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diff --git a/lib/avb/libavb_ab/avb_ab_flow.h b/lib/avb/libavb_ab/avb_ab_flow.h
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+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#if !defined(AVB_INSIDE_LIBAVB_AB_H) && !defined(AVB_COMPILATION)
+#error "Never include this file directly, include libavb/libavb_ab.h instead."
+#endif
+
+#ifndef AVB_AB_FLOW_H_
+#define AVB_AB_FLOW_H_
+
+#include "avb_ab_ops.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Magic for the A/B struct when serialized. */
+#define AVB_AB_MAGIC "\0AB0"
+#define AVB_AB_MAGIC_LEN 4
+
+/* Versioning for the on-disk A/B metadata - keep in sync with avbtool. */
+#define AVB_AB_MAJOR_VERSION 1
+#define AVB_AB_MINOR_VERSION 0
+
+/* Size of AvbABData struct. */
+#define AVB_AB_DATA_SIZE 32
+
+/* Maximum values for slot data */
+#define AVB_AB_MAX_PRIORITY 15
+#define AVB_AB_MAX_TRIES_REMAINING 7
+
+/* Struct used for recording per-slot metadata.
+ *
+ * When serialized, data is stored in network byte-order.
+ */
+typedef struct AvbABSlotData {
+  /* Slot priority. Valid values range from 0 to AVB_AB_MAX_PRIORITY,
+   * both inclusive with 1 being the lowest and AVB_AB_MAX_PRIORITY
+   * being the highest. The special value 0 is used to indicate the
+   * slot is unbootable.
+   */
+  uint8_t priority;
+
+  /* Number of times left attempting to boot this slot ranging from 0
+   * to AVB_AB_MAX_TRIES_REMAINING.
+   */
+  uint8_t tries_remaining;
+
+  /* Non-zero if this slot has booted successfully, 0 otherwise. */
+  uint8_t successful_boot;
+
+  /* Reserved for future use. */
+  uint8_t reserved[1];
+} AVB_ATTR_PACKED AvbABSlotData;
+
+/* Struct used for recording A/B metadata.
+ *
+ * When serialized, data is stored in network byte-order.
+ */
+typedef struct AvbABData {
+  /* Magic number used for identification - see AVB_AB_MAGIC. */
+  uint8_t magic[AVB_AB_MAGIC_LEN];
+
+  /* Version of on-disk struct - see AVB_AB_{MAJOR,MINOR}_VERSION. */
+  uint8_t version_major;
+  uint8_t version_minor;
+
+  /* Padding to ensure |slots| field start eight bytes in. */
+  uint8_t reserved1[2];
+
+  /* Per-slot metadata. */
+  AvbABSlotData slots[2];
+
+  /* Reserved for future use. */
+  uint8_t reserved2[12];
+
+  /* CRC32 of all 28 bytes preceding this field. */
+  uint32_t crc32;
+} AVB_ATTR_PACKED AvbABData;
+
+/* Copies |src| to |dest|, byte-swapping fields in the
+ * process. Returns false if the data is invalid (e.g. wrong magic,
+ * wrong CRC32 etc.), true otherwise.
+ */
+bool avb_ab_data_verify_and_byteswap(const AvbABData* src, AvbABData* dest);
+
+/* Copies |src| to |dest|, byte-swapping fields in the process. Also
+ * updates the |crc32| field in |dest|.
+ */
+void avb_ab_data_update_crc_and_byteswap(const AvbABData* src, AvbABData* dest);
+
+/* Initializes |data| such that it has two slots and both slots have
+ * maximum tries remaining. The CRC is not set.
+ */
+void avb_ab_data_init(AvbABData* data);
+
+/* Reads A/B metadata from the 'misc' partition using |ops|. Returned
+ * data is properly byteswapped. Returns AVB_IO_RESULT_OK on
+ * success, error code otherwise.
+ *
+ * If the data read from disk is invalid (e.g. wrong magic or CRC
+ * checksum failure), the metadata will be reset using
+ * avb_ab_data_init() and then written to disk.
