From 5289c868637f8ddecb170d299e9c4b4bd659f68a Mon Sep 17 00:00:00 2001
From: Enno Boland <g@s01.de>
Date: Sun, 20 Aug 2023 20:41:24 +0200
Subject: [PATCH 1/2] file_iterator: always map at least one block.

This is needed for consistent behavior between implementations that
ignore desired_size and implementations that honor it.
---
 lib/file/file_iterator.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/lib/file/file_iterator.c b/lib/file/file_iterator.c
index 2e8b0fac2..6aaee3896 100644
--- a/lib/file/file_iterator.c
+++ b/lib/file/file_iterator.c
@@ -135,16 +135,12 @@ map_block_uncompressed(
 		size_t desired_size) {
 	int rv = 0;
 	const struct SqshFile *file = iterator->file;
-
 	sqsh_index_t block_index = iterator->block_index;
 	struct SqshMapReader *reader = &iterator->map_reader;
-	if (rv < 0) {
-		goto out;
-	}
-
 	const uint64_t block_count = sqsh_file_block_count(file);
 	uint64_t outer_size = 0;
 	const size_t remaining_direct = sqsh__map_reader_remaining_direct(reader);
+
 	for (; iterator->sparse_size == 0 && block_index < block_count;
 		 block_index++) {
 		if (sqsh_file_block_is_compressed(file, block_index)) {
@@ -277,6 +273,14 @@ sqsh_file_iterator_next(
 
 	sqsh__extract_view_cleanup(&iterator->extract_view);
 
+	// Desired size of 0 would result in a noop for uncompressed blocks,
+	// resulting in inconsistend behavior depending whether the block is
+	// compressed, which ignores the desired size, or uncompressed, which
+	// honors the desired size.
+	if (desired_size == 0) {
+		desired_size = 1;
+	}
+
 	if (iterator->sparse_size > 0) {
 		return map_zero_block(iterator);
 	} else if (iterator->block_index < block_count) {

From d32ea29f60838878312e9f7d61f0bfef361a2350 Mon Sep 17 00:00:00 2001
From: Enno Boland <g@s01.de>
Date: Sun, 20 Aug 2023 23:16:49 +0200
Subject: [PATCH 2/2] tools/fs-common.c: workaround error at end of file

OpenBSD requests a chunk of data at the end of the file. Currently
sqsh_file_reader_advance() returns an error in this case. This
commit works around this behavior by returning early when
zero size is requested.
---
 tools/fs-common.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/fs-common.c b/tools/fs-common.c
index 5e27fb454..01d3f570f 100644
--- a/tools/fs-common.c
+++ b/tools/fs-common.c
@@ -145,6 +145,15 @@ fs_common_read(
 		size = file_size - offset;
 	}
 
+
+	// This works around a bug in sqsh_file_reader_advance:
+	// Reading a 0 size at the end of the file will return
+	// SQSH_ERROR_OUT_OF_BOUNDS. This should succeed instead,
+	// providing an empty buffer.
+	if (size == 0) {
+		return 0;
+	}
+
 	rv = sqsh_file_reader_advance(*reader, offset, size);
 	if (rv < 0) {
 		goto out;