void png_read_filter_row_avg4_sse2(png_row_infop row_info, png_bytep row,
png_const_bytep prev)
{
/* The Avg filter predicts each pixel as the (truncated) average of a and b.
* There's no pixel to the left of the first pixel. Luckily, it's
* predicted to be half of the pixel above it. So again, this works
* perfectly with our loop if we make sure a starts at zero.
*/
png_size_t rb;
const __m128i zero = _mm_setzero_si128();
__m128i b;
__m128i a, d = zero;
png_debug(1, "in png_read_filter_row_avg4_sse2");
rb = row_info->rowbytes+4;
while (rb > 4) {
__m128i avg;
b = load4(prev);
a = d; d = load4(row );
/* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
avg = _mm_avg_epu8(a,b);
/* ...but we can fix it up by subtracting off 1 if it rounded up. */
avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
_mm_set1_epi8(1)));
d = _mm_add_epi8(d, avg);
store4(row, d);
prev += 4;
row += 4;
rb -= 4;
}
}
void png_read_filter_row_paeth4_sse2(png_row_infop row_info, png_bytep row,
png_const_bytep prev)
{
/* Paeth tries to predict pixel d using the pixel to the left of it, a,
* and two pixels from the previous row, b and c:
* prev: c b
* row: a d
* The Paeth function predicts d to be whichever of a, b, or c is nearest to
* p=a+b-c.
*
* The first pixel has no left context, and so uses an Up filter, p = b.
* This works naturally with our main loop's p = a+b-c if we force a and c
* to zero.
* Here we zero b and d, which become c and a respectively at the start of
* the loop.
*/
png_debug(1, "in png_read_filter_row_paeth4_sse2");
const __m128i zero = _mm_setzero_si128();
__m128i c, b = zero,
a, d = zero;
int rb = row_info->rowbytes;
while (rb > 0) {
/* It's easiest to do this math (particularly, deal with pc) with 16-bit
* intermediates.
*/
c = b; b = _mm_unpacklo_epi8(load4(prev), zero);
a = d; d = _mm_unpacklo_epi8(load4(row ), zero);
/* (p-a) == (a+b-c - a) == (b-c) */
__m128i pa = _mm_sub_epi16(b,c);
/* (p-b) == (a+b-c - b) == (a-c) */
__m128i pb = _mm_sub_epi16(a,c);
/* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
__m128i pc = _mm_add_epi16(pa,pb);
pa = abs_i16(pa); /* |p-a| */
pb = abs_i16(pb); /* |p-b| */
pc = abs_i16(pc); /* |p-c| */
__m128i smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
/* Paeth breaks ties favoring a over b over c. */
__m128i nearest = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
c));
/* Note `_epi8`: we need addition to wrap modulo 255. */
d = _mm_add_epi8(d, nearest);
store4(row, _mm_packus_epi16(d,d));
prev += 4;
row += 4;
rb -= 4;
}
}
static void store3(void* p, __m128i v) {
/* We'll pull from SSE as a 32-bit int, then write
* its bottom two bytes, then its third byte.
*/
png_uint_32 v012;
store4(&v012, v);
png_uint_16* p01 = p;
png_byte* p2 = (png_byte*)(p01+1);
*p01 = v012;
*p2 = v012 >> 16;
}
void png_read_filter_row_sub4_sse2(png_row_infop row_info, png_bytep row,
png_const_bytep prev)
{
/* The Sub filter predicts each pixel as the previous pixel, a.
* There is no pixel to the left of the first pixel. It's encoded directly.
* That works with our main loop if we just say that left pixel was zero.
