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Optimized text for full unicode and some escape sequences (#129169) #7

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82 changes: 67 additions & 15 deletions ...t/impl/src/main/java/org/elasticsearch/xcontent/provider/json/ESUTF8StreamJsonParser.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,9 +21,14 @@

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

public class ESUTF8StreamJsonParser extends UTF8StreamJsonParser {
protected int stringEnd = -1;
protected int stringLength;

private final List<Integer> backslashes = new ArrayList<>();

public ESUTF8StreamJsonParser(
IOContext ctxt,
Expand All @@ -43,15 +48,12 @@ public ESUTF8StreamJsonParser(
/**
* Method that will try to get underlying UTF-8 encoded bytes of the current string token.
* This is only a best-effort attempt; if there is some reason the bytes cannot be retrieved, this method will return null.
* Currently, this is only implemented for ascii-only strings that do not contain escaped characters.
*/
public Text getValueAsText() throws IOException {
if (_currToken == JsonToken.VALUE_STRING && _tokenIncomplete) {
if (stringEnd > 0) {
final int len = stringEnd - 1 - _inputPtr;
// For now, we can use `len` for `stringLength` because we only support ascii-encoded unescaped strings,
// which means each character uses exactly 1 byte.
return new Text(new XContentString.UTF8Bytes(_inputBuffer, _inputPtr, len), len);
return new Text(new XContentString.UTF8Bytes(_inputBuffer, _inputPtr, len), stringLength);
}
Comment on lines 52 to 57
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@coderabbitai coderabbitai bot Feb 12, 2026

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⚠️ Potential issue | 🟠 Major

Ensure repeated getValueAsText() calls return de‑escaped bytes.

When backslashes are present, _finishAndReturnText() returns a rebuilt buffer without escapes, but subsequent calls hit the stringEnd fast path and return a slice of the original input (still containing backslashes). That makes repeated calls inconsistent.

Consider caching the rebuilt bytes (or rebuilding on demand when backslashes exist) and using them in the stringEnd path.

🔧 One way to make repeated calls consistent 
@@
-    private final List<Integer> backslashes = new ArrayList<>();
+    private final List<Integer> backslashes = new ArrayList<>();
+    private byte[] stringBytes;
@@
-            if (stringEnd > 0) {
-                final int len = stringEnd - 1 - _inputPtr;
-                return new Text(new XContentString.UTF8Bytes(_inputBuffer, _inputPtr, len), stringLength);
-            }
+            if (stringEnd > 0) {
+                if (stringBytes != null) {
+                    return new Text(new XContentString.UTF8Bytes(stringBytes), stringLength);
+                }
+                final int len = stringEnd - 1 - _inputPtr;
+                return new Text(new XContentString.UTF8Bytes(_inputBuffer, _inputPtr, len), stringLength);
+            }
@@
-        stringLength = 0;
-        backslashes.clear();
+        stringLength = 0;
+        backslashes.clear();
+        stringBytes = null;
@@
-            return new Text(new XContentString.UTF8Bytes(buff), stringLength);
+            stringBytes = buff;
+            return new Text(new XContentString.UTF8Bytes(buff), stringLength);
🤖 Prompt for AI Agents 
In
`@libs/x-content/impl/src/main/java/org/elasticsearch/xcontent/provider/json/ESUTF8StreamJsonParser.java`
around lines 52 - 57, getValueAsText() currently returns a raw slice from
_inputBuffer when stringEnd > 0 which preserves escape sequences, causing
inconsistency after _finishAndReturnText() rebuilds de-escaped bytes; modify
getValueAsText() to detect when the token contains backslashes (or when
_finishAndReturnText() previously rebuilt bytes) and return the cached
de-escaped bytes instead of the original slice: call or reuse
_finishAndReturnText() (or store its result in a field like cachedTextBytes)
when escapes are present, and in the stringEnd fast path return a Text backed by
those de-escaped bytes (use identifiers _finishAndReturnText, cached buffer
field, stringEnd, _inputBuffer, _inputPtr, stringLength, _tokenIncomplete to
locate code).

