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192 lignes
3.6 KiB
192 lignes
3.6 KiB
#pragma once
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#include <stdint.h>
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#include <endian.hpp>
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#include <string>
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#include <iostream>
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#include <assert.h>
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// Unix-y stuff
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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struct errno_exception : public std::runtime_error {
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errno_exception(int err)
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: runtime_error{std::string{"errno with value "}+std::to_string(err)}
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{}
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};
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void throw_errno_if(bool pred)
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{
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if(pred)
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{
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throw errno_exception{errno};
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}
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}
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constexpr size_t page_size = 4096;
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struct [[gnu::packed]] record_identifier{
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bitops::regulated<uint32_t> x = 0;
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bitops::regulated<uint32_t> y = 0;
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std::array<uint8_t, 16> uuid = {0};
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};
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template<>
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struct std::hash<record_identifier> {
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uint64_t operator() (const record_identifier& value) {
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uint64_t v = *(uint32_t*)&value.x.internal;
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v <<= 4;
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v += *(uint32_t*)&value.y.internal;
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v ^= *(uint64_t*)&value.uuid;
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v ^= *(((uint64_t*)&value.uuid)+1);
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return v;
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}
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};
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struct record{
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record()
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{}
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union{
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std::array<uint8_t, 24> full;
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record_identifier split = record_identifier();
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} record_head;
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bitops::regulated<uint64_t> timestamp = 0;
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size_t offset = 0;
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};
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using db_page = std::array<uint8_t, 16384>;
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template<typename T>
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struct mmap_ptr{
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T* start = nullptr;
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size_t offset = 0;
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T& operator*(){
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return start[offset];
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}
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T& operator[](const size_t& n){
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return start[offset+n];
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}
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mmap_ptr operator+(size_t offset) {
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mmap_ptr ret;
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ret.start = start;
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ret.offset = offset + this->offset;
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return ret;
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}
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mmap_ptr operator++() {
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offset+=1;
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mmap_ptr ret = *this;
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return ret;
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}
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mmap_ptr operator++(int) {
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mmap_ptr ret = *this;
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offset+=1;
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return ret;
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}
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bool operator==(const mmap_ptr& oth) {
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return (start == oth.start) && (offset == oth.offset);
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}
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bool operator!=(const mmap_ptr& oth) {
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return !(*this == oth);
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}
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};
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template<typename T>
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class mmap_array : public mmap_ptr<T>
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{
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size_t mapping_size = 0;
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int fd = 0;
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size_t item_size = 0;
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public:
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mmap_array() = default;
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mmap_array(size_t nb_elem, const std::string& filename)
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: mmap_ptr<T>() {
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const size_t expected_size = nb_elem*sizeof(T);
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const size_t expected_size_mod = expected_size + (
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(expected_size%page_size != 0)?
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page_size - expected_size%page_size
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: 0
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);
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fd = open(
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filename.c_str(),
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O_RDWR | O_CREAT,
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S_ISUID + S_ISGID + S_IRUSR + S_IWUSR + S_IRGRP + S_IWGRP
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);
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throw_errno_if(fd < 0);
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struct stat data;
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int status = fstat(fd, &data);
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throw_errno_if(status < 0);
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if((size_t)data.st_size < expected_size_mod)
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{
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status = ftruncate(fd, expected_size_mod);
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throw_errno_if(status < 0);
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}
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this->start = (T*)mmap(NULL, expected_size_mod, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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throw_errno_if(this->start == nullptr);
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mapping_size = expected_size_mod;
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item_size = mapping_size / sizeof(T);
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auto map_access = MADV_RANDOM;
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if(expected_size_mod <= 1 << 20) {
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map_access |= MADV_WILLNEED;
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}
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#ifdef MADV_DONTDUMP
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map_access |= MADV_DONTDUMP;
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#endif
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this->offset = 0;
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posix_madvise(this->start, mapping_size, map_access);
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}
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void enforce_caching() {
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posix_madvise(this->start, mapping_size, MADV_WILLNEED);
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}
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constexpr size_t size() {
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return item_size;
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}
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constexpr mmap_ptr<T> begin() const {
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mmap_ptr<T> ret = *this;
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return ret;
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}
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constexpr mmap_ptr<T> end() const {
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mmap_ptr<T> ret = *this;
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return ret+item_size;
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}
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void clear() {
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munmap(this->start, mapping_size);
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close(fd);
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}
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~mmap_array() {
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//std::cerr << "unmapping disabled" << std::endl;
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if(false)//this->start != nullptr)
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{
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munmap(this->start, mapping_size);
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close(fd);
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}
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}
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};
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