Source code for mxnet.recordio
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"""Read and write for the RecordIO data format."""
from collections import namedtuple
from multiprocessing import current_process
import ctypes
import struct
import numbers
import numpy as np
from .base import _LIB
from .base import RecordIOHandle
from .base import check_call
from .base import c_str
try:
import cv2
except ImportError:
cv2 = None
[docs]class MXRecordIO(object):
"""Reads/writes `RecordIO` data format, supporting sequential read and write.
Examples
---------
>>> record = mx.recordio.MXRecordIO('tmp.rec', 'w')
<mxnet.recordio.MXRecordIO object at 0x10ef40ed0>
>>> for i in range(5):
... record.write('record_%d'%i)
>>> record.close()
>>> record = mx.recordio.MXRecordIO('tmp.rec', 'r')
>>> for i in range(5):
... item = record.read()
... print(item)
record_0
record_1
record_2
record_3
record_4
>>> record.close()
Parameters
----------
uri : string
Path to the record file.
flag : string
'w' for write or 'r' for read.
"""
def __init__(self, uri, flag):
self.uri = c_str(uri)
self.handle = RecordIOHandle()
self.flag = flag
self.pid = None
self.is_open = False
self.open()
[docs] def open(self):
"""Opens the record file."""
if self.flag == "w":
check_call(_LIB.MXRecordIOWriterCreate(self.uri, ctypes.byref(self.handle)))
self.writable = True
elif self.flag == "r":
check_call(_LIB.MXRecordIOReaderCreate(self.uri, ctypes.byref(self.handle)))
self.writable = False
else:
raise ValueError(f"Invalid flag {self.flag}")
# pylint: disable=not-callable
# It's bug from pylint(astroid). See https://github.com/PyCQA/pylint/issues/1699
self.pid = current_process().pid
self.is_open = True
def __del__(self):
self.close()
def __getstate__(self):
"""Override pickling behavior."""
# pickling pointer is not allowed
is_open = self.is_open
self.close()
d = dict(self.__dict__)
d['is_open'] = is_open
uri = self.uri.value
try:
uri = uri.decode('utf-8')
except AttributeError:
pass
del d['handle']
d['uri'] = uri
return d
def __setstate__(self, d):
"""Restore from pickled."""
self.__dict__ = d
is_open = d['is_open']
self.is_open = False
self.handle = RecordIOHandle()
self.uri = c_str(self.uri)
if is_open:
self.open()
def _check_pid(self, allow_reset=False):
"""Check process id to ensure integrity, reset if in new process."""
# pylint: disable=not-callable
# It's bug from pylint(astroid). See https://github.com/PyCQA/pylint/issues/1699
if not self.pid == current_process().pid:
if allow_reset:
self.reset()
else:
raise RuntimeError("Forbidden operation in multiple processes")
[docs] def close(self):
"""Closes the record file."""
if not self.is_open:
return
if self.writable:
check_call(_LIB.MXRecordIOWriterFree(self.handle))
else:
check_call(_LIB.MXRecordIOReaderFree(self.handle))
self.is_open = False
self.pid = None
[docs] def reset(self):
"""Resets the pointer to first item.
If the record is opened with 'w', this function will truncate the file to empty.
Examples
---------
>>> record = mx.recordio.MXRecordIO('tmp.rec', 'r')
>>> for i in range(2):
... item = record.read()
... print(item)
record_0
record_1
>>> record.reset() # Pointer is reset.
>>> print(record.read()) # Started reading from start again.
record_0
>>> record.close()
"""
self.close()
self.open()
[docs] def write(self, buf):
"""Inserts a string buffer as a record.
Examples
---------
>>> record = mx.recordio.MXRecordIO('tmp.rec', 'w')
>>> for i in range(5):
... record.write('record_%d'%i)
>>> record.close()
Parameters
----------
buf : string (python2), bytes (python3)
Buffer to write.
"""
assert self.writable
self._check_pid(allow_reset=False)
check_call(_LIB.MXRecordIOWriterWriteRecord(self.handle,
ctypes.c_char_p(buf),
ctypes.c_size_t(len(buf))))
[docs] def read(self):
"""Returns record as a string.
Examples
---------
>>> record = mx.recordio.MXRecordIO('tmp.rec', 'r')
>>> for i in range(5):
... item = record.read()
... print(item)
record_0
record_1
record_2
record_3
record_4
>>> record.close()
Returns
----------
buf : string
Buffer read.
