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fix(pdfium): serialise PDFium calls across documents on JVM and Android #16

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fix(pdfium): serialise PDFium calls across documents on JVM and Android #16

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22 changes: 7 additions & 15 deletions pdfium/src/androidMain/kotlin/dev/nucleusframework/pdfium/PdfDocument.android.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,7 @@ import androidx.compose.ui.graphics.asImageBitmap
import dev.nucleusframework.pdfium.jvm.FPDF_ANNOT
import dev.nucleusframework.pdfium.jvm.Pdfium
import dev.nucleusframework.pdfium.jvm.PdfiumBridge
import java.util.concurrent.ExecutorService
import java.util.concurrent.atomic.AtomicInteger
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.withContext

Expand All @@ -19,8 +17,6 @@ internal actual class PdfDocument internal constructor(
// Per-document FPDF_FORMHANDLE (parallel to [handles]). May be 0 if PDFium refused;
// render code falls back to no widget overlay in that case.
private val formHandles: LongArray,
private val dispatchers: Array<CoroutineDispatcher>,
private val executors: Array<ExecutorService>,
) {
actual val pageCount: Int = PdfiumBridge.nGetPageCount(handles[0])
actual val metadata: PdfMetadata = PdfMetadata(
Expand All @@ -37,7 +33,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageSize(pageIndex: Int): PageSize {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext PageSize(0f, 0f)
Expand All @@ -59,7 +55,7 @@ internal actual class PdfDocument internal constructor(
quality: RenderQuality,
): ImageBitmap {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val bitmap = Bitmap.createBitmap(widthPx, heightPx, Bitmap.Config.ARGB_8888)
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
Expand All @@ -85,7 +81,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageText(pageIndex: Int): String {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext ""
Expand All @@ -99,7 +95,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageTextLayout(pageIndex: Int): PageTextLayout {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext PageTextLayout.Empty
Expand Down Expand Up @@ -143,7 +139,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageLinks(pageIndex: Int): PageLinks {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext PageLinks.Empty
Expand All @@ -169,15 +165,14 @@ internal actual class PdfDocument internal constructor(
actual fun close() {
runBlocking {
for (i in handles.indices) {
withContext(dispatchers[i]) {
withContext(Pdfium.sharedDispatcher) {
// Form-fill env must be torn down BEFORE its underlying document.
PdfiumBridge.nCloseFormEnv(formHandles[i])
PdfiumBridge.nCloseDocument(handles[i])
}
}
}
PdfiumBridge.nFreeBuffer(bufferAddr)
executors.forEach { it.shutdown() }
}

private fun RenderQuality.toFlags(): Int = when (this) {
Expand Down Expand Up @@ -206,11 +201,8 @@ internal actual suspend fun openPdfDocument(bytes: ByteArray, password: String?)
}
handles[i] = h
}
val pairs = Array(POOL_SIZE) { Pdfium.newDispatcher() }
val dispatchers = Array(POOL_SIZE) { pairs[it].first }
val executors = Array(POOL_SIZE) { pairs[it].second }
val formHandles = LongArray(POOL_SIZE) { PdfiumBridge.nInitFormEnv(handles[it]) }
PdfDocument(bufferAddr, bytes.size, handles, formHandles, dispatchers, executors)
PdfDocument(bufferAddr, bytes.size, handles, formHandles)
} catch (t: Throwable) {
PdfiumBridge.nFreeBuffer(bufferAddr)
throw t
Expand Down
15 changes: 0 additions & 15 deletions pdfium/src/androidMain/kotlin/dev/nucleusframework/pdfium/jvm/Pdfium.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -2,25 +2,10 @@ package dev.nucleusframework.pdfium.jvm

import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.asCoroutineDispatcher
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
import java.util.concurrent.atomic.AtomicInteger

internal object Pdfium {
private val counter = AtomicInteger()

val sharedDispatcher: CoroutineDispatcher = Executors.newSingleThreadExecutor { runnable ->
Thread(runnable, "pdfium-shared").apply { isDaemon = true }
}.asCoroutineDispatcher()

