From fdbddd580039f0266fe1b962df36d8151e94c3b1 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Mon, 24 Feb 2025 15:51:05 +0000
Subject: [PATCH] fix slightly incorrect cluster boundaries written by
 shadow_image

---
 src/shadow-image.c | 14 ++++++++------
 src/shadow-image.h |  1 +
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/shadow-image.c b/src/shadow-image.c
index 7aef0c9..a09a63d 100644
--- a/src/shadow-image.c
+++ b/src/shadow-image.c
@@ -106,6 +106,7 @@ enum ec3_status shadow_image_init(
 	cluster_table_init_empty_table(&out->img_cluster_table);
 
 	out->img_nr_bytes = sizeof header;
+	out->img_cluster_data_offset = out->img_nr_bytes;
 	out->img_extent_table = b_buffer_create(sizeof(struct ec3_extent_info));
 	out->img_tag_table = b_buffer_create(sizeof(struct ec3_tag_info));
 
@@ -434,7 +435,7 @@ static enum ec3_status put_empty_cluster(
 
 	struct cluster cluster = {0};
 	cluster.c_id = image->img_nr_clusters;
-	cluster.c_base = image->img_nr_bytes;
+	cluster.c_base = image->img_nr_bytes - image->img_cluster_data_offset;
 	cluster.c_len = encoded_size;
 
 	image->img_nr_clusters++;
@@ -493,7 +494,7 @@ static enum ec3_status copy_cached_cluster(
 
 	struct cluster cluster = {0};
 	cluster.c_id = image->img_nr_clusters;
-	cluster.c_base = image->img_nr_bytes;
+	cluster.c_base = image->img_nr_bytes - image->img_cluster_data_offset;
 	cluster.c_len = encoded_size;
 
 	image->img_nr_clusters++;
@@ -577,7 +578,8 @@ static enum ec3_status copy_cluster_range(
 		}
 
 		cluster.c_id = dest->img_nr_clusters;
-		cluster.c_base = dest->img_nr_bytes;
+		cluster.c_base
+			= dest->img_nr_bytes - dest->img_cluster_data_offset;
 
 		size_t nr_written = 0;
 		status2 = b_file_write(
@@ -611,7 +613,7 @@ static enum ec3_status write_wseq_tag(
 {
 	size_t cluster_id_offset = dest->img_nr_clusters;
 	size_t cluster_id_limit = cluster_id_offset;
-	size_t data_offset = dest->img_nr_bytes;
+	size_t data_offset = dest->img_nr_bytes - dest->img_cluster_data_offset;
 	size_t first_logical_cluster = 0;
 
 	struct cluster_table *clusters = &ioctx->io_cluster_table;
@@ -785,7 +787,7 @@ enum ec3_status shadow_image_write_tag(
 		return status;
 	}
 
-	size_t last_cluster = dest->img_nr_clusters;
+	size_t nr_clusters = dest->img_nr_clusters - first_cluster;
 
 	struct ec3_extent_info *extent = NULL;
 	b_buffer_push_back(dest->img_extent_table, 1, (void **)&extent);
@@ -793,7 +795,7 @@ enum ec3_status shadow_image_write_tag(
 	extent->ex_owner = tag->tag_ident;
 	extent->ex_logical_cluster = 0;
 	extent->ex_physical_cluster = first_cluster;
-	extent->ex_count = last_cluster - first_cluster;
+	extent->ex_count = nr_clusters;
 
 	b_buffer_append(dest->img_tag_table, tag, 1);
 
diff --git a/src/shadow-image.h b/src/shadow-image.h
index 98a040d..2ac71ca 100644
--- a/src/shadow-image.h
+++ b/src/shadow-image.h
@@ -15,6 +15,7 @@ struct ec3_tag_info;
 struct shadow_image {
 	size_t img_nr_clusters;
 	size_t img_nr_bytes;
+	size_t img_cluster_data_offset;
 	struct b_file *img_f_data;
 	struct b_file *img_f_cluster_table;
 	struct cluster_table img_cluster_table;