Use short-circuiting content comparison instead of hash comparison wh…

…en possible
PaperMC · Nov 17, 2023 · f9b0dda · f9b0dda
1 parent c7d0820
commit f9b0dda
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Showing 2 changed files with 35 additions and 2 deletions.
diff --git a/paperweight-lib/src/main/kotlin/io/papermc/paperweight/util/file.kt b/paperweight-lib/src/main/kotlin/io/papermc/paperweight/util/file.kt
@@ -30,6 +30,7 @@ import java.nio.file.Files
 import java.nio.file.Path
 import java.nio.file.PathMatcher
 import java.nio.file.attribute.DosFileAttributeView
+import java.util.Arrays
 import java.util.stream.Collectors
 import java.util.stream.Stream
 import java.util.stream.StreamSupport
@@ -160,6 +161,38 @@ fun Path.hashFile(algorithm: HashingAlgorithm): ByteArray = inputStream().use {
 
 fun Path.sha256asHex(): String = hashFile(HashingAlgorithm.SHA256).asHexString()
 
+fun Path.contentEquals(file: Path, bufferSizeBytes: Int = 8192): Boolean {
+    inputStream().use { one ->
+        file.inputStream().use { two ->
+
+            val bufOne = ByteArray(bufferSizeBytes)
+            val bufTwo = ByteArray(bufferSizeBytes)
+
+            while (true) {
+                val readOne = one.read(bufOne)
+                val readTwo = two.read(bufTwo)
+
+                if (readOne != readTwo) {
+                    // length differs
+                    return false
+                }
+
+                if (readOne == -1) {
+                    // end of content
+                    break
+                }
+
+                if (!Arrays.equals(bufOne, 0, readOne, bufTwo, 0, readOne)) {
+                    // content differs
+                    return false
+                }
+            }
+        }
+    }
+
+    return true
+}
+
 fun Path.withDifferentExtension(ext: String): Path = resolveSibling("$nameWithoutExtension.$ext")
 
 // Returns true if our process already owns the lock

diff --git a/paperweight-lib/src/main/kotlin/io/papermc/paperweight/util/ivy-repository.kt b/paperweight-lib/src/main/kotlin/io/papermc/paperweight/util/ivy-repository.kt
@@ -88,12 +88,12 @@ private fun upToDate(
     binaryIn: Path,
     xmlIn: String
 ): Boolean {
-    val bin = binDest.isRegularFile() && binDest.sha256asHex() == binaryIn.sha256asHex()
+    val bin = binDest.isRegularFile() && binDest.contentEquals(binaryIn)
     val xml = ivyXml.isRegularFile() && ivyXml.readText(Charsets.UTF_8) == xmlIn
     val sources = if (sourcesIn == null) {
         sourcesDest.notExists()
     } else {
-        sourcesDest.isRegularFile() && sourcesDest.sha256asHex() == sourcesIn.sha256asHex()
+        sourcesDest.isRegularFile() && sourcesDest.contentEquals(sourcesIn)
     }
     return bin && xml && sources
 }