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Merged
mcculls merged 2 commits into from
Oct 29, 2026
Merged

Reduce temporary strings and repeated field reads #156

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45c3160
Avoid temporary string allocation of constructor and simple call meth…
mcculls Oct 29, 2026
9eed179
Avoid repeated field lookups in the same method
mcculls Oct 29, 2026
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5 changes: 3 additions & 2 deletions class-inject/src/main/java/datadog/instrument/classinject/ClassInjector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -116,10 +116,11 @@ public static List<Class<?>> injectClasses(Map<String, byte[]> bytecode, Protect
private ClassInjector() {}

private static BiFunction classDefiner() {
if (defineClassGlue == null) {
BiFunction glue = defineClassGlue;
if (glue == null) {
throw new IllegalStateException("Class injection not enabled");
}
return defineClassGlue;
return glue;
}

private static volatile BiFunction defineClassGlue;
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45 changes: 27 additions & 18 deletions class-match/src/main/java/datadog/instrument/classmatch/ClassFile.java
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Expand Up @@ -37,6 +37,10 @@ public final class ClassFile {
private static final int ACC_INTERFACE = 0x0200;
private static final int ACC_MODULE = 0x8000;

private static final byte[] JAVA_LANG_OBJECT_BYTES = JAVA_LANG_OBJECT.getBytes(US_ASCII);
private static final byte[] CONSTRUCTOR_BYTES = CONSTRUCTOR.getBytes(US_ASCII);
private static final byte[] SIMPLE_CALL_BYTES = SIMPLE_CALL.getBytes(US_ASCII);

// attribute header for annotations that are visible at runtime
private static final byte[] RUNTIME_ANNOTATIONS = "RuntimeVisibleAnnotations".getBytes(US_ASCII);

Expand Down Expand Up @@ -210,10 +214,11 @@ private static ClassHeader parse(byte[] bytecode, int offset, boolean onlyHeader
if ((access & ACC_INTERFACE) != 0) {
superName = JAVA_LANG_OBJECT;
} else if (access != ACC_MODULE) {
superName = utf(bytecode, cp[cp[u2(bytecode, cursor)]]);
if (JAVA_LANG_OBJECT.equals(superName)) {
superName = JAVA_LANG_OBJECT;
}
int superNameOffset = cp[cp[u2(bytecode, cursor)]];
superName =
utfEquals(bytecode, superNameOffset, JAVA_LANG_OBJECT_BYTES)
? JAVA_LANG_OBJECT
: utf(bytecode, superNameOffset);
} else {
superName = null;
}
Expand Down Expand Up @@ -266,6 +271,8 @@ private static ClassHeader parse(byte[] bytecode, int offset, boolean onlyHeader
fields = NO_FIELDS;
}

final Map<UtfKey, String> ofInterest = annotationsOfInterest;

// optional list of methods
MethodOutline[] methods;
int methodsCount = u2(bytecode, cursor);
Expand All @@ -275,18 +282,20 @@ private static ClassHeader parse(byte[] bytecode, int offset, boolean onlyHeader
for (int i = 0; i < methodsCount; i++) {
int methodAccess = u2(bytecode, cursor);
cursor += 2;
String methodName = utf(bytecode, cp[u2(bytecode, cursor)]);
if (CONSTRUCTOR.equals(methodName)) {
methodName = CONSTRUCTOR;
}
int methodNameOffset = cp[u2(bytecode, cursor)];
String methodName =
utfEquals(bytecode, methodNameOffset, CONSTRUCTOR_BYTES)
? CONSTRUCTOR
: utf(bytecode, methodNameOffset);
cursor += 2;
String descriptor = utf(bytecode, cp[u2(bytecode, cursor)]);
if (SIMPLE_CALL.equals(descriptor)) {
descriptor = SIMPLE_CALL;
}
int descriptorOffset = cp[u2(bytecode, cursor)];
String descriptor =
utfEquals(bytecode, descriptorOffset, SIMPLE_CALL_BYTES)
? SIMPLE_CALL
: utf(bytecode, descriptorOffset);
cursor += 2;
String[] annotations = NO_ANNOTATIONS;
Map<UtfKey, String> ofInterest = annotationsOfInterest;
boolean scanAnnotations = ofInterest != null;
int attributesCount = u2(bytecode, cursor);
cursor += 2;
for (int j = 0; j < attributesCount; j++) {
Expand All @@ -295,9 +304,9 @@ private static ClassHeader parse(byte[] bytecode, int offset, boolean onlyHeader
int attributeLength = u4(bytecode, cursor);
cursor += 4;
// only interested in the attribute that lists runtime visible annotations
if (ofInterest != null && utfEquals(bytecode, cp[nameIndex], RUNTIME_ANNOTATIONS)) {
if (scanAnnotations && utfEquals(bytecode, cp[nameIndex], RUNTIME_ANNOTATIONS)) {
annotations = parseAnnotations(ofInterest, bytecode, cursor, cp);
ofInterest = null; // there's at most one of these attributes per-table
scanAnnotations = false; // there's at most one of these attributes per-table
}
cursor += attributeLength; // jump to end of attribute
}
Expand All @@ -309,7 +318,7 @@ private static ClassHeader parse(byte[] bytecode, int offset, boolean onlyHeader
}