*/
png_debug(1, "in png_read_filter_row_sub4_sse2");
__m128i a, d = _mm_setzero_si128();
int rb = row_info->rowbytes;
while (rb > 0) {
a = d; d = load4(row);
d = _mm_add_epi8(d, a);
store4(row, d);
row += 4;
rb -= 4;
}
}
void
fht_SSE2(FLOAT * fz, int n)
{
const FLOAT *tri = costab;
int k4;
FLOAT *fi, *gi;
FLOAT const *fn;
n <<= 1; /* to get BLKSIZE, because of 3DNow! ASM routine */
fn = fz + n;
k4 = 4;
do {
FLOAT s1, c1;
int i, k1, k2, k3, kx;
kx = k4 >> 1;
k1 = k4;
k2 = k4 << 1;
k3 = k2 + k1;
k4 = k2 << 1;
fi = fz;
gi = fi + kx;
do {
FLOAT f0, f1, f2, f3;
f1 = fi[0] - fi[k1];
f0 = fi[0] + fi[k1];
f3 = fi[k2] - fi[k3];
f2 = fi[k2] + fi[k3];
fi[k2] = f0 - f2;
fi[0] = f0 + f2;
fi[k3] = f1 - f3;
fi[k1] = f1 + f3;
f1 = gi[0] - gi[k1];
f0 = gi[0] + gi[k1];
f3 = SQRT2 * gi[k3];
f2 = SQRT2 * gi[k2];
gi[k2] = f0 - f2;
gi[0] = f0 + f2;
gi[k3] = f1 - f3;
gi[k1] = f1 + f3;
gi += k4;
fi += k4;
} while (fi < fn);
c1 = tri[0];
s1 = tri[1];
for (i = 1; i < kx; i++) {
__m128 v_s2;
__m128 v_c2;
__m128 v_c1;
__m128 v_s1;
FLOAT c2, s2, s1_2 = s1+s1;
c2 = 1 - s1_2 * s1;
s2 = s1_2 * c1;
fi = fz + i;
gi = fz + k1 - i;
v_c1 = _mm_set_ps1(c1);
v_s1 = _mm_set_ps1(s1);
v_c2 = _mm_set_ps1(c2);
v_s2 = _mm_set_ps1(s2);
{
static const vecfloat_union sign_mask = {{0x80000000,0,0,0}};
v_c1 = _mm_xor_ps(sign_mask._m128, v_c1); /* v_c1 := {-c1, +c1, +c1, +c1} */
}
{
static const vecfloat_union sign_mask = {{0,0x80000000,0,0}};
v_s1 = _mm_xor_ps(sign_mask._m128, v_s1); /* v_s1 := {+s1, -s1, +s1, +s1} */
}
{
static const vecfloat_union sign_mask = {{0,0,0x80000000,0x80000000}};
v_c2 = _mm_xor_ps(sign_mask._m128, v_c2); /* v_c2 := {+c2, +c2, -c2, -c2} */
}
do {
__m128 p, q, r;
q = _mm_setr_ps(fi[k1], fi[k3], gi[k1], gi[k3]); /* Q := {fi_k1,fi_k3,gi_k1,gi_k3}*/
p = _mm_mul_ps(_mm_set_ps1(s2), q); /* P := s2 * Q */
q = _mm_mul_ps(v_c2, q); /* Q := c2 * Q */
q = _mm_shuffle_ps(q, q, _MM_SHUFFLE(1,0,3,2)); /* Q := {-c2*gi_k1,-c2*gi_k3,c2*fi_k1,c2*fi_k3} */
p = _mm_add_ps(p, q);
r = _mm_setr_ps(gi[0], gi[k2], fi[0], fi[k2]); /* R := {gi_0,gi_k2,fi_0,fi_k2} */
q = _mm_sub_ps(r, p); /* Q := {gi_0-p0,gi_k2-p1,fi_0-p2,fi_k2-p3} */
r = _mm_add_ps(r, p); /* R := {gi_0+p0,gi_k2+p1,fi_0+p2,fi_k2+p3} */
p = _mm_shuffle_ps(q, r, _MM_SHUFFLE(2,0,2,0)); /* P := {q0,q2,r0,r2} */
p = _mm_shuffle_ps(p, p, _MM_SHUFFLE(3,1,2,0)); /* P := {q0,r0,q2,r2} */
q = _mm_shuffle_ps(q, r, _MM_SHUFFLE(3,1,3,1)); /* Q := {q1,q3,r1,r3} */
r = _mm_mul_ps(v_c1, q);
q = _mm_mul_ps(v_s1, q);
q = _mm_shuffle_ps(q, q, _MM_SHUFFLE(0,1,2,3)); /* Q := {q3,q2,q1,q0} */
q = _mm_add_ps(q, r);
store4(_mm_sub_ps(p, q), &gi[k3], &gi[k2], &fi[k3], &fi[k2]);
store4(_mm_add_ps(p, q), &gi[k1], &gi[ 0], &fi[k1], &fi[ 0]);
gi += k4;
fi += k4;
} while (fi < fn);
c2 = c1;
c1 = c2 * tri[0] - s1 * tri[1];
s1 = c2 * tri[1] + s1 * tri[0];
}
tri += 2;
} while (k4 < n);
}
void lzvn_decode(lzvn_decoder_state *state) {
#if HAVE_LABELS_AS_VALUES
// Jump table for all instructions
static const void *opc_tbl[256] = {
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&eos, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&nop, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&nop, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&udef, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&udef, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&udef, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&udef, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&udef, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef,
&&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d,
&&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d,
&&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d,
&&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d, &&med_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&sml_d, &&pre_d, &&lrg_d,
&&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef,
&&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef, &&udef,
&&lrg_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l,
&&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l, &&sml_l,
&&lrg_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m,
&&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m, &&sml_m};
#endif
size_t src_len = state->src_end - state->src;
size_t dst_len = state->dst_end - state->dst;
if (src_len == 0 || dst_len == 0)
return; // empty buffer
const unsigned char *src_ptr = state->src;
unsigned char *dst_ptr = state->dst;
size_t D = state->d_prev;
size_t M;
size_t L;
size_t opc_len;
// Do we have a partially expanded match saved in state?