fun newDispatcher(): Pair<CoroutineDispatcher, ExecutorService> {
val id = counter.incrementAndGet()
val exec = Executors.newSingleThreadExecutor { runnable ->
Thread(runnable, "pdfium-worker-$id").apply {
isDaemon = true
priority = Thread.NORM_PRIORITY
}
}
return exec.asCoroutineDispatcher() to exec
}
}
22 changes: 7 additions & 15 deletions pdfium/src/jvmMain/kotlin/dev/nucleusframework/pdfium/PdfDocument.jvm.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,7 @@ import androidx.compose.ui.graphics.asComposeImageBitmap
import dev.nucleusframework.pdfium.jvm.FPDF_ANNOT
import dev.nucleusframework.pdfium.jvm.Pdfium
import dev.nucleusframework.pdfium.jvm.PdfiumBridge
import java.util.concurrent.ExecutorService
import java.util.concurrent.atomic.AtomicInteger
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.withContext
import org.jetbrains.skia.Bitmap
Expand All @@ -29,8 +27,6 @@ internal actual class PdfDocument internal constructor(
// Per-document FPDF_FORMHANDLE (parallel to [handles]). May be 0 if PDFium refused to
// init the form-fill environment for that handle; render code falls back to no overlay.
private val formHandles: LongArray,
private val dispatchers: Array<CoroutineDispatcher>,
private val executors: Array<ExecutorService>,
) {
actual val pageCount: Int = PdfiumBridge.nGetPageCount(handles[0])
actual val metadata: PdfMetadata = PdfMetadata(
Expand All @@ -47,7 +43,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageSize(pageIndex: Int): PageSize {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext PageSize(0f, 0f)
Expand All @@ -69,7 +65,7 @@ internal actual class PdfDocument internal constructor(
quality: RenderQuality,
): ImageBitmap {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val info = ImageInfo.makeN32(widthPx, heightPx, ColorAlphaType.PREMUL)
val bitmap = Bitmap().apply { allocPixels(info) }
Expand Down Expand Up @@ -99,7 +95,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageText(pageIndex: Int): String {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext ""
Expand All @@ -113,7 +109,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageTextLayout(pageIndex: Int): PageTextLayout {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext PageTextLayout.Empty
Expand Down Expand Up @@ -159,7 +155,7 @@ internal actual class PdfDocument internal constructor(

actual suspend fun pageLinks(pageIndex: Int): PageLinks {
val slot = pickSlot()
return withContext(dispatchers[slot]) {
return withContext(Pdfium.sharedDispatcher) {
val handle = handles[slot]
val page = PdfiumBridge.nLoadPage(handle, pageIndex)
if (page == 0L) return@withContext PageLinks.Empty
Expand Down Expand Up @@ -190,7 +186,7 @@ internal actual class PdfDocument internal constructor(
actual fun close() {
runBlocking {
for (i in handles.indices) {
withContext(dispatchers[i]) {
withContext(Pdfium.sharedDispatcher) {
// Form-fill env must be torn down BEFORE its underlying document —
// FPDFDOC_ExitFormFillEnvironment dereferences the FPDF_DOCUMENT.
PdfiumBridge.nCloseFormEnv(formHandles[i])
Expand All @@ -199,7 +195,6 @@ internal actual class PdfDocument internal constructor(
}
}
PdfiumBridge.nFreeBuffer(bufferAddr)
executors.forEach { it.shutdown() }
}

private fun RenderQuality.toFlags(): Int = when (this) {
Expand Down Expand Up @@ -231,14 +226,11 @@ internal actual suspend fun openPdfDocument(bytes: ByteArray, password: String?)
}
handles[i] = h
}
val pairs = Array(POOL_SIZE) { Pdfium.newDispatcher() }
val dispatchers = Array(POOL_SIZE) { pairs[it].first }
val executors = Array(POOL_SIZE) { pairs[it].second }
// Init one form-fill env per document handle. PDFium tolerates docs without forms
// (the handle still returns non-zero) — FPDF_FFLDraw is a no-op for pages with
// no widgets, so eager init costs only a small struct allocation per document.
val formHandles = LongArray(POOL_SIZE) { PdfiumBridge.nInitFormEnv(handles[it]) }
PdfDocument(bufferAddr, bytes.size, handles, formHandles, dispatchers, executors)
PdfDocument(bufferAddr, bytes.size, handles, formHandles)
} catch (t: Throwable) {
PdfiumBridge.nFreeBuffer(bufferAddr)
throw t
Expand Down
27 changes: 3 additions & 24 deletions pdfium/src/jvmMain/kotlin/dev/nucleusframework/pdfium/jvm/Pdfium.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -2,37 +2,16 @@ package dev.nucleusframework.pdfium.jvm

import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.asCoroutineDispatcher
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors
import java.util.concurrent.atomic.AtomicInteger

/**
* PDFium is not thread-safe. A single-threaded dispatcher per document gives us:
* - per-call serialization for a given document (no concurrent clobber of PDFium state)
* - independent docs render in parallel (no global lock)
* PDFium is not thread-safe, including across documents (FreeType's `FT_Library` is a
* process-wide singleton). Every PDFium call runs on [sharedDispatcher], which gives us:
* - global serialization (no concurrent clobber of PDFium or FreeType state)
* - stable carrier thread (useful for any thread-affine PDFium state)
*/
internal object Pdfium {
private val counter = AtomicInteger()

/**
* Shared dispatcher for library-level operations (init, open, close). A shared single
* thread prevents races during PDFium's global state setup. Per-document dispatchers
* (from [newDispatcher]) are used for everything else so documents render in parallel.
*/
val sharedDispatcher: CoroutineDispatcher = Executors.newSingleThreadExecutor { runnable ->
Thread(runnable, "pdfium-shared").apply { isDaemon = true }
}.asCoroutineDispatcher()

/** Create a fresh single-threaded dispatcher + the underlying executor. Caller owns shutdown. */
fun newDispatcher(): Pair<CoroutineDispatcher, ExecutorService> {
val id = counter.incrementAndGet()
val exec = Executors.newSingleThreadExecutor { runnable ->
Thread(runnable, "pdfium-worker-$id").apply {
isDaemon = true
priority = Thread.NORM_PRIORITY
}
}
return exec.asCoroutineDispatcher() to exec
}
}