From 9b074e32a04977e1a9c7286b4791dfe7d1c0d44c Mon Sep 17 00:00:00 2001
From: lucasxia01 <lucasxia01@gmail.com>
Date: Fri, 12 Jan 2024 21:10:39 +0000
Subject: [PATCH 1/3] updated test to include failing case

---
 .../barretenberg/crypto/poseidon2/poseidon2.test.cpp  | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.test.cpp b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.test.cpp
index 9649f757728..895e07a11f3 100644
--- a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.test.cpp
+++ b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.test.cpp
@@ -53,13 +53,16 @@ TEST(Poseidon2, HashBufferConsistencyCheck)
     // element
     barretenberg::fr a(std::string("00000b615c4d3e2fa0b1c2d3e4f56789fedcba9876543210abcdef0123456789"));
 
-    auto input_vec = to_buffer(a);      // takes field element and converts it to 32 bytes
+    // takes field element and converts it to 32 bytes
+    auto input_vec = to_buffer(a);
+    barretenberg::fr result1 = crypto::Poseidon2<crypto::Poseidon2Bn254ScalarFieldParams>::hash_buffer(input_vec);
     input_vec.erase(input_vec.begin()); // erase first byte since we want 31 bytes
+    barretenberg::fr result2 = crypto::Poseidon2<crypto::Poseidon2Bn254ScalarFieldParams>::hash_buffer(input_vec);
+
     std::vector<barretenberg::fr> input{ a };
     auto expected = crypto::Poseidon2<crypto::Poseidon2Bn254ScalarFieldParams>::hash(input);
 
-    barretenberg::fr result = crypto::Poseidon2<crypto::Poseidon2Bn254ScalarFieldParams>::hash_buffer(input_vec);
-
-    EXPECT_EQ(result, expected);
+    EXPECT_NE(result1, expected);
+    EXPECT_EQ(result2, expected);
 }
 } // namespace poseidon2_tests
\ No newline at end of file

From 17b72369b9be74193058f3966e3c49e4b47f4f75 Mon Sep 17 00:00:00 2001
From: lucasxia01 <lucasxia01@gmail.com>
Date: Fri, 12 Jan 2024 21:10:57 +0000
Subject: [PATCH 2/3] updated to use span instead of vector

---
 .../cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp      | 5 ++---
 .../cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp      | 2 +-
 .../cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp | 5 ++---
 .../cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp | 2 +-
 .../barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp    | 3 ++-
 5 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp
index ad96dc31271..65c6dc0f168 100644
--- a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp
+++ b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp
@@ -5,10 +5,9 @@ namespace crypto {
  * @brief Hashes a vector of field elements
  */
 template <typename Params>
-typename Poseidon2<Params>::FF Poseidon2<Params>::hash(const std::vector<typename Poseidon2<Params>::FF>& input)
+typename Poseidon2<Params>::FF Poseidon2<Params>::hash(const std::span<typename Poseidon2<Params>::FF>& input)
 {
-    auto input_span = input;
-    return Sponge::hash_fixed_length(input_span);
+    return Sponge::hash_fixed_length(input);
 }
 
 /**
diff --git a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp
index 6969c680e17..6f86bb35e3f 100644
--- a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp
+++ b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp
@@ -16,7 +16,7 @@ template <typename Params> class Poseidon2 {
     /**
      * @brief Hashes a vector of field elements
      */
-    static FF hash(const std::vector<FF>& input);
+    static FF hash(const std::span<FF>& input);
     /**
      * @brief Hashes vector of bytes by chunking it into 31 byte field elements and calling hash()
      * @details Slice function cuts out the required number of bytes from the byte vector
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp
index ff8e31dd56e..167c6779c77 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp
@@ -8,15 +8,14 @@ using namespace proof_system;
 /**
  * @brief Hash a vector of field_ct.
  */
-template <typename C> field_t<C> poseidon2<C>::hash(C& builder, const std::vector<field_ct>& inputs)
+template <typename C> field_t<C> poseidon2<C>::hash(C& builder, const std::span<field_ct>& inputs)
 {
 
