HF Tokenizer: get charspans (#1584)

* Add getTokenCharSpans to rust lib

* Implement Java char spans

* fix char span path

* Create char spans tests

* Add javadocs and copyright

* Add javadoc

Change-Id: Ic72c4bd89be325d4ade3a4f86c35846a24f9b08c

Co-authored-by: Frank Liu <frankfliu2000@gmail.com>

extensions/tokenizers/rust/src/lib.rs

@@ -16,11 +16,13 @@ extern crate tokenizers as tk;
 
 use std::str::FromStr;
 use tk::tokenizer::{EncodeInput, Encoding};
-use tk::FromPretrainedParameters;
 use tk::Tokenizer;
+use tk::{FromPretrainedParameters, Offsets};
 
-use jni::objects::{JObject, JString};
-use jni::sys::{jboolean, jlong, jlongArray, jobjectArray, jsize, JNI_TRUE};
+use jni::objects::{JClass, JMethodID, JObject, JString, JValue};
+use jni::sys::{
+    jboolean, jint, jlong, jlongArray, jobjectArray, jsize, JNI_TRUE,
+};
 use jni::JNIEnv;
 
 #[no_mangle]
@@ -256,7 +258,8 @@ pub extern "system" fn Java_ai_djl_huggingface_tokenizers_jni_TokenizersLibrary_
         .unwrap();
     for (i, token) in tokens.iter().enumerate() {
         let item: JString = env.new_string(&token).unwrap();
-        env.set_object_array_element(array, i as jsize, item).unwrap();
+        env.set_object_array_element(array, i as jsize, item)
+            .unwrap();
     }
     array
 }
@@ -299,6 +302,48 @@ pub extern "system" fn Java_ai_djl_huggingface_tokenizers_jni_TokenizersLibrary_
     array
 }
 
+#[no_mangle]
+pub extern "system" fn Java_ai_djl_huggingface_tokenizers_jni_TokenizersLibrary_getTokenCharSpans(
+    env: JNIEnv,
+    _: JObject,
+    handle: jlong,
+) -> jobjectArray {
+    let encoding = cast_handle::<Encoding>(handle);
+    let tokens = encoding.get_tokens();
+    let len = tokens.len() as jsize;
+
+    let array: jobjectArray = env
+        .new_object_array(
+            len,
+            "ai/djl/huggingface/tokenizers/jni/CharSpan",
+            JObject::null(),
+        )
+        .unwrap();
+    for (i, _) in tokens.iter().enumerate() {
+        let opt_offsets: Option<(usize, Offsets)> = encoding.token_to_chars(i);
+        match &opt_offsets {
+            Some((_, offsets)) => {
+                let class_id = "ai/djl/huggingface/tokenizers/jni/CharSpan";
+                let method_id = "<init>";
+                let params = "(II)V";
+                let cls: JClass = env.find_class(class_id).unwrap();
+                let constructor: JMethodID = env.get_method_id(cls, method_id, params).unwrap();
+                let offsets_vec: Vec<JValue> = vec![
+                    JValue::Int((*offsets).0 as jint),
+                    JValue::Int((*offsets).1 as jint),
+                ];
+                let obj = env
+                    .new_object_unchecked(cls, constructor, &offsets_vec[..])
+                    .unwrap();
+                env.set_object_array_element(array, i as jsize, obj)
+                    .unwrap();
+            }
+            None => {}
+        }
+    }
+    array
+}
+
 fn to_handle<T: 'static>(val: T) -> jlong {
     let handle = Box::into_raw(Box::new(val)) as jlong;
     handle

extensions/tokenizers/src/main/java/ai/djl/huggingface/tokenizers/Encoding.java

@@ -12,6 +12,8 @@
  */
 package ai.djl.huggingface.tokenizers;
 
+import ai.djl.huggingface.tokenizers.jni.CharSpan;
+
 /** A class holds token encoding information. */
 public class Encoding {
 
@@ -21,20 +23,23 @@ public class Encoding {
     private long[] wordIds;
     private long[] attentionMask;
     private long[] specialTokenMask;
+    private CharSpan[] charTokenSpans;
 
     Encoding(
             long[] ids,
             long[] typeIds,
             String[] tokens,
             long[] wordIds,
             long[] attentionMask,
-            long[] specialTokenMask) {
+            long[] specialTokenMask,
+            CharSpan[] charTokenSpans) {
         this.ids = ids;
         this.typeIds = typeIds;
         this.tokens = tokens;
         this.wordIds = wordIds;
         this.attentionMask = attentionMask;
         this.specialTokenMask = specialTokenMask;
+        this.charTokenSpans = charTokenSpans;
     }
 
