Project 4 Virtual machine threading API (I Solved in C)

ECS150
Project 4

You will be working with a partner for this project, you specify your partner in your
readme file. This specification is subject to change at anytime for additional clarification.
For this project, you and a partner will be implementing a virtual machine threading API
in either C or C++. Your virtual machine will be tested on the CSIF machines. You
must submit your source files, readme and Makefile in a tgz file to Canvas prior to the
deadline.
You will be continuing the development of your virtual machine. You will be adding the
ability to mount and manipulate a FAT file system image. Except were specified in this
description the API will remain as stated in the Project 2 & 3 descriptions. Files that are
opened in the virtual machine will now be opened on the FAT image instead of in the
host file system. The reading and writing of the files will affect the FAT image with the
exception of file descriptor 0 – 2, which will still affect the standard in, out, and error
files. The fatgen103.pdf in the resources is the Microsoft white paper on FAT. You do
not need to fully implement all possible FAT file systems. You may make the following
assumptions:
1. All images have 512 byte sectors
2. All images are FAT 16
3. Long file name entries will contiguously proceed the corresponding short file
name entry
You must implement the ability to create, read and write files that are in the root
directory and to open and read the root directory. You must be able to read all of the short
file name entries (long file name entries can be skipped) in the root directory.
A working example of the vm and apps can be found in /home/cjnitta/ecs150. The vm
syntax is vm [options] appname [appargs]. The possible options for vm are -t, -h, -s and -
f; -t specifies the tick time in millisecond, -h specifies the size of the heap this is the size
of the VM_MEMORY_POOL_ID_SYSTEM memory pool, -s specifies the size of the
shared memory used between the virtual machine and machine, and -f specifies the FAT
image to be mounted. By default the tick time is set to 100ms, for debugging purposes
you can increase this value to slow the running of the vm. The size of the heap by default
is 16MiB, and the shared memory is 16KiB. The default FAT image is fat.ima. When
specifying the application name the ./ should be prepended otherwise vm may fail to load
the shared object file. In addition you will find several programs that will help create and
manipulate the fat images in the /home/cjnitta/ecs150 directory.
Several functions have been provided for you in the VirtualMachineUtils.c that you
might find useful, not all will be necessary: VMDateTime,
VMFileSystemValidPathName, VMFileSystemIsRelativePath,
VMFileSystemIsAbsolutePath, VMFileSystemGetAbsolutePath,
VMFileSystemPathIsOnMount, VMFileSystemDirectoryFromFullPath,
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VMFileSystemFileFromFullPath, VMFileSystemConsolidatePath,
VMFileSystemSimplifyPath, VMFileSystemRelativePath.
The function specifications for both the virtual machine and machine are provided in the
subsequent pages.
You should avoid using existing source code as a primer that is currently available on the
Internet. You must specify in your readme file any sources of code that you or your
partner have viewed to help you complete this project. All class projects will be
submitted to MOSS to determine if pairs of students have excessively collaborated with
other pairs. Excessive collaboration, or failure to list external code sources will result in
the matter being transferred to Student Judicial Affairs.
Extra Credit:
Add support for subdirectories, this includes creating, deleting, and modifying files and
directories anywhere in the directory structure. Implement the VMDirectoryUnlink and
VMDirectoryCreate functions. Add support for long file names, the long file names
should be both read correctly from directories as well as created when new files are
added to the mounted file system.
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Name
VMStart – Start the virtual machine.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMStart(int tickms, TVMMemorySize heapsize, TVMMemorySize
sharedsize, const char *mount,
int argc, char *argv[]);
Description
VMStart() starts the virtual machine by loading the module specified by argv[0]. The
argc and argv are passed directly into the VMMain() function that exists in the loaded
module. The time in milliseconds of the virtual machine tick is specified by the tickms
parameter. The heap size of the virtual machine is specified by heapsize. The heap is
accessed by the applications through the VM_MEMORY_POOL_ID_SYSTEM memory
pool. The size of the shared memory space between the virtual machine and the machine
is specified by the sharedsize. The name of the FAT file system image is specified by
mount.
Return Value
Upon successful loading and running of the VMMain() function, VMStart() will return
VM_STATUS_SUCCESS after VMMain() returns. If the module fails to load, or the
module does not contain a VMMain() function, or if the mount FAT file system image
cannot be loaded, VM_STATUS_FAILURE is returned.
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Name
VMFileOpen – Opens and possibly creates a file in the mounted FAT file system.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMFileOpen(const char *filename, int flags, int mode,
int *filedescriptor);
Description
VMFileOpen() attempts to open the file specified by filename, using the flags specified
by flags parameter, and mode specified by mode parameter. The file descriptor of the
newly opened file will be placed in the location specified by filedescriptor. The flags and
mode values follow the same format as that of open system call. The filedescriptor
returned can be used in subsequent calls to VMFileClose(), VMFileRead(),
VMFileWrite(), and VMFileSeek(). When a thread calls VMFileOpen() it blocks in the
wait state VM_THREAD_STATE_WAITING until the either successful or unsuccessful
opening of the file is completed. In order to prevent confusion with standard in, out and
error, the file descriptor returned in the location specified by filedescriptor will be 3 or
larger.
