/usr/include/bobcat/sharedmemory is in libbobcat-dev 3.23.01-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#define INCLUDED_BOBCAT_SHAREDMEMORY_
#include <ios>
#include <bobcat/fswap>
#include <bobcat/sharedpos>
#include <bobcat/exception>
namespace FBB
{
class SharedSegment;
struct SharedEnum__
{
enum SizeUnit
{
kB = 10,
MB = 20,
GB = 30
};
};
class SharedMemory: public virtual SharedEnum__
{
friend std::ostream &operator<<(std::ostream &out,
SharedMemory const &mem);
enum { PAGESIZE = 1 << 12 };
// updated by the non-default constructors.
int d_id = -1; // id of SharedSegment
SharedSegment *d_sharedSegment = 0; // points to the attached shared
// memory. This is NOT a pointer
// to dynamically allocated memory
// but a static_cast pointer to
// the attached shared data segment
SharedPos d_pos;
size_t d_lockCount = 0; // # of nested locks
char *d_data = 0; // pointer to shared memory data
public:
SharedMemory() = default;
SharedMemory(SharedMemory const &other) = delete;
SharedMemory(size_t maxSize, SizeUnit sizeUnit,
size_t access = 0600); // 2: creation mode;
SharedMemory(int id); // 3
~SharedMemory();
SharedMemory &operator=(SharedMemory &&tmp);
std::streamsize blockOffset() const;// offset matching offset(),
// relative to the current data
// block.
void clear(); // clear all existing data and reduce
// until only the segment at
// d_sharedSegment
size_t dataSegmentSize() const;
int get(); // get char from d_segmentData
// locks), or EOF
int id() const; // id of the d_sharedSegment segment
// after kill/remove: shared segment is unusable
void kill(); // delete all shared segments w/o locks
std::streamsize maxOffset() const;
std::streamsize nReadable() const; // beyond last readable byte
std::streamsize offset() const; // read/write offset relative to
// ios::beg
char *ptr(); // 0 if at maxOffset
int put(int ch); // put char at d_offset (locks),
// ch == EOF immediately returns EOF
// read len chars, return nRead or -1,
// locks
int read(char *data, std::streamsize len);
template <typename Type>
int read(Type *value); // 1.f
template <typename Type> // 2.f
int read(std::ios::off_type offset, Type *value,
std::ios::seekdir origin = std::ios::beg);
// after kill/remove: shared segment is unusable
void remove(); // delete all shared segments.
// returns -1 if inaccessible
std::ios::pos_type seek(std::ios::off_type offset,
std::ios::seekdir origin = std::ios::beg);
std::streamsize showmanyc();
void swap(SharedMemory &other);
bool truncate(std::streamsize offset); // nReadable is reduced to
// offset
// write len bytes at d_offset
// locks, returns #written or -1
int write(char const *data, std::streamsize len);
template <typename Type>
int write(Type const *value); // 1.f
template <typename Type> // 2.f
int write(std::ios::off_type offset, Type const *value,
std::ios::seekdir origin = std::ios::beg);
template <typename SharedType, typename ... Params>
SharedType *install(std::streamsize *offset, Params &&...params);
private:
std::ostream &insert(std::ostream &out) const;
// lockAll: d_lockCount should be 0.
void lockAll(); // lock all block[] mutexes
void unlockAll(); // unlock all block[] mutexes
void lock(size_t idx); // (recursively) lock block idx
void unlock(size_t idx); // unlock block idx
void clearAll(); // clear without locking
bool blockAvailable(size_t idx);
void map(); // 1 maps shared data to d_data
void map(size_t idx); // 2 only called by load
int writeBlock(char const *data, size_t len); // locks, returns
// #written or -1
int readBlock(char *data, size_t len); // same, but now reads
// both update offset
static size_t computeSegmentSize(
size_t *nBlocks,
long long maxMemory, SizeUnit sizeUnit);
void validate() const;
};
inline std::streamsize SharedMemory::blockOffset() const
{
return d_pos.blockOffset();
}
inline size_t SharedMemory::dataSegmentSize() const
{
return d_sharedSegment ? d_sharedSegment->segmentSize() : 0;
}
inline int SharedMemory::id() const
{
return d_id;
}
template <typename SharedType, typename ... Params>
SharedType *SharedMemory::install(std::streamsize *offsetPtr,
Params &&...params)
{
size_t segmentSize = dataSegmentSize();
if (segmentSize == 0)
throw Exception() << "SharedMemory::install: no memory";
// find a suitable offset for the shared memory object
size_t begin = blockOffset();
size_t end = (begin + sizeof(SharedType)) % segmentSize;
if (begin + sizeof(SharedType) != end)
seek((1 + offset() / segmentSize) * segmentSize);
// determine the object's offset and address
std::streamsize location = offset();
void *address = ptr();
// go to the object's last byte
if (address == 0 || seek(sizeof(SharedType) - 1) == -1)
throw Exception() << "SharedMemory::install: out of memory.";
// make sure shmem knows it exists by writing a byte at its last
// byte location
put(0);
if (offsetPtr)
*offsetPtr = location;
// install the object at 'address'
return new (address) SharedType(std::forward<Params>(params)...);
}
inline std::streamsize SharedMemory::maxOffset() const
{
return d_pos.maxOffset();
}
inline std::streamsize SharedMemory::nReadable() const
{
return d_sharedSegment ? d_sharedSegment->nReadable() : 0;
}
inline std::streamsize SharedMemory::offset() const
{
return d_pos.offset();
}
inline SharedMemory &SharedMemory::operator=(SharedMemory &&tmp)
{
swap(tmp);
return *this;
}
inline std::ostream &operator<<(std::ostream &out, SharedMemory const &mem)
{
return mem.insert(out);
}
template <typename Type>
inline int SharedMemory::read(Type *value)
{
return read(reinterpret_cast<char *>(value), sizeof(Type));
}
template <typename Type>
int SharedMemory::read(std::ios::off_type offset, Type *value,
std::ios::seekdir origin)
{
if (seek(offset, origin) == -1)
throw Exception() << "SharedMemory::read: seek to " << offset <<
"failed";
return read(value);
}
inline void SharedMemory::swap(SharedMemory &other)
{
FBB::fswap(*this, other);
}
template <typename Type>
inline int SharedMemory::write(Type const *value)
{
return write(reinterpret_cast<char const *>(value), sizeof(Type));
}
template <typename Type>
int SharedMemory::write(std::ios::off_type offset, Type const *value,
std::ios::seekdir origin)
{
if (seek(offset, origin) == -1)
throw Exception() << "SharedMemory::write: seek to " << offset <<
"failed";
return write(value);
}
} // FBB
#endif
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