zircon/system/ulib/fvm-host/include/fvm-host/sparse-paver.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <fvm-host/file-wrapper.h>
#include <fvm/sparse-reader.h>

#include "format.h"

struct SparsePartitionInfo {
    fvm::partition_descriptor_t descriptor;
    fbl::Vector<fvm::extent_descriptor_t> extents;
    fbl::unique_ptr<Format> format;
};

// Given a target path and partition data from a SparseReader, generates a full FVM image.
class SparsePaver {
public:
    // Creates a SparsePaver with the given attributes.
    static zx_status_t Create(fbl::unique_ptr<fvm::host::FileWrapper> wrapper,
                              size_t slice_size, size_t disk_offset,
                              size_t disk_size, fbl::unique_ptr<SparsePaver>* out);

    // Allocates the partition and slices described by |partition| to info_, and writes out
    // corresponding data from |reader| to the FVM. |partition| will not be modified.
    zx_status_t AddPartition(const SparsePartitionInfo* partition, fvm::SparseReader* reader);

    // Commits the FVM image by writing the metadata to disk.
    zx_status_t Commit();
private:
    SparsePaver(size_t disk_offset, size_t disk_size) : disk_offset_(disk_offset),
                                                        disk_size_(disk_size) {}

    // Initializes the FVM metadata.
    zx_status_t Init(fbl::unique_ptr<fvm::host::FileWrapper> wrapper, size_t slice_size);

    // Allocates the extent described by |extent| to the partition at |vpart_index|, as well as
    // allocating its slices and persisting all associated data.
    zx_status_t AddExtent(uint32_t vpart_index, fvm::extent_descriptor_t* extent,
                          fvm::SparseReader* reader);

    // Writes the next slice out to disk, reading as many of |bytes_left| as possible from |reader|
    // and appending zeroes if necessary.
    zx_status_t WriteSlice(size_t* bytes_left, fvm::SparseReader* reader);

    FvmInfo info_;
    fbl::unique_ptr<fvm::host::FileWrapper> file_;
    size_t disk_offset_; // Offset into fd_ at which to create FVM.
    size_t disk_size_; // Number of bytes allocated for the FVM.
    size_t disk_ptr_; // Marks the current offset within the target image.
    fbl::unique_ptr<uint8_t[]> data_; // Buffer to hold data to be written to disk.
};