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# Step 04 - generate Java literals.
#
# Java byte-code has ridiculous restrictions. There is no such thing as
# "array literal" - those are implemented as series of data[x] = y;
# as a consequence N-byte array will use 7N bytes in class, plus N bytes
# in instantiated variable. Also no literal could be longer than 64KiB.
#
# To keep dictionary data compact both in source code and in compiled format
# we use the following tricks:
# * use String as a data container
# * store only lowest 7 bits; i.e. all characters fit ASCII table; this allows
# efficient conversion to byte array; also ASCII characters use only 1 byte
#. of memory (UTF-8 encoding)
# * RLE-compress sequence of 8-th bits
#
# This script generates literals used in Java code.
bin_path = "dictionary.bin"
with open(bin_path, "rb") as raw:
data = raw.read()
low = []
hi = []
is_skip = True
skip_flip_offset = 36
cntr = skip_flip_offset
for b in data:
value = ord(b)
low.append(chr(value & 0x7F))
if is_skip:
if value < 0x80:
cntr += 1
else:
is_skip = False
hi.append(unichr(cntr))
cntr = skip_flip_offset + 1
else:
if value >= 0x80:
cntr += 1
else:
is_skip = True
hi.append(unichr(cntr))
cntr = skip_flip_offset + 1
hi.append(unichr(cntr))
low0 = low[0 : len(low) // 2]
low1 = low[len(low) // 2 : len(low)]
def escape(chars):
result = []
for c in chars:
if "\r" == c:
result.append("\\r")
elif "\n" == c:
result.append("\\n")
elif "\t" == c:
result.append("\\t")
elif "\"" == c:
result.append("\\\"")
elif "\\" == c:
result.append("\\\\")
elif ord(c) < 32 or ord(c) >= 127:
result.append("\\u%04X" % ord(c))
else:
result.append(c);
return result
source_code = [
" private static final String DATA0 = \"", "".join(escape(low0)), "\";\n",
" private static final String DATA1 = \"", "".join(escape(low1)), "\";\n",
" private static final String SKIP_FLIP = \"", "".join(escape(hi)), "\";\n"
]
src_path = "DictionaryData.inc.java"
with open(src_path, "w") as source:
source.write("".join(source_code))