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// Copyright (C) 2017 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#include <algorithm>
#include <limits>
#include <utility>
#include <vector>
#include "update_engine/payload_consumer/file_descriptor.h"
namespace chromeos_update_engine {
// A fake file descriptor with configurable errors. The file descriptor always
// reads a fixed sequence of bytes, consisting of the concatenation of the
// numbers 0, 1, 2... each one encoded in 4 bytes as the big-endian 16-bit
// number encoded in hexadecimal. For example, the beginning of the stream in
// ASCII is 0000000100020003... which corresponds to the numbers 0, 1, 2 and 3.
class FakeFileDescriptor : public FileDescriptor {
FakeFileDescriptor() = default;
~FakeFileDescriptor() override = default;
// FileDescriptor override methods.
bool Open(const char* path, int flags, mode_t mode) override {
if (open_)
return false;
open_ = true;
return true;
bool Open(const char* path, int flags) override {
return Open(path, flags, 0);
ssize_t Read(void* buf, size_t count) override;
ssize_t Write(const void* buf, size_t count) override {
// Read-only block device.
errno = EROFS;
return -1;
off64_t Seek(off64_t offset, int whence) override;
uint64_t BlockDevSize() override { return size_; }
bool BlkIoctl(int request,
uint64_t start,
uint64_t length,
int* result) override {
return false;
bool Flush() override {
return open_;
bool Close() override {
if (!open_)
return false;
open_ = false;
return true;
bool IsSettingErrno() override { return true; }
bool IsOpen() override { return open_; }
// Fake class configuration methods.
// Set the size of the file.
void SetFileSize(uint64_t size) { size_ = size; }
// Marks the range starting from |offset| bytes into the file and |length|
// size as a failure range. Reads from this range will always fail.
void AddFailureRange(uint64_t offset, uint64_t length) {
if (length == 0)
failure_ranges_.emplace_back(offset, length);
// Return the list of ranges of bytes requested with a Read() as (offset,
// length), regardless of the Read() return value.
std::vector<std::pair<uint64_t, uint64_t>> GetReadOps() const {
return read_ops_;
// Whether the fake file is open.
bool open_{false};
// The current file pointer offset into the fake file.
uint64_t offset_{0};
// The size of the file. Reads beyond |max_size_| will an EOF condition.
off64_t size_{std::numeric_limits<off64_t>::max()};
// The list of ranges represented as (start, length) in bytes where reads will
// always fail.
std::vector<std::pair<uint64_t, uint64_t>> failure_ranges_;
// List of reads performed as (offset, length) of the read request.
std::vector<std::pair<uint64_t, uint64_t>> read_ops_;
} // namespace chromeos_update_engine