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from __future__ import print_function

import collections

import re

import sys

import gzip

import zlib

_COMPRESSED_MARKER = 0xFF

def check_non_ascii(msg):

for c in msg:

if ord(c) >= 0x80:

print(

'Unable to generate compressed data: message "{}" contains a non-ascii character "{}".'.format(

msg, c

),

file=sys.stderr,

)

sys.exit(1)

# Replace <char><space> with <char | 0x80>.

# Trival scheme to demo/test.

def space_compression(error_strings):

for line in error_strings:

check_non_ascii(line)

result = ""

for i in range(len(line)):

if i > 0 and line[i] == " ":

result = result[:-1]

result += "\\{:03o}".format(ord(line[i - 1]))

else:

result += line[i]

error_strings[line] = result

return None

# Replace common words with <0x80 | index>.

# Index is into a table of words stored as aaaaa<0x80|a>bbb<0x80|b>...

# Replaced words are assumed to have spaces either side to avoid having to store the spaces in the compressed strings.

def word_compression(error_strings):

topn = collections.Counter()

for line in error_strings.keys():

check_non_ascii(line)

for word in line.split(" "):

topn[word] += 1

# Order not just by frequency, but by expected saving. i.e. prefer a longer string that is used less frequently.

# Use the word itself for ties so that compression is deterministic.

def bytes_saved(item):

w, n = item

return -((len(w) + 1) * (n - 1)), w

top128 = sorted(topn.items(), key=bytes_saved)[:128]

index = [w for w, _ in top128]

index_lookup = {w: i for i, w in enumerate(index)}

for line in error_strings.keys():

result = ""

need_space = False

for word in line.split(" "):

if word in index_lookup:

result += "\\{:03o}".format(0b10000000 | index_lookup[word])

need_space = False

else:

if need_space:

result += " "

need_space = True

result += word

error_strings[line] = result.strip()

return "".join(w[:-1] + "\\{:03o}".format(0b10000000 | ord(w[-1])) for w in index)

# Replace chars in text with variable length bit sequence.

# For comparison only (the table is not emitted).

def huffman_compression(error_strings):

# https://github.com/tannewt/huffman

import huffman

all_strings = "".join(error_strings)

cb = huffman.codebook(collections.Counter(all_strings).items())

for line in error_strings:

b = "1"

for c in line:

b += cb[c]

n = len(b)

if n % 8 != 0:

n += 8 - (n % 8)

result = ""

for i in range(0, n, 8):

result += "\\{:03o}".format(int(b[i : i + 8], 2))

if len(result) > len(line) * 4:

result = line

error_strings[line] = result

# TODO: This would be the prefix lengths and the table ordering.

return "_" * (10 + len(cb))

# Replace common N-letter sequences with <0x80 | index>, where

# the common sequences are stored in a separate table.

# This isn't very useful, need a smarter way to find top-ngrams.

def ngram_compression(error_strings):

topn = collections.Counter()

N = 2

for line in error_strings.keys():

check_non_ascii(line)

if len(line) < N:

continue

for i in range(0, len(line) - N, N):

topn[line[i : i + N]] += 1

def bytes_saved(item):

w, n = item

return -(len(w) * (n - 1))

top128 = sorted(topn.items(), key=bytes_saved)[:128]

index = [w for w, _ in top128]

index_lookup = {w: i for i, w in enumerate(index)}

for line in error_strings.keys():

result = ""

for i in range(0, len(line) - N + 1, N):

word = line[i : i + N]

if word in index_lookup:

result += "\\{:03o}".format(0b10000000 | index_lookup[word])

else:

result += word

if len(line) % N != 0:

result += line[len(line) - len(line) % N :]

error_strings[line] = result.strip()

return "".join(index)

def main(collected_path, fn):

error_strings = collections.OrderedDict()

max_uncompressed_len = 0

num_uses = 0

# Read in all MP_ERROR_TEXT strings.

with open(collected_path, "r") as f:

for line in f:

line = line.strip()

if not line:

continue

num_uses += 1

error_strings[line] = None

max_uncompressed_len = max(max_uncompressed_len, len(line))

# So that objexcept.c can figure out how big the buffer needs to be.

print("#define MP_MAX_UNCOMPRESSED_TEXT_LEN ({})".format(max_uncompressed_len))

# Run the compression.

compressed_data = fn(error_strings)

# Print the data table.

print('MP_COMPRESSED_DATA("{}")'.format(compressed_data))

# Print the replacements.

for uncomp, comp in error_strings.items():

if uncomp == comp:

prefix = ""

else:

prefix = "\\{:03o}".format(_COMPRESSED_MARKER)

print('MP_MATCH_COMPRESSED("{}", "{}{}")'.format(uncomp, prefix, comp))

# Used to calculate the "true" length of the (escaped) compressed strings.

def unescape(s):

return re.sub(r"\\\d\d\d", "!", s)

# Stats. Note this doesn't include the cost of the decompressor code.

uncomp_len = sum(len(s) + 1 for s in error_strings.keys())

comp_len = sum(1 + len(unescape(s)) + 1 for s in error_strings.values())

data_len = len(compressed_data) + 1 if compressed_data else 0

print("// Total input length: {}".format(uncomp_len))

print("// Total compressed length: {}".format(comp_len))

print("// Total data length: {}".format(data_len))

print("// Predicted saving: {}".format(uncomp_len - comp_len - data_len))

# Somewhat meaningless comparison to zlib/gzip.

all_input_bytes = "\\0".join(error_strings.keys()).encode()

print()

if hasattr(gzip, "compress"):

gzip_len = len(gzip.compress(all_input_bytes)) + num_uses * 4

print("// gzip length: {}".format(gzip_len))

print("// Percentage of gzip: {:.1f}%".format(100 * (comp_len + data_len) / gzip_len))

if hasattr(zlib, "compress"):

zlib_len = len(zlib.compress(all_input_bytes)) + num_uses * 4

print("// zlib length: {}".format(zlib_len))

print("// Percentage of zlib: {:.1f}%".format(100 * (comp_len + data_len) / zlib_len))

if __name__ == "__main__":

main(sys.argv[1], word_compression)