fastboot: Move some helpers into util.h/.cpp.

Bug: 266982466
Test: builds
Change-Id: Ib744d763e11d8a7f7e3f417b331defff61fe4559
diff --git a/fastboot/util.h b/fastboot/util.h
index c719df2..290d0d5 100644
--- a/fastboot/util.h
+++ b/fastboot/util.h
@@ -4,8 +4,14 @@
 #include <stdlib.h>
 
 #include <string>
+#include <vector>
 
+#include <android-base/unique_fd.h>
 #include <bootimg.h>
+#include <liblp/liblp.h>
+#include <sparse/sparse.h>
+
+using SparsePtr = std::unique_ptr<sparse_file, decltype(&sparse_file_destroy)>;
 
 /* util stuff */
 double now();
@@ -19,3 +25,15 @@
 void verbose(const char* fmt, ...) __attribute__((__format__(__printf__, 1, 2)));
 
 void die(const std::string& str) __attribute__((__noreturn__));
+
+bool should_flash_in_userspace(const android::fs_mgr::LpMetadata& metadata,
+                               const std::string& partition_name);
+bool is_sparse_file(android::base::borrowed_fd fd);
+int64_t get_file_size(android::base::borrowed_fd fd);
+
+class ImageSource {
+  public:
+    virtual ~ImageSource(){};
+    virtual bool ReadFile(const std::string& name, std::vector<char>* out) const = 0;
+    virtual android::base::unique_fd OpenFile(const std::string& name) const = 0;
+};