/
physical_view.py
180 lines (154 loc) · 5.65 KB
/
physical_view.py
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##
# Represents the physical view of the DFS.
##
import os.path
import shutil
import dfs_state
import error as err
from base import Base
from lock import Lock
shareFolderPath = os.path.expanduser("~/Share/")
saveStateName = '.state'
class PhysicalView(Base):
def __init__(self, dfs):
Base.__init__(self, dfs)
self.lock_ = Lock(dfs)
self.createBaseFolder()
def read(self, fileName, buf, offset, bufsize):
# TODO add thread safetly
filePath = os.path.join(self.getBasePath(), fileName)
size = self.getFileSize(fileName)
if offset + bufsize > size:
self.log_.w('tried to read ' + fileName + ' but size is ' + str(size) +
' and bufsize + offset = ' + str(offset + bufsize))
return err.InvalidBufferSize
self.lock_.acquire()
try:
f = open(filePath, "r")
except Exception, ex:
self.log_.e('error opening file in read mode ' + filePath + ': ' + str(ex))
self.lock_.release()
return err.FileNotFound
status = err.OK
f.seek(offset)
try:
data = f.read(bufsize)
for i, d in enumerate(data):
buf[i] = d
except Exception, ex:
self.log_.e('failed to read ' + filePath + ' from ' + str(offset) + ' to ' + str(offset + bufsize) + ': ' + str(ex))
status = err.CannotReadFile
f.close()
self.lock_.release()
return status
def write(self, fileName, buf, offset, bufsize):
status = err.OK
size = self.getFileSize(fileName)
self.lock_.acquire()
f = open(os.path.join(self.getBasePath(), fileName), "r+")
if(offset > size):
f.seek(0, 2)
f.write(' ' * (offset - size))
f.seek(offset)
try:
for i in range(bufsize):
f.write(buf[i])
except Exception, ex:
self.log_.e('failed to write ' + fileName + ' from ' + str(offset) + ' to ' + str(offset + bufsize) + ': ' + str(ex))
status = err.CannotReadFile
f.close()
self.lock_.release()
return status
def getChunk(self, fileName, chunk):
filePath = os.path.join(self.getBasePath(), fileName)
self.lock_.acquire()
try:
f = open(filePath, 'r')
except Exception, ex:
self.log_.e('getChunk - failed to open ' + filePath)
return None
data = None
try:
f.seek(chunk * dfs_state.CHUNK_SIZE)
data = f.read(dfs_state.CHUNK_SIZE)
except Exception, ex:
self.log_.e('getChunk - failed to seek to chunk ' + chunk + ' in ' + filePath)
f.close()
self.lock_.release()
return data
def writeChunk(self, fileName, chunkNum, data):
# Assume data is no longer than size CHUNK_SIZE
filePath = os.path.join(self.getBasePath(), fileName)
size = self.getFileSize(fileName)
if size < chunkNum * dfs_state.CHUNK_SIZE:
buf = [' '] * (chunkNum * dfs_state.CHUNK_SIZE - size)
self.write(fileName, buf, size, len(buf))
self.lock_.acquire()
f = open(filePath, "r+")
f.seek(chunkNum * dfs_state.CHUNK_SIZE)
f.write(data)
# Resize the file b/c the last chunk may be smaller then CHUNK_SIZE
if len(data) < dfs_state.CHUNK_SIZE: # is this the last chunk?
f.truncate()
f.close()
self.lock_.release()
def trim(self, fileName, size):
self.lock_.acquire()
filePath = os.path.join(self.getBasePath(), fileName)
f = open(filePath, 'r+')
f.truncate(size)
f.close()
self.lock_.release()
def getNumChunks(self, fileName):
self.lock_.acquire()
size = self.getFileSize(fileName)
self.lock_.release()
return int(size / dfs_state.CHUNK_SIZE) + 1
def copyFile(self, src, des):
self.lock_.acquire()
shutil.copyfile(os.path.join(self.getBasePath(), src), os.path.join(self.getBasePath(), des))
self.lock_.release()
def deleteFile(self, fileName):
self.lock_.acquire()
os.remove(os.path.join(self.getBasePath(), fileName))
self.lock_.release()
def writeState(self, serializedState):
path = os.path.join(self.getBasePath(), saveStateName)
self.lock_.acquire()
f = open(path, 'w')
f.write(serializedState)
f.close()
self.lock_.release()
def readState(self):
path = os.path.join(self.getBasePath(), saveStateName)
if not os.path.exists(path):
return None
self.lock_.acquire()
f = open(path, 'r')
state = f.read()
f.close()
self.lock_.release()
return state
##
# Private methods
##
def createBaseFolder(self):
if not os.path.isdir(shareFolderPath):
os.mkdir(shareFolderPath)
if not os.path.isdir(self.getBasePath()):
os.mkdir(self.getBasePath())
def exists(self, fileName):
return os.path.exists(os.path.join(self.getBasePath(), fileName))
def getBasePath(self):
dirName = "peer_" + str(self.dfs_.id)
return shareFolderPath + dirName + "/"
def fillEmptyFile(self, fileName, size):
self.lock_.acquire()
path = os.path.join(self.getBasePath(), fileName)
if not os.path.isfile(path):
w = open(path, 'w')
w.write(' ' * size) # fill the file with empty space
w.close()
self.lock_.release()
def getFileSize(self, fileName):
return os.path.getsize(os.path.join(self.getBasePath(), fileName))