Port LimitToLast to C++ SDK.

PiperOrigin-RevId: 298915552

Author: wu-hui

firestore/src/android/query_android.cc

@@ -46,8 +46,8 @@ Query QueryInternal::OrderBy(const FieldPath& field,
 
 Query QueryInternal::Limit(int32_t limit) {
   JNIEnv* env = firestore_->app()->GetJNIEnv();
-  // Although the backend supports signed int32, Android client SDK use long
-  // as parameter type. So we up-cast it to jlong instead of jint here.
+  // Although the backend supports signed int32, Android client SDK uses long
+  // as parameter type. So we cast it to jlong instead of jint here.
   jobject query = env->CallObjectMethod(obj_, query::GetMethodId(query::kLimit),
                                         static_cast<jlong>(limit));
   CheckAndClearJniExceptions(env);
@@ -58,6 +58,20 @@ Query QueryInternal::Limit(int32_t limit) {
   return Query{internal};
 }
 
+Query QueryInternal::LimitToLast(int32_t limit) {
+  JNIEnv* env = firestore_->app()->GetJNIEnv();
+  // Although the backend supports signed int32, Android client SDK uses long
+  // as parameter type. So we cast it to jlong instead of jint here.
+  jobject query = env->CallObjectMethod(
+      obj_, query::GetMethodId(query::kLimitToLast), static_cast<jlong>(limit));
+  CheckAndClearJniExceptions(env);
+  QueryInternal* internal = new QueryInternal{firestore_, query};
+  env->DeleteLocalRef(query);
+
+  CheckAndClearJniExceptions(env);
+  return Query{internal};
+}
+
 Future<QuerySnapshot> QueryInternal::Get(Source source) {
   JNIEnv* env = firestore_->app()->GetJNIEnv();
   jobject task =

firestore/src/android/query_android.h

@@ -61,6 +61,8 @@ enum class QueryFn {
     "Lcom/google/firebase/firestore/Query$Direction;)"              \
     "Lcom/google/firebase/firestore/Query;"),                       \
   X(Limit, "limit", "(J)Lcom/google/firebase/firestore/Query;"),    \
+  X(LimitToLast, "limitToLast",                                     \
+      "(J)Lcom/google/firebase/firestore/Query;"),                  \
   X(StartAtSnapshot, "startAt",                                     \
     "(Lcom/google/firebase/firestore/DocumentSnapshot;)"            \
     "Lcom/google/firebase/firestore/Query;"),                       \
@@ -235,15 +237,26 @@ class QueryInternal : public WrapperFuture<QueryFn, QueryFn::kCount> {
   Query OrderBy(const FieldPath& field, Query::Direction direction);
 
   /**
-   * @brief Creates and returns a new Query that's additionally limited to only
-   * return up to the specified number of documents.
+   * @brief Creates and returns a new Query that only returns the first matching
+   * documents up to the specified number.
    *
    * @param[in] limit A non-negative integer to specify the maximum number of
    * items to return.
    *
    * @return The created Query.
    */
-  Query Limit(int32_t limit);
+  virtual Query Limit(int32_t limit);
+
+  /**
+   * @brief Creates and returns a new Query that only returns the last matching
+   * documents up to the specified number.
+   *
+   * @param[in] limit A non-negative integer to specify the maximum number of
+   * items to return.
+   *
+   * @return The created Query.
+   */
+  virtual Query LimitToLast(int32_t limit);
 
   /**
    * @brief Creates and returns a new Query that starts at the provided document

firestore/src/common/query.cc

@@ -192,6 +192,11 @@ Query Query::Limit(int32_t limit) {
   return internal_->Limit(limit);
 }
 
+Query Query::LimitToLast(int32_t limit) {
+  if (!internal_) return {};
+  return internal_->LimitToLast(limit);
+}
+
 Query Query::StartAt(const DocumentSnapshot& snapshot) {
   if (!internal_) return {};
   return internal_->StartAt(snapshot);

firestore/src/include/firebase/firestore/query.h

@@ -393,8 +393,8 @@ class Query {
                         Direction direction = Direction::kAscending);
 
   /**
-   * @brief Creates and returns a new Query that's additionally limited to only
-   * return up to the specified number of documents.
+   * @brief Creates and returns a new Query that only returns the first matching
+   * documents up to the specified number.
    *
    * @param[in] limit A non-negative integer to specify the maximum number of
    * items to return.
@@ -403,6 +403,17 @@ class Query {
    */
   virtual Query Limit(int32_t limit);
 
+  /**
+   * @brief Creates and returns a new Query that only returns the last matching
+   * documents up to the specified number.
+   *
+   * @param[in] limit A non-negative integer to specify the maximum number of
+   * items to return.
+   *
+   * @return The created Query.
+   */
+  virtual Query LimitToLast(int32_t limit);
+
   /**
    * @brief Creates and returns a new Query that starts at the provided document
    * (inclusive). The starting position is relative to the order of the query.

firestore/src/ios/query_ios.cc

@@ -53,6 +53,10 @@ Query QueryInternal::Limit(int32_t limit) {
   return MakePublic(query_.LimitToFirst(limit));
 }
 
+Query QueryInternal::LimitToLast(int32_t limit) {
+  return MakePublic(query_.LimitToLast(limit));
+}
+
 Future<QuerySnapshot> QueryInternal::Get(Source source) {
   auto promise = promise_factory_.CreatePromise<QuerySnapshot>(AsyncApis::kGet);
   auto listener = ListenerWithPromise<api::QuerySnapshot>(promise);

firestore/src/ios/query_ios.h

@@ -30,6 +30,7 @@ class QueryInternal {
 
   Query OrderBy(const FieldPath& field, Query::Direction direction);
   Query Limit(int32_t limit);
+  Query LimitToLast(int32_t limit);
 
   virtual Future<QuerySnapshot> Get(Source source);
   virtual Future<QuerySnapshot> GetLastResult();