Implement getting of covers and add tests for it

src/calibre/db/backend.py

@@ -16,15 +16,14 @@ import apsw
 from calibre import isbytestring, force_unicode, prints
 from calibre.constants import (iswindows, filesystem_encoding,
         preferred_encoding)
-from calibre.ptempfile import PersistentTemporaryFile, SpooledTemporaryFile
-from calibre.db import SPOOL_SIZE
+from calibre.ptempfile import PersistentTemporaryFile
 from calibre.db.schema_upgrades import SchemaUpgrade
 from calibre.library.field_metadata import FieldMetadata
 from calibre.ebooks.metadata import title_sort, author_to_author_sort
 from calibre.utils.icu import strcmp
 from calibre.utils.config import to_json, from_json, prefs, tweaks
 from calibre.utils.date import utcfromtimestamp, parse_date
-from calibre.utils.filenames import is_case_sensitive
+from calibre.utils.filenames import (is_case_sensitive, samefile, hardlink_file)
 from calibre.db.tables import (OneToOneTable, ManyToOneTable, ManyToManyTable,
         SizeTable, FormatsTable, AuthorsTable, IdentifiersTable,
         CompositeTable, LanguagesTable)
@@ -863,10 +862,16 @@ class DB(object):
     def has_format(self, book_id, fmt):
         return self.format_abspath(book_id, fmt) is not None
 
-    def cover(self, path, as_file=False, as_image=False,
-            as_path=False):
+    def copy_cover_to(self, path, dest, windows_atomic_move=None, use_hardlink=False):
         path = os.path.join(self.library_path, path, 'cover.jpg')
-        ret = None
+        if windows_atomic_move is not None:
+            if not isinstance(dest, basestring):
+                raise Exception("Error, you must pass the dest as a path when"
+                        " using windows_atomic_move")
+            if os.access(path, os.R_OK) and dest and not samefile(dest, path):
+                windows_atomic_move.copy_path_to(path, dest)
+                return True
+        else:
             if os.access(path, os.R_OK):
                 try:
                     f = lopen(path, 'rb')
@@ -874,23 +879,22 @@ class DB(object):
                     time.sleep(0.2)
                 f = lopen(path, 'rb')
                 with f:
-                if as_path:
-                    pt = PersistentTemporaryFile('_dbcover.jpg')
-                    with pt:
-                        shutil.copyfileobj(f, pt)
-                    return pt.name
-                if as_file:
-                    ret = SpooledTemporaryFile(SPOOL_SIZE)
-                    shutil.copyfileobj(f, ret)
-                    ret.seek(0)
-                else:
-                    ret = f.read()
-                    if as_image:
-                        from PyQt4.Qt import QImage
-                        i = QImage()
-                        i.loadFromData(ret)
-                        ret = i
-        return ret
+                    if hasattr(dest, 'write'):
+                        shutil.copyfileobj(f, dest)
+                        if hasattr(dest, 'flush'):
+                            dest.flush()
+                        return True
+                    elif dest and not samefile(dest, path):
+                        if use_hardlink:
+                            try:
+                                hardlink_file(path, dest)
+                                return True
+                            except:
+                                pass
+                        with lopen(dest, 'wb') as d:
+                            shutil.copyfileobj(f, d)
+                        return True
+        return False
 
    # }}}
 

src/calibre/db/cache.py

@@ -8,9 +8,11 @@ __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import os, traceback
+from io import BytesIO
 from collections import defaultdict
 from functools import wraps, partial
 
+from calibre.db import SPOOL_SIZE
 from calibre.db.categories import get_categories
 from calibre.db.locking import create_locks, RecordLock
 from calibre.db.fields import create_field
@@ -18,6 +20,7 @@ from calibre.db.search import Search
 from calibre.db.tables import VirtualTable
 from calibre.db.lazy import FormatMetadata, FormatsList
 from calibre.ebooks.metadata.book.base import Metadata
+from calibre.ptempfile import PersistentTemporaryFile, SpooledTemporaryFile
 from calibre.utils.date import now
 from calibre.utils.icu import sort_key
 
@@ -397,15 +400,43 @@ class Cache(object):
         :param as_path: If True return the image as a path pointing to a
                         temporary file
         '''
+        if as_file:
+            ret = SpooledTemporaryFile(SPOOL_SIZE)
+            if not self.copy_cover_to(book_id, ret): return
+            ret.seek(0)
+        elif as_path:
+            pt = PersistentTemporaryFile('_dbcover.jpg')
+            with pt:
+                if not self.copy_cover_to(book_id, pt): return
+            ret = pt.name
+        else:
+            buf = BytesIO()
+            if not self.copy_cover_to(book_id, buf): return
+            ret = buf.getvalue()
+            if as_image:
+                from PyQt4.Qt import QImage
+                i = QImage()
+                i.loadFromData(ret)
+                ret = i
+        return ret
+
+    @api
+    def copy_cover_to(self, book_id, dest):
+        '''
+        Copy the cover to the file like object ``dest``. Returns False
+        if no cover exists or dest is the same file as the current cover.
+        dest can also be a path in which case the cover is
+        copied to it iff the path is different from the current path (taking
+        case sensitivity into account).
+        '''
         with self.read_lock:
             try:
                 path = self._field_for('path', book_id).replace('/', os.sep)
             except:
-                return None
+                return False
 
         with self.record_lock.lock(book_id):
-            return self.backend.cover(path, as_file=as_file, as_image=as_image,
-                    as_path=as_path)
+            return self.backend.copy_cover_to(path, dest)
 
     @read_api
     def multisort(self, fields, ids_to_sort=None):

src/calibre/db/tests/reading.py

@@ -176,6 +176,10 @@ class ReadingTest(BaseTest):
         old_metadata = {i:old.get_metadata(
             i, index_is_id=True, get_cover=True, cover_as_data=True) for i in
                 xrange(1, 4)}
+        for mi in old_metadata.itervalues():
+            mi.format_metadata = dict(mi.format_metadata)
+            if mi.formats:
+                mi.formats = tuple(mi.formats)
         old = None
 
         cache = self.init_cache(self.library_path)
@@ -186,6 +190,24 @@ class ReadingTest(BaseTest):
         for mi2, mi1 in zip(new_metadata.values(), old_metadata.values()):
             self.compare_metadata(mi1, mi2)
 
+    def test_get_cover(self): # {{{
+        'Test cover() returns the same data for both backends'
+        from calibre.library.database2 import LibraryDatabase2
+        old = LibraryDatabase2(self.library_path)
+        covers = {i: old.cover(i, index_is_id=True) for i in (1, 2, 3)}
+        old = None
+        cache = self.init_cache(self.library_path)
+        for book_id, cdata in covers.iteritems():
+            self.assertEqual(cdata, cache.cover(book_id), 'Reading of cover failed')
+            f = cache.cover(book_id, as_file=True)
+            self.assertEqual(cdata, f.read() if f else f, 'Reading of cover as file failed')
+            if cdata:
+                with open(cache.cover(book_id, as_path=True), 'rb') as f:
+                    self.assertEqual(cdata, f.read(), 'Reading of cover as path failed')
+            else:
+                self.assertEqual(cdata, cache.cover(book_id, as_path=True),
+                                 'Reading of null cover as path failed')
+
     # }}}
 
     def test_searching(self): # {{{