Ensure uploaded logs match debug log viewer.

debuglogs-viewer/lib/build.gradle.kts

@@ -13,6 +13,7 @@ android {
 
 dependencies {
   implementation(project(":core-util"))
+  implementation(project(":core-util-jvm"))
 
   implementation(libs.kotlin.reflect)
   implementation(libs.jackson.module.kotlin)

debuglogs-viewer/lib/src/main/assets/debuglogs-viewer.js

@@ -220,4 +220,13 @@ function applyFilter() {
   editor.setValue(filtered, -1);
 }
 
+function readLines(offset, limit) {
+  const lines = logLines.split("\n")
+  if (offset >= lines.length) {
+    return "<<END OF INPUT>>";
+  }
+
+  return lines.slice(offset, offset + limit).join("\n")
+}
+
 main();

debuglogs-viewer/lib/src/main/java/org/signal/debuglogsviewer/DebugLogsViewer.kt

@@ -11,8 +11,10 @@ import android.webkit.ValueCallback
 import android.webkit.WebView
 import android.webkit.WebViewClient
 import kotlinx.coroutines.Runnable
+import org.json.JSONArray
 import org.json.JSONObject
 import org.signal.core.util.ThreadUtil
+import java.util.concurrent.CountDownLatch
 import java.util.function.Consumer
 
 object DebugLogsViewer {
@@ -47,6 +49,27 @@ object DebugLogsViewer {
     ThreadUtil.runOnMain { webview.evaluateJavascript("editor.insert($escaped); logLines+=$escaped;", null) }
   }
 
+  @JvmStatic
+  fun readLogs(webview: WebView): LogReader {
+    var position = 0
+    return LogReader { size ->
+      val latch = CountDownLatch(1)
+      var result: String? = null
+      ThreadUtil.runOnMain {
+        webview.evaluateJavascript("readLines($position, $size)") { value ->
+          // Annoying, string returns from javascript land are always encoded as JSON strings (wrapped in quotes, various strings escaped, etc)
+          val parsed = JSONArray("[$value]").getString(0)
+          result = parsed.takeUnless { it == "<<END OF INPUT>>" }
+          position += size
+          latch.countDown()
+        }
+      }
+
+      latch.await()
+      result
+    }
+  }
+
   @JvmStatic
   fun scrollToTop(webview: WebView) {
     webview.evaluateJavascript("editor.scrollToRow(0);", null)
@@ -107,4 +130,9 @@ object DebugLogsViewer {
   fun onSearchClose(webview: WebView) {
     webview.evaluateJavascript("onSearchClose();", null)
   }
+
+  fun interface LogReader {
+    /** Returns the next bit of log, containing at most [size] lines (but may be less), or null if there are no logs remaining. */
+    fun nextChunk(size: Int): String?
+  }
 }