def __init__(self, path, fail_msg="cannot open 2bit file", debug=False): self.debug = debug self.file = OpenFile(path, "rb", fail_msg) self.ReadHeader() self.ReadSequenceIndices() self.ReadSequenceHeaders()
class TwoBitFileCls:
def __init__(self, path, fail_msg="cannot open 2bit file", debug=False):
self.debug = debug
self.file = OpenFile(path, "rb", fail_msg)
self.ReadHeader()
self.ReadSequenceIndices()
self.ReadSequenceHeaders()
# end def
def __del__(self):
self.file.close()
# end def
def ResetFile(self):
self.file.seek(0)
# end def
# field size in bytes
def ReadField(self, field_type=TWO_BIT_DEFAULT_TYPE):
if (field_type not in ELEMENT_LENGTHS):
raise TwoBitError("invalid number type: %s. Valid types: %s" %
(field_type, ", ".join(sorted(ELEMENT_LENGTHS.keys()))))
# end if
# read the number of bytes needed for one element of the specified type
num_bytes = ELEMENT_LENGTHS[field_type]
# bytes_str is a string of chars (each char is one byte)
bytes_str = self.file.read(num_bytes)
# convert to a tuple of numbers
bytes_tup = ConvertBytesToNumbers(bytes_str, self.byte_swap, field_type)
# return the first value of the tuple
return bytes_tup[0]
# if the field size was 1 byte (8 bits, 1 single char)
#if (1 == field_type):
# # convert to a tuple of chars
# bytes_tup = ConvertBytesToNumbers(bytes_str, self.byte_swap, "char")
# # return the value as a single long
# return bytes_tup[0]
## if the field size was 4 bytes (32 bits, 1 single long)
#if (TWO_BIT_FIELD_SIZE == field_type):
# # convert to a tuple of longs
# bytes_tup = ConvertBytesToNumbers(bytes_str, self.byte_swap, "long")
# # return the value as a single long
# return bytes_tup[0]
#else:
# raise TwoBitError \
# ("invalid field size: %i byte(s). Valid field sizes: " % field_type +
# "1 byte (8 bits), %i bytes (%i bits)" %
# (TWO_BIT_FIELD_SIZE, TWO_BIT_FIELD_SIZE*8))
# end if
# end def
def ReadChars(self, num_chars):
# just read the specified number of chars (1 byte per char) and return them
return self.file.read(num_chars)
# end def
def ReadArray(self, array_size, element_type=TWO_BIT_DEFAULT_TYPE):
if (element_type not in ELEMENT_LENGTHS):
raise TwoBitError("invalid number type: %s. Valid types: %s" %
(field_type, ", ".join(sorted(ELEMENT_LENGTHS.keys()))))
# end if
# read enough bytes for the specified number of elements
# of the specified type
num_bytes = array_size * ELEMENT_LENGTHS[element_type]
# bytes_str is a string of chars (each char is one byte)
bytes_str = self.file.read(num_bytes)
# convert to a tuple of numbers
bytes_tup = ConvertBytesToNumbers(bytes_str, self.byte_swap, element_type)
# return the tuple
return bytes_tup
# end def
def ReadHeader(self):
# read the signature and check whether we need to byte-swap
self.ReadSignature()
# read the version number and check that it is valid
self.ReadVersion()
# read the number of sequences
self.ReadSequenceCount()
# skip the reserved field
self.ReadField()
# end def
def ReadSignature(self):
# assume we do not need to byte-swap
self.byte_swap = False
# get the signature
sig = self.ReadField()
if (self.debug):
ErrMsg("signature: %i" % TWO_BIT_SIG)
ErrMsg("sig read: %i" % sig)
# end if
# check the signature (to see if we need to byte-swap)
if (TWO_BIT_SIG != sig):
self.ResetFile()
self.byte_swap = True
sig = self.ReadField()
if (self.debug):
ErrMsg("enabling byte-swapping")
ErrMsg("sig read: %i" % sig)
# end if
if (TWO_BIT_SIG != sig):
raise TwoBitError("invalid signature: %i. Should be %i." %
(sig, TWO_BIT_SIG))
# end if
# end if
# end def
def ReadVersion(self):
version = self.ReadField()
if (TWO_BIT_VER != version):
raise TwoBitError("invalid two-bit version: %i. Should be %i." %
(version, TWO_BIT_VER))
# end if
# end def
def ReadSequenceCount(self):
self.num_seqs = self.ReadField()
if (self.debug):
ErrMsg("Number of sequences in file: %i" % self.num_seqs)
# end if
# end def
def ReadSequenceIndices(self):
self.chrom_sequences = dict()
#ErrMsg("ReadSequenceIndices TEMPORARILY DISABLED FOR TESTING")
for i in xrange(self.num_seqs):
self.ReadSequenceIndex()
# end for
# end def
def ReadSequenceIndex(self):
name_length = self.ReadField('char') # a single byte
sequence_name = self.ReadChars(name_length)
header_start = self.ReadField()
if (self.debug):
ErrMsg("Name length: %i" % name_length)
ErrMsg("Name: %s" % sequence_name)
ErrMsg("Offset: %i" % header_start)
# end if
new_sequence = \
TwoBitSequenceCls(sequence_name, header_start, debug=self.debug)
self.chrom_sequences[sequence_name] = new_sequence
# end def
def ReadSequenceHeaders(self):
#ErrMsg("ReadSequenceHeaders TEMPORARILY DISABLED FOR TESTING")
for sequence in self.chrom_sequences.itervalues():
self.ReadSequenceHeader(sequence)
# end for
# end def
def ReadSequenceHeader(self, sequence):
