diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 3752331..2b9f4ef 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -54,6 +54,7 @@ file(GLOB SOURCES
     "ogawayama/stub/*.cpp"
     "tateyama/utils/*.cpp"
     "jogasaki/serializer/*.cpp"
+    "jogasaki/utils/*.cpp"
 )
 
 set_source_files_properties(
diff --git a/src/jogasaki/utils/decimal.cpp b/src/jogasaki/utils/decimal.cpp
new file mode 100644
index 0000000..a161766
--- /dev/null
+++ b/src/jogasaki/utils/decimal.cpp
@@ -0,0 +1,197 @@
+/*
+ * Copyright 2018-2023 Project Tsurugi.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "decimal.h"
+
+namespace jogasaki::utils {
+
+constexpr static std::size_t npos = static_cast<std::size_t>(-1);
+
+std::pair<std::size_t, bool> most_significant_non_zero_offset(std::uint64_t v, std::uint64_t zero) {
+    for (std::size_t offset = 0; offset < sizeof(std::uint64_t); ++offset) {
+        std::uint64_t octet = (v >> ((sizeof(std::uint64_t) - offset - 1U) * 8U)) & 0xffU;
+        if (octet != zero) {
+            if ((octet & 0x80U) != 0) {
+                return {offset, true};
+            }
+            return {offset, false};
+        }
+    }
+    return {npos, false};
+}
+
+std::tuple<std::uint64_t, std::uint64_t, std::size_t> make_signed_coefficient_full(takatori::decimal::triple value) {
+    std::uint64_t c_hi = value.coefficient_high();
+    std::uint64_t c_lo = value.coefficient_low();
+
+    if (value.sign() >= 0) {
+        if(auto [offset, expanded] = most_significant_non_zero_offset(c_hi, 0); offset != npos) {
+            std::size_t size { sizeof(std::uint64_t) * 2 - offset };
+            if(expanded) {
+                ++size;
+            }
+            return { c_hi, c_lo, size };
+        }
+        if(auto [offset, expanded] = most_significant_non_zero_offset(c_lo, 0); offset != npos) {
+            std::size_t size { sizeof(std::uint64_t) - offset };
+            if(expanded) {
+                ++size;
+            }
+            return { c_hi, c_lo, size };
+        }
+        // all values zero
+        return { c_hi, c_lo, 1 };
+    }
+
+    // for negative numbers
+
+    if (value.sign() < 0) {
+        c_lo = ~c_lo + 1;
+        c_hi = ~c_hi;
+        if (c_lo == 0) {
+            c_hi += 1; // carry up
+        }
+    }
+
+    if(auto [offset, expanded] = most_significant_non_zero_offset(c_hi, 0xffU); offset != npos) {
+        std::size_t size { sizeof(std::uint64_t) * 2 - offset };
+        if(expanded) {
+            ++size;
+        }
+        return { c_hi, c_lo, size };
+    }
+    if(auto [offset, expanded] = most_significant_non_zero_offset(c_lo, 0xffU); offset != npos) {
+        std::size_t size { sizeof(std::uint64_t) - offset };
+        if(expanded) {
+            ++size;
+        }
+        return { c_hi, c_lo, size };
+    }
+    return { c_hi, c_lo, 1 };
+}
+
+constexpr std::size_t max_decimal_coefficient_size = sizeof(std::uint64_t) * 2 + 1;
+
+bool validate_decimal_coefficient(
+    std::string_view buf
+) {
+    if(buf.size() < max_decimal_coefficient_size) {
+        return true;
+    }
+    auto first = static_cast<std::uint8_t>(buf[0]);
+    // positive is OK because coefficient is [0, 2^128)
+    if (first == 0) {
+        return true;
+    }
+
+    if (first == 0xffU) {
+        // check negative value to avoid -2^128 (0xff 0x00.. 0x00)
+        auto const* found = std::find_if(
+            buf.begin() + 1,
+            buf.end(),
+            [](auto c) { return c != '\0'; });
+        if (found != buf.end()) {
+            return true;
+        }
+    }
+    return false;
+}
+
+takatori::decimal::triple read_decimal(std::string_view data, std::size_t scale) {
+    // extract lower 8-octets of coefficient
+    std::uint64_t c_lo{};
+    std::uint64_t shift{};
+    for (std::size_t offset = 0;
+        offset < data.size() && offset < sizeof(std::uint64_t);
+        ++offset) {
+        auto pos = data.size() - offset - 1;
+        std::uint64_t octet { static_cast<std::uint8_t>(data[pos]) };
+        c_lo |= octet << shift;
+        shift += 8;
+    }
+
+    // extract upper 8-octets of coefficient
+    std::uint64_t c_hi {};
+    shift = 0;
+    for (
+        std::size_t offset = sizeof(std::uint64_t);
+        offset < data.size() && offset < sizeof(std::uint64_t) * 2;
+        ++offset) {
+        auto pos = data.size() - offset - 1;