     /* Run the sponge by absorbing all the input and squeezing one output.
      * This should just call the sponge variable length hash function
      *
      */
-    auto input{ inputs };
-    return Sponge::hash_fixed_length(builder, input);
+    return Sponge::hash_fixed_length(builder, inputs);
 }
 
 /**
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp
index fcfb93f91d2..521a33413bc 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp
@@ -26,7 +26,7 @@ template <typename Builder> class poseidon2 {
     using Sponge = FieldSponge<Params::t - 1, 1, Params::t, Permutation, Builder>;
 
   public:
-    static field_ct hash(Builder& builder, const std::vector<field_ct>& in);
+    static field_ct hash(Builder& builder, const std::span<field_ct>& in);
     static field_ct hash_buffer(Builder& builder, const stdlib::byte_array<Builder>& input);
 };
 
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp
index 797cec6669c..f4dae1642e4 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp
@@ -68,7 +68,8 @@ template <typename Builder> class StdlibPoseidon2 : public testing::Test {
 
         // num_inputs - 1 iterations since the first hash hashes two elements
         for (size_t i = 0; i < num_inputs - 1; ++i) {
-            left = poseidon2::hash(builder, { left, right });
+            std::vector<fr_ct> inputs = { left, right };
+            left = poseidon2::hash(builder, inputs);
         }
 
         builder.set_public_input(left.witness_index);

From e58d3ac4072207dde940f99e99f93d5b31578479 Mon Sep 17 00:00:00 2001
From: lucasxia01 <lucasxia01@gmail.com>
Date: Fri, 12 Jan 2024 22:01:21 +0000
Subject: [PATCH 3/3] updating consts

---
 .../cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp    | 2 +-
 .../cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp    | 2 +-
 .../src/barretenberg/crypto/poseidon2/sponge/sponge.hpp    | 7 ++++---
 .../src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp   | 2 +-
 .../src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp   | 2 +-
 .../barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp  | 3 +--
 .../barretenberg/stdlib/hash/poseidon2/sponge/sponge.hpp   | 6 +++---
 7 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp
index 65c6dc0f168..2f74f7fc250 100644
--- a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp
+++ b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.cpp
@@ -5,7 +5,7 @@ namespace crypto {
  * @brief Hashes a vector of field elements
  */
 template <typename Params>
-typename Poseidon2<Params>::FF Poseidon2<Params>::hash(const std::span<typename Poseidon2<Params>::FF>& input)
+typename Poseidon2<Params>::FF Poseidon2<Params>::hash(const std::vector<typename Poseidon2<Params>::FF>& input)
 {
     return Sponge::hash_fixed_length(input);
 }
diff --git a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp
index 6f86bb35e3f..6969c680e17 100644
--- a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp
+++ b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/poseidon2.hpp
@@ -16,7 +16,7 @@ template <typename Params> class Poseidon2 {
     /**
      * @brief Hashes a vector of field elements
      */
-    static FF hash(const std::span<FF>& input);
+    static FF hash(const std::vector<FF>& input);
     /**
      * @brief Hashes vector of bytes by chunking it into 31 byte field elements and calling hash()
      * @details Slice function cuts out the required number of bytes from the byte vector
diff --git a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/sponge/sponge.hpp b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/sponge/sponge.hpp
index bc4a2c5c1dc..80aab6d4589 100644
--- a/barretenberg/cpp/src/barretenberg/crypto/poseidon2/sponge/sponge.hpp
+++ b/barretenberg/cpp/src/barretenberg/crypto/poseidon2/sponge/sponge.hpp
@@ -129,7 +129,8 @@ template <typename FF, size_t rate, size_t capacity, size_t t, typename Permutat
      * @param input
      * @return std::array<FF, out_len>
      */
-    template <size_t out_len, bool is_variable_length> static std::array<FF, out_len> hash_internal(std::span<FF> input)
+    template <size_t out_len, bool is_variable_length>
+    static std::array<FF, out_len> hash_internal(std::span<const FF> input)
     {
         size_t in_len = input.size();
         const uint256_t iv = (static_cast<uint256_t>(in_len) << 64) + out_len - 1;
@@ -153,11 +154,11 @@ template <typename FF, size_t rate, size_t capacity, size_t t, typename Permutat
         return output;
     }
 
