Add window-bounded String and char overloads to SubSequence by dougqh · Pull Request #11796 · DataDog/dd-trace-java

dougqh · 2026-06-30T01:04:46Z

What Does This Do

Rounds out SubSequence to support the other string comparison methods.

Motivation

SubSequence is intended as a drop-in replacement for a String.substring call followed up a comparison operation. To fulfill that purpose, this PR adds methods that were missing in prior PRs.

Additional Notes

Since normally the String equivalents don't typically accept CharSequence, most comparison methods have been modified to just take String.

This simplifies the implementation of the methods and should also make them a little faster, since String methods are often intrinsified.

String's startsWith(prefix, off) / regionMatches / indexOf(…, from) bound-check against the backing string's full length, not the view's endIndex. So each method first guards against this view's window, then delegates:

method	delegate	window guard
`equals(String)`	`regionMatches(beginIndex, o, 0, o.length())`	`o.length() == length()`
`equalsIgnoreCase(String)`	`regionMatches(true, …)`	`o.length() == length()`
`startsWith(String)`	`startsWith(prefix, beginIndex)`	`prefix.length() <= length()`
`endsWith(String)`	`startsWith(suffix, endIndex - len)`	`len <= length()`
`indexOf(String)`	`indexOf(needle, beginIndex)`	`idx + needle.length() <= endIndex`
`lastIndexOf(String)`	`lastIndexOf(needle, endIndex - len)`	`idx >= beginIndex`
`startsWith(char)`	`charAt(beginIndex)`	`beginIndex < endIndex`
`endsWith(char)`	`charAt(endIndex - 1)`	`beginIndex < endIndex`
`indexOf(char)`	`indexOf(c, beginIndex)`	`idx < endIndex`
`lastIndexOf(char)`	`lastIndexOf(c, endIndex - 1)`	`idx >= beginIndex`

indexOf/lastIndexOf return a window-relative offset (or -1). A needle/char present in the backing string but outside the view is correctly not found.

Equality

Mirrors String's split between equals and contentEquals:

equals(String) — region-compare fast path.
contentEquals(CharSequence) — general char-by-char comparison (null → false); two views with equal content are content-equal.
equals(Object) — String → the fast path; any other CharSequence (incl. another SubSequence) → contentEquals.

equalsIgnoreCase(null) returns false, matching String.equalsIgnoreCase.

hashCode() is the String hash polynomial computed directly over the window (same value as toString().hashCode(), but without materializing the substring), so it stays consistent with equals while preserving the zero-copy property even when a view is hashed.

Tests

SubSequenceTest gains coverage for case-sensitivity, over/undershoot of both window ends (String and char), the equals(Object) dispatch and contentEquals, the empty window, and window-relative indexOf/lastIndexOf.

🤖 Generated with Claude Code

Also fixes

A latent bug in SubSequence.subSequence(int start, int end) (from #10640): the absolute end index was computed as beginIndex + start + end, overshooting by start (only correct when start == 0). The CharSequence contract treats start/end as offsets in this view's coordinates, so it is now beginIndex + end. Latent — no production caller passed start > 0 — with a regression test added (incl. the nested-subSequence case).

dd-octo-sts · 2026-06-30T01:42:30Z

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	14.00 s	13.96 s	[-0.4%; +1.0%] (no difference)
startup:insecure-bank:tracing:Agent	12.97 s	13.00 s	[-1.0%; +0.5%] (no difference)
startup:petclinic:appsec:Agent	16.35 s	16.80 s	[-7.1%; +1.7%] (no difference)
startup:petclinic:iast:Agent	16.79 s	16.58 s	[-3.4%; +5.8%] (no difference)
startup:petclinic:profiling:Agent	16.17 s	16.77 s	[-8.0%; +0.9%] (no difference)
startup:petclinic:sca:Agent	16.85 s	16.89 s	[-1.2%; +0.8%] (no difference)
startup:petclinic:tracing:Agent	16.08 s	16.05 s	[-0.8%; +1.3%] (no difference)

Commit:c46c918a · CI Pipeline · Benchmarking Platform UI

Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.

equals/equalsIgnoreCase/startsWith/endsWith/indexOf take a String and delegate to String's region/offset methods (regionMatches, startsWith, indexOf) instead of a per-char CharSequence loop. Each guards against this view's [beginIndex, endIndex) window first so the delegated read stays in range, then reuses the JDK's backing-array compare (Latin1 fast path / intrinsics). equals(Object) now routes Strings through the fast path, keeping the charAt loop only for non-String CharSequences. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Single-character leading/trailing/search checks (e.g. a leading '{' or a trailing ';') read charAt(beginIndex)/charAt(endIndex-1) or delegate to String.indexOf(int, from), each bounded to the [beginIndex, endIndex) window. indexOf(char) returns a window-relative offset or -1. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