if (state->L != 0 || state->M != 0) {
L = state->L;
M = state->M;
D = state->D;
opc_len = 0; // we already skipped the op
state->L = state->M = state->D = 0;
if (M == 0)
goto copy_literal;
if (L == 0)
goto copy_match;
goto copy_literal_and_match;
}
unsigned char opc = src_ptr[0];
#if HAVE_LABELS_AS_VALUES
goto *opc_tbl[opc];
#else
for (;;) {
switch (opc) {
#endif
// ===============================================================
// These four opcodes (sml_d, med_d, lrg_d, and pre_d) encode both a
// literal and a match. The bulk of their implementations are shared;
// each label here only does the work of setting the opcode length (not
// including any literal bytes), and extracting the literal length, match
// length, and match distance (except in pre_d). They then jump into the
// shared implementation to actually output the literal and match bytes.
//
// No error checking happens in the first stage, except for ensuring that
// the source has enough length to represent the full opcode before
// reading past the first byte.
sml_d:
#if !HAVE_LABELS_AS_VALUES
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
case 8:
case 9:
case 10:
case 11:
case 12:
case 13:
case 16:
case 17:
case 18:
case 19:
case 20:
case 21:
case 24:
case 25:
case 26:
case 27:
case 28:
case 29:
case 32:
case 33:
case 34:
case 35:
case 36:
case 37:
case 40:
case 41:
case 42:
case 43:
case 44:
case 45:
case 48:
case 49:
case 50:
case 51:
case 52:
case 53:
case 56:
case 57:
case 58:
case 59:
case 60:
case 61:
case 64:
case 65:
case 66:
case 67:
case 68:
case 69:
case 72:
case 73:
case 74:
case 75:
case 76:
case 77:
case 80:
case 81:
case 82:
case 83:
case 84:
case 85:
case 88:
case 89:
case 90:
case 91:
case 92:
case 93:
case 96:
case 97:
case 98:
case 99:
case 100:
case 101:
case 104:
case 105:
case 106:
case 107:
case 108:
case 109:
case 128:
case 129:
case 130:
case 131:
case 132:
case 133:
case 136:
case 137:
case 138:
case 139:
case 140:
case 141:
case 144:
case 145:
case 146:
case 147:
case 148:
case 149:
case 152:
case 153:
case 154:
case 155:
case 156:
case 157:
case 192:
case 193:
case 194:
case 195:
case 196:
case 197:
case 200:
case 201:
case 202:
case 203:
case 204:
case 205:
#endif
UPDATE_GOOD;
// "small distance": This opcode has the structure LLMMMDDD DDDDDDDD LITERAL
// where the length of literal (0-3 bytes) is encoded by the high 2 bits of
// the first byte. We first extract the literal length so we know how long
// the opcode is, then check that the source can hold both this opcode and
// at least one byte of the next (because any valid input stream must be
// terminated with an eos token).
opc_len = 2;
L = (size_t)extract(opc, 6, 2);
M = (size_t)extract(opc, 3, 3) + 3;
// We need to ensure that the source buffer is long enough that we can
// safely read this entire opcode, the literal that follows, and the first
// byte of the next opcode. Once we satisfy this requirement, we can
// safely unpack the match distance. A check similar to this one is
// present in all the opcode implementations.