return _finishAndReturnText();
}
Expand All @@ -69,21 +71,71 @@ protected Text _finishAndReturnText() throws IOException {
final int[] codes = INPUT_CODES_UTF8;
final int max = _inputEnd;
final byte[] inputBuffer = _inputBuffer;
while (ptr < max) {
stringLength = 0;
backslashes.clear();

loop: while (true) {
if (ptr >= max) {
return null;
}
int c = inputBuffer[ptr] & 0xFF;
if (codes[c] != 0) {
if (c == INT_QUOTE) {
stringEnd = ptr + 1;
final int len = ptr - startPtr;
// For now, we can use `len` for `stringLength` because we only support ascii-encoded unescaped strings,
// which means each character uses exactly 1 byte.
return new Text(new XContentString.UTF8Bytes(inputBuffer, startPtr, len), len);
switch (codes[c]) {
case 0 -> {
++ptr;
++stringLength;
}
case 1 -> {
if (c == INT_QUOTE) {
// End of the string
break loop;
}
assert c == INT_BACKSLASH;
backslashes.add(ptr);
++ptr;
if (ptr >= max) {
// Backslash at end of file
return null;
}
c = inputBuffer[ptr] & 0xFF;
if (c == '"' || c == '/' || c == '\\') {
ptr += 1;
stringLength += 1;
} else {
// Any other escaped sequence requires replacing the sequence with
// a new character, which we don't support in the optimized path
return null;
}
}
case 2, 3, 4 -> {
int bytesToSkip = codes[c];
if (ptr + bytesToSkip > max) {
return null;
}
ptr += bytesToSkip;
++stringLength;
}
default -> {
return null;
}
return null;
}
++ptr;
}
return null;

stringEnd = ptr + 1;
if (backslashes.isEmpty()) {
return new Text(new XContentString.UTF8Bytes(inputBuffer, startPtr, ptr - startPtr), stringLength);
} else {
byte[] buff = new byte[ptr - startPtr - backslashes.size()];
int copyPtr = startPtr;
int destPtr = 0;
for (Integer backslash : backslashes) {
int length = backslash - copyPtr;
System.arraycopy(inputBuffer, copyPtr, buff, destPtr, length);
destPtr += length;
copyPtr = backslash + 1;
}
System.arraycopy(inputBuffer, copyPtr, buff, destPtr, ptr - copyPtr);
return new Text(new XContentString.UTF8Bytes(buff), stringLength);
}
}

@Override
Expand Down
129 changes: 101 additions & 28 deletions ...l/src/test/java/org/elasticsearch/xcontent/provider/json/ESUTF8StreamJsonParserTests.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,16 +13,14 @@
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;

import org.elasticsearch.common.Strings;
import org.elasticsearch.core.CheckedConsumer;
import org.elasticsearch.test.ESTestCase;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentString;
import org.elasticsearch.xcontent.json.JsonXContent;
import org.hamcrest.Matchers;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Locale;

public class ESUTF8StreamJsonParserTests extends ESTestCase {

Expand All @@ -45,11 +43,13 @@ public void testGetValueAsText() throws IOException {
assertThat(parser.nextFieldName(), Matchers.equalTo("foo"));
assertThat(parser.nextValue(), Matchers.equalTo(JsonToken.VALUE_STRING));

var textRef = parser.getValueAsText().bytes();
assertThat(textRef, Matchers.notNullValue());
assertThat(textRef.offset(), Matchers.equalTo(9));
assertThat(textRef.offset() + textRef.length(), Matchers.equalTo(12));
assertTextRef(textRef, "bar");
var text = parser.getValueAsText();
assertThat(text, Matchers.notNullValue());

var bytes = text.bytes();
assertThat(bytes.offset(), Matchers.equalTo(9));
assertThat(bytes.offset() + bytes.length(), Matchers.equalTo(12));
assertTextRef(bytes, "bar");

assertThat(parser.getValueAsString(), Matchers.equalTo("bar"));
assertThat(parser.getValueAsText(), Matchers.nullValue());
Expand All @@ -62,17 +62,36 @@ public void testGetValueAsText() throws IOException {
assertThat(parser.nextFieldName(), Matchers.equalTo("foo"));
assertThat(parser.nextValue(), Matchers.equalTo(JsonToken.VALUE_STRING));

var text = parser.getValueAsText();
assertThat(text, Matchers.notNullValue());
assertTextRef(text.bytes(), "bar\"baz\"");
});

testParseJson("{\"foo\": \"b\\u00e5r\"}", parser -> {
assertThat(parser.nextToken(), Matchers.equalTo(JsonToken.START_OBJECT));
assertThat(parser.nextFieldName(), Matchers.equalTo("foo"));
assertThat(parser.nextValue(), Matchers.equalTo(JsonToken.VALUE_STRING));

assertThat(parser.getValueAsText(), Matchers.nullValue());
assertThat(parser.getValueAsString(), Matchers.equalTo("bar\"baz\""));
assertThat(parser.getValueAsString(), Matchers.equalTo("bår"));
});

testParseJson("{\"foo\": \"bår\"}", parser -> {
assertThat(parser.nextToken(), Matchers.equalTo(JsonToken.START_OBJECT));
assertThat(parser.nextFieldName(), Matchers.equalTo("foo"));
assertThat(parser.nextValue(), Matchers.equalTo(JsonToken.VALUE_STRING));

