Serialize and deserialize next sequence id properly instead of string encoding.

TODO.md

@@ -90,8 +90,8 @@
 - ~~Use rocksdb batch put for atomic insertion~~
 - ~~Proper logging~~
 - ~~Handle store-get() not finding a key~~
+- ~~Deprecate converting integer to string verbatim~~ 
 - Deprecate union type punning
-- Deprecate converting integer to string verbatim 
 - NOT operator support
 - > INT32_MAX validation for float field
 - highlight of string arrays?

include/collection.h

@@ -78,8 +78,6 @@ public:
 
     void increment_next_seq_id_field();
 
-    static uint32_t deserialize_seq_id_key(std::string serialized_seq_id);
-
     Option<uint32_t> doc_id_to_seq_id(std::string doc_id);
 
     std::vector<std::string> get_facet_fields();

include/replicator.h

@@ -161,7 +161,7 @@ public:
 
             // last 4 bytes of the key would be the serialized version of the sequence id
             std::string serialized_seq_id = replication_event->key.substr(replication_event->key.length() - 4);
-            uint32_t seq_id = Collection::deserialize_seq_id_key(serialized_seq_id);
+            uint32_t seq_id = StringUtils::deserialize_uint32_t(serialized_seq_id);
             collection->index_in_memory(document, seq_id);
         }
 

include/store.h

@@ -11,6 +11,7 @@
 #include <rocksdb/options.h>
 #include <rocksdb/merge_operator.h>
 #include <rocksdb/transaction_log.h>
+#include "string_utils.h"
 #include "logger.h"
 
 class UInt64AddOperator : public rocksdb::AssociativeMergeOperator {
@@ -19,9 +20,9 @@ public:
                        std::string* new_value, rocksdb::Logger* logger) const override {
         uint64_t existing = 0;
         if (existing_value) {
-            existing = (uint64_t) std::stoi(existing_value->ToString());
+            existing = StringUtils::deserialize_uint32_t(existing_value->ToString());
         }
-        *new_value = std::to_string(existing + std::stoi(value.ToString()));
+        *new_value = StringUtils::serialize_uint32_t(existing + StringUtils::deserialize_uint32_t(value.ToString()));
         return true;
     }
 
@@ -134,7 +135,7 @@ public:
     }
 
     void increment(const std::string & key, uint32_t value) {
-        db->Merge(rocksdb::WriteOptions(), key, std::to_string(value));
+        db->Merge(rocksdb::WriteOptions(), key, StringUtils::serialize_uint32_t(value));
     }
 
     uint64_t get_latest_seq_number() const {

include/string_utils.h

@@ -177,4 +177,20 @@ struct StringUtils {
 
         return out;
     }
+
+    static std::string serialize_uint32_t(uint32_t num) {
+        unsigned char bytes[4];
+        bytes[0] = (unsigned char) ((num >> 24) & 0xFF);
+        bytes[1] = (unsigned char) ((num >> 16) & 0xFF);
+        bytes[2] = (unsigned char) ((num >> 8) & 0xFF);
+        bytes[3] = (unsigned char) ((num & 0xFF));
+
+        return std::string(bytes, bytes+4);
+    }
+
+    static uint32_t deserialize_uint32_t(std::string serialized_num) {
+        uint32_t seq_id = ((serialized_num[0] & 0xFF) << 24) | ((serialized_num[1] & 0xFF) << 16) |
+                          ((serialized_num[2] & 0xFF) << 8)  | (serialized_num[3] & 0xFF);
+        return seq_id;
+    }
 };

src/collection.cpp

@@ -731,19 +731,8 @@ std::string Collection::get_next_seq_id_key(const std::string & collection_name)
 std::string Collection::get_seq_id_key(uint32_t seq_id) {
     // We can't simply do std::to_string() because we want to preserve the byte order.
     // & 0xFF masks all but the lowest eight bits.
-    unsigned char bytes[4];
-    bytes[0] = (unsigned char) ((seq_id >> 24) & 0xFF);
-    bytes[1] = (unsigned char) ((seq_id >> 16) & 0xFF);
-    bytes[2] = (unsigned char) ((seq_id >> 8) & 0xFF);
-    bytes[3] = (unsigned char) ((seq_id & 0xFF));
-
-    return get_seq_id_collection_prefix() + "_" + std::string(bytes, bytes+4);
-}
-
-uint32_t Collection::deserialize_seq_id_key(std::string serialized_seq_id) {
-    uint32_t seq_id = ((serialized_seq_id[0] & 0xFF) << 24) | ((serialized_seq_id[1] & 0xFF) << 16) |
-                      ((serialized_seq_id[2] & 0xFF) << 8)  | (serialized_seq_id[3] & 0xFF);
-    return seq_id;
+    const std::string & serialized_id = StringUtils::serialize_uint32_t(seq_id);
+    return get_seq_id_collection_prefix() + "_" + serialized_id;
 }
 
 std::string Collection::get_doc_id_key(const std::string & doc_id) {

src/collection_manager.cpp

@@ -83,7 +83,7 @@ Option<bool> CollectionManager::init(Store *store, const std::string & auth_key,
         }
 
         uint32_t collection_next_seq_id = next_seq_id_status == StoreStatus::NOT_FOUND ? 0 :
-                                          (const uint32_t) std::stoi(collection_next_seq_id_str);
+                                          StringUtils::deserialize_uint32_t(collection_next_seq_id_str);
 
         Collection* collection = init_collection(collection_meta, collection_next_seq_id);
 
@@ -167,7 +167,7 @@ Option<Collection*> CollectionManager::create_collection(std::string name, const
     next_collection_id++;
 
     rocksdb::WriteBatch batch;
-    batch.Put(Collection::get_next_seq_id_key(name), std::to_string(0));
+    batch.Put(Collection::get_next_seq_id_key(name), StringUtils::serialize_uint32_t(0));
     batch.Put(Collection::get_meta_key(name), collection_meta.dump());
     batch.Put(NEXT_COLLECTION_ID_KEY, std::to_string(next_collection_id));
     bool write_ok = store->batch_write(batch);

test/collection_manager_test.cpp

@@ -3,6 +3,7 @@
 #include <vector>
 #include <fstream>
 #include <collection_manager.h>
+#include "string_utils.h"
 #include "collection.h"
 
 class CollectionManagerTest : public ::testing::Test {
@@ -77,7 +78,8 @@ TEST_F(CollectionManagerTest, CollectionCreation) {
     store->get(CollectionManager::NEXT_COLLECTION_ID_KEY, next_collection_id);
 
     ASSERT_EQ(3, num_keys);
-    ASSERT_EQ("1", next_seq_id); // we already call `collection1->get_next_seq_id` above, which is side-effecting
+    // we already call `collection1->get_next_seq_id` above, which is side-effecting
+    ASSERT_EQ(1, StringUtils::deserialize_uint32_t(next_seq_id));
     ASSERT_EQ("{\"fields\":[{\"facet\":false,\"name\":\"title\",\"type\":\"string\"},"
               "{\"facet\":false,\"name\":\"starring\",\"type\":\"string\"},"
               "{\"facet\":true,\"name\":\"cast\",\"type\":\"string[]\"},"