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require 'spreadsheet/encodings'
module Spreadsheet
module Excel
module Writer
##
# This Module collects writer methods such as unicode_string that are specific
# to Biff8. This Module is likely to be expanded as Support for older Versions
# of Excel grows and methods get moved here for disambiguation.
module Biff8
include Spreadsheet::Encodings
##
# Check whether the string _data_ can be compressed (i.e. every second byte
# is a Null-byte) and perform compression.
# Returns the data and compression_status (0/1)
def compress_unicode_string data
compressed = internal('')
expect_null = false
data.each_byte do |byte|
if expect_null
if byte != 0
return [data, 1] # 1 => Data consists of wide Chars
end
expect_null = false
else
compressed << byte
expect_null = true
end
end
[compressed, 0] # 0 => Data consists of compressed Chars
end
##
# Encode _string_ into a Biff8 Unicode String. Header and body are encoded
# separately by #_unicode_string. This method simply combines the two.
def unicode_string string, count_length=1
header, data, _ = _unicode_string string, count_length
header << data
end
@@bytesize = RUBY_VERSION >= '1.9' ? :bytesize : :size
##
# Encode _string_ into a Biff8 Unicode String Header and Body.
def _unicode_string string, count_length=1
data = internal string
size = data.send(@@bytesize) / 2
fmt = count_length == 1 ? 'C2' : 'vC'
data, wide = compress_unicode_string data
opts = wide
header = [
size, # Length of the string (character count, ln)
opts, # Option flags:
# Bit Mask Contents
# 0 0x01 Character compression (ccompr):
# 0 = Compressed (8-bit characters)
# 1 = Uncompressed (16-bit characters)
# 2 0x04 Asian phonetic settings (phonetic):
# 0 = Does not contain Asian phonetic settings
# 1 = Contains Asian phonetic settings
# 3 0x08 Rich-Text settings (richtext):
# 0 = Does not contain Rich-Text settings
# 1 = Contains Rich-Text settings
#0x00,# (optional, only if richtext=1) Number of Rich-Text
# formatting runs (rt)
#0x00,# (optional, only if phonetic=1) Size of Asian phonetic
# settings block (in bytes, sz)
].pack fmt
data << '' # (optional, only if richtext=1)
# List of rt formatting runs (➜ 3.2)
data << '' # (optional, only if phonetic=1)
# Asian Phonetic Settings Block (➜ 3.4.2)
[header, data, wide]
end
end
end
end
end
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