"""
assert not self.writable
# trying to implicitly read from multiple processes is forbidden,
# there's no elegant way to handle unless lock is introduced
self._check_pid(allow_reset=False)
buf = ctypes.c_char_p()
size = ctypes.c_size_t()
check_call(_LIB.MXRecordIOReaderReadRecord(self.handle,
ctypes.byref(buf),
ctypes.byref(size)))
if buf:
buf = ctypes.cast(buf, ctypes.POINTER(ctypes.c_char*size.value))
return buf.contents.raw
else:
return None
[docs]class MXIndexedRecordIO(MXRecordIO):
"""Reads/writes `RecordIO` data format, supporting random access.
Examples
---------
>>> for i in range(5):
... record.write_idx(i, 'record_%d'%i)
>>> record.close()
>>> record = mx.recordio.MXIndexedRecordIO('tmp.idx', 'tmp.rec', 'r')
>>> record.read_idx(3)
record_3
Parameters
----------
idx_path : str
Path to the index file.
uri : str
Path to the record file. Only supports seekable file types.
flag : str
'w' for write or 'r' for read.
key_type : type
Data type for keys.
"""
def __init__(self, idx_path, uri, flag, key_type=int):
self.idx_path = idx_path
self.idx = {}
self.keys = []
self.key_type = key_type
self.fidx = None
super(MXIndexedRecordIO, self).__init__(uri, flag)
[docs] def open(self):
super(MXIndexedRecordIO, self).open()
self.fidx = open(self.idx_path, self.flag)
if self.writable:
self.idx = {}
self.keys = []
elif not self.idx:
for line in iter(self.fidx.readline, ''):
line = line.strip().split('\t')
key = self.key_type(line[0])
self.idx[key] = int(line[1])
self.keys.append(key)
[docs] def close(self):
"""Closes the record file."""
if not self.is_open:
return
super(MXIndexedRecordIO, self).close()
self.fidx.close()
def __getstate__(self):
"""Override pickling behavior."""
d = super(MXIndexedRecordIO, self).__getstate__()
d['fidx'] = None
return d
[docs] def seek(self, idx):
"""Sets the current read pointer position.
This function is internally called by `read_idx(idx)` to find the current
reader pointer position. It doesn't return anything."""
assert not self.writable
self._check_pid(allow_reset=True)
pos = ctypes.c_size_t(self.idx[idx])
check_call(_LIB.MXRecordIOReaderSeek(self.handle, pos))
[docs] def tell(self):
"""Returns the current position of write head.
Examples
---------
>>> record = mx.recordio.MXIndexedRecordIO('tmp.idx', 'tmp.rec', 'w')
>>> print(record.tell())
0
>>> for i in range(5):
... record.write_idx(i, 'record_%d'%i)
... print(record.tell())
16
32
48
64
80
"""
assert self.writable
pos = ctypes.c_size_t()
check_call(_LIB.MXRecordIOWriterTell(self.handle, ctypes.byref(pos)))
return pos.value
[docs] def read_idx(self, idx):
"""Returns the record at given index.
Examples
---------
>>> record = mx.recordio.MXIndexedRecordIO('tmp.idx', 'tmp.rec', 'w')
>>> for i in range(5):
... record.write_idx(i, 'record_%d'%i)
>>> record.close()
>>> record = mx.recordio.MXIndexedRecordIO('tmp.idx', 'tmp.rec', 'r')
>>> record.read_idx(3)
record_3
"""
self.seek(idx)
return self.read()
[docs] def write_idx(self, idx, buf):
"""Inserts input record at given index.
Examples
---------
>>> for i in range(5):
... record.write_idx(i, 'record_%d'%i)
>>> record.close()
Parameters
----------
idx : int
Index of a file.
buf :
Record to write.
"""
key = self.key_type(idx)
pos = self.tell()
self.write(buf)
self.fidx.write(f'{str(key)}\t{pos}\n')
self.idx[key] = pos
self.keys.append(key)
IRHeader = namedtuple('HEADER', ['flag', 'label', 'id', 'id2'])
"""An alias for HEADER. Used to store metadata (e.g. labels) accompanying a record.
See mxnet.recordio.pack and mxnet.recordio.pack_img for example uses.
Parameters
----------
flag : int
Available for convenience, can be set arbitrarily.
label : float or an array of float
Typically used to store label(s) for a record.
id: int
Usually a unique id representing record.
id2: int
Higher order bits of the unique id, should be set to 0 (in most cases).
