perf(writer): replace recursive reachable-ref walk with iterative stack

[Mythie]

Avoids potential stack overflow on deeply nested object graphs,
consistent with the fix in 6db670a.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
core	Ready	Preview, Comment	Mar 11, 2026 8:10am

[github-actions]

Benchmark Results

Comparison

Load PDF

Benchmark	Mean	p99	RME	Samples
libpdf	2.19ms	2.93ms	±1.1%	229
pdf-lib	39.48ms	44.39ms	±4.5%	13
@cantoo/pdf-lib	38.80ms	42.59ms	±2.4%	13

Create blank PDF

Benchmark	Mean	p99	RME	Samples
libpdf	56μs	114μs	±1.4%	8856
pdf-lib	432μs	1.55ms	±3.1%	1157
@cantoo/pdf-lib	425μs	1.52ms	±2.5%	1178

Add 10 pages

Benchmark	Mean	p99	RME	Samples
libpdf	99μs	159μs	±1.0%	5054
pdf-lib	507μs	1.84ms	±2.6%	987
@cantoo/pdf-lib	470μs	2.12ms	±3.0%	1065

Draw 50 rectangles

Benchmark	Mean	p99	RME	Samples
libpdf	311μs	738μs	±1.3%	1606
pdf-lib	1.74ms	7.39ms	±7.4%	289
@cantoo/pdf-lib	1.83ms	4.45ms	±4.5%	273

Load and save PDF

Benchmark	Mean	p99	RME	Samples
libpdf	2.25ms	2.94ms	±1.4%	222
pdf-lib	89.75ms	102.09ms	±5.6%	10
@cantoo/pdf-lib	154.78ms	163.02ms	±2.1%	10

Load, modify, and save PDF

Benchmark	Mean	p99	RME	Samples
libpdf	42.36ms	55.56ms	±7.4%	12
pdf-lib	85.32ms	93.31ms	±4.0%	10
@cantoo/pdf-lib	151.66ms	155.69ms	±0.9%	10

Extract single page from 100-page PDF

Benchmark	Mean	p99	RME	Samples
libpdf	3.68ms	5.88ms	±1.8%	136
pdf-lib	9.11ms	11.66ms	±1.8%	55
@cantoo/pdf-lib	9.76ms	11.99ms	±2.6%	52

Split 100-page PDF into single-page PDFs

Benchmark	Mean	p99	RME	Samples
libpdf	32.76ms	38.31ms	±3.2%	16
pdf-lib	88.85ms	94.51ms	±4.0%	6
@cantoo/pdf-lib	101.33ms	119.21ms	±9.7%	6

Split 2000-page PDF into single-page PDFs (0.9MB)

Benchmark	Mean	p99	RME	Samples
libpdf	614.72ms	614.72ms	±0.0%	1
pdf-lib	1.63s	1.63s	±0.0%	1
@cantoo/pdf-lib	1.70s	1.70s	±0.0%	1

Copy 10 pages between documents

Benchmark	Mean	p99	RME	Samples
libpdf	4.94ms	8.10ms	±3.7%	102
pdf-lib	12.30ms	15.30ms	±2.5%	41
@cantoo/pdf-lib	13.48ms	16.38ms	±2.3%	38

Merge 2 x 100-page PDFs

Benchmark	Mean	p99	RME	Samples
libpdf	14.34ms	19.09ms	±2.4%	35
pdf-lib	55.74ms	71.18ms	±8.4%	9
@cantoo/pdf-lib	62.88ms	65.95ms	±3.2%	8

Fill FINTRAC form fields

Benchmark	Mean	p99	RME	Samples
libpdf	20.94ms	25.92ms	±4.3%	24
pdf-lib	34.31ms	50.69ms	±7.8%	15
@cantoo/pdf-lib	34.66ms	41.33ms	±4.6%	15

