AuroraRuntime/Source/IO/FS/FileAdvisory.Unix.cpp
2023-09-23 08:15:50 +01:00

178 lines
5.2 KiB
C++

/***
Copyright (C) 2022 J Reece Wilson (a/k/a "Reece"). All rights reserved.
File: FileAdvisory.Unix.cpp
Date: 2022-1-29
Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "FS.hpp"
#include "FileAdvisory.hpp"
#include "FileAdvisory.Unix.hpp"
#include <sys/file.h>
#if defined(AURORA_COMPILER_CLANG)
// warning: enumeration values 'kEnumCount' and 'kEnumInvalid' not handled in switch [-Wswitch
#pragma clang diagnostic ignored "-Wswitch"
// Yea, I don't give a shit.
#endif
namespace Aurora::IO::FS
{
bool ApplyDumbAdvisoryLock(int fd, EFileAdvisoryLockLevel level)
{
#if !defined(AURORA_IS_LINUX_DERIVED)
int operation = LOCK_NB;
switch (level)
{
case EFileAdvisoryLockLevel::eEnumCount:
case EFileAdvisoryLockLevel::eNoSafety:
return true;
case EFileAdvisoryLockLevel::eBlockWrite:
operation |= LOCK_SH;
break;
case EFileAdvisoryLockLevel::eBlockReadWrite:
operation |= LOCK_EX;
break;
}
// Assume:
// "Furthermore, the lock is release either by an explicit LOCK_UN
// operation on any of these duplicate file descriptors, or when
// all such file descriptors have been closed"
return ::flock(fd, operation) == 0;
#else
// Linux
int lease {};
switch (level)
{
case EFileAdvisoryLockLevel::eEnumCount:
case EFileAdvisoryLockLevel::eNoSafety:
return true;
case EFileAdvisoryLockLevel::eBlockWrite:
lease = F_RDLCK;
break;
case EFileAdvisoryLockLevel::eBlockReadWrite:
lease = F_WRLCK;
break;
}
// Ignore warning bc idc
// I assume c++ compilers under posix land allow for struct init the c way
struct flock lck =
{
.l_whence = SEEK_SET,
.l_start = 0,
.l_len = 0,
.l_type = lease
};
// Assume this is true:
// * If a process closes any file descriptor referring to a file,
// then all of the process's locks on that file are released,
// regardless of the file descriptor(s) on which the locks were
// obtained. This is bad: it means that a process can lose its
// locks on a file such as /etc/passwd or /etc/mtab when for some
// reason a library function decides to open, read, and close the
// same file.
// [...]
//
// Open file description locks solve both of these problems.
//
// OFD's description implies it inherits non-ofd behaviour
// I wanted to confirm a l_len zero would work to lock all contents,
// even on expansion of the file. The docs didn't mention anything;
// however, I don't really see any real difference len processing in
// the kernel. Furthermore, I saw the kernels implementation checking
// for MAX_OFFSET of int type (-1) before overloading l_len with zero.
//
// I assume this will work. Linux locking is trash.
return ::fcntl(fd, F_OFD_SETLK, &lck) == 0;
#endif
}
bool ApplyFileSectionLock(AuSPtr<IIOHandle> pHandle,
EFileAdvisoryLockLevel level,
AuUInt64 uOffset,
AuUInt64 uLength)
{
int lease {};
auto opt = pHandle->GetOSHandleSafe();
if (!opt)
{
SysPushErrorIOResourceRejected();
return false;
}
int fd = (int)opt.ValueOr((int)-1);
if (fd == -1)
{
SysPushErrorIOResourceRejected();
return false;
}
switch (level)
{
case EFileAdvisoryLockLevel::eEnumCount:
case EFileAdvisoryLockLevel::eNoSafety:
return true;
case EFileAdvisoryLockLevel::eBlockWrite:
lease = F_RDLCK;
break;
case EFileAdvisoryLockLevel::eBlockReadWrite:
lease = F_WRLCK;
break;
}
struct flock lck =
{
.l_whence = SEEK_SET,
.l_start = uLength,
.l_len = uOffset,
.l_type = lease
};
#if defined(AURORA_IS_LINUX_DERIVED)
return ::fcntl(fd, F_OFD_SETLK, &lck) == 0;
#else
return ::fcntl(fd, F_SETLK, &lck) == 0;
#endif
}
bool UnapplyFileSectionLock(AuSPtr<IIOHandle> pHandle,
AuUInt64 uOffset,
AuUInt64 uLength)
{
auto opt = pHandle->GetOSHandleSafe();
if (!opt)
{
SysPushErrorIOResourceRejected();
return false;
}
int fd = (int)opt.ValueOr((int)-1);
if (fd == -1)
{
SysPushErrorIOResourceRejected();
return false;
}
struct flock lck =
{
.l_whence = SEEK_SET,
.l_start = uLength,
.l_len = uOffset,
.l_type = F_UNLCK
};
#if defined(AURORA_IS_LINUX_DERIVED)
return ::fcntl(fd, F_OFD_SETLK, &lck) == 0;
#else
return ::fcntl(fd, F_SETLK, &lck) == 0;
#endif
}
}