Create a String column from UTF8 String byte arrays (#8257)

This PR is to support creating a `ColumnVector ` from the byte arrays of UTF8 Strings.

And also let the `Struct` children creation support UTF8 Strings.

Closes #8137

Signed-off-by: Firestarman <[email protected]>

Authors:
  - Liangcai Li (https://github.com/firestarman)

Approvers:
  - Allen Xu (https://github.com/wjxiz1992)
  - Jason Lowe (https://github.com/jlowe)
  - Robert (Bobby) Evans (https://github.com/revans2)
  - Alfred Xu (https://github.com/sperlingxx)

URL: #8257

java/src/main/java/ai/rapids/cudf/ColumnVector.java

@@ -1276,6 +1276,16 @@ public static ColumnVector fromStrings(String... values) {
     }
   }
 
+  /**
+   * Create a new string vector from the given values.  This API
+   * supports inline nulls.
+   */
+  public static ColumnVector fromUTF8Strings(byte[]... values) {
+    try (HostColumnVector host = HostColumnVector.fromUTF8Strings(values)) {
+      return host.copyToDevice();
+    }
+  }
+
   /**
    * Create a new vector from the given values.  This API supports inline nulls,
    * but is much slower than building from primitive array of unscaledValues.

java/src/main/java/ai/rapids/cudf/HostColumnVector.java

@@ -29,6 +29,7 @@
 import java.util.Objects;
 import java.util.Optional;
 import java.util.StringJoiner;
+import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 
 /**
@@ -577,6 +578,40 @@ public static HostColumnVector fromStrings(String... values) {
     });
   }
 
+  /**
+   * Create a new string vector from the given values.  This API
+   * supports inline nulls.
+   */
+  public static HostColumnVector fromUTF8Strings(byte[]... values) {
+    int rows = values.length;
+    long nullCount = 0;
+    long bufferSize = 0;
+    // How many bytes do we need to hold the data.
+    for (byte[] s: values) {
+      if (s == null) {
+        nullCount++;
+      } else {
+        bufferSize += s.length;
+      }
+    }
+
+    BiConsumer<Builder, byte[]> appendUTF8 = nullCount == 0 ?
+      (b, s) -> b.appendUTF8String(s) :
+      (b, s) -> {
+        if (s == null) {
+          b.appendNull();
+        } else {
+          b.appendUTF8String(s);
+        }
+      };
+
+    return build(rows, bufferSize, (b) -> {
+      for (byte[] s: values) {
+        appendUTF8.accept(b, s);
+      }
+    });
+  }
+
   /**
    * Create a new vector from the given values.  This API supports inline nulls,
    * but is much slower than building from primitive array of unscaledValues.
@@ -1085,9 +1120,11 @@ private void appendChildOrNull(ColumnBuilder childBuilder, Object listElement) {
       } else if (listElement instanceof BigDecimal) {
         childBuilder.append((BigDecimal) listElement);
       } else if (listElement instanceof List) {
-        childBuilder.append((List) listElement);
+        childBuilder.append((List<?>) listElement);
       } else if (listElement instanceof StructData) {
         childBuilder.append((StructData) listElement);
+      } else if (listElement instanceof byte[]) {
+        childBuilder.appendUTF8String((byte[]) listElement);
       } else {
         throw new IllegalStateException("Unexpected element type: " + listElement.getClass());
       }

java/src/test/java/ai/rapids/cudf/ColumnVectorTest.java

@@ -29,6 +29,7 @@
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -176,6 +177,19 @@ void testStringCreation() {
     }
   }
 
+  @Test
+  void testUTF8StringCreation() {
+    try (ColumnVector cv = ColumnVector.fromUTF8Strings(
+            "d".getBytes(StandardCharsets.UTF_8),
+            "sd".getBytes(StandardCharsets.UTF_8),
+            "sde".getBytes(StandardCharsets.UTF_8),
+            null,
+            "END".getBytes(StandardCharsets.UTF_8));
+         ColumnVector expected = ColumnVector.fromStrings("d", "sd", "sde", null, "END")) {
+      TableTest.assertColumnsAreEqual(expected, cv);
+    }
+  }
+
   @Test
   void testRefCountLeak() throws InterruptedException {
     assumeTrue(Boolean.getBoolean("ai.rapids.cudf.flaky-tests-enabled"));