String[] annotations = NO_ANNOTATIONS;
Map<UtfKey, String> ofInterest = annotationsOfInterest;
boolean scanAnnotations = ofInterest != null;
int attributesCount = u2(bytecode, cursor);
cursor += 2;
for (int j = 0; j < attributesCount; j++) {
Expand All @@ -318,9 +327,9 @@ private static ClassHeader parse(byte[] bytecode, int offset, boolean onlyHeader
int attributeLength = u4(bytecode, cursor);
cursor += 4;
// only interested in the attribute that lists runtime visible annotations
if (ofInterest != null && utfEquals(bytecode, cp[nameIndex], RUNTIME_ANNOTATIONS)) {
if (scanAnnotations && utfEquals(bytecode, cp[nameIndex], RUNTIME_ANNOTATIONS)) {
annotations = parseAnnotations(ofInterest, bytecode, cursor, cp);
ofInterest = null; // there's at most one of these attributes per-table
scanAnnotations = false; // there's at most one of these attributes per-table
}
cursor += attributeLength; // jump to end of attribute
}
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7 changes: 4 additions & 3 deletions class-match/src/main/java/datadog/instrument/classmatch/FieldOutline.java
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Expand Up @@ -50,9 +50,10 @@ TypeString typeString() {
}
int start = 1;
int end = descriptor.length() - 1;
if (typeStringHash == 0) {
typeStringHash = TypeString.computeHash(descriptor, start, end);
int hash = typeStringHash;
if (hash == 0) {
typeStringHash = hash = TypeString.computeHash(descriptor, start, end);
}
return new TypeString(descriptor, start, end, typeStringHash);
return new TypeString(descriptor, start, end, hash);
}
}
16 changes: 9 additions & 7 deletions class-match/src/main/java/datadog/instrument/classmatch/MethodOutline.java
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Expand Up @@ -99,13 +99,14 @@ TypeString returnTypeString() {

/** Gets a previously cached {@link TypeString} hash; otherwise computes and caches a new hash. */
private int getHash(int typeStringIndex, int start, int end) {
if (typeStringHashes == null) {
int[] hashes = typeStringHashes;
if (hashes == null) {
// allow for one hash per parameter, plus one for return type
typeStringHashes = new int[descriptorBoundaries.length + 1];
typeStringHashes = hashes = new int[descriptorBoundaries.length + 1];
}
int hash = typeStringHashes[typeStringIndex];
int hash = hashes[typeStringIndex];
if (hash == 0) {
typeStringHashes[typeStringIndex] = hash = TypeString.computeHash(descriptor, start, end);
hashes[typeStringIndex] = hash = TypeString.computeHash(descriptor, start, end);
}
return hash;
}
Expand All @@ -119,10 +120,11 @@ private int getHash(int typeStringIndex, int start, int end) {
* parameters then the return descriptor always starts at index 2.)
*/
int[] descriptorBoundaries() {
if (descriptorBoundaries == null) {
descriptorBoundaries = parseBoundaries(descriptor);
int[] boundaries = descriptorBoundaries;
if (boundaries == null) {
descriptorBoundaries = boundaries = parseBoundaries(descriptor);
}
return descriptorBoundaries;
return boundaries;
}

/** Partitions method descriptor into boundaries between each parameter/return descriptor. */
Expand Down
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