-    template <size_t out_len> static std::array<FF, out_len> hash_fixed_length(std::span<FF> input)
+    template <size_t out_len> static std::array<FF, out_len> hash_fixed_length(std::span<const FF> input)
     {
         return hash_internal<out_len, false>(input);
     }
-    static FF hash_fixed_length(std::span<FF> input) { return hash_fixed_length<1>(input)[0]; }
+    static FF hash_fixed_length(std::span<const FF> input) { return hash_fixed_length<1>(input)[0]; }
 
     template <size_t out_len> static std::array<FF, out_len> hash_variable_length(std::span<FF> input)
     {
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp
index 167c6779c77..9004ff3002b 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp
@@ -8,7 +8,7 @@ using namespace proof_system;
 /**
  * @brief Hash a vector of field_ct.
  */
-template <typename C> field_t<C> poseidon2<C>::hash(C& builder, const std::span<field_ct>& inputs)
+template <typename C> field_t<C> poseidon2<C>::hash(C& builder, const std::vector<field_ct>& inputs)
 {
 
     /* Run the sponge by absorbing all the input and squeezing one output.
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp
index 521a33413bc..fcfb93f91d2 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.hpp
@@ -26,7 +26,7 @@ template <typename Builder> class poseidon2 {
     using Sponge = FieldSponge<Params::t - 1, 1, Params::t, Permutation, Builder>;
 
   public:
-    static field_ct hash(Builder& builder, const std::span<field_ct>& in);
+    static field_ct hash(Builder& builder, const std::vector<field_ct>& in);
     static field_ct hash_buffer(Builder& builder, const stdlib::byte_array<Builder>& input);
 };
 
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp
index f4dae1642e4..797cec6669c 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp
@@ -68,8 +68,7 @@ template <typename Builder> class StdlibPoseidon2 : public testing::Test {
 
         // num_inputs - 1 iterations since the first hash hashes two elements
         for (size_t i = 0; i < num_inputs - 1; ++i) {
-            std::vector<fr_ct> inputs = { left, right };
-            left = poseidon2::hash(builder, inputs);
+            left = poseidon2::hash(builder, { left, right });
         }
 
         builder.set_public_input(left.witness_index);
diff --git a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/sponge/sponge.hpp b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/sponge/sponge.hpp
index 359faf50f94..667e0daa886 100644
--- a/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/sponge/sponge.hpp
+++ b/barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/sponge/sponge.hpp
@@ -135,7 +135,7 @@ template <size_t rate, size_t capacity, size_t t, typename Permutation, typename
      * @return std::array<field_t, out_len>
      */
     template <size_t out_len, bool is_variable_length>
-    static std::array<field_t, out_len> hash_internal(Builder& builder, std::span<field_t> input)
+    static std::array<field_t, out_len> hash_internal(Builder& builder, std::span<const field_t> input)
     {
         size_t in_len = input.size();
         const uint256_t iv = (static_cast<uint256_t>(in_len) << 64) + out_len - 1;
@@ -160,11 +160,11 @@ template <size_t rate, size_t capacity, size_t t, typename Permutation, typename
     }
 
     template <size_t out_len>
-    static std::array<field_t, out_len> hash_fixed_length(Builder& builder, std::span<field_t> input)
+    static std::array<field_t, out_len> hash_fixed_length(Builder& builder, std::span<const field_t> input)
     {
         return hash_internal<out_len, false>(builder, input);
     }
-    static field_t hash_fixed_length(Builder& builder, std::span<field_t> input)
+    static field_t hash_fixed_length(Builder& builder, std::span<const field_t> input)
     {
         return hash_fixed_length<1>(builder, input)[0];
     }