feat: built-in-function: support char(int) function #817

hybridse/src/codegen/udf_ir_builder_test.cc

@@ -1007,6 +1007,12 @@ TEST_F(UdfIRBuilderTest, degrees) {
     CheckUdf<double, double>(udf_name, -90.0, -pi/2);
     CheckUdf<Nullable<double>, Nullable<double>>(udf_name, nullptr, nullptr);
 }
+TEST_F(UdfIRBuilderTest, charTest) {
+    auto udf_name = "char";
+    CheckUdf<StringRef, int32_t>(udf_name, StringRef("A"), 65);
+    CheckUdf<StringRef, int32_t>(udf_name, StringRef("B"), 322);
+    CheckUdf<StringRef, int32_t>(udf_name, StringRef("N"), -178);
+    CheckUdf<Nullable<StringRef>, Nullable<int32_t>>(udf_name, nullptr, nullptr);
 TEST_F(UdfIRBuilderTest, degree_to_radius_check) {
     auto udf_name = "radians";
     CheckUdf<double, double>(udf_name, 3.141592653589793238463, 180);

hybridse/src/udf/default_udf_library.cc

@@ -895,6 +895,20 @@ void DefaultUdfLibrary::InitStringUdf() {
             @since 0.4.0)");
     RegisterAlias("lower", "lcase");
     RegisterAlias("upper", "ucase");
+    RegisterExternal("char")
+        .args<int32_t>(
+            static_cast<void (*)(int32_t, StringRef*)>(udf::v1::int_to_char))
+        .return_by_arg(true)
+        .doc(R"(
+            @brief Returns the ASCII character having the binary equivalent to expr. If n is larger than 256 the result is equivalent to char(n % 256).
+
+            Example:
+
+            @code{.sql}
+                SELECT char(65);
+                --output "A"
+            @endcode
+            @since 0.6.0)");
 }
 
 void DefaultUdfLibrary::InitMathUdf() {

hybridse/src/udf/udf.cc

@@ -157,6 +157,17 @@ int32_t weekofyear(Date *date) {
     }
 }
 
+void int_to_char(int32_t val, StringRef* output) {
+    if (val > 256 || val < -256)
+        val = val % 256;
+    output->size_ = 1;
+    char v = static_cast<char>(val);
+    char *buffer = AllocManagedStringBuf(1);
+    output->size_ = 1;
+    memcpy(buffer, &v, output->size_);
+    output->data_ = buffer;
+}
+
 float Cotf(float x) { return cosf(x) / sinf(x); }
 
 double degree_to_radius(double degree) {

hybridse/src/udf/udf.h

@@ -224,6 +224,7 @@ int32_t weekofyear(int64_t ts);
 int32_t weekofyear(Timestamp *ts);
 int32_t weekofyear(Date *ts);
 
+void int_to_char(int32_t, StringRef*);
 double degree_to_radius(double degree);
 
 float Cotf(float x);