assertThat(parser.getValueAsText(), Matchers.nullValue());
var text = parser.getValueAsText();
assertThat(text, Matchers.notNullValue());

var bytes = text.bytes();
assertThat(bytes.offset(), Matchers.equalTo(9));
assertThat(bytes.offset() + bytes.length(), Matchers.equalTo(13));
assertTextRef(bytes, "bår");

assertThat(parser.getValueAsString(), Matchers.equalTo("bår"));

assertThat(parser.nextToken(), Matchers.equalTo(JsonToken.END_OBJECT));
});

testParseJson("{\"foo\": [\"lorem\", \"ipsum\", \"dolor\"]}", parser -> {
Expand Down Expand Up @@ -112,43 +131,97 @@ public void testGetValueAsText() throws IOException {
});
}

private boolean validForTextRef(String value) {
for (char c : value.toCharArray()) {
if (c == '"') {
return false;
private record TestInput(String input, String result, boolean supportsOptimized) {}

private static final TestInput[] ESCAPE_SEQUENCES = {
new TestInput("\\b", "\b", false),
new TestInput("\\t", "\t", false),
new TestInput("\\n", "\n", false),
new TestInput("\\f", "\f", false),
new TestInput("\\r", "\r", false),
new TestInput("\\\"", "\"", true),
new TestInput("\\/", "/", true),
new TestInput("\\\\", "\\", true) };

private int randomCodepoint(boolean includeAscii) {
while (true) {
char val = Character.toChars(randomInt(0xFFFF))[0];
if (val <= 0x7f && includeAscii == false) {
continue;
}
if (c == '\\') {
return false;
if (val >= Character.MIN_SURROGATE && val <= Character.MAX_SURROGATE) {
continue;
}
if ((int) c < 32 || (int) c >= 128) {
return false;
return val;
}
}

private TestInput buildRandomInput(int length) {
StringBuilder input = new StringBuilder(length);
StringBuilder result = new StringBuilder(length);
boolean forceSupportOptimized = randomBoolean();
boolean doesSupportOptimized = true;
for (int i = 0; i < length; ++i) {
if (forceSupportOptimized == false && randomBoolean()) {
switch (randomInt(9)) {
case 0 -> {
var escape = randomFrom(ESCAPE_SEQUENCES);
input.append(escape.input());
result.append(escape.result());
doesSupportOptimized = doesSupportOptimized && escape.supportsOptimized();
}
case 1 -> {
int value = randomCodepoint(true);
input.append(String.format(Locale.ENGLISH, "\\u%04x", value));
result.append(Character.toChars(value));
doesSupportOptimized = false;
}
default -> {
var value = Character.toChars(randomCodepoint(false));
input.append(value);
result.append(value);
}
}
} else {
var value = randomAlphanumericOfLength(1);
input.append(value);
result.append(value);
}
}
return true;
return new TestInput(input.toString(), result.toString(), doesSupportOptimized);
}

public void testGetValueRandomized() throws IOException {
XContentBuilder jsonBuilder = JsonXContent.contentBuilder().startObject();
StringBuilder inputBuilder = new StringBuilder();
inputBuilder.append('{');

final int numKeys = 128;
String[] keys = new String[numKeys];
String[] values = new String[numKeys];
TestInput[] inputs = new TestInput[numKeys];
for (int i = 0; i < numKeys; i++) {
String currKey = randomAlphanumericOfLength(6);
String currVal = randomUnicodeOfLengthBetween(0, 512);
jsonBuilder.field(currKey, currVal);
var currVal = buildRandomInput(randomInt(512));
inputBuilder.append('"');
inputBuilder.append(currKey);
inputBuilder.append("\":\"");
inputBuilder.append(currVal.input());
inputBuilder.append('"');
if (i < numKeys - 1) {
inputBuilder.append(',');
}
keys[i] = currKey;
values[i] = currVal;
inputs[i] = currVal;
}

jsonBuilder.endObject();
testParseJson(Strings.toString(jsonBuilder), parser -> {
inputBuilder.append('}');
testParseJson(inputBuilder.toString(), parser -> {
assertThat(parser.nextToken(), Matchers.equalTo(JsonToken.START_OBJECT));
for (int i = 0; i < numKeys; i++) {
assertThat(parser.nextFieldName(), Matchers.equalTo(keys[i]));
assertThat(parser.nextValue(), Matchers.equalTo(JsonToken.VALUE_STRING));

String currVal = values[i];
if (validForTextRef(currVal)) {
String currVal = inputs[i].result();
if (inputs[i].supportsOptimized()) {
assertTextRef(parser.getValueAsText().bytes(), currVal);
} else {
assertThat(parser.getValueAsText(), Matchers.nullValue());
Expand Down