mirror of https://github.com/YosysHQ/icestorm.git
136 lines
3.7 KiB
Python
Executable File
136 lines
3.7 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# This is free and unencumbered software released into the public domain.
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#
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# Anyone is free to copy, modify, publish, use, compile, sell, or
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# distribute this software, either in source code form or as a compiled
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# binary, for any purpose, commercial or non-commercial, and by any
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# means.
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def make_int_bits(value, nbits):
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bits = list()
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for i in range(nbits-1, -1, -1):
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bits.append((value & (1 << i)) != 0)
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return bits
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def ice_compress_bits(inbits):
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outbits = list()
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outbits += make_int_bits(0x49434543, 32)
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outbits += make_int_bits(0x4f4d5052, 32)
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deltas = list()
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numzeros = 0
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for bit in inbits:
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if bit:
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deltas.append(numzeros)
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numzeros = 0
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else:
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numzeros += 1
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i = 0
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while i < len(deltas):
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raw_len = 0
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compr_len = 0
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best_compr_raw_diff = -1
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best_compr_raw_idx = -1
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best_compr_raw_len = -1
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for j in range(len(deltas) - i):
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delta = deltas[i+j]
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raw_len += delta + 1
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if delta < 4:
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compr_len += 3
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elif delta < 32:
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compr_len += 7
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elif delta < 256:
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compr_len += 11
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else:
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compr_len += 26
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if compr_len - raw_len < max(best_compr_raw_diff - 4, 0) or raw_len > 64:
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break
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if compr_len - raw_len > best_compr_raw_diff:
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best_compr_raw_diff = compr_len - raw_len
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best_compr_raw_idx = j
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best_compr_raw_len = raw_len
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if best_compr_raw_diff > 9:
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outbits.append(False)
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outbits.append(False)
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outbits.append(False)
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outbits.append(True)
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outbits += make_int_bits(best_compr_raw_len-1, 6)
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for j in range(0, best_compr_raw_idx+1):
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delta = deltas[i+j]
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for k in range(delta):
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outbits.append(False)
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if j < best_compr_raw_idx:
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outbits.append(True)
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i += best_compr_raw_idx + 1
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continue
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delta = deltas[i]
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i += 1
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if delta < 4:
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outbits.append(True)
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outbits += make_int_bits(delta, 2)
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elif delta < 32:
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outbits.append(False)
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outbits.append(True)
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outbits += make_int_bits(delta, 5)
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elif delta < 256:
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outbits.append(False)
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outbits.append(False)
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outbits.append(True)
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outbits += make_int_bits(delta, 8)
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else:
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outbits.append(False)
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outbits.append(False)
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outbits.append(False)
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outbits.append(False)
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outbits.append(True)
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outbits += make_int_bits(delta, 23)
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outbits.append(False)
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outbits.append(False)
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outbits.append(False)
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outbits.append(False)
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outbits.append(False)
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outbits += make_int_bits(numzeros, 23)
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return outbits
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def ice_compress_bytes(inbytes):
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inbits = list()
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for byte in inbytes:
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for i in range(7, -1, -1):
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inbits.append((byte & (1 << i)) != 0)
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outbits = ice_compress_bits(inbits)
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outbytes = list()
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for i in range(0, len(outbits), 8):
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byte = 0
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for k in range(i, min(i+8, len(outbits))):
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if outbits[k]: byte |= 1 << (7-(k-i))
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outbytes.append(byte)
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return bytes(outbytes)
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# ------------------------------------------------------
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# Usage example:
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# python3 icecompr.py < example_8k.bin > example_8k.compr
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if __name__ == '__main__':
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import sys
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inbytes = sys.stdin.buffer.read()
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outbytes = ice_compress_bytes(inbytes)
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sys.stdout.buffer.write(outbytes)
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