Fill and flatten FINTRAC form

Benchmark	Mean	p99	RME	Samples
libpdf	19.25ms	24.23ms	±4.5%	26
pdf-lib	FAILED	-	-	0
@cantoo/pdf-lib	38.97ms	44.17ms	±3.4%	13

Copying

Copy pages between documents

Benchmark	Mean	p99	RME	Samples
copy 1 page	950μs	1.84ms	±2.2%	527
copy 10 pages from 100-page PDF	4.46ms	6.44ms	±2.0%	113
copy all 100 pages	7.20ms	8.14ms	±1.0%	70

Duplicate pages within same document

Benchmark	Mean	p99	RME	Samples
duplicate page 0	864μs	1.59ms	±1.2%	579
duplicate all pages (double the document)	857μs	1.56ms	±1.1%	584

Merge PDFs

Benchmark	Mean	p99	RME	Samples
merge 2 small PDFs	1.42ms	2.66ms	±1.3%	353
merge 10 small PDFs	7.23ms	9.27ms	±1.2%	70
merge 2 x 100-page PDFs	13.26ms	13.99ms	±0.8%	38

Drawing

benchmarks/drawing.bench.ts

Benchmark	Mean	p99	RME	Samples
draw 100 rectangles	583μs	1.49ms	±2.5%	858
draw 100 circles	1.28ms	3.02ms	±2.6%	390
draw 100 lines	511μs	1.18ms	±1.5%	979
draw 100 text lines (standard font)	1.57ms	2.26ms	±1.2%	320
create 10 pages with mixed content	1.33ms	2.28ms	±1.7%	376

Forms

benchmarks/forms.bench.ts

Benchmark	Mean	p99	RME	Samples
get form fields	3.19ms	6.08ms	±3.1%	157
fill text fields	11.82ms	16.52ms	±4.4%	43
read field values	2.89ms	4.13ms	±1.2%	173
flatten form	8.21ms	11.83ms	±2.8%	61

Loading

benchmarks/loading.bench.ts

Benchmark	Mean	p99	RME	Samples
load small PDF (888B)	58μs	151μs	±0.7%	8601
load medium PDF (19KB)	91μs	182μs	±0.6%	5482
load form PDF (116KB)	1.37ms	2.60ms	±2.3%	364
load heavy PDF (9.9MB)	2.22ms	2.67ms	±0.6%	226

Saving

benchmarks/saving.bench.ts

Benchmark	Mean	p99	RME	Samples
save unmodified (19KB)	106μs	251μs	±0.9%	4701
save with modifications (19KB)	743μs	1.35ms	±1.1%	674
incremental save (19KB)	160μs	336μs	±0.9%	3123
save heavy PDF (9.9MB)	2.18ms	2.69ms	±0.6%	230
incremental save heavy PDF (9.9MB)	8.49ms	9.97ms	±3.1%	59

Splitting

Extract single page

Benchmark	Mean	p99	RME	Samples
extractPages (1 page from small PDF)	997μs	2.16ms	±2.9%	502
extractPages (1 page from 100-page PDF)	3.54ms	5.03ms	±1.1%	142
extractPages (1 page from 2000-page PDF)	56.02ms	57.53ms	±1.1%	10

Split into single-page PDFs

Benchmark	Mean	p99	RME	Samples
split 100-page PDF (0.1MB)	31.26ms	35.87ms	±3.1%	16
split 2000-page PDF (0.9MB)	583.49ms	583.49ms	±0.0%	1

Batch page extraction

Benchmark	Mean	p99	RME	Samples
extract first 10 pages from 2000-page PDF	57.71ms	60.89ms	±1.7%	9
extract first 100 pages from 2000-page PDF	61.15ms	63.69ms	±1.8%	9
extract every 10th page from 2000-page PDF (200 pages)	65.64ms	66.86ms	±1.3%	8

Environment

• Runner: Linux (X64)
• Runtime: Bun 1.3.10

Results are machine-dependent.