+ */
+AvbIOResult avb_ab_data_read(AvbABOps* ab_ops, AvbABData* data);
+
+/* Writes A/B metadata to the 'misc' partition using |ops|. This will
+ * byteswap and update the CRC as needed. Returns AVB_IO_RESULT_OK on
+ * success, error code otherwise.
+ */
+AvbIOResult avb_ab_data_write(AvbABOps* ab_ops, const AvbABData* data);
+
+/* Return codes used in avb_ab_flow(), see that function for
+ * documentation of each value.
+ */
+typedef enum {
+  AVB_AB_FLOW_RESULT_OK,
+  AVB_AB_FLOW_RESULT_ERROR_OOM,
+  AVB_AB_FLOW_RESULT_ERROR_IO,
+  AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS
+} AvbABFlowResult;
+
+/* High-level function to select a slot to boot. The following
+ * algorithm is used:
+ *
+ * 1. A/B metadata is loaded and validated using the
+ * read_ab_metadata() operation. Typically this means it's read from
+ * the 'misc' partition and if it's invalid then it's reset using
+ * avb_ab_data_init() and this reset metadata is returned.
+ *
+ * 2. All bootable slots listed in the A/B metadata are verified using
+ * avb_slot_verify(). If a slot fails verification, it will be marked
+ * as unbootable in the A/B metadata and the metadata will be saved to
+ * disk before returning.
+ *
+ * 3. If there are no bootable slots, the value
+ * AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS is returned.
+ *
+ * 4. For each bootable slot, the Stored Rollback Indexes are updated
+ * such that for each rollback index slot, the Stored Rollback Index
+ * is the largest number smaller than or equal to the Rollback Index
+ * of each slot.
+ *
+ * 5. The bootable slot with the highest priority is selected and
+ * returned in |out_data|. If this slot is already marked as
+ * successful, the A/B metadata is not modified. However, if the slot
+ * is not marked as bootable its |tries_remaining| count is
+ * decremented and the A/B metadata is saved to disk before returning.
+ * In either case the value AVB_AB_FLOW_RESULT_OK is returning.
+ *
+ * The partitions to load is given in |requested_partitions| as a
+ * NULL-terminated array of NUL-terminated strings. Typically the
+ * |requested_partitions| array only contains a single item for the
+ * boot partition, 'boot'.
+ *
+ * If an I/O operation - such as loading/saving metadata or checking
+ * rollback indexes - fail, the value AVB_AB_FLOW_RESULT_ERROR_IO is
+ * returned.
+ *
+ * If memory allocation fails, AVB_AB_FLOW_RESULT_ERROR_OOM is
+ * returned.
+ *
+ * Reasonable behavior for handling AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS
+ * is to initiate device recovery (which is device-dependent).
+ */
+AvbABFlowResult avb_ab_flow(AvbABOps* ab_ops,
+                            const char* const* requested_partitions,
+                            AvbSlotVerifyData** out_data);
+
+/* Marks the slot with the given slot number as active. Returns
+ * AVB_IO_RESULT_OK on success, error code otherwise.
+ *
+ * This function is typically used by the OS updater when completing
+ * an update. It can also used by the firmware for implementing the
+ * "set_active" command.
+ */
+AvbIOResult avb_ab_mark_slot_active(AvbABOps* ab_ops, unsigned int slot_number);
+
+/* Marks the slot with the given slot number as unbootable. Returns
+ * AVB_IO_RESULT_OK on success, error code otherwise.
+ *
+ * This function is typically used by the OS updater before writing to
+ * a slot.
+ */
+AvbIOResult avb_ab_mark_slot_unbootable(AvbABOps* ab_ops,
+                                        unsigned int slot_number);
+
+/* Marks the slot with the given slot number as having booted
+ * successfully. Returns AVB_IO_RESULT_OK on success, error code
+ * otherwise.
+ *
+ * Calling this on an unbootable slot is an error - AVB_IO_RESULT_OK
+ * will be returned yet the function will have no side-effects.
+ *
+ * This function is typically used by the OS updater after having
+ * confirmed that the slot works as intended.
+ */
+AvbIOResult avb_ab_mark_slot_successful(AvbABOps* ab_ops,
+                                        unsigned int slot_number);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* AVB_AB_FLOW_H_ */