sparsemap/bin/gen_chunk_vector_size_table.py
2024-07-15 10:37:16 -04:00

65 lines
2.3 KiB
Python

#!/usr/bin/env python
# Gererate a C function that contains a pre-calculated static table where each
# 8bit offset into that table encodes the required additional space for what is
# described.
# The 2 bit patters are:
# 00 -> 0 additional sm_bitvec_t (ZEROS)
# 11 -> 0 additional sm_bitvec_t (ONES)
# 10 -> 1 additional sm_bitvec_t (MIXED)
# 01 -> 0 additional sm_bitvec_t (NONE)
# The goal is to output this:
# /**
# * Calculates the number of sm_bitvec_ts required by a single byte with flags
# * (in m_data[0]).
# */
# static size_t
# __sm_chunk_calc_vector_size(uint8_t b)
# {
# // clang-format off
# static int lookup[] = {
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 2, 1, 1, 2, 1,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 2, 1, 1, 2, 1,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 2, 1, 1, 2, 1,
# 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 2, 1, 1, 2, 1,
# 2, 2, 3, 2, 2, 2, 3, 2, 3, 3, 4, 3, 2, 2, 3, 2,
# 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 2, 1, 1, 2, 1,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0,
# 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 2, 1, 1, 2, 1,
# 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 1, 0, 0, 1, 0
# };
# // clang-format on
# return (size_t)lookup[b];
# }
def create_lookup_table_c_format():
"""Creates a lookup table in C-style format."""
lookup_table = []
for byte in range(256):
count = 0
for i in range(3):
if (byte >> (i * 2)) & 3 == 2:
count += 1
lookup_table.append(count)
# Format the output as a C array
output = "static int lookup[] = {\n"
for i in range(0, 256, 16):
line = " " + ", ".join(str(x) for x in lookup_table[i:i+16]) + ",\n"
output += line
output += "};"
print(output)
if __name__ == "__main__":
create_lookup_table_c_format()