def pack_ibm_floats(values):
"""Pack floats into binary-encoded big-endian single-precision IBM floats.
Args:
values: An iterable series of numeric values.
Returns:
A sequence of bytes.
"""
return EMPTY_BYTE_STRING.join(bytes(IBMFloat.from_real(value)) for value in values)
def write_extended_textual_headers(fh, pages, encoding):
"""Write extended textual headers.
Args:
fh: A file-like object open in binary mode for writing.
pages: An iterables series of sequences of Unicode strings, where the outer iterable
represents 3200 byte pages, each comprised of a sequence of exactly 40 strings of nominally 80 characters
each. Although Unicode strings are accepted, and when encoded they should result in exact 80 bytes
sequences. To produce a valid data structure for pages, consider using format_extended_textual_header()
encoding: Either 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be position at the first byte after the extended textual headers, which is
also the first byte of the first trace-header.
Raises:
ValueError: If the provided header data has the wrong shape.
UnicodeError: If the textual data could not be encoded into the specified encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing extended textual header",
encoding)
fh.seek(REEL_HEADER_NUM_BYTES)
encoded_pages = []
for page_index, page in enumerate(pages):
encoded_page = []
# TODO: Share some of this code with writing the textual reel header.
for line_index, line in enumerate(page):
encoded_line = line.encode(encoding)
num_encoded_bytes = len(encoded_line)
if num_encoded_bytes != CARD_LENGTH:
raise ValueError(
"Extended textual header line {} of page {} at {} bytes is not "
"{} bytes".format(line_index, page_index,
num_encoded_bytes, CARD_LENGTH))
encoded_page.append(encoded_line)
num_encoded_lines = len(encoded_page)
if num_encoded_lines != CARDS_PER_HEADER:
raise ValueError("Extended textual header page {} number of "
"lines {} is not {}".format(
page_index, num_encoded_lines,
CARDS_PER_HEADER))
encoded_pages.append(encoded_page),
for encoded_page in encoded_pages:
concatenated_page = EMPTY_BYTE_STRING.join(encoded_page)
assert (len(concatenated_page) == TEXTUAL_HEADER_NUM_BYTES)
fh.write(concatenated_page)
def write_extended_textual_headers(fh, pages, encoding):
"""Write extended textual headers.
Args:
fh: A file-like object open in binary mode for writing.
pages: An iterables series of sequences of Unicode strings, where the outer iterable
represents 3200 byte pages, each comprised of a sequence of exactly 40 strings of nominally 80 characters
each. Although Unicode strings are accepted, and when encoded they should result in exact 80 bytes
sequences. To produce a valid data structure for pages, consider using format_extended_textual_header()
encoding: Either 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be position at the first byte after the extended textual headers, which is
also the first byte of the first trace-header.
Raises:
ValueError: If the provided header data has the wrong shape.
UnicodeError: If the textual data could not be encoded into the specified encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing extended textual header", encoding)
fh.seek(REEL_HEADER_NUM_BYTES)
encoded_pages = []
for page_index, page in enumerate(pages):
encoded_page = []
# TODO: Share some of this code with writing the textual reel header.
for line_index, line in enumerate(page):
encoded_line = line.encode(encoding)
num_encoded_bytes = len(encoded_line)
if num_encoded_bytes != CARD_LENGTH:
raise ValueError("Extended textual header line {} of page {} at {} bytes is not "
"{} bytes".format(line_index, page_index, num_encoded_bytes, CARD_LENGTH))
encoded_page.append(encoded_line)
num_encoded_lines = len(encoded_page)
if num_encoded_lines != CARDS_PER_HEADER:
raise ValueError("Extended textual header page {} number of "
"lines {} is not {}".format(num_encoded_lines, CARDS_PER_HEADER))
encoded_pages.append(encoded_page)
for encoded_page in encoded_pages:
concatenated_page = EMPTY_BYTE_STRING.join(encoded_page)
assert(len(concatenated_page) == TEXTUAL_HEADER_NUM_BYTES)
fh.write(concatenated_page)
def write_textual_reel_header(fh, lines, encoding):
"""Write the SEG Y card image header, also known as the textual header
Args:
fh: A file-like object open in binary mode positioned such that the
beginning of the textual header will be the next byte to read.
lines: An iterable series of forty lines, each of which must be a
Unicode string of CARD_LENGTH characters. The first three characters
of each line are often "C 1" to "C40" (as required by the SEG Y
standard) although this is not enforced by this function, since
many widespread SEG Y readers and writers do not adhere to this
constraint. To produce a SEG Y compliant series of header lines
consider using the format_standard_textual_header() function.
Any lines longer than CARD_LENGTH characters will be truncated without
warning. Any excess lines over CARDS_PER_HEADER will be discarded. Short
or omitted lines will be padded with spaces.
encoding: Typically 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be positioned at the first byte following the textual
header.
Raises:
UnsupportedEncodingError: If encoding is neither EBCDIC nor ASCII.
UnicodeError: If the data provided in lines cannot be encoded with the encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing textual reel header", encoding)
fh.seek(0)
padded_lines = [line.encode(encoding).ljust(CARD_LENGTH, ' '.encode(encoding))[:CARD_LENGTH]
for line in pad(lines, padding='', size=CARDS_PER_HEADER)]
joined_header = EMPTY_BYTE_STRING.join(padded_lines)
assert len(joined_header) == 3200
fh.write(joined_header)
fh.seek(TEXTUAL_HEADER_NUM_BYTES)
def write_textual_reel_header(fh, lines, encoding):
"""Write the SEG Y card image header, also known as the textual header
Args:
fh: A file-like object open in binary mode positioned such that the
beginning of the textual header will be the next byte to read.
lines: An iterable series of forty lines, each of which must be a
Unicode string of CARD_LENGTH characters. The first three characters
of each line are often "C 1" to "C40" (as required by the SEG Y
standard) although this is not enforced by this function, since
many widespread SEG Y readers and writers do not adhere to this
constraint. To produce a SEG Y compliant series of header lines
consider using the format_standard_textual_header() function.
Any lines longer than CARD_LENGTH characters will be truncated without
warning. Any excess lines over CARDS_PER_HEADER will be discarded. Short
or omitted lines will be padded with spaces.
encoding: Typically 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be positioned at the first byte following the textual
header.
Raises:
UnsupportedEncodingError: If encoding is neither EBCDIC nor ASCII.
UnicodeError: If the data provided in lines cannot be encoded with the encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing textual reel header", encoding)
fh.seek(0)
padded_lines = [line.encode(encoding).ljust(CARD_LENGTH, ' '.encode(encoding))[:CARD_LENGTH]
for line in pad(lines, padding='', size=CARDS_PER_HEADER)]
joined_header = EMPTY_BYTE_STRING.join(padded_lines)
assert len(joined_header) == 3200
fh.write(joined_header)
fh.seek(TEXTUAL_HEADER_NUM_BYTES)
def pack(self, values):
return EMPTY_BYTE_STRING.join(
bytes(IBMFloat.from_real(value)) for value in values)
def pack_ibm_floats_py(values):
return EMPTY_BYTE_STRING.join(
bytes(IBMFloat.from_real(value)) for value in values)
def pack(self, values):
return EMPTY_BYTE_STRING.join(bytes(IBMFloat.from_real(value))
for value in values)
