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deflate: write zlib FLEVEL based on compression level

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Randy 2022-02-08 23:24:02 +01:00
parent 842a20e586
commit cd1dc96d27
1 changed files with 23 additions and 2 deletions
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25
miniz_tdef.c
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@ -602,6 +602,8 @@ static mz_bool tdefl_compress_block(tdefl_compressor *d, mz_bool static_block)
return tdefl_compress_lz_codes(d);
}
static const mz_uint s_tdefl_num_probes[11];
static int tdefl_flush_block(tdefl_compressor *d, int flush)
{
mz_uint saved_bit_buf, saved_bits_in;
@ -622,8 +624,27 @@ static int tdefl_flush_block(tdefl_compressor *d, int flush)
if ((d->m_flags & TDEFL_WRITE_ZLIB_HEADER) && (!d->m_block_index))
{
TDEFL_PUT_BITS(0x78, 8);
TDEFL_PUT_BITS(0x01, 8);
const mz_uint8 cmf = 0x78;
mz_uint8 flg, flevel = 3;
mz_uint header, i, n = sizeof(s_tdefl_num_probes) / sizeof(mz_uint);
/* Determine compression level by reversing the process in tdefl_create_comp_flags_from_zip_params() */
for (i=0; i < n; i++)
if (s_tdefl_num_probes[i] == (d->m_flags & 0xFFF)) break;
if (i < 2)
flevel = 0;
else if (i < 6)
flevel = 1;
else if (i == 6)
flevel = 2;
header = cmf << 8 | (flevel << 6);
header += 31 - (header % 31);
flg = header & 0xFF;
TDEFL_PUT_BITS(cmf, 8);
TDEFL_PUT_BITS(flg, 8);
}
TDEFL_PUT_BITS(flush == TDEFL_FINISH, 1);