Return Value
Upon successful opening of the file, VMFileOpen() returns VM_STATUS_SUCCESS,
upon failure VMFileOpen() returns VM_STATUS_FAILURE. If either filename or
filedescriptor are NULL, VMFileOpen() returns
VM_STATUS_ERROR_INVALID_PARAMETER.
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Name
VMFileClose – Closes a file that was previously opened in the mounted FAT file system.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMFileClose(int filedescriptor);
Description
VMFileClose() closes a file previously opened with a call to VMFileOpen().When a
thread calls VMFileClose() it blocks in the wait state
VM_THREAD_STATE_WAITING until the either successful or unsuccessful closing of
the file is completed.
Return Value
Upon successful closing of the file VMFileClose() returns VM_STATUS_SUCCESS,
upon failure VMFileClose() returns VM_STATUS_FAILURE.
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Name
VMFileRead – Reads data from a file.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMFileRead(int filedescriptor, void *data, int *length);
Description
VMFileRead() attempts to read the number of bytes specified in the integer referenced by
length into the location specified by data from the file specified by filedescriptor. The
filedescriptor should have been obtained by a previous call to VMFileOpen(). The actual
number of bytes transferred by the read will be updated in the length location. When a
thread calls VMFileRead() it blocks in the wait state VM_THREAD_STATE_WAITING
until the either successful or unsuccessful reading of the file is completed. If the
filedescriptor is less than 3 the reading will be attempted on the main file system, if the
value of filedescriptor is 3 or larger the reading will be attempted on the mounted FAT
file system file.
Return Value
Upon successful reading from the file, VMFileRead() returns VM_STATUS_SUCCESS,
upon failure VMFileRead() returns VM_STATUS_FAILURE. If data or length
parameters are NULL, VMFileRead() returns
VM_STATUS_ERROR_INVALID_PARAMETER.
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Name
VMFileWrite – Writes data to a file.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMFileWrite(int filedescriptor, void *data, int *length);
Description
VMFileWrite() attempts to write the number of bytes specified in the integer referenced
by length from the location specified by data to the file specified by filedescriptor. The
filedescriptor should have been obtained by a previous call to VMFileOpen(). The actual
number of bytes transferred by the write will be updated in the length location. When a
thread calls VMFileWrite() it blocks in the wait state
VM_THREAD_STATE_WAITING until the either successful or unsuccessful writing of
the file is completed. If the filedescriptor is less than 3 the writing will be attempted on
the main file system, if the value of filedescriptor is 3 or larger the writing will be
attempted on the mounted FAT file system file.
Return Value
Upon successful writing from the file, VMFileWrite() returns VM_STATUS_SUCCESS,
upon failure VMFileWrite() returns VM_STATUS_FAILURE. If data or length
parameters are NULL, VMFileWrite() returns
VM_STATUS_ERROR_INVALID_PARAMETER.
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Name
VMFileSeek – Seeks within a file.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMFileSeek(int filedescriptor, int offset, int whence,
int *newoffset);
Description
VMFileSeek() attempts to seek the number of bytes specified by offset from the location
specified by whence in the file specified by filedescriptor. The filedescriptor should have
been obtained by a previous call to VMFileOpen(). The new offset placed in the
newoffset location if the parameter is not NULL. When a thread calls VMFileSeek() it
blocks in the wait state VM_THREAD_STATE_WAITING until the either successful or
unsuccessful seeking in the file is completed. If the filedescriptor is less than 3 the
seeking will be attempted on the main file system, if the value of filedescriptor is 3 or
larger the seeking will be attempted on the mounted FAT file system file.
Return Value
Upon successful seeking in the file, VMFileSeek () returns VM_STATUS_SUCCESS,
upon failure VMFileSeek() returns VM_STATUS_FAILURE.
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Name
VMDirectoryOpen – Opens a directory for reading in the mounted FAT file system.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryOpen(const char *dirname, int *dirdescriptor);
Description
VMDirectoryOpen() attempts to open the directory specified by dirname. The directory
descriptor of the newly opened directory will be placed in the location specified by
dirdescriptor. The directory descriptor returned can be used in subsequent calls to
VMDirectoryClose(), VMDirectoryRead(), and VMDirectoryRewind(). When a thread
calls VMDirectoryOpen() it must block in the wait state
VM_THREAD_STATE_WAITING if the opening of the directory cannot be completed
immediately. In order to prevent confusion with standard in, out and error, the file
descriptor returned in the location specified by dirdescriptor will be 3 or larger.