"""
_IR_FORMAT = 'IfQQ'
_IR_SIZE = struct.calcsize(_IR_FORMAT)
[docs]def pack(header, s):
"""Pack a string into MXImageRecord.
Parameters
----------
header : IRHeader
Header of the image record.
``header.label`` can be a number or an array. See more detail in ``IRHeader``.
s : str
Raw image string to be packed.
Returns
-------
s : str
The packed string.
Examples
--------
>>> label = 4 # label can also be a 1-D array, for example: label = [1,2,3]
>>> id = 2574
>>> header = mx.recordio.IRHeader(0, label, id, 0)
>>> with open(path, 'r') as file:
... s = file.read()
>>> packed_s = mx.recordio.pack(header, s)
"""
header = IRHeader(*header)
if isinstance(header.label, numbers.Number):
header = header._replace(flag=0)
else:
label = np.asarray(header.label, dtype=np.float32)
header = header._replace(flag=label.size, label=0)
s = label.tostring() + s
s = struct.pack(_IR_FORMAT, *header) + s
return s
[docs]def unpack(s):
"""Unpack a MXImageRecord to string.
Parameters
----------
s : str
String buffer from ``MXRecordIO.read``.
Returns
-------
header : IRHeader
Header of the image record.
s : str
Unpacked string.
Examples
--------
>>> record = mx.recordio.MXRecordIO('test.rec', 'r')
>>> item = record.read()
>>> header, s = mx.recordio.unpack(item)
>>> header
HEADER(flag=0, label=14.0, id=20129312, id2=0)
"""
header = IRHeader(*struct.unpack(_IR_FORMAT, s[:_IR_SIZE]))
s = s[_IR_SIZE:]
if header.flag > 0:
header = header._replace(label=np.frombuffer(s, np.float32, header.flag))
s = s[header.flag*4:]
return header, s
[docs]def unpack_img(s, iscolor=-1):
"""Unpack a MXImageRecord to image.
Parameters
----------
s : str
String buffer from ``MXRecordIO.read``.
iscolor : int
Image format option for ``cv2.imdecode``.
Returns
-------
header : IRHeader
Header of the image record.
img : numpy.ndarray
Unpacked image.
Examples
--------
>>> record = mx.recordio.MXRecordIO('test.rec', 'r')
>>> item = record.read()
>>> header, img = mx.recordio.unpack_img(item)
>>> header
HEADER(flag=0, label=14.0, id=20129312, id2=0)
>>> img
array([[[ 23, 27, 45],
[ 28, 32, 50],
...,
[ 36, 40, 59],
[ 35, 39, 58]],
...,
[[ 91, 92, 113],
[ 97, 98, 119],
...,
[168, 169, 167],
[166, 167, 165]]], dtype=uint8)
"""
header, s = unpack(s)
img = np.frombuffer(s, dtype=np.uint8)
assert cv2 is not None
img = cv2.imdecode(img, iscolor)
return header, img
[docs]def pack_img(header, img, quality=95, img_fmt='.jpg'):
"""Pack an image into ``MXImageRecord``.
Parameters
----------
header : IRHeader
Header of the image record.
``header.label`` can be a number or an array. See more detail in ``IRHeader``.
img : numpy.ndarray
Image to be packed.
quality : int
Quality for JPEG encoding in range 1-100, or compression for PNG encoding in range 1-9.
img_fmt : str
Encoding of the image (.jpg for JPEG, .png for PNG).
Returns
-------
s : str
The packed string.
Examples
--------
>>> label = 4 # label can also be a 1-D array, for example: label = [1,2,3]
>>> id = 2574
>>> header = mx.recordio.IRHeader(0, label, id, 0)
>>> img = cv2.imread('test.jpg')
>>> packed_s = mx.recordio.pack_img(header, img)
"""
assert cv2 is not None
jpg_formats = ['.JPG', '.JPEG']
png_formats = ['.PNG']
encode_params = None
if img_fmt.upper() in jpg_formats:
encode_params = [cv2.IMWRITE_JPEG_QUALITY, quality]
elif img_fmt.upper() in png_formats:
encode_params = [cv2.IMWRITE_PNG_COMPRESSION, quality]
ret, buf = cv2.imencode(img_fmt, img, encode_params)
assert ret, 'failed to encode image'
return pack(header, buf.tostring())
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