walkero
/
nghttp2
1
0
Fork 0
Code Issues Pull Requests Projects Releases 1 Wiki Activity

Faster huffman decoding

This commit is contained in:
Tatsuhiro Tsujikawa 2019-10-08 23:27:58 +09:00
parent 0d855bfc1b
commit 5d6964cf81
7 changed files with 4200 additions and 4144 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
lib/nghttp2_hd_huffman.c
View File

@ -104,41 +104,37 @@ int nghttp2_hd_huff_encode(nghttp2_bufs *bufs, const uint8_t *src,
}
void nghttp2_hd_huff_decode_context_init(nghttp2_hd_huff_decode_context *ctx) {
ctx->state = 0;
ctx->accept = 1;
ctx->fstate = NGHTTP2_HUFF_ACCEPTED;
}
ssize_t nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
nghttp2_buf *buf, const uint8_t *src,
size_t srclen, int final) {
size_t i;
const uint8_t *end = src + srclen;
nghttp2_huff_decode node = {ctx->fstate, 0};
const nghttp2_huff_decode *t = &node;
uint8_t c;
/* We use the decoding algorithm described in
http://graphics.ics.uci.edu/pub/Prefix.pdf */
for (i = 0; i < srclen; ++i) {
const nghttp2_huff_decode *t;
t = &huff_decode_table[ctx->state][src[i] >> 4];
if (t->flags & NGHTTP2_HUFF_FAIL) {
return NGHTTP2_ERR_HEADER_COMP;
}
if (t->flags & NGHTTP2_HUFF_SYM) {
for (; src != end;) {
c = *src++;
t = &huff_decode_table[t->fstate & 0x1ff][c >> 4];
if (t->fstate & NGHTTP2_HUFF_SYM) {
*buf->last++ = t->sym;
}
t = &huff_decode_table[t->state][src[i] & 0xf];
if (t->flags & NGHTTP2_HUFF_FAIL) {
return NGHTTP2_ERR_HEADER_COMP;
}
if (t->flags & NGHTTP2_HUFF_SYM) {
t = &huff_decode_table[t->fstate & 0x1ff][c & 0xf];
if (t->fstate & NGHTTP2_HUFF_SYM) {
*buf->last++ = t->sym;
}
ctx->state = t->state;
ctx->accept = (t->flags & NGHTTP2_HUFF_ACCEPTED) != 0;
}
if (final && !ctx->accept) {
ctx->fstate = t->fstate;
if (final && !(ctx->fstate & NGHTTP2_HUFF_ACCEPTED)) {
return NGHTTP2_ERR_HEADER_COMP;
}
return (ssize_t)i;
return (ssize_t)srclen;
}

29
lib/nghttp2_hd_huffman.h
View File

@ -34,21 +34,20 @@
typedef enum {
/* FSA accepts this state as the end of huffman encoding
sequence. */
NGHTTP2_HUFF_ACCEPTED = 1,
NGHTTP2_HUFF_ACCEPTED = 1 << 14,
/* This state emits symbol */
NGHTTP2_HUFF_SYM = (1 << 1),
/* If state machine reaches this state, decoding fails. */
NGHTTP2_HUFF_FAIL = (1 << 2)
NGHTTP2_HUFF_SYM = 1 << 15,
} nghttp2_huff_decode_flag;
typedef struct {
/* huffman decoding state, which is actually the node ID of internal
huffman tree. We have 257 leaf nodes, but they are identical to
root node other than emitting a symbol, so we have 256 internal
nodes [1..255], inclusive. */
uint8_t state;
/* bitwise OR of zero or more of the nghttp2_huff_decode_flag */
uint8_t flags;
/* fstate is the current huffman decoding state, which is actually
the node ID of internal huffman tree with
nghttp2_huff_decode_flag OR-ed. We have 257 leaf nodes, but they
are identical to root node other than emitting a symbol, so we
have 256 internal nodes [1..255], inclusive. The node ID 256 is
a special node and it is a terminal state that means decoding
failed. */
uint16_t fstate;
/* symbol if NGHTTP2_HUFF_SYM flag set */
uint8_t sym;
} nghttp2_huff_decode;
@ -56,12 +55,8 @@ typedef struct {
typedef nghttp2_huff_decode huff_decode_table_type[16];
typedef struct {
/* Current huffman decoding state. We stripped leaf nodes, so the
value range is [0..255], inclusive. */
uint8_t state;
/* nonzero if we can say that the decoding process succeeds at this
state */
uint8_t accept;
/* fstate is the current huffman decoding state. */
uint16_t fstate;
} nghttp2_hd_huff_decode_context;
typedef struct {

