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// Copyright (C) 2019 Google LLC
//
// 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.
// Copyright 2012 Google Inc. All Rights Reserved.
// Author: sbanacho@google.com (Scott Banachowski)
//
// This class is a helper for mmapping a file.
// Use as a scoped allocator, the memory is mapped
// on construction and released on destruction.
#ifndef ICING_LEGACY_INDEX_ICING_MMAPPER_H_
#define ICING_LEGACY_INDEX_ICING_MMAPPER_H_
#include <unistd.h>
#include <cstddef>
#include <cstdint>
namespace icing {
namespace lib {
class IcingMMapper {
public:
// Provide a valid, open file description (with matching permissions
// for read or write). The location into the file you wish to map,
// and the size. "flags" are passed in directly to mmap.
IcingMMapper(int fd, bool read_only, uint64_t location, size_t size,
int flags);
// Set up Mmapper, but delay mapping until Remap is called.
IcingMMapper(bool read_only, int flags);
// Will unmap the region on delete. Does not close the file.
~IcingMMapper();
// Move the location of the mapping to a new location. Returns
// true if valid.
bool Remap(int fd, uint64_t location, size_t size);
// Close the mapping and become invalid.
void Unmap();
// Sync the mapped region to the filesystem.
bool Sync();
// Check to see if the file was successfully mapped.
bool is_valid() const { return (address_ != nullptr); }
// The address in memory of the mapped file, returns NULL if the
// mapping of the region was unsuccesful.
const uint8_t *address() const { return address_; }
uint8_t *address() { return address_; }
size_t len() const { return len_; }
uint64_t location() const { return location_; }
static size_t __attribute__((const)) system_page_size() {
static const size_t page_size = sysconf(_SC_PAGE_SIZE);
return page_size;
}
// Rounds `size` up to a multiple of the system page size.
static size_t page_aligned_size(uint32_t size) {
return ((size + system_page_size() - 1) / system_page_size()) *
system_page_size();
}
private:
void DoMapping(int fd, uint64_t location, size_t size);
uint8_t *address_;
size_t len_; // the requested mapping length
const int flags_; // flags passed in to mmap
uint64_t location_; // the requested mapping file location
size_t mmap_len_; // the actual mapping length
void *mmap_result_;
const bool read_only_;
};
} // namespace lib
} // namespace icing
#endif // ICING_LEGACY_INDEX_ICING_MMAPPER_H_
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