     /**
@@ -90,4 +95,13 @@ public long[] getAttentionMask() {
     public long[] getSpecialTokenMask() {
         return specialTokenMask;
     }
+
+    /**
+     * Returns char token spans.
+     *
+     * @return char token spans
+     */
+    public CharSpan[] getCharTokenSpans() {
+        return charTokenSpans;
+    }
 }

extensions/tokenizers/src/main/java/ai/djl/huggingface/tokenizers/HuggingFaceTokenizer.java

@@ -12,6 +12,7 @@
  */
 package ai.djl.huggingface.tokenizers;
 
+import ai.djl.huggingface.tokenizers.jni.CharSpan;
 import ai.djl.huggingface.tokenizers.jni.LibUtils;
 import ai.djl.huggingface.tokenizers.jni.TokenizersLibrary;
 import ai.djl.modality.nlp.preprocess.Tokenizer;
@@ -200,8 +201,10 @@ private Encoding toEncoding(long encoding) {
         long[] wordIds = TokenizersLibrary.LIB.getWordIds(encoding);
         long[] attentionMask = TokenizersLibrary.LIB.getAttentionMask(encoding);
         long[] specialTokenMask = TokenizersLibrary.LIB.getSpecialTokenMask(encoding);
+        CharSpan[] charSpans = TokenizersLibrary.LIB.getTokenCharSpans(encoding);
 
         TokenizersLibrary.LIB.deleteEncoding(encoding);
-        return new Encoding(ids, typeIds, tokens, wordIds, attentionMask, specialTokenMask);
+        return new Encoding(
+                ids, typeIds, tokens, wordIds, attentionMask, specialTokenMask, charSpans);
     }
 }

extensions/tokenizers/src/main/java/ai/djl/huggingface/tokenizers/jni/CharSpan.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
+ * with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
+ * OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
+ * and limitations under the License.
+ */
+
+/** A class holds character span information. */
+package ai.djl.huggingface.tokenizers.jni;
+
+/** A class holds character span information. */
+public class CharSpan {
+
+    private final int start;
+    private final int end;
+
+    /**
+     * Constructs a new {@code CharSpan} instance.
+     *
+     * @param start the start position
+     * @param end the end position
+     */
+    public CharSpan(int start, int end) {
+        this.start = start;
+        this.end = end;
+    }
+
+    /**
+     * Returns the start position.
+     *
+     * @return the start position
+     */
+    public int getStart() {
+        return start;
+    }
+
+    /**
+     * Returns the end position.
+     *
+     * @return the end position
+     */
+    public int getEnd() {
+        return end;
+    }
+}

extensions/tokenizers/src/main/java/ai/djl/huggingface/tokenizers/jni/TokenizersLibrary.java

@@ -45,4 +45,6 @@ private TokenizersLibrary() {}
     public native long[] getAttentionMask(long encoding);
 
     public native long[] getSpecialTokenMask(long encoding);
+
+    public native CharSpan[] getTokenCharSpans(long encoding);
 }

extensions/tokenizers/src/test/java/ai/djl/huggingface/tokenizers/HuggingFaceTokenizerTest.java

@@ -13,6 +13,7 @@
 
 package ai.djl.huggingface.tokenizers;
 
+import ai.djl.huggingface.tokenizers.jni.CharSpan;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
@@ -49,6 +50,34 @@ public void testTokenizer() {
             Assert.assertEquals(attentionMask, encoding.getAttentionMask());
             Assert.assertEquals(specialTokenMask, encoding.getSpecialTokenMask());
 
+            CharSpan[] charSpansExpected = {
+                null,
+                new CharSpan(0, 5),
+                new CharSpan(5, 6),
+                new CharSpan(7, 8),
+                new CharSpan(8, 9),
+                new CharSpan(9, 12),
+                new CharSpan(12, 13),
+                new CharSpan(14, 17),
+                new CharSpan(18, 21),
+                new CharSpan(22, 25),
+                new CharSpan(26, 30),
+                new CharSpan(31, 32),
+                null
+            };
+            int expectedLength = charSpansExpected.length;
+            CharSpan[] charSpansResult = encoding.getCharTokenSpans();
+
+            Assert.assertEquals(expectedLength, charSpansResult.length);
+            Assert.assertEquals(charSpansExpected[0], charSpansResult[0]);
+            Assert.assertEquals(
+                    charSpansExpected[expectedLength - 1], charSpansResult[expectedLength - 1]);
+
+            for (int i = 1; i < expectedLength - 1; i++) {
+                Assert.assertEquals(charSpansExpected[i].getStart(), charSpansResult[i].getStart());
+                Assert.assertEquals(charSpansExpected[i].getEnd(), charSpansResult[i].getEnd());
+            }
+
             Encoding[] encodings = tokenizer.batchEncode(Arrays.asList(inputs));
             Assert.assertEquals(encodings.length, 2);
         }