From 82678ada78e8bed7eb720b031513baa7020040cc Mon Sep 17 00:00:00 2001
From: Pratik Joseph Dabre <pratik@Pratiks-MacBook-Pro.local>
Date: Fri, 5 Jan 2024 02:07:39 -0800
Subject: [PATCH] Add from_ieee754_32 Scalar function

---
 velox/docs/functions/presto/binary.rst        |  4 +++
 velox/functions/prestosql/BinaryFunctions.h   | 14 ++++++++
 .../BinaryFunctionsRegistration.cpp           |  2 ++
 .../prestosql/tests/BinaryFunctionsTest.cpp   | 34 +++++++++++++++++++
 4 files changed, 54 insertions(+)

diff --git a/velox/docs/functions/presto/binary.rst b/velox/docs/functions/presto/binary.rst
index 13ea96859e51d..8b785040fd9be 100644
--- a/velox/docs/functions/presto/binary.rst
+++ b/velox/docs/functions/presto/binary.rst
@@ -94,6 +94,10 @@ Binary Functions
 
     Encodes ``real`` in a 32-bit big-endian binary according to IEEE 754 single-precision floating-point format.
 
+.. function:: from_ieee754_32(binary) -> real
+
+    Decodes the 32-bit big-endian ``binary`` in IEEE 754 single-precision floating-point format.
+
 .. function:: to_ieee754_64(double) -> varbinary
 
     Encodes ``double`` in a 64-bit big-endian binary according to IEEE 754 double-precision floating-point format.
diff --git a/velox/functions/prestosql/BinaryFunctions.h b/velox/functions/prestosql/BinaryFunctions.h
index 35648c8921234..bebea83855d25 100644
--- a/velox/functions/prestosql/BinaryFunctions.h
+++ b/velox/functions/prestosql/BinaryFunctions.h
@@ -436,4 +436,18 @@ struct ToIEEE754Bits32 {
   }
 };
 
+template <typename T>
+struct FromIEEE754Bits32 {
+  VELOX_DEFINE_FUNCTION_TYPES(T);
+
+  FOLLY_ALWAYS_INLINE void call(
+      out_type<float>& result,
+      const arg_type<Varbinary>& input) {
+    static constexpr auto kTypeLength = sizeof(int32_t);
+    VELOX_USER_CHECK_EQ(input.size(), kTypeLength, "Expected 4-byte input");
+    memcpy(&result, input.data(), kTypeLength);
+    result = folly::Endian::big(result);
+  }
+};
+
 } // namespace facebook::velox::functions
diff --git a/velox/functions/prestosql/registration/BinaryFunctionsRegistration.cpp b/velox/functions/prestosql/registration/BinaryFunctionsRegistration.cpp
index 78bcea6c12030..6cba321b7a9a5 100644
--- a/velox/functions/prestosql/registration/BinaryFunctionsRegistration.cpp
+++ b/velox/functions/prestosql/registration/BinaryFunctionsRegistration.cpp
@@ -64,6 +64,8 @@ void registerSimpleFunctions(const std::string& prefix) {
       {prefix + "to_ieee754_64"});
   registerFunction<ToIEEE754Bits32, Varbinary, float>(
       {prefix + "to_ieee754_32"});
+  registerFunction<FromIEEE754Bits32, float, Varbinary>(
+      {prefix + "from_ieee754_32"});
 }
 } // namespace
 
diff --git a/velox/functions/prestosql/tests/BinaryFunctionsTest.cpp b/velox/functions/prestosql/tests/BinaryFunctionsTest.cpp
index 47a1e67dfedb8..3883f85dd6fa7 100644
--- a/velox/functions/prestosql/tests/BinaryFunctionsTest.cpp
+++ b/velox/functions/prestosql/tests/BinaryFunctionsTest.cpp
@@ -662,4 +662,38 @@ TEST_F(BinaryFunctionsTest, toIEEE754Bits32) {
       hexToDec("FF7FFFFF"),
       toIEEE754Bits32(std::numeric_limits<float>::lowest()));
 }
+
+TEST_F(BinaryFunctionsTest, fromIEEE754Bits32) {
+  const auto fromIEEE754Bits32 = [&](const std::optional<std::string>& arg) {
+    return evaluateOnce<float, std::string>(
+        "from_ieee754_32(c0)", {arg}, {VARBINARY()});
+  };
+
+  const auto toIEEE754Bits32 = [&](std::optional<float> arg) {
+    return evaluateOnce<std::string, float>("to_ieee754_32(c0)", arg);
+  };
+
+  EXPECT_EQ(std::nullopt, fromIEEE754Bits32(std::nullopt));
+  EXPECT_EQ(1.0f, fromIEEE754Bits32(hexToDec("3F800000")));
+  EXPECT_EQ(3.14f, fromIEEE754Bits32(hexToDec("4048F5C3")));
+  EXPECT_EQ(3.4028235E38f, fromIEEE754Bits32(hexToDec("7f7fffff")));
+  EXPECT_EQ(-3.4028235E38f, fromIEEE754Bits32(hexToDec("ff7fffff")));
+  EXPECT_EQ(1.4E-45f, fromIEEE754Bits32(hexToDec("00000001")));
+  EXPECT_EQ(-1.4E-45f, fromIEEE754Bits32(hexToDec("80000001")));
+  EXPECT_EQ(
+      std::numeric_limits<float>::infinity(),
+      fromIEEE754Bits32(hexToDec("7f800000")));
+  EXPECT_EQ(
+      -std::numeric_limits<float>::infinity(),
+      fromIEEE754Bits32(hexToDec("ff800000")));
+  EXPECT_THROW(fromIEEE754Bits32("YQ"), VeloxUserError);
+  EXPECT_EQ(3.4028235E38f, fromIEEE754Bits32(toIEEE754Bits32(3.4028235E38f)));
+  EXPECT_EQ(-3.4028235E38f, fromIEEE754Bits32(toIEEE754Bits32(-3.4028235E38f)));
+  EXPECT_EQ(1.4E-45f, fromIEEE754Bits32(toIEEE754Bits32(1.4E-45f)));
+  EXPECT_EQ(-1.4E-45f, fromIEEE754Bits32(toIEEE754Bits32(-1.4E-45f)));
+  EXPECT_EQ(
+      std::numeric_limits<float>::infinity(),
+      fromIEEE754Bits32(
+          toIEEE754Bits32(std::numeric_limits<float>::infinity())));
+}
 } // namespace