8211
lib/nghttp2_hd_huffman_data.c
View File

File diff suppressed because it is too large Load Diff

35
mkhufftbl.py
View File

@ -357,9 +357,8 @@ def _build_transition_table(ctx, node):
def huffman_tree_build_transition_table(ctx):
_build_transition_table(ctx, ctx.root)
NGHTTP2_HUFF_ACCEPTED = 1
NGHTTP2_HUFF_SYM = 1 << 1
NGHTTP2_HUFF_FAIL = 1 << 2
NGHTTP2_HUFF_ACCEPTED = 1 << 14
NGHTTP2_HUFF_SYM = 1 << 15
def _print_transition_table(node):
if node.term is not None:
@ -374,8 +373,7 @@ def _print_transition_table(node):
out = sym
flags |= NGHTTP2_HUFF_SYM
if nd is None:
id = 0
flags |= NGHTTP2_HUFF_FAIL
id = 256
else:
id = nd.id
if id is None:
@ -384,13 +382,32 @@ def _print_transition_table(node):
flags |= NGHTTP2_HUFF_ACCEPTED
elif nd.accept:
flags |= NGHTTP2_HUFF_ACCEPTED
print ' {{{}, 0x{:02x}, {}}},'.format(id, flags, out)
print ' {{0x{:02x}, {}}},'.format(id | flags, out)
print '},'
_print_transition_table(node.left)
_print_transition_table(node.right)
def huffman_tree_print_transition_table(ctx):
_print_transition_table(ctx.root)
print '/* 256 */'
print '{'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print ' {0x100, 0},'
print '},'
if __name__ == '__main__':
ctx = Context()
@ -436,14 +453,12 @@ const nghttp2_huff_sym huff_sym_table[] = {'''
enum {{
NGHTTP2_HUFF_ACCEPTED = {},
NGHTTP2_HUFF_SYM = {},
NGHTTP2_HUFF_FAIL = {},
}} nghttp2_huff_decode_flag;
'''.format(NGHTTP2_HUFF_ACCEPTED, NGHTTP2_HUFF_SYM, NGHTTP2_HUFF_FAIL)
'''.format(NGHTTP2_HUFF_ACCEPTED, NGHTTP2_HUFF_SYM)
print '''\
typedef struct {
uint8_t state;
uint8_t flags;
uint16_t fstate;
uint8_t sym;
} nghttp2_huff_decode;
'''

1
tests/main.c
View File

@ -402,6 +402,7 @@ int main() {
test_nghttp2_hd_deflate_hd_vec) ||
!CU_add_test(pSuite, "hd_decode_length", test_nghttp2_hd_decode_length) ||
!CU_add_test(pSuite, "hd_huff_encode", test_nghttp2_hd_huff_encode) ||
!CU_add_test(pSuite, "hd_huff_decode", test_nghttp2_hd_huff_decode) ||
!CU_add_test(pSuite, "adjust_local_window_size",
test_nghttp2_adjust_local_window_size) ||
!CU_add_test(pSuite, "check_header_name",

29
tests/nghttp2_hd_test.c
View File

@ -1538,3 +1538,32 @@ void test_nghttp2_hd_huff_encode(void) {
nghttp2_bufs_free(&bufs);
}
void test_nghttp2_hd_huff_decode(void) {
const uint8_t e[] = {0x1f, 0xff, 0xff, 0xff, 0xff, 0xff};
nghttp2_hd_huff_decode_context ctx;
nghttp2_buf outbuf;
uint8_t b[256];
ssize_t len;
nghttp2_buf_wrap_init(&outbuf, b, sizeof(b));
nghttp2_hd_huff_decode_context_init(&ctx);
len = nghttp2_hd_huff_decode(&ctx, &outbuf, e, 1, 1);
CU_ASSERT(1 == len);
CU_ASSERT(0 == memcmp("a", outbuf.pos, 1));
/* Premature sequence must elicit decoding error */
nghttp2_buf_wrap_init(&outbuf, b, sizeof(b));
nghttp2_hd_huff_decode_context_init(&ctx);
len = nghttp2_hd_huff_decode(&ctx, &outbuf, e, 2, 1);
CU_ASSERT(NGHTTP2_ERR_HEADER_COMP == len);
/* Fully decoding EOS is error */
nghttp2_buf_wrap_init(&outbuf, b, sizeof(b));
nghttp2_hd_huff_decode_context_init(&ctx);
len = nghttp2_hd_huff_decode(&ctx, &outbuf, e, 2, 6);
CU_ASSERT(NGHTTP2_ERR_HEADER_COMP == len);
}

1
tests/nghttp2_hd_test.h
View File

@ -50,5 +50,6 @@ void test_nghttp2_hd_public_api(void);
void test_nghttp2_hd_deflate_hd_vec(void);
void test_nghttp2_hd_decode_length(void);
void test_nghttp2_hd_huff_encode(void);
void test_nghttp2_hd_huff_decode(void);
#endif /* NGHTTP2_HD_TEST_H */