+        std::uint64_t octet { static_cast<std::uint8_t>(data[pos]) };
+        c_hi |= octet << shift;
+        shift += 8;
+    }
+
+    bool negative = (static_cast<std::uint8_t>(data[0]) & 0x80U) != 0;
+
+    if (negative) {
+        // sign extension
+        if (data.size() < sizeof(std::uint64_t) * 2) {
+            auto mask = std::numeric_limits<std::uint64_t>::max(); // 0xfff.....
+            if(data.size() < sizeof(std::uint64_t)) {
+                std::size_t rest = data.size() * 8U;
+                c_lo |= mask << rest;
+                c_hi = mask;
+            } else {
+                std::size_t rest = (data.size() - sizeof(std::uint64_t)) * 8U;
+                c_hi |= mask << rest;
+            }
+        }
+
+        c_lo = ~c_lo + 1;
+        c_hi = ~c_hi;
+        if (c_lo == 0) {
+            c_hi += 1; // carry up
+        }
+    }
+
+    return takatori::decimal::triple{
+        negative ? -1 : +1,
+        c_hi,
+        c_lo,
+        -static_cast<std::int32_t>(scale),
+    };
+}
+
+void create_decimal(
+    std::int8_t sign,
+    std::uint64_t lo,
+    std::uint64_t hi,
+    std::size_t sz,
+    decimal_buffer& out
+) {
+    auto base_ = out.data();
+    std::size_t pos_ = 0;
+
+    if (sz > sizeof(std::uint64_t) * 2) {
+        // write sign bit
+        *(base_ + pos_) = sign >= 0 ? '\x00' : '\xFF';  // NOLINT
+        ++pos_;
+        --sz;
+    }
+
+    for (std::size_t offset = 0, n = std::min(sz, sizeof(std::uint64_t)); offset < n; ++offset) {
+        *(base_ + pos_ + sz - offset - 1) = static_cast<char>(lo >> (offset * 8U));  //NOLINT
+    }
+    if (sz > sizeof(std::uint64_t)) {
+        for (std::size_t offset = 0, n = std::min(sz - sizeof(std::uint64_t), sizeof(std::uint64_t)); offset < n; ++offset) {
+            *(base_ + pos_ + sz - offset - sizeof(std::uint64_t) - 1) = static_cast<char>(hi >> (offset * 8U));  //NOLINT
+        }
+    }
+}
+
+}
+
diff --git a/src/jogasaki/utils/decimal.h b/src/jogasaki/utils/decimal.h
new file mode 100644
index 0000000..d604eb5
--- /dev/null
+++ b/src/jogasaki/utils/decimal.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2018-2023 Project Tsurugi.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <initializer_list>
+#include <tuple>
+#include <string_view>
+
+#include <takatori/value/decimal.h>
+
+namespace jogasaki::utils {
+
+/**
+ * @brief create signed coefficient from triple that has unsigned components
+ * @param value source triple
+ * @return `hi`, `lo` and `sz` return values:
+ * hi - more significant 64-bit
+ * lo - less significant 64 bit
+ * sz - min size in bytes to represent the signed coefficient. The `sz` bytes from the least significant byte in
+ * result 128-bit (concatenated `hi` with `lo`) represents the result. For valid input, `sz` ranges from 1 to 17.
+ * The `sz` being 17 is the special case where most significant byte (not part of `hi` or `lo`) is 0x00 or 0xFF
+ * to represent only sign.
+ */
+std::tuple<std::uint64_t, std::uint64_t, std::size_t> make_signed_coefficient_full(takatori::decimal::triple value);
+
+/**
+ * @brief validate the decimal data in the buffer
+ * @param buf the data to validate
+ * @return true if buffer has valid decimal coefficient
+ * @return false otherwise
+ */
+bool validate_decimal_coefficient(std::string_view buf);
+
+/**
+ * @brief read decimal from the buffer and return triple
+ * @param data the decimal data to read
+ * @param scale the scale of the result decimal
+ * @return the triple to represent the decimal data
+ */
+takatori::decimal::triple read_decimal(std::string_view data, std::size_t scale);
+
+constexpr std::size_t max_decimal_length = sizeof(std::uint64_t) * 2 + 1;
+
+using decimal_buffer = std::array<std::uint8_t, max_decimal_length>;
+
+/**
+ * @brief write decimal to the buffer
+ * @param triple the decimal triple to write to the output buffer
+ * @param out the output buffer
+ */
+void create_decimal(
+    std::int8_t sign,
+    std::uint64_t lo,
+    std::uint64_t hi,
+    std::size_t sz,
+    decimal_buffer& out
+);
+
+}
diff --git a/src/ogawayama/stub/transaction.cpp b/src/ogawayama/stub/transaction.cpp
index a3bb922..7e6c421 100644
--- a/src/ogawayama/stub/transaction.cpp
+++ b/src/ogawayama/stub/transaction.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include "jogasaki/utils/decimal.h"
 #include "prepared_statementImpl.h"
 #include "transactionImpl.h"
 
