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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2026
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include "td/utils/port/MemoryMapping.h"
#include "td/utils/misc.h"
#include "td/utils/SliceBuilder.h"
// TODO:
// windows,
// anonymous maps,
// huge pages?
#if TD_WINDOWS
#else
#include <sys/mman.h>
#include <unistd.h>
#endif
namespace td {
class MemoryMapping::Impl {
public:
Impl(MutableSlice data, int64 offset) : data_(data), offset_(offset) {
}
Slice as_slice() const {
return data_.substr(narrow_cast<size_t>(offset_));
}
MutableSlice as_mutable_slice() const {
return {};
}
private:
MutableSlice data_;
int64 offset_;
};
#if !TD_WINDOWS
static Result<int64> get_page_size() {
static Result<int64> page_size = []() -> Result<int64> {
auto page_size = sysconf(_SC_PAGESIZE);
if (page_size < 0) {
return OS_ERROR("Can't load page size from sysconf");
}
return page_size;
}();
return page_size.clone();
}
#endif
Result<MemoryMapping> MemoryMapping::create_anonymous(const MemoryMapping::Options &options) {
return Status::Error("Unsupported yet");
}
Result<MemoryMapping> MemoryMapping::create_from_file(const FileFd &file_fd, const MemoryMapping::Options &options) {
#if TD_WINDOWS
return Status::Error("Unsupported yet");
#else
if (file_fd.empty()) {
return Status::Error("Can't create memory mapping: file is empty");
}
TRY_RESULT(stat, file_fd.stat());
auto fd = file_fd.get_native_fd().fd();
auto begin = options.offset;
if (begin < 0) {
return Status::Error(PSLICE() << "Can't create memory mapping: negative offset " << options.offset);
}
int64 end;
if (options.size < 0) {
end = stat.size_;
} else {
end = begin + stat.size_;
}
TRY_RESULT(page_size, get_page_size());
auto fixed_begin = begin / page_size * page_size;
auto data_offset = begin - fixed_begin;
TRY_RESULT(data_size, narrow_cast_safe<size_t>(end - fixed_begin));
void *data = mmap(nullptr, data_size, PROT_READ, MAP_PRIVATE, fd, narrow_cast<off_t>(fixed_begin));
if (data == MAP_FAILED) {
return OS_ERROR("mmap call failed");
}
return MemoryMapping(make_unique<Impl>(MutableSlice(static_cast<char *>(data), data_size), data_offset));
#endif
}
MemoryMapping::MemoryMapping(MemoryMapping &&) noexcept = default;
MemoryMapping &MemoryMapping::operator=(MemoryMapping &&) noexcept = default;
MemoryMapping::~MemoryMapping() = default;
MemoryMapping::MemoryMapping(unique_ptr<Impl> impl) : impl_(std::move(impl)) {
}
Slice MemoryMapping::as_slice() const {
return impl_->as_slice();
}
MutableSlice MemoryMapping::as_mutable_slice() {
return impl_->as_mutable_slice();
}
} // namespace td
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