…uals - lastIndexOf(String) and lastIndexOf(char), window-bounded like indexOf, returning a window-relative offset. - Restructure equality to mirror String's API: equals(String) is the region-compare fast path, contentEquals(CharSequence) is the general char-by-char comparison, and equals(Object) dispatches String -> the fast path, any other CharSequence -> contentEquals. This keeps two equal-content views equal() while giving String args the fast path. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Replace toString().hashCode() with the String hash polynomial evaluated directly over [beginIndex, endIndex). Same value (so equals/hashCode stay consistent), but hashing a view no longer materializes a substring -- preserving the zero-copy property the class exists for. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

The #11736 CharSequence (charAt-loop) versions are superseded by the String-delegating overloads here; String-literal callers (SQLCommenter) bind to the String overloads. Removes the redundant pair + their tests. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

The CharSequence contract treats start/end as offsets in this view's coordinates, so absolute end is beginIndex+end, not beginIndex+start+end (which overshoots by start; only correct when start==0). Latent since test including the nested case the bug broke worst. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

…metry Add a String-specialized contentEquals(String) using String.regionMatches, avoiding the CharSequence path's virtual charAt dispatch, and make equals(String) a thin alias for it so contentEquals is the primary content-comparison API. Suppress the SpotBugs EQ_CHECK_FOR_OPERAND_NOT_COMPATIBLE_WITH_THIS on equals(Object) -- the cross-type view equality is intentional and documented. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bric3

Pre-approving

dd-octo-sts · 2026-07-17T19:25:05Z

/merge

gh-worker-devflow-routing-ef8351 · 2026-07-17T19:25:09Z

View all feedbacks in Devflow UI.

2026-07-17 19:25:09 UTC ℹ️ Start processing command /merge

2026-07-17 19:25:13 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in master is approximately 2h (p90).

2026-07-17 20:22:44 UTC ℹ️ MergeQueue: This merge request was merged

dougqh changed the title ~~Add window-bounded String overloads to SubSequence~~Add window-bounded String and char overloads to SubSequenceJun 30, 2026

dougqh added comp: core Tracer core tag: ai generated Largely based on code generated by an AI or LLM tag: performance Performance related changes type: feature Enhancements and improvements tag: no release notes Changes to exclude from release notes labels Jun 30, 2026

dougqh changed the base branch from dougqh/dbcommenter-scan-overload to masterJune 30, 2026 20:28

dougqh force-pushed the dougqh/subsequence-string-methods branch from e3acc99 to 5ec05e7Compare June 30, 2026 20:28

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dougqh marked this pull request as ready for review June 30, 2026 21:51

dougqh requested a review from a team as a code owner June 30, 2026 21:51

dougqh requested a review from manuel-alvarez-alvarez June 30, 2026 21:51

dougqh added the type: bug fix Bug fix label Jun 30, 2026

dougqhand others added 7 commits July 14, 2026 15:38

dougqh force-pushed the dougqh/subsequence-string-methods branch from a3c8305 to 093793bCompare July 14, 2026 19:59

bric3 approved these changes Jul 17, 2026
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Comment threadinternal-api/src/main/java/datadog/trace/util/SubSequence.java
Comment threadinternal-api/src/main/java/datadog/trace/util/SubSequence.java

Merge branch 'master' into dougqh/subsequence-string-methods
c46c918

dougqh enabled auto-merge July 17, 2026 18:37

dougqh added this pull request to the merge queue Jul 17, 2026

github-merge-queueBot removed this pull request from the merge queue due to failed status checks Jul 17, 2026

gh-worker-dd-mergequeue-cf854dBot merged commit b82b440 into masterJul 17, 2026
587 checks passed

gh-worker-dd-mergequeue-cf854dBot deleted the dougqh/subsequence-string-methods branch July 17, 2026 20:22

github-actionsBot added this to the 1.65.0 milestone Jul 17, 2026

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Add window-bounded String and char overloads to SubSequence - #11796

Add window-bounded String and char overloads to SubSequence#11796
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What Does This Do

Motivation

Additional Notes

Equality

Tests

Also fixes

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🟢 Java Benchmark SLOs — All performance SLOs passed

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