roverlay/util/fileio: TextFile class

object representing a text file (with a 'dirty' flag)

1 files changed, 184 insertions, 0 deletions

diff --git a/roverlay/util/fileio.py b/roverlay/util/fileio.py
index a8d2e01..151e7f1 100644
--- a/roverlay/util/fileio.py
+++ b/roverlay/util/fileio.py
@@ -8,8 +8,12 @@ import gzip
 import bz2
 import mimetypes
 import sys
+import os.path
+import shutil
+import errno
 
 import roverlay.util.common
+import roverlay.util.objects
 import roverlay.strutil
 from roverlay.strutil import bytes_try_decode
 
@@ -145,3 +149,183 @@ def write_text_file (
 
    return True
 # --- end of write_text_file (...) ---
+
+
+class TextFile ( roverlay.util.objects.PersistentContent ):
+
+   READ_PREPARSE   = True
+   READ_TRY_HARDER = True
+
+   def __init__ ( self, filepath, compression=None ):
+      super ( TextFile, self ).__init__()
+
+      self._filepath    = None
+      self._compression = None
+
+      self.first_line   = None
+      self.lino         = None
+
+      self.set_filepath ( filepath )
+      self.set_compression ( compression )
+   # --- end of __init__ (...) ---
+
+   @roverlay.util.objects.abstractmethod
+   def parse_line ( self, line ):
+      return True
+   # --- end of parse_line (...) ---
+
+   def parse_header_line ( self, line ):
+      return self.parse_line ( line )
+   # --- end of parse_header_line (...) ---
+
+   @roverlay.util.objects.abstractmethod
+   def gen_lines ( self ):
+      #yield ...
+      return
+   # --- end of gen_lines (...) ---
+
+   def start_reading ( self ):
+      pass
+   # --- end of start_reading (...) ---
+
+   def done_reading ( self ):
+      pass
+   # --- end of done_reading (...) ---
+
+   def set_filepath ( self, filepath ):
+      self._filepath = filepath
+   # --- end of set_filepath (...) ---
+
+   def set_compression ( self, compression ):
+      if not compression or compression in { 'default', 'none' }:
+         self._compression = None
+      elif compression in SUPPORTED_COMPRESSION:
+         self._compression = compression
+      else:
+         raise ValueError (
+            "unknown file compression {!r}".format ( compression )
+         )
+   # --- end of set_compression (...) ---
+
+   def backup_file ( self, destfile=None, move=False, ignore_missing=False ):
+      """Creates a backup copy of the file.
+
+      arguments:
+      * destfile       -- backup file path
+                          Defaults to <dfile> + '.bak'.
+      * move           -- move dfile (instead of copying)
+      * ignore_missing -- return False if file does not exist instead of
+                          raising an exception. Defaults to False.
+      """
+      dest = destfile or ( self._filepath + '.bak' )
+      try:
+         roverlay.util.dodir ( os.path.dirname ( dest ), mkdir_p=True )
+         if move:
+            shutil.move ( self._filepath, dest )
+            return True
+         else:
+            shutil.copyfile ( self._filepath, dest )
+            return True
+      except IOError as ioerr:
+         if ignore_missing and ioerr.errno == errno.ENOENT:
+            return False
+         else:
+            raise
+   # --- end of backup_file (...) ---
+
+   def backup_and_write ( self,
+      destfile=None, backup_file=None,
+      force=False, move=False, ignore_missing=True
+   ):
+      """Creates a backup copy of the distmap file and writes the modified
+      distmap afterwards.
+
+      arguments:
+      * destfile       -- file path to be written (defaults to self._filepath)
+      * backup_file    -- backup file path (see backup_file())
+      * force          -- enforce writing even if file content not modified
+      * move           -- move distmap (see backup_file())
+      * ignore_missing -- do not fail if the file does not exist when
+                          creating a backup copy.
+                          Defaults to True.
+      """
+      if force or self.dirty:
+         self.backup_file (
+            destfile=backup_file, move=move, ignore_missing=ignore_missing
+         )
+         return self.write ( filepath=destfile, force=True )
+      else:
+         return True
+   # --- end of backup_and_write (...) ---
+
+   def file_exists ( self ):
+      """Returns True if the file exists, else False."""
+      return os.path.isfile ( self._filepath )
+   # --- end of file_exists (...) ---
+
+   def try_read ( self, *args, **kwargs ):
+      """Tries to read the file."""
+      try:
+         self.read ( *args, **kwargs )
+      except IOError as ioerr:
+         if ioerr.errno == errno.ENOENT:
+            pass
+         else:
+            raise
+   # --- end of try_read (...) ---
+
+   def read ( self, filepath=None ):
+      """Reads the file.
+
+      arguments:
+      * filepath -- path to the distmap file (defaults to self.dbfile)
+      """
+      fpath = self._filepath if filepath is None else filepath
+
+      self.start_reading()
+
+      self.first_line = True
+      self.lino       = 0
+      for lino, line in enumerate (
+         read_text_file ( fpath,
+            preparse=self.READ_PREPARSE, try_harder=self.READ_TRY_HARDER
+         )
+      ):
+         self.lino = lino
+         if self.first_line:
+            self.first_line = False
+            # parse_header_line() can reset first_line to True
+            self.parse_header_line ( line )
+         else:
+            self.parse_line ( line )
+
+      if filepath is not None:
+         self.set_dirty()
+
+      self.done_reading()
+   # --- end of read (...) ---
+
+   def write ( self, filepath=None, force=False ):
+      """Writes the file.
+
+      arguments:
+      * filepath -- path to the file to be written (defaults to self._filepath)
+      * force    -- enforce writing even if file content not modified
+      """
+      if force or self.dirty or filepath is not None:
+         fpath = self._filepath if filepath is None else filepath
+         write_text_file (
+            fpath, self.gen_lines(),
+            compression=self._compression, create_dir=True
+         )
+
+         if filepath is None:
+            self.reset_dirty()
+         # else keep
+
+         return True
+      else:
+         return False
+   # --- end of write (...) ---
+
+# --- end of TextFile ---