Clean up fuse_sideload and add a testcase.

This CL mainly changes:
a) moving the interface in struct provider_vtab to std::function;
b) code cleanup, such as moving the declaration closer to the uses,
   using explicit type conversion.

Test: recovery_component_test
Test: minadbd_test
Test: Sideload a package on marlin.
Change-Id: Id0e3c70f1ada54a4cd985b54c84438c23ed4687e

fuse_sdcard_provider.cpp

@@ -14,72 +14,70 @@
  * limitations under the License.
  */
 
-#include <stdlib.h>
+#include "fuse_sdcard_provider.h"
+
+#include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
-#include <errno.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#include <fcntl.h>
+
+#include <functional>
 
 #include <android-base/file.h>
 
 #include "fuse_sideload.h"
 
 struct file_data {
-    int fd;  // the underlying sdcard file
+  int fd;  // the underlying sdcard file
 
-    uint64_t file_size;
-    uint32_t block_size;
+  uint64_t file_size;
+  uint32_t block_size;
 };
 
-static int read_block_file(void* cookie, uint32_t block, uint8_t* buffer, uint32_t fetch_size) {
-    file_data* fd = reinterpret_cast<file_data*>(cookie);
-
-    off64_t offset = ((off64_t) block) * fd->block_size;
-    if (TEMP_FAILURE_RETRY(lseek64(fd->fd, offset, SEEK_SET)) == -1) {
-        fprintf(stderr, "seek on sdcard failed: %s\n", strerror(errno));
-        return -EIO;
-    }
+static int read_block_file(const file_data& fd, uint32_t block, uint8_t* buffer,
+                           uint32_t fetch_size) {
+  off64_t offset = static_cast<off64_t>(block) * fd.block_size;
+  if (TEMP_FAILURE_RETRY(lseek64(fd.fd, offset, SEEK_SET)) == -1) {
+    fprintf(stderr, "seek on sdcard failed: %s\n", strerror(errno));
+    return -EIO;
+  }
 
-    if (!android::base::ReadFully(fd->fd, buffer, fetch_size)) {
-        fprintf(stderr, "read on sdcard failed: %s\n", strerror(errno));
-        return -EIO;
-    }
-
-    return 0;
-}
+  if (!android::base::ReadFully(fd.fd, buffer, fetch_size)) {
+    fprintf(stderr, "read on sdcard failed: %s\n", strerror(errno));
+    return -EIO;
+  }
 
-static void close_file(void* cookie) {
-    file_data* fd = reinterpret_cast<file_data*>(cookie);
-    close(fd->fd);
+  return 0;
 }
 
 bool start_sdcard_fuse(const char* path) {
-    struct stat sb;
-    if (stat(path, &sb) == -1) {
-        fprintf(stderr, "failed to stat %s: %s\n", path, strerror(errno));
-        return false;
-    }
+  struct stat sb;
+  if (stat(path, &sb) == -1) {
+    fprintf(stderr, "failed to stat %s: %s\n", path, strerror(errno));
+    return false;
+  }
 
-    file_data fd;
-    fd.fd = open(path, O_RDONLY);
-    if (fd.fd == -1) {
-        fprintf(stderr, "failed to open %s: %s\n", path, strerror(errno));
-        return false;
-    }
-    fd.file_size = sb.st_size;
-    fd.block_size = 65536;
+  file_data fd;
+  fd.fd = open(path, O_RDONLY);
+  if (fd.fd == -1) {
+    fprintf(stderr, "failed to open %s: %s\n", path, strerror(errno));
+    return false;
+  }
+  fd.file_size = sb.st_size;
+  fd.block_size = 65536;
 
-    provider_vtab vtab;
-    vtab.read_block = read_block_file;
-    vtab.close = close_file;
+  provider_vtab vtab;
+  vtab.read_block = std::bind(&read_block_file, fd, std::placeholders::_1, std::placeholders::_2,
+                              std::placeholders::_3);
+  vtab.close = [&fd]() { close(fd.fd); };
 
-    // The installation process expects to find the sdcard unmounted.
-    // Unmount it with MNT_DETACH so that our open file continues to
-    // work but new references see it as unmounted.
-    umount2("/sdcard", MNT_DETACH);
+  // The installation process expects to find the sdcard unmounted. Unmount it with MNT_DETACH so
+  // that our open file continues to work but new references see it as unmounted.
+  umount2("/sdcard", MNT_DETACH);
 
-    return run_fuse_sideload(&vtab, &fd, fd.file_size, fd.block_size) == 0;
+  return run_fuse_sideload(vtab, fd.file_size, fd.block_size) == 0;
 }