Return Value
Upon successful opening of the directory, VMDirectoryOpen() returns
VM_STATUS_SUCCESS, upon failure VMDirectoryOpen() returns
VM_STATUS_FAILURE. If either dirname or dirdescriptor are NULL,
VMDirectoryOpen() returns VM_STATUS_ERROR_INVALID_PARAMETER.
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Name
VMDirectoryClose – Closes a directory that was previously opened in the mounted FAT
file system.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryClose(int dirdescriptor);
Description
VMDirectoryClose() closes a directory previously opened with a call to
VMDirectoryOpen().When a thread calls VMDirectoryClose() it blocks in the wait state
VM_THREAD_STATE_WAITING if the closing of the directory cannot be completed
immediately.
Return Value
Upon successful closing of the directory VMDirectoryClose() returns
VM_STATUS_SUCCESS, upon failure VMDirectoryClose() returns
VM_STATUS_FAILURE.
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Name
VMDirectoryRead – Reads a directory entry from a directory in the mounted FAT file
system.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryRead(int dirdescriptor,
SVMDirectoryEntryRef dirent);
Description
VMDirectoryRead() attempts to read the next directory entry into the location specified
by dirent from the file specified by dirdescriptor. The dirdescriptor should have been
obtained by a previous call to VMDirectoryOpen(). When a thread calls
VMDirectoryRead() it blocks in the wait state VM_THREAD_STATE_WAITING if the
reading of the directory entry cannot be completed immediately.
Return Value
Upon successful reading from the directory, VMDirectoryRead() returns
VM_STATUS_SUCCESS, upon failure VMDirectoryRead() returns
VM_STATUS_FAILURE. If dirent parameter is NULL, VMDirectoryRead() returns
VM_STATUS_ERROR_INVALID_PARAMETER.
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Name
VMDirectoryRewind – Rewinds a previously opened directory to the beginning.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryRewind(int dirdescriptor);
Description
VMDirectoryRewind() attempts to rewind the directory specified by dirdescriptor to the
beginning. The dirdescriptor should have been obtained by a previous call to
VMDirectoryOpen(). When a thread calls VMDirectoryRewind() it should block in the
wait state VM_THREAD_STATE_WAITING if it is not possible to complete the rewind
operation immediately.
Return Value
Upon successful rewinding of the directory, VMDirectoryRewind() returns
VM_STATUS_SUCCESS, upon failure VMDirectoryRewind() returns
VM_STATUS_FAILURE.
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Name
VMDirectoryCurrent – Fill the absolute path with the current working directory in the
mounted FAT filesystem.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryCurrent(char *abspath);
Description
VMDirectoryCurrent() attempts to place the absolute path of the current working
directory in the location specified by abspath.
Return Value
Upon successful copying of the directory name into abspath, VMDirectoryCurrent()
returns VM_STATUS_SUCCESS, if abspath is NULL then VMDirectoryCurrent()
returns VM_STATUS_INVALID_PARAMETER.
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Name
VMDirectoryChange – Changes the current working directory of the mounted FAT file
system.
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryChange(const char *path);
Description
VMDirectoryChange() attempts to change the current working directory of the mounted
FAT file system to the name specified by path.
Return Value
Upon successful changing of the directory to path, VMDirectoryChange() returns
VM_STATUS_SUCCESS, if path specified by path does not exist,
VMDirectoryChange() returns VM_STATUS_FAILURE. If path is NULL then
VMDirectoryChange() returns VM_STATUS_INVALID_PARAMETER.
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Name
VMDirectoryCreate – Attempts to create a directory in the mounted FAT file system.
(EXTRA CREDIT ONLY)
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryCreate(const char *dirname);
Description
VMDirectoryCreate() attempts to create a directory in the mounted FAT file system
specified by dirname.
Return Value
Upon successful creation of the directory, VMDirectoryCreate() returns
VM_STATUS_SUCCESS, if dirname is NULL then VMDirectoryCreate() returns
VM_STATUS_INVALID_PARAMETER. If the directory is unable to be created,
VMDirectoryCreate() returns VM_STATUS_FAILURE.
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Name
VMDirectoryUnlink – Removes a directory or file from the mounted FAT file system.
(EXTRA CREDIT ONLY)
Synopsys
#include "VirtualMachine.h"
TVMStatus VMDirectoryUnlink(const char *path);
Description
VMDirectoryUnlink() attempts to remove the file or directory specified by path from the
mounted FAT file system. VMDirectoryUnlink() will fail if the file or directory is current
opened, or if the directory attempting to be unlinked is a parent of an open file or
directory.
Return Value
Upon successful removing of the directory or file, VMDirectoryUnlink() returns
VM_STATUS_SUCCESS, upon failure VMDirectoryUnlink() returns
VM_STATUS_FAILURE. If path is NULL then VMDirectoryUnlink() returns
VM_STATUS_INVALID_PARAMETER.