upload android base code part3

android/bootable/recovery/fuse_sdcard_provider.cpp

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include <android-base/file.h>
+
+#include "fuse_sideload.h"
+
+struct file_data {
+    int fd;  // the underlying sdcard file
+
+    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;
+    }
+
+    if (!android::base::ReadFully(fd->fd, buffer, fetch_size)) {
+        fprintf(stderr, "read on sdcard failed: %s\n", strerror(errno));
+        return -EIO;
+    }
+
+    return 0;
+}
+
+static void close_file(void* cookie) {
+    file_data* fd = reinterpret_cast<file_data*>(cookie);
+    close(fd->fd);
+}
+
+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;
+    }
+
+    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;
+
+    // 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;
+}