@@ -112,86 +113,21 @@ class parameter {
         v->set_nano_adjustment(data.first.subsecond().count());
         return parameter_;
     }
+
     ::jogasaki::proto::sql::request::Parameter operator()(const decimal_type& triple) {
         auto* value = &parameter_;
-        auto [c_hi, c_lo, c_size] = make_signed_coefficient_full(triple);
+        auto [hi, lo, sz] = jogasaki::utils::make_signed_coefficient_full(triple);
+        jogasaki::utils::decimal_buffer out{};
+        jogasaki::utils::create_decimal(triple.sign(), lo, hi, sz, out);
 
-        // the following part is taken from https://github.com/project-tsurugi/jogasaki/blob/206d07d700adc25d19c031bc1df9a08aee16555c/src/jogasaki/api/kvsservice/serializer.cpp#L219-L245 with using make_signed_coefficient_full()
-        {
-            std::string buf{};
-            const auto buflen = sizeof(c_lo) + sizeof(c_hi);
-            buf.reserve(buflen);
-            auto v = c_lo;
-            for (int i = 0; i < 8; i++) {
-                buf[15 - i] = static_cast<char>(v & 0xffU);
-                v >>= 8U;
-            }
-            v = c_hi;
-            for (int i = 0; i < 8; i++) {
-                buf[7 - i] = static_cast<char>(v & 0xffU);
-                v >>= 8U;
-            }
-            // skip zero-padding
-            std::size_t start = 0;
-            while (start < buflen - 1) {
-                if (buf[start] != 0) {
-                    break;
-                }
-                start++;
-            }
-            auto *decimal = value->mutable_decimal_value();
-            // NOTE: buf.size() returns 0, not 16
-            decimal->set_unscaled_value(std::addressof(buf[start]), buflen - start);
-            decimal->set_exponent(triple.exponent());
-        }
+        auto *decimal = value->mutable_decimal_value();
+        decimal->set_unscaled_value(out.data(), sz);
+        decimal->set_exponent(triple.exponent());
         return parameter_;
     }
 
 private:
     ::jogasaki::proto::sql::request::Parameter parameter_{};
-
-    // the following method is the copy of https://github.com/project-tsurugi/jogasaki/blob/2a404cdaf6e5599d1b2b8742d3568de58b3ee670/src/jogasaki/serializer/value_output.cpp#L165-L205
-    std::tuple<std::uint64_t, std::uint64_t, std::size_t> make_signed_coefficient_full(takatori::decimal::triple value) {
-        std::uint64_t c_hi = value.coefficient_high();
-        std::uint64_t c_lo = value.coefficient_low();
-
-        if (value.sign() >= 0) {
-            for (std::size_t offset = 0; offset < sizeof(std::uint64_t); ++offset) {
-                std::uint64_t octet = (c_hi >> ((sizeof(std::uint64_t) - offset - 1U) * 8U)) & 0xffU;
-                if (octet != 0) {
-                    std::size_t size { sizeof(std::uint64_t) * 2 - offset };
-                    if ((octet & 0x80U) != 0) {
-                        ++size;
-                    }
-                    return { c_hi, c_lo, size };
-                }
-            }
-            return { c_hi, c_lo, sizeof(std::uint64_t) + 1 };
-        }
-
-        // for negative numbers
-
-        if (value.sign() < 0) {
-            c_lo = ~c_lo + 1;
-            c_hi = ~c_hi;
-            if (c_lo == 0) {
-                c_hi += 1; // carry up
-            }
-        }
-
-        for (std::size_t offset = 0; offset < sizeof(std::uint64_t); ++offset) {
-            std::uint64_t octet = (c_hi >> ((sizeof(std::uint64_t) - offset - 1U) * 8U)) & 0xffU;
-            if (octet != 0xffU) {
-                std::size_t size { sizeof(std::uint64_t) * 2 - offset };
-                if ((octet & 0x80U) == 0) {
-                    ++size;
-                }
-                return { c_hi, c_lo, size };
-            }
-        }
-        return { c_hi, c_lo, sizeof(std::uint64_t) + 1 };
-    }
-
 };
 
 /**