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preetwinder
erp5
Commits
0fbad18f
Commit
0fbad18f
authored
May 31, 2012
by
Vincent Pelletier
Committed by
Sebastien Robin
Aug 07, 2014
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Plain Diff
Expose a storage-efficient way to access a large area.
parent
a10190ff
Changes
1
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1 changed file
with
23 additions
and
9 deletions
+23
-9
product/ERP5Type/BTreeData.py
product/ERP5Type/BTreeData.py
+23
-9
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product/ERP5Type/BTreeData.py
View file @
0fbad18f
from
cStringIO
import
StringIO
from
BTrees.LOBTree
import
LOBTree
from
persistent
import
Persistent
...
...
@@ -101,6 +100,21 @@ class BTreeData(Persistent):
Returns string of read data.
"""
return
''
.
join
(
self
.
iterate
(
offset
,
size
))
def
iterate
(
self
,
offset
=
0
,
size
=
None
):
"""
Return file data in storage-efficient chunks.
offset (int)
Offset of first byte to read.
size (int, None)
Number of bytes to read.
If None, the whole file is read.
Yields data chunks as they are read from storage (or locally generated,
when padding over sparse area).
"""
if
offset
<
0
:
raise
negative_offset_error
tree
=
self
.
_tree
...
...
@@ -113,15 +127,14 @@ class BTreeData(Persistent):
# - avoid loading last key if its past the end of read request
# Would simlify the loop, but might duplicate code... And CPU is not
# expected to be the bottleneck here.
result
=
StringIO
()
write
=
result
.
write
written
=
0
if
size
is
None
:
size
=
len
(
self
)
-
offset
next_byte
=
offset
for
key
in
tree
.
iterkeys
(
key
):
next_byte
=
offset
+
written
padding
=
min
(
size
,
key
-
next_byte
)
if
padding
>
0
:
write
(
'
\
x00
'
*
padding
)
written
+=
padding
next_byte
+=
padding
size
-=
padding
chunk_offset
=
0
else
:
...
...
@@ -134,10 +147,9 @@ class BTreeData(Persistent):
# cache by discarding chunks earlier.
chunk
.
_p_deactivate
()
to_write_len
=
len
(
to_write
)
write
(
to_write
)
size
-=
to_write_len
written
+=
to_write_len
return
result
.
getvalue
()
next_byte
+=
to_write_len
yield
to_write
def
truncate
(
self
,
offset
):
"""
...
...
@@ -173,8 +185,10 @@ if __name__ == '__main__':
def
check
(
tree
,
length
,
read_offset
,
read_length
,
data
,
keys
=
None
):
tree_length
=
len
(
tree
)
tree_data
=
tree
.
read
(
read_offset
,
read_length
)
tree_iterator_data
=
''
.
join
(
tree
.
iterate
(
read_offset
,
read_length
))
assert
tree_length
==
length
,
tree_length
assert
tree_data
==
data
,
repr
(
tree_data
)
assert
tree_iterator_data
==
data
,
repr
(
tree_iterator_data
)
if
keys
is
not
None
:
tree_keys
=
list
(
tree
.
_tree
.
keys
())
assert
tree_keys
==
keys
,
tree_keys
...
...
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