Add io_pread().

It will be used by --list.

1 files changed, 25 insertions, 0 deletions

diff --git a/src/xz/file_io.c b/src/xz/file_io.c
index d94e2321..a07501c1 100644
--- a/src/xz/file_io.c
+++ b/src/xz/file_io.c
@@ -812,6 +812,31 @@ io_read(file_pair *pair, io_buf *buf_union, size_t size)
 }
 
 
+extern bool
+io_pread(file_pair *pair, io_buf *buf, size_t size, off_t pos)
+{
+	// Using lseek() and read() is more portable than pread() and
+	// for us it is as good as real pread().
+	if (lseek(pair->src_fd, pos, SEEK_SET) != pos) {
+		message_error(_("%s: Error seeking the file: %s"),
+				pair->src_name, strerror(errno));
+		return true;
+	}
+
+	const size_t amount = io_read(pair, buf, size);
+	if (amount == SIZE_MAX)
+		return true;
+
+	if (amount != size) {
+		message_error(_("%s: Unexpected end of file"),
+				pair->src_name);
+		return true;
+	}
+
+	return false;
+}
+
+
 static bool
 is_sparse(const io_buf *buf)
 {