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Remove the now-unused cache digest code #328

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Jun 5, 2026
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Remove the now-unused cache digest code #328

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176 changes: 0 additions & 176 deletions mod_http2/h2_push.c
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Original file line number Diff line number Diff line change
Expand Up @@ -699,179 +699,3 @@ apr_array_header_t *h2_push_collect_update(struct h2_stream *stream,
pushes = h2_push_collect(stream->pool, req, stream->push_policy, res);
return h2_push_diary_update(stream->session, pushes);
}

typedef struct {
h2_push_diary *diary;
unsigned char log2p;
int mask_bits;
int delta_bits;
int fixed_bits;
apr_uint64_t fixed_mask;
apr_pool_t *pool;
unsigned char *data;
apr_size_t datalen;
apr_size_t offset;
unsigned int bit;
apr_uint64_t last;
} gset_encoder;

static int cmp_puint64(const void *p1, const void *p2)
{
const apr_uint64_t *pu1 = p1, *pu2 = p2;
return (*pu1 > *pu2)? 1 : ((*pu1 == *pu2)? 0 : -1);
}

/* in golomb bit stream encoding, bit 0 is the 8th of the first char, or
* more generally:
* char(bit/8) & cbit_mask[(bit % 8)]
*/
static unsigned char cbit_mask[] = {
0x80u,
0x40u,
0x20u,
0x10u,
0x08u,
0x04u,
0x02u,
0x01u,
};

static apr_status_t gset_encode_bit(gset_encoder *encoder, int bit)
{
if (++encoder->bit >= 8) {
if (++encoder->offset >= encoder->datalen) {
apr_size_t nlen = encoder->datalen*2;
unsigned char *ndata = apr_pcalloc(encoder->pool, nlen);
if (!ndata) {
return APR_ENOMEM;
}
memcpy(ndata, encoder->data, encoder->datalen);
encoder->data = ndata;
encoder->datalen = nlen;
}
encoder->bit = 0;
encoder->data[encoder->offset] = 0xffu;
}
if (!bit) {
encoder->data[encoder->offset] &= ~cbit_mask[encoder->bit];
}
return APR_SUCCESS;
}

static apr_status_t gset_encode_next(gset_encoder *encoder, apr_uint64_t pval)
{
apr_uint64_t delta, flex_bits;
apr_status_t status = APR_SUCCESS;
int i;

delta = pval - encoder->last;
encoder->last = pval;
flex_bits = (delta >> encoder->fixed_bits);
/* Intentional no APLOGNO */
ap_log_perror(APLOG_MARK, GCSLOG_LEVEL, 0, encoder->pool,
"h2_push_diary_enc: val=%"APR_UINT64_T_HEX_FMT", delta=%"
APR_UINT64_T_HEX_FMT" flex_bits=%"APR_UINT64_T_FMT", "
", fixed_bits=%d, fixed_val=%"APR_UINT64_T_HEX_FMT,
pval, delta, flex_bits, encoder->fixed_bits, delta&encoder->fixed_mask);
for (; flex_bits != 0; --flex_bits) {
status = gset_encode_bit(encoder, 1);
if (status != APR_SUCCESS) {
return status;
}
}
status = gset_encode_bit(encoder, 0);
if (status != APR_SUCCESS) {
return status;
}

for (i = encoder->fixed_bits-1; i >= 0; --i) {
status = gset_encode_bit(encoder, (delta >> i) & 1);
if (status != APR_SUCCESS) {
return status;
}
}
return APR_SUCCESS;
}

/**
* Get a cache digest as described in
* https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/
* from the contents of the push diary.
*
* @param diary the diary to calculdate the digest from
* @param p the pool to use
* @param pdata on successful return, the binary cache digest
* @param plen on successful return, the length of the binary data
*/
apr_status_t h2_push_diary_digest_get(h2_push_diary *diary, apr_pool_t *pool,
int maxP, const char *authority,
const char **pdata, apr_size_t *plen)
{
int nelts, N;
unsigned char log2n, log2pmax;
gset_encoder encoder;
apr_uint64_t *hashes;
apr_size_t hash_count, i;

nelts = diary->entries->nelts;
N = ceil_power_of_2(nelts);
log2n = h2_log2(N);

/* Now log2p is the max number of relevant bits, so that
* log2p + log2n == mask_bits. We can use a lower log2p
* and have a shorter set encoding...
*/
log2pmax = h2_log2(ceil_power_of_2(maxP));

memset(&encoder, 0, sizeof(encoder));
encoder.diary = diary;
encoder.log2p = H2MIN(diary->mask_bits - log2n, log2pmax);
encoder.mask_bits = log2n + encoder.log2p;
encoder.delta_bits = diary->mask_bits - encoder.mask_bits;
encoder.fixed_bits = encoder.log2p;
encoder.fixed_mask = 1;
encoder.fixed_mask = (encoder.fixed_mask << encoder.fixed_bits) - 1;
encoder.pool = pool;
encoder.datalen = 512;
encoder.data = apr_pcalloc(encoder.pool, encoder.datalen);

encoder.data[0] = log2n;
encoder.data[1] = encoder.log2p;
encoder.offset = 1;
encoder.bit = 8;
encoder.last = 0;

/* Intentional no APLOGNO */
ap_log_perror(APLOG_MARK, GCSLOG_LEVEL, 0, pool,
"h2_push_diary_digest_get: %d entries, N=%d, log2n=%d, "
"mask_bits=%d, enc.mask_bits=%d, delta_bits=%d, enc.log2p=%d, authority=%s",
(int)nelts, (int)N, (int)log2n, diary->mask_bits,
(int)encoder.mask_bits, (int)encoder.delta_bits,
(int)encoder.log2p, authority);

if (!authority || !diary->authority
|| !strcmp("*", authority) || !strcmp(diary->authority, authority)) {
hash_count = diary->entries->nelts;
hashes = apr_pcalloc(encoder.pool, hash_count);
for (i = 0; i < hash_count; ++i) {
hashes[i] = ((&APR_ARRAY_IDX(diary->entries, i, h2_push_diary_entry))->hash
>> encoder.delta_bits);
}

qsort(hashes, hash_count, sizeof(apr_uint64_t), cmp_puint64);
for (i = 0; i < hash_count; ++i) {
if (!i || (hashes[i] != hashes[i-1])) {
gset_encode_next(&encoder, hashes[i]);
}
}
/* Intentional no APLOGNO */
ap_log_perror(APLOG_MARK, GCSLOG_LEVEL, 0, pool,
"h2_push_diary_digest_get: golomb compressed hashes, %d bytes",
(int)encoder.offset + 1);
}
*pdata = (const char *)encoder.data;
*plen = encoder.offset + 1;

return APR_SUCCESS;
}

15 changes: 0 additions & 15 deletions mod_http2/h2_push.h
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Original file line number Diff line number Diff line change
Expand Up @@ -140,19 +140,4 @@ apr_array_header_t *h2_push_collect_update(struct h2_stream *stream,
const struct h2_headers *res);
#endif

/**
* Get a cache digest as described in
* https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/
* from the contents of the push diary.
*
* @param diary the diary to calculdate the digest from
* @param p the pool to use
* @param authority the authority to get the data for, use NULL/"*" for all
* @param pdata on successful return, the binary cache digest
* @param plen on successful return, the length of the binary data
*/
apr_status_t h2_push_diary_digest_get(h2_push_diary *diary, apr_pool_t *p,
int maxP, const char *authority,
const char **pdata, apr_size_t *plen);

#endif /* defined(__mod_h2__h2_push__) */
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