Add method for creating a Js5MasterIndex

Signed-off-by: Graham <gpe@openrs2.org>

cache/src/main/kotlin/org/openrs2/cache/Js5MasterIndex.kt

@@ -1,6 +1,8 @@
 package org.openrs2.cache
 
 import io.netty.buffer.ByteBuf
+import org.openrs2.buffer.crc32
+import org.openrs2.buffer.use
 
 public inline class Js5MasterIndex(public val entries: MutableList<Entry> = mutableListOf()) {
     public data class Entry(public var version: Int, public var checksum: Int)
@@ -13,6 +15,34 @@ public inline class Js5MasterIndex(public val entries: MutableList<Entry> = muta
     }
 
     public companion object {
+        public fun create(store: Store): Js5MasterIndex {
+            val index = Js5MasterIndex()
+
+            var nextArchive = 0
+            for (archive in store.list(Js5Archive.ARCHIVESET)) {
+                /*
+                 * Fill in gaps with zeroes. I think this is consistent with
+                 * the official implementation: the TFU client warns that
+                 * entries with a zero CRC are probably invalid.
+                 */
+                for (i in nextArchive until archive) {
+                    index.entries += Entry(0, 0)
+                }
+
+                val entry = store.read(Js5Archive.ARCHIVESET, archive).use { buf ->
+                    val checksum = buf.crc32()
+                    val version = Js5Index.read(buf).version
+                    // TODO(gpe): should we throw an exception if there are trailing bytes here?
+                    Entry(version, checksum)
+                }
+
+                index.entries += entry
+                nextArchive = archive + 1
+            }
+
+            return index
+        }
+
         public fun read(buf: ByteBuf): Js5MasterIndex {
             require(buf.readableBytes() % 8 == 0)
 

cache/src/test/kotlin/org/openrs2/cache/Js5MasterIndexTest.kt

@@ -0,0 +1,26 @@
+package org.openrs2.cache
+
+import java.nio.file.Paths
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+object Js5MasterIndexTest {
+    private val ROOT = Paths.get(FlatFileStoreTest::class.java.getResource("master-index").toURI())
+
+    @Test
+    fun testCreate() {
+        val index = Store.open(ROOT).use { store ->
+            Js5MasterIndex.create(store)
+        }
+
+        assertEquals(Js5MasterIndex(mutableListOf(
+            Js5MasterIndex.Entry(0, 379203374),
+            Js5MasterIndex.Entry(0x12345678, -717247318),
+            Js5MasterIndex.Entry(0, 0),
+            Js5MasterIndex.Entry(0x9ABCDEF0.toInt(), 895417101),
+            Js5MasterIndex.Entry(0, 0),
+            Js5MasterIndex.Entry(0, 0),
+            Js5MasterIndex.Entry(0xAA55AA55.toInt(), -627983571)
+        )), index)
+    }
+}