GH-49034 [C++][Gandiva] Fix binary_string to not trigger error for null strings (#49035)

### Rationale for this change

The binary_string function will attempt to allocate 0 bytes of memory, which results in a null ptr being returned and the function interprets that as an error.

### What changes are included in this PR?
Add kCanReturnErrors to the function definition to match other string functions. 
Move the check for 0 byte length input earlier in the binary_string function to prevent the 0 allocation.
Add a unit test.

### Are these changes tested?
Yes, unit and integration testing.

### Are there any user-facing changes?
No.

* GitHub Issue: #49034

Authored-by: Logan Riggs <logan.riggs@dremio.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

Author: lriggs

cpp/src/gandiva/function_registry_string.cc

@@ -432,7 +432,8 @@ std::vector<NativeFunction> GetStringFunctionRegistry() {
                      NativeFunction::kNeedsContext | NativeFunction::kCanReturnErrors),
 
       NativeFunction("binary_string", {}, DataTypeVector{utf8()}, binary(),
-                     kResultNullIfNull, "binary_string", NativeFunction::kNeedsContext),
+                     kResultNullIfNull, "binary_string",
+                     NativeFunction::kNeedsContext | NativeFunction::kCanReturnErrors),
 
       NativeFunction("left", {}, DataTypeVector{utf8(), int32()}, utf8(),
                      kResultNullIfNull, "left_utf8_int32", NativeFunction::kNeedsContext),

cpp/src/gandiva/precompiled/string_ops.cc

@@ -2252,6 +2252,11 @@ const char* right_utf8_int32(gdv_int64 context, const char* text, gdv_int32 text
 FORCE_INLINE
 const char* binary_string(gdv_int64 context, const char* text, gdv_int32 text_len,
                           gdv_int32* out_len) {
+  if (text_len == 0) {
+    *out_len = 0;
+    return "";
+  }
+
   gdv_binary ret =
       reinterpret_cast<gdv_binary>(gdv_fn_context_arena_malloc(context, text_len));
 
@@ -2261,11 +2266,6 @@ const char* binary_string(gdv_int64 context, const char* text, gdv_int32 text_le
     return "";
   }
 
-  if (text_len == 0) {
-    *out_len = 0;
-    return "";
-  }
-
   // converting hex encoded string to normal string
   int j = 0;
   for (int i = 0; i < text_len; i++, j++) {

cpp/src/gandiva/precompiled/string_ops_test.cc

@@ -1883,10 +1883,6 @@ TEST(TestStringOps, TestBinaryString) {
   std::string output = std::string(out_str, out_len);
   EXPECT_EQ(output, "TestString");
 
-  out_str = binary_string(ctx_ptr, "", 0, &out_len);
-  output = std::string(out_str, out_len);
-  EXPECT_EQ(output, "");
-
   out_str = binary_string(ctx_ptr, "T", 1, &out_len);
   output = std::string(out_str, out_len);
   EXPECT_EQ(output, "T");
@@ -1912,6 +1908,22 @@ TEST(TestStringOps, TestBinaryString) {
   EXPECT_EQ(output, "OM");
 }
 
+TEST(TestStringOps, TestBinaryStringNull) {
+  // This test is only valid if it is the first to trigger a memory allocation in the
+  // context.
+  gandiva::ExecutionContext ctx;
+  uint64_t ctx_ptr = reinterpret_cast<gdv_int64>(&ctx);
+  gdv_int32 out_len = 0;
+  const char* out_str;
+
+  std::string output;
+
+  out_str = binary_string(ctx_ptr, "", 0, &out_len);
+  ASSERT_FALSE(ctx.has_error());
+  output = std::string(out_str, out_len);
+  EXPECT_EQ(output, "");
+}
+
 TEST(TestStringOps, TestSplitPart) {
   gandiva::ExecutionContext ctx;
   uint64_t ctx_ptr = reinterpret_cast<gdv_int64>(&ctx);