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/*
* HPACK encoding table generator. It produces a stream of
* <len><idx><name> and a table pointing to the first <len> of each series.
* The end of the stream is marked by <len>=0. In parallel, a length-indexed
* table is built to access the first entry of each length.
*
* Build like this :
* gcc -I../../include -o gen-enc gen-enc.c
*/
#define HPACK_STANDALONE
#include <ctype.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <import/ist.h>
#include <haproxy/hpack-tbl-t.h>
#include "../../src/hpack-tbl.c"
struct idxhdr {
const char *ptr;
int len;
int idx;
};
struct idxhdr idxhdr[HPACK_SHT_SIZE];
static int positions[32];
static char known_hdr[1024];
/* preferred ordering of headers of similar size. Those not mentioned will be
* less prioritized.
*/
const struct {
const char *name;
const int rank;
} ranks[] = {
{ .name = "age", .rank = 1 },
{ .name = "via", .rank = 2 },
{ .name = "date", .rank = 1 },
{ .name = "host", .rank = 2 },
{ .name = "accept", .rank = 1 },
{ .name = "server", .rank = 2 },
{ .name = "cookie", .rank = 3 },
{ .name = "referer", .rank = 1 },
{ .name = "expires", .rank = 2 },
{ .name = "location", .rank = 1 },
{ .name = "user-agent", .rank = 1 },
{ .name = "set-cookie", .rank = 2 },
{ .name = "content-type", .rank = 1 },
{ .name = "cache-control", .rank = 1 },
{ .name = "last-modified", .rank = 2 },
{ .name = "accept-ranges", .rank = 3 },
{ .name = "if-none-match", .rank = 4 },
{ .name = "content-length", .rank = 1 },
{ .name = "accept-encoding", .rank = 1 },
{ .name = "accept-language", .rank = 2 },
{ .name = "content-encoding", .rank = 1 },
{ .name = "transfer-encoding", .rank = 1 },
{ .name = "if-modified-since", .rank = 2 },
{ .name = "content-disposition", .rank = 1 },
};
/* returns the rank of header <name> or 255 if not found */
int get_hdr_rank(const char *name)
{
int i;
for (i = 0; i < sizeof(ranks) / sizeof(ranks[0]); i++) {
if (strcmp(ranks[i].name, name) == 0)
return ranks[i].rank;
}
return 255;
}
/* sorts first on the length, second on the name, and third on the idx, so that
* headers which appear with multiple occurrences are always met first.
*/
int cmp_idx(const void *l, const void *r)
{
const struct idxhdr *a = l, *b = r;
int ranka, rankb;
int ret;
if (a->len < b->len)
return -1;
else if (a->len > b->len)
return 1;
ranka = get_hdr_rank(a->ptr);
rankb = get_hdr_rank(b->ptr);
if (ranka < rankb)
return -1;
else if (ranka > rankb)
return 1;
/* same rank, check for duplicates and use index */
ret = strcmp(a->ptr, b->ptr);
if (ret != 0)
return ret;
if (a->idx < b->idx)
return -1;
else if (a->idx > b->idx)
return 1;
else
return 0;
}
int main(int argc, char **argv)
{
int pos;
int prev;
int len;
int i;
for (len = 0; len < 32; len++)
positions[len] = -1;
for (i = 0; i < HPACK_SHT_SIZE; i++) {
idxhdr[i].ptr = hpack_sht[i].n.ptr;
idxhdr[i].len = hpack_sht[i].n.len;
idxhdr[i].idx = i;
}
/* sorts all header names by length first, then by name, and finally by
* idx so that we meet smaller headers first, that within a length they
* appear in frequency order, and that multiple occurrences appear with
* the smallest index first.
*/
qsort(&idxhdr[1], HPACK_SHT_SIZE - 1, sizeof(idxhdr[0]), cmp_idx);
pos = 0;
prev = -1;
for (i = 1; i < HPACK_SHT_SIZE; i++) {
len = idxhdr[i].len;
if (len > 31) {
//printf("skipping %s (len=%d)\n", idxhdr[i].ptr, idxhdr[i].len);
continue;
}
/* first occurrence of this length? */
if (positions[len] == -1)
positions[len] = pos;
else if (prev >= 0 &&
memcmp(&known_hdr[prev] + 2, idxhdr[i].ptr, len) == 0) {
/* duplicate header field */
continue;
}
/* store <len> <idx> <name> in the output array */
if (pos + 1 + len + 2 >= sizeof(known_hdr))
abort();
prev = pos;
known_hdr[pos++] = len;
known_hdr[pos++] = idxhdr[i].idx;
memcpy(&known_hdr[pos], idxhdr[i].ptr, len);
pos += len;
//printf("%d %d %s\n", len, idxhdr[i].idx, idxhdr[i].ptr);
}
if (pos + 1 >= sizeof(known_hdr))
abort();
known_hdr[pos++] = 0; // size zero ends the stream
printf("const char hpack_enc_stream[%d] = {\n", pos);
for (i = 0; i < pos; i++) {
if ((i & 7) == 0)
printf("\t /* % 4d: */", i);
printf(" 0x%02x,", known_hdr[i]);
if ((i & 7) == 7 || (i == pos - 1))
putchar('\n');
}
printf("};\n\n");
printf("const signed short hpack_pos_len[32] = {\n");
for (i = 0; i < 32; i++) {
if ((i & 7) == 0)
printf("\t /* % 4d: */", i);
printf(" % 4d,", positions[i]);
if ((i & 7) == 7 || (i == pos - 1))
putchar('\n');
}
printf("};\n\n");
return 0;
}
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