From b29675bbd1a8a9bac8e122da5bba413758aa2995 Mon Sep 17 00:00:00 2001
From: Terence Boldt <terence@boldt.ca>
Date: Sun, 18 Jan 2026 17:30:02 -0500
Subject: [PATCH] Fix data corruption reading tree files

---
 prodos/file.go | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/prodos/file.go b/prodos/file.go
index 6b768d6..3b52793 100644
--- a/prodos/file.go
+++ b/prodos/file.go
@@ -30,7 +30,7 @@ func LoadFile(reader io.ReaderAt, path string) ([]byte, error) {
 	buffer := make([]byte, fileEntry.EndOfFile)
 	var block []byte
 
-	for i := uint16(0); i < uint16(len(blockList)); i++ {
+	for i := uint32(0); i < uint32(len(blockList)); i++ {
 		if blockList[i] == 0 {
 			block = zeroData()
 		} else {
@@ -39,7 +39,7 @@ func LoadFile(reader io.ReaderAt, path string) ([]byte, error) {
 				return nil, err
 			}
 		}
-		for j := uint16(0); j < 512 && uint32(i)*512+uint32(j) < fileEntry.EndOfFile; j++ {
+		for j := uint32(0); j < 512 && uint32(i)*512+uint32(j) < fileEntry.EndOfFile; j++ {
 			buffer[i*512+j] = block[j]
 		}
 	}
@@ -352,9 +352,9 @@ func getBlocklist(reader io.ReaderAt, fileEntry FileEntry, dataOnly bool) ([]uin
 	case StorageTree:
 		// the number of dataBlocks in the list can be longer than the actual blocks used
 		// because of sparse files
-		dataBlocks := make([]uint16, fileEntry.EndOfFile/512)
+		dataBlocks := make([]uint16, fileEntry.EndOfFile/512+1)
 		// this can be more than needed
-		numberOfIndexBlocks := fileEntry.BlocksUsed/256 + 2
+		numberOfIndexBlocks := fileEntry.EndOfFile/512 + 2
 		indexBlocks := make([]uint16, numberOfIndexBlocks)
 		masterIndex, err := ReadBlock(reader, fileEntry.KeyPointer)
 		if err != nil {
@@ -379,17 +379,18 @@ func getBlocklist(reader io.ReaderAt, fileEntry FileEntry, dataOnly bool) ([]uin
 				return nil, err
 			}
 			for j := uint16(0); j < 256 && bytesRemaining > 0; j++ {
-				if (uint16(index[j]) + uint16(index[j+256])*256) == 0 {
-					break
-				}
+				dataBlocks[numberOfDataBlocks] = uint16(index[j]) + uint16(index[j+256])*256
 				numberOfDataBlocks++
-				bytesRemaining -= 512
-				dataBlocks[i*256+j] = uint16(index[j]) + uint16(index[j+256])*256
+				if bytesRemaining < 512 {
+					bytesRemaining = 0
+				} else {
+					bytesRemaining -= 512
+				}
 			}
 		}
 
 		if dataOnly {
-			return dataBlocks, nil
+			return dataBlocks[0:numberOfDataBlocks], nil
 		}
 
 		blocks = append(indexBlocks[0:numberOfIndexBlocks], dataBlocks[0:numberOfDataBlocks]...)