if (src_len <= opc_len + L)
return; // source truncated
D = (size_t)extract(opc, 0, 3) << 8 | src_ptr[1];
goto copy_literal_and_match;
med_d:
#if !HAVE_LABELS_AS_VALUES
case 160:
case 161:
case 162:
case 163:
case 164:
case 165:
case 166:
case 167:
case 168:
case 169:
case 170:
case 171:
case 172:
case 173:
case 174:
case 175:
case 176:
case 177:
case 178:
case 179:
case 180:
case 181:
case 182:
case 183:
case 184:
case 185:
case 186:
case 187:
case 188:
case 189:
case 190:
case 191:
#endif
UPDATE_GOOD;
// "medium distance": This is a minor variant of the "small distance"
// encoding, where we will now use two extra bytes instead of one to encode
// the restof the match length and distance. This allows an extra two bits
// for the match length, and an extra three bits for the match distance. The
// full structure of the opcode is 101LLMMM DDDDDDMM DDDDDDDD LITERAL.
opc_len = 3;
L = (size_t)extract(opc, 3, 2);
if (src_len <= opc_len + L)
return; // source truncated
uint16_t opc23 = load2(&src_ptr[1]);
M = (size_t)((extract(opc, 0, 3) << 2 | extract(opc23, 0, 2)) + 3);
D = (size_t)extract(opc23, 2, 14);
goto copy_literal_and_match;
lrg_d:
#if !HAVE_LABELS_AS_VALUES
case 7:
case 15:
case 23:
case 31:
case 39:
case 47:
case 55:
case 63:
case 71:
case 79:
case 87:
case 95:
case 103:
case 111:
case 135:
case 143:
case 151:
case 159:
case 199:
case 207:
#endif
UPDATE_GOOD;
// "large distance": This is another variant of the "small distance"
// encoding, where we will now use two extra bytes to encode the match
// distance, which allows distances up to 65535 to be represented. The full
// structure of the opcode is LLMMM111 DDDDDDDD DDDDDDDD LITERAL.
opc_len = 3;
L = (size_t)extract(opc, 6, 2);
M = (size_t)extract(opc, 3, 3) + 3;
if (src_len <= opc_len + L)
return; // source truncated
D = load2(&src_ptr[1]);
goto copy_literal_and_match;
pre_d:
#if !HAVE_LABELS_AS_VALUES
case 70:
case 78:
case 86:
case 94:
case 102:
case 110:
case 134:
case 142:
case 150:
case 158:
case 198:
case 206:
#endif
UPDATE_GOOD;
// "previous distance": This opcode has the structure LLMMM110, where the
// length of the literal (0-3 bytes) is encoded by the high 2 bits of the
// first byte. We first extract the literal length so we know how long
// the opcode is, then check that the source can hold both this opcode and
// at least one byte of the next (because any valid input stream must be
// terminated with an eos token).
opc_len = 1;
L = (size_t)extract(opc, 6, 2);
M = (size_t)extract(opc, 3, 3) + 3;
if (src_len <= opc_len + L)
return; // source truncated
goto copy_literal_and_match;
copy_literal_and_match:
// Common implementation of writing data for opcodes that have both a
// literal and a match. We begin by advancing the source pointer past
// the opcode, so that it points at the first literal byte (if L
// is non-zero; otherwise it points at the next opcode).
PTR_LEN_INC(src_ptr, src_len, opc_len);
// Now we copy the literal from the source pointer to the destination.
if (__builtin_expect(dst_len >= 4 && src_len >= 4, 1)) {
// The literal is 0-3 bytes; if we are not near the end of the buffer,
// we can safely just do a 4 byte copy (which is guaranteed to cover
// the complete literal, and may include some other bytes as well).
store4(dst_ptr, load4(src_ptr));
} else if (L <= dst_len) {
// We are too close to the end of either the input or output stream
// to be able to safely use a four-byte copy, but we will not exhaust
// either stream (we already know that the source will not be
// exhausted from checks in the individual opcode implementations,
// and we just tested that dst_len > L). Thus, we need to do a
// byte-by-byte copy of the literal. This is slow, but it can only ever
// happen near the very end of a buffer, so it is not an important case to
// optimize.
for (size_t i = 0; i < L; ++i)
dst_ptr[i] = src_ptr[i];
} else {
// Destination truncated: fill DST, and store partial match
// Copy partial literal
for (size_t i = 0; i < dst_len; ++i)
dst_ptr[i] = src_ptr[i];
// Save state
state->src = src_ptr + dst_len;
state->dst = dst_ptr + dst_len;
state->L = L - dst_len;
state->M = M;
state->D = D;
return; // destination truncated
}
// Having completed the copy of the literal, we advance both the source
// and destination pointers by the number of literal bytes.
