From 78e17b9d87c3b5a869921f4f0d5e96c9cf7536fe Mon Sep 17 00:00:00 2001
From: Steve Kemp <steve@steve.org.uk>
Date: Mon, 15 Jul 2024 19:54:42 +0300
Subject: [PATCH] Better handling for file-sizes

---
 cpm/cpm_bdos.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/cpm/cpm_bdos.go b/cpm/cpm_bdos.go
index 1aa1c73..3d577dc 100644
--- a/cpm/cpm_bdos.go
+++ b/cpm/cpm_bdos.go
@@ -1584,6 +1584,16 @@ func BdosSysCallFileSize(cpm *CPM) error {
 	// of records
 	records := int(fileSize / 128)
 
+	// Block size is used so round up, if we need to.
+	if (fileSize % blkSize) != 0 {
+		records += 1
+	}
+
+	// Cap the size appropriately.
+	if records >= 65536 {
+		records = 65536
+	}
+
 	// Store the value in the three fields
 	fcbPtr.R0 = uint8(records & 0xFF)
 	fcbPtr.R1 = uint8(records >> 8)