
+++ b/include/simdjson/generic/ondemand/value_iterator-inl.h
@@ -462,7 +462,7 @@ simdjson_really_inline error_code value_iterator::advance_container_start(const
   // If we're not at the position anymore, we don't want to advance the cursor.
   if (!is_at_start()) {
 #ifdef SIMDJSON_DEVELOPMENT_CHECKS
-    if (!is_at_container_start()) { return OUT_OF_ORDER_ITERATION; }
+    if (!is_at_iterator_start()) { return OUT_OF_ORDER_ITERATION; }
 #endif
     json = peek_start();
     return SUCCESS;
@@ -503,6 +503,10 @@ simdjson_really_inline bool value_iterator::is_at_start() const noexcept {
 simdjson_really_inline bool value_iterator::is_at_container_start() const noexcept {
   return _json_iter->token.index == _start_position + 1;
 }
+simdjson_really_inline bool value_iterator::is_at_iterator_start() const noexcept {
+  auto delta = _json_iter->token.index - _start_position;
+  return delta == 1 || delta == 2;
+}
 
 simdjson_really_inline void value_iterator::assert_at_start() const noexcept {
   SIMDJSON_ASSUME( _json_iter->token.index == _start_position );
diff --git a/include/simdjson/generic/ondemand/value_iterator.h b/include/simdjson/generic/ondemand/value_iterator.h
index 72656378..0e49a65e 100644
--- a/include/simdjson/generic/ondemand/value_iterator.h
+++ b/include/simdjson/generic/ondemand/value_iterator.h
@@ -285,6 +285,7 @@ protected:
 
   simdjson_really_inline bool is_at_start() const noexcept;
   simdjson_really_inline bool is_at_container_start() const noexcept;
+  simdjson_really_inline bool is_at_iterator_start() const noexcept;
   simdjson_really_inline void assert_at_start() const noexcept;
   simdjson_really_inline void assert_at_container_start() const noexcept;
   simdjson_really_inline void assert_at_root() const noexcept;