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Create headers based on compression parameters.

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Instead of using a constant as default zlib header, create the header on the fly. Both zlib
header bytes depend on the wbits and compression level used.
Make sure that ISA-L compression level 0 is advertised as the fastest compression in
both the gzip header (setting xfl flag to 0x04) and the zlib header (as 0, fastest, other levels are 1, fast).

Change-Id: I1f30e4397a0f5fcf6df593c40178e7d6f6c05328
Signed-off-by: Ruben Vorderman <r.h.p.vorderman@lumc.nl>
This commit is contained in:
Ruben Vorderman 2021-08-18 09:56:58 +02:00 committed by Greg Tucker
parent 1db0363c49
commit 94ec6026ce
1 changed files with 47 additions and 9 deletions
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56
igzip/igzip.c
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@ -1706,10 +1706,42 @@ int isal_deflate(struct isal_zstream *stream)
return ret;
}
// Helper function to avoid code duplication.
static void _zlib_header_in_buffer(struct isal_zstream *stream, uint8_t * buffer)
{
uint8_t hist_bits, info, level, cmf, flg;
uint8_t dict_flag = 0;
if (stream->hist_bits == 0) // default hist_bits
hist_bits = ISAL_DEF_MAX_HIST_BITS;
else
hist_bits = stream->hist_bits;
if (hist_bits > 8)
info = hist_bits - 8;
else
info = 0; // For low window sizes ensure correct cmf flag.
if (stream->level == 0)
level = 0; // Fastest algorithm
else
level = 1; // ISA-L levels 1-3 are fast algorithms.
cmf = DEFLATE_METHOD | (info << 4);
flg = (level << 6) | dict_flag;
flg += 31 - ((256 * cmf + flg) % 31);
buffer[0] = cmf;
buffer[1] = flg;
return;
}
static int write_stream_header_stateless(struct isal_zstream *stream)
{
uint32_t hdr_bytes;
const uint8_t *hdr;
// Create a 10-byte buffer. Since the gzip header is almost fixed (9 of 10
// bytes are fixed) use it to initialize the buffer.
uint8_t buffer[10] = {
0x1f, 0x8b, 0x08, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0xff
};
uint32_t next_flag;
if (stream->internal_state.has_wrap_hdr)
@ -1717,12 +1749,12 @@ static int write_stream_header_stateless(struct isal_zstream *stream)
if (stream->gzip_flag == IGZIP_ZLIB) {
hdr_bytes = zlib_hdr_bytes;
hdr = zlib_hdr;
_zlib_header_in_buffer(stream, buffer);
next_flag = IGZIP_ZLIB_NO_HDR;
} else {
hdr_bytes = gzip_hdr_bytes;
hdr = gzip_hdr;
if (stream->level == 0)
buffer[8] = 0x04; // Fastest algorithm in xfl flag
next_flag = IGZIP_GZIP_NO_HDR;
}
@ -1732,7 +1764,7 @@ static int write_stream_header_stateless(struct isal_zstream *stream)
stream->avail_out -= hdr_bytes;
stream->total_out += hdr_bytes;
memcpy(stream->next_out, hdr, hdr_bytes);
memcpy(stream->next_out, buffer, hdr_bytes);
stream->next_out += hdr_bytes;
stream->internal_state.has_wrap_hdr = 1;
@ -1746,17 +1778,23 @@ static void write_stream_header(struct isal_zstream *stream)
struct isal_zstate *state = &stream->internal_state;
int bytes_to_write;
uint32_t hdr_bytes;
const uint8_t *hdr;
// Create a 10-byte buffer. Since the gzip header is almost fixed (9 of 10
// bytes are fixed) use it to initialize the buffer.
uint8_t buffer[10] = {
0x1f, 0x8b, 0x08, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0xff
};
if (stream->internal_state.has_wrap_hdr)
return;
if (stream->gzip_flag == IGZIP_ZLIB) {
hdr_bytes = zlib_hdr_bytes;
hdr = zlib_hdr;
_zlib_header_in_buffer(stream, buffer);
} else {
if (stream->level == 0)
buffer[8] = 0x04; // Fastest algorithm in xfl flag
hdr_bytes = gzip_hdr_bytes;
hdr = gzip_hdr;
}
bytes_to_write = hdr_bytes;
@ -1765,7 +1803,7 @@ static void write_stream_header(struct isal_zstream *stream)
if (bytes_to_write > stream->avail_out)
bytes_to_write = stream->avail_out;
memcpy(stream->next_out, hdr + state->count, bytes_to_write);
memcpy(stream->next_out, buffer + state->count, bytes_to_write);
state->count += bytes_to_write;
if (state->count == hdr_bytes) {