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#ifndef UTIL_MMAP_H
#define UTIL_MMAP_H
// Utilities for mmaped files.
#include <cstddef>
#include <limits>
#include <stdint.h>
#include <sys/types.h>
namespace util {
class scoped_fd;
long SizePage();
// (void*)-1 is MAP_FAILED; this is done to avoid including the mmap header here.
class scoped_mmap {
public:
scoped_mmap() : data_((void*)-1), size_(0) {}
scoped_mmap(void *data, std::size_t size) : data_(data), size_(size) {}
~scoped_mmap();
void *get() const { return data_; }
const uint8_t *begin() const { return reinterpret_cast<uint8_t*>(data_); }
const uint8_t *end() const { return reinterpret_cast<uint8_t*>(data_) + size_; }
std::size_t size() const { return size_; }
void reset(void *data, std::size_t size) {
scoped_mmap other(data_, size_);
data_ = data;
size_ = size;
}
void reset() {
reset((void*)-1, 0);
}
private:
void *data_;
std::size_t size_;
scoped_mmap(const scoped_mmap &);
scoped_mmap &operator=(const scoped_mmap &);
};
/* For when the memory might come from mmap, new char[], or malloc. Uses NULL
* and 0 for blanks even though mmap signals errors with (void*)-1). The reset
* function checks that blank for mmap.
*/
class scoped_memory {
public:
typedef enum {MMAP_ALLOCATED, ARRAY_ALLOCATED, MALLOC_ALLOCATED, NONE_ALLOCATED} Alloc;
scoped_memory(void *data, std::size_t size, Alloc source)
: data_(data), size_(size), source_(source) {}
scoped_memory() : data_(NULL), size_(0), source_(NONE_ALLOCATED) {}
~scoped_memory() { reset(); }
void *get() const { return data_; }
const char *begin() const { return reinterpret_cast<char*>(data_); }
const char *end() const { return reinterpret_cast<char*>(data_) + size_; }
std::size_t size() const { return size_; }
Alloc source() const { return source_; }
void reset() { reset(NULL, 0, NONE_ALLOCATED); }
void reset(void *data, std::size_t size, Alloc from);
// realloc allows the current data to escape hence the need for this call
// If realloc fails, destroys the original too and get() returns NULL.
void call_realloc(std::size_t to);
private:
void *data_;
std::size_t size_;
Alloc source_;
scoped_memory(const scoped_memory &);
scoped_memory &operator=(const scoped_memory &);
};
typedef enum {
// mmap with no prepopulate
LAZY,
// On linux, pass MAP_POPULATE to mmap.
POPULATE_OR_LAZY,
// Populate on Linux. malloc and read on non-Linux.
POPULATE_OR_READ,
// malloc and read.
READ,
// malloc and read in parallel (recommended for Lustre)
PARALLEL_READ,
} LoadMethod;
extern const int kFileFlags;
// Wrapper around mmap to check it worked and hide some platform macros.
void *MapOrThrow(std::size_t size, bool for_write, int flags, bool prefault, int fd, uint64_t offset = 0);
void MapRead(LoadMethod method, int fd, uint64_t offset, std::size_t size, scoped_memory &out);
void MapAnonymous(std::size_t size, scoped_memory &to);
// Open file name with mmap of size bytes, all of which are initially zero.
void *MapZeroedWrite(int fd, std::size_t size);
void *MapZeroedWrite(const char *name, std::size_t size, scoped_fd &file);
// msync wrapper
void SyncOrThrow(void *start, size_t length);
// Forward rolling memory map with no overlap.
class Rolling {
public:
Rolling() {}
explicit Rolling(void *data) { Init(data); }
Rolling(const Rolling ©_from, uint64_t increase = 0);
Rolling &operator=(const Rolling ©_from);
// For an actual rolling mmap.
explicit Rolling(int fd, bool for_write, std::size_t block, std::size_t read_bound, uint64_t offset, uint64_t amount);
// For a static mapping
void Init(void *data) {
ptr_ = data;
current_end_ = std::numeric_limits<uint64_t>::max();
current_begin_ = 0;
// Mark as a pass-through.
fd_ = -1;
}
void IncreaseBase(uint64_t by) {
file_begin_ += by;
ptr_ = static_cast<uint8_t*>(ptr_) + by;
if (!IsPassthrough()) current_end_ = 0;
}
void DecreaseBase(uint64_t by) {
file_begin_ -= by;
ptr_ = static_cast<uint8_t*>(ptr_) - by;
if (!IsPassthrough()) current_end_ = 0;
}
void *ExtractNonRolling(scoped_memory &out, uint64_t index, std::size_t size);
// Returns base pointer
void *get() const { return ptr_; }
// Returns base pointer.
void *CheckedBase(uint64_t index) {
if (index >= current_end_ || index < current_begin_) {
Roll(index);
}
return ptr_;
}
// Returns indexed pointer.
void *CheckedIndex(uint64_t index) {
return static_cast<uint8_t*>(CheckedBase(index)) + index;
}
private:
void Roll(uint64_t index);
// True if this is just a thin wrapper on a pointer.
bool IsPassthrough() const { return fd_ == -1; }
void *ptr_;
uint64_t current_begin_;
uint64_t current_end_;
scoped_memory mem_;
int fd_;
uint64_t file_begin_;
uint64_t file_end_;
bool for_write_;
std::size_t block_;
std::size_t read_bound_;
};
} // namespace util
#endif // UTIL_MMAP_H
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