Added a new MemoryReadAt for reading pmtiles from byte arrays.

bramp · Feb 1, 2024 · 9f7d933 · 9f7d933
1 parent fec17b5
commit 9f7d933
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diff --git a/packages/pmtiles/lib/src/archive.dart b/packages/pmtiles/lib/src/archive.dart
@@ -349,6 +349,10 @@ class PmTilesArchive {
     return fromReadAt(FileAt(f));
   }
 
+  static Future<PmTilesArchive> fromBytes(List<int> bytes) async {
+    return fromReadAt(MemoryAt(bytes));
+  }
+
   Future<void> close() async {
     return _f.close();
   }

diff --git a/packages/pmtiles/lib/src/io.dart b/packages/pmtiles/lib/src/io.dart
@@ -1,4 +1,5 @@
 import 'dart:collection';
+import 'dart:math' as math;
 import 'package:http/http.dart';
 
 // Browsers don't support the File APIs
@@ -85,3 +86,26 @@ class CordBuffer {
         .toList(growable: growable);
   }
 }
+
+/// In memory implementation of ReadAt.
+class MemoryAt implements ReadAt {
+  final List<int> bytes;
+
+  MemoryAt(this.bytes);
+
+  @override
+  Future<ByteStream> readAt(int offset, int length) async {
+    if (offset >= bytes.length) {
+      return ByteStream.fromBytes([]);
+    }
+
+    return ByteStream.fromBytes(
+      bytes.sublist(offset, math.min(bytes.length, offset + length)),
+    );
+  }
+
+  @override
+  Future<void> close() async {
+    // Does nothing.
+  }
+}