if (self.debug):
ErrMsg("Reading sequence header for %s..." % sequence.name)
# end if
# seek to the start of the header for the current sequence
self.file.seek(sequence.header_start)
# get the number of bases in the sequence
sequence.num_bases = self.ReadField()
# read the N-block information for the sequence
self.ReadNBlockInfo(sequence)
# read the mask-block information for the sequence
self.ReadMaskBlockInfo(sequence)
# skip the reserved field
self.ReadField()
# store the position in bytes from the beginning of the file of
# the first base in the sequence
sequence.seq_start = self.file.tell()
# calculate the position in bytes from the beginning of the file of
# the first base in the sequence
#sequence.CalculateFirstSequenceBytePosition()
# mark that the header for the sequence has been succesfully read
sequence.header_read = True
# end def
def ReadNBlockInfo(self, sequence):
# get the number of N-blocks in the sequence
num_blocks = self.ReadField()
if (self.debug):
ErrMsg("Number of N-blocks: %i" % num_blocks)
# end if
# read the block starts
sequence.n_block_starts = self.ReadArray(num_blocks)
# read the block sizes
sequence.n_block_sizes = self.ReadArray(num_blocks)
# end def
def ReadMaskBlockInfo(self, sequence):
# get the number of mask-blocks in the sequence
num_blocks = self.ReadField()
if (self.debug):
ErrMsg("Number of mask-blocks: %i" % num_blocks)
# end if
# read the block starts
sequence.mask_block_starts = self.ReadArray(num_blocks)
# read the block sizes
sequence.mask_block_sizes = self.ReadArray(num_blocks)
# end def
def GetSequence(self, chromosome, start=None, end=None, apply_mask=False):
# check the query region, and select the appropriate chromosome
(chrom_seq, start, end) = self.CheckQueryRegion(chromosome, start, end)
# get the starting byte position (convert 1-based to 0-based)
(start_byte, extra_start_bases) = chrom_seq.GetStartByte(start-1)
# get the ending byte position (convert 1-based to 0-based)
(end_byte, extra_end_bases) = chrom_seq.GetEndByte(end-1)
if (self.debug):
ErrMsg("Start byte: %i" % start_byte)
ErrMsg("Extra start bases: %i" % extra_start_bases)
ErrMsg("End byte: %i" % end_byte)
ErrMsg("Extra end bases: %i" % extra_end_bases)
# end if
# get the sequence fragment
seq_frag = self.GetSequenceFragment(start_byte, end_byte)
# trim the sequence fragment as required
seq_frag = self.TrimSequence(seq_frag, extra_start_bases, extra_end_bases)
seq_frag = chrom_seq.ApplyNBlocks(seq_frag, start-1, end-1)
if (apply_mask):
seq_frag = chrom_seq.ApplyMaskBlocks(seq_frag, start-1, end-1)
# end if
return seq_frag
# end def
def CheckQueryRegion(self, chromosome, start, end):
errors = list()
# check that chromosome is a valid sequence identifier
chrom_valid = True
if (chromosome not in self.chrom_sequences):
# if it does not already start with "chr", try adding "chr"
if (not chromosome.startswith("chr")):
if ("chr%s" % chromosome in self.chrom_sequences):
chromosome = "chr%s" % chromosome
else:
chrom_valid = False
# end if
else:
chrom_valid = False
# end if
if (not chrom_valid):
errors.append("invalid chromosome: %s." % chromosome)
# end if
# end if
# check that start and end are valid base coordinates
if (None == start): #{
start = 1
elif (1 > start):
errors.append("invalid start coordinate: "
"%i. Must be 1 or greater." % start)
# end if
if (chrom_valid):
chrom_seq = self.chrom_sequences[chromosome]
# check that sequence has had its header read
if (not chrom_seq.header_read):
self.ReadSequenceHeader(chrom_seq)
# end if
if (None == end): #{
end = chrom_seq.num_bases
elif (chrom_seq.num_bases < end):
errors.append("invalid end coordinate: %i. Must be %i or less." %
(end, chrom_seq.num_bases))
# end if
# end if
if (end < start):
errors.append("invalid coordinates: "
"start (%i) must be less than or equal to end (%i)." % (start, end))
# end if
if (0 < len(errors)):
raise TwoBitError("Invalid sequence region query:\n"
"%s" % "\n".join(errors))
# end if
return (chrom_seq, start, end)
# end def
def GetSequenceFragment(self, start_byte, end_byte):
# move to the first byte
self.file.seek(start_byte)
# read the correct number of bytes
num_bytes = end_byte - start_byte + 1
bytes = self.ReadChars(num_bytes)
# convert the bytes to a bit string
bits = BytesToBitString(bytes)
# convert the bit string to bases
bases = BitStringToBaseString(bits)
if (self.debug):
ErrMsg("Full sequence fragment:\n%s" % bases)
# end if
# return the bases
return bases
# end def
def TrimSequence(self, seq, start_trim, end_trim):
if (0 == end_trim):
trimmed_seq = seq[start_trim:]
else:
trimmed_seq = seq[start_trim:-end_trim]
# end if
if (self.debug):
ErrMsg("Trimmed sequence:\n%s" % trimmed_seq)
# end if
return trimmed_seq
