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I did a little test about isal_deflate_set_dict, the test looks below: (small change of igzip/igzip_example.c)
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#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "igzip_lib.h"
#define BUF_SIZE 512
struct isal_zstream stream;
int main(int argc, char *argv[])
{
uint8_t inbuf[BUF_SIZE], outbuf[BUF_SIZE];
FILE *in, *out;
if (argc != 3) {
fprintf(stderr, "Usage: igzip_example infile outfile\n");
exit(0);
}
in = fopen(argv[1], "rb");
if (!in) {
fprintf(stderr, "Can't open %s for reading\n", argv[1]);
exit(0);
}
out = fopen(argv[2], "wb");
if (!out) {
fprintf(stderr, "Can't open %s for writing\n", argv[2]);
exit(0);
}
printf("igzip_example\nWindow Size: %d K\n", IGZIP_HIST_SIZE / 1024);
fflush(0);
isal_deflate_init(&stream);
stream.end_of_stream = 0;
stream.flush = NO_FLUSH;
stream.gzip_flag = ISAL_ZLIB;
stream.level = 3;
stream.level_buf = malloc(ISAL_DEF_LVL3_DEFAULT);
stream.level_buf_size = ISAL_DEF_LVL3_DEFAULT;
if (stream.level_buf == 0) {
printf("Failed to allocate level compression buffer\n");
exit(0);
}
// delete below 3 lines when not using dictionary
char dict[5] = "hello";
int len = 5;
isal_deflate_set_dict(&stream, dict, len);
do {
stream.avail_in = (uint32_t) fread(inbuf, 1, BUF_SIZE, in);
stream.end_of_stream = feof(in) ? 1 : 0;
stream.next_in = inbuf;
do {
stream.avail_out = BUF_SIZE;
stream.next_out = outbuf;
isal_deflate(&stream);
fwrite(outbuf, 1, BUF_SIZE - stream.avail_out, out);
} while (stream.avail_out == 0);
assert(stream.avail_in == 0);
} while (stream.internal_state.state != ZSTATE_END);
fclose(out);
fclose(in);
printf("End of igzip_example\n\n");
return 0;
}
I used this test to compress the same data, the only difference is isal_deflate_set_dict.
When using dictionary, the result looks below:
On the other hand, the result looks below:
Therefore, the zlib header is the same in both cases. I don't think that's correct, since the zlib header should contains the dictionary message.
Does isa-l deflater don't write the zlib header correctly when using dictionary?
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