From 4126e3d7e0d307ac6f4b3970f20529d4227e79ca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20Ko=C5=BEusznik?= <jan@kozusznik.cz>
Date: Mon, 29 Mar 2021 10:02:23 +0200
Subject: [PATCH] LocalReader solution
---
.../java/koz01/java2/lab08/IndexReader.java | 45 ++++++++++++++++++-
1 file changed, 43 insertions(+), 2 deletions(-)
diff --git a/src/main/java/koz01/java2/lab08/IndexReader.java b/src/main/java/koz01/java2/lab08/IndexReader.java
index 8ae3d52..252eefd 100644
--- a/src/main/java/koz01/java2/lab08/IndexReader.java
+++ b/src/main/java/koz01/java2/lab08/IndexReader.java
@@ -55,7 +55,48 @@ public class IndexReader {
return LocalFile;
}
- private byte[] getData(FileChannel fc, int index) throws IOException {
- return new byte[0];
+ private byte[] getData(FileChannel fc, int i) throws IOException {
+ // 0...3 - number of images
+ // 4 ... 7 - Position of 1. image data in file
+ // 8 ... 11 - Lenght of 1. image
+
+ // position_in_index = 4 + i*8
+
+ // position_of_image = readInt(position_in_index)
+ // size_of_image = readInt(position_in_index + 4)
+
+ // data = readData(position_of_image, size_of_image)
+ // return data
+
+ // go to position ... fc.position(position)
+ // read data .... fc.read(bb) - bb is ByteBuffer
+
+ // create ByteBuffer 8 bytes long
+ ByteBuffer bb = ByteBuffer.allocate(8);
+ fc.position(0);
+ fc.read(bb);
+ bb.flip();
+ int numberOfImages = bb.getInt();
+ if (i < 0 || numberOfImages <= i) {
+ return new byte[0];
+ }
+ bb.clear();
+ fc.position(4 + i * 8);
+ fc.read(bb);
+ bb.flip();
+ int position = bb.getInt();
+ int size = bb.getInt();
+
+ bb = ByteBuffer.allocate(size);
+ fc.position(position);
+ fc.read(bb);
+ bb.flip();
+ return bb.array();
+
+ // read data .... fc.read(bb) - bb is ByteBuffer
+ // bb.flip()
+ // bb.getInt(), bb.getInt()
+
+
}
}
--
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