PTR_LEN_INC(dst_ptr, dst_len, L);
PTR_LEN_INC(src_ptr, src_len, L);
// Check if the match distance is valid; matches must not reference
// bytes that preceed the start of the output buffer, nor can the match
// distance be zero.
if (D > dst_ptr - state->dst_begin || D == 0)
goto invalid_match_distance;
copy_match:
// Now we copy the match from dst_ptr - D to dst_ptr. It is important to keep
// in mind that we may have D < M, in which case the source and destination
// windows overlap in the copy. The semantics of the match copy are *not*
// those of memmove( ); if the buffers overlap it needs to behave as though
// we were copying byte-by-byte in increasing address order. If, for example,
// D is 1, the copy operation is equivalent to:
//
// memset(dst_ptr, dst_ptr[-1], M);
//
// i.e. it splats the previous byte. This means that we need to be very
// careful about using wide loads or stores to perform the copy operation.
if (__builtin_expect(dst_len >= M + 7 && D >= 8, 1)) {
// We are not near the end of the buffer, and the match distance
// is at least eight. Thus, we can safely loop using eight byte
// copies. The last of these may slop over the intended end of
// the match, but this is OK because we know we have a safety bound
// away from the end of the destination buffer.
for (size_t i = 0; i < M; i += 8)
store8(&dst_ptr[i], load8(&dst_ptr[i - D]));
} else if (M <= dst_len) {
// Either the match distance is too small, or we are too close to
// the end of the buffer to safely use eight byte copies. Fall back
// on a simple byte-by-byte implementation.
for (size_t i = 0; i < M; ++i)
dst_ptr[i] = dst_ptr[i - D];
} else {
// Destination truncated: fill DST, and store partial match
// Copy partial match
for (size_t i = 0; i < dst_len; ++i)
dst_ptr[i] = dst_ptr[i - D];
// Save state
state->src = src_ptr;
state->dst = dst_ptr + dst_len;
state->L = 0;
state->M = M - dst_len;
state->D = D;
return; // destination truncated
}
// Update the destination pointer and length to account for the bytes
// written by the match, then load the next opcode byte and branch to
// the appropriate implementation.
PTR_LEN_INC(dst_ptr, dst_len, M);
opc = src_ptr[0];
#if HAVE_LABELS_AS_VALUES
goto *opc_tbl[opc];
#else
break;
#endif
// ===============================================================
// Opcodes representing only a match (no literal).
// These two opcodes (lrg_m and sml_m) encode only a match. The match
// distance is carried over from the previous opcode, so all they need
// to encode is the match length. We are able to reuse the match copy
// sequence from the literal and match opcodes to perform the actual
// copy implementation.
sml_m:
#if !HAVE_LABELS_AS_VALUES
case 241:
case 242:
case 243:
case 244:
case 245:
case 246:
case 247:
case 248:
case 249:
case 250:
case 251:
case 252:
case 253:
case 254:
case 255:
#endif
UPDATE_GOOD;
// "small match": This opcode has no literal, and uses the previous match
// distance (i.e. it encodes only the match length), in a single byte as
// 1111MMMM.
opc_len = 1;
if (src_len <= opc_len)
return; // source truncated
M = (size_t)extract(opc, 0, 4);
PTR_LEN_INC(src_ptr, src_len, opc_len);
goto copy_match;
lrg_m:
#if !HAVE_LABELS_AS_VALUES
case 240:
#endif
UPDATE_GOOD;
// "large match": This opcode has no literal, and uses the previous match
// distance (i.e. it encodes only the match length). It is encoded in two
// bytes as 11110000 MMMMMMMM. Because matches smaller than 16 bytes can
// be represented by sml_m, there is an implicit bias of 16 on the match
// length; the representable values are [16,271].
opc_len = 2;
if (src_len <= opc_len)
return; // source truncated
M = src_ptr[1] + 16;
PTR_LEN_INC(src_ptr, src_len, opc_len);
goto copy_match;
// ===============================================================
// Opcodes representing only a literal (no match).
// These two opcodes (lrg_l and sml_l) encode only a literal. There is no
// match length or match distance to worry about (but we need to *not*
// touch D, as it must be preserved between opcodes).
sml_l:
#if !HAVE_LABELS_AS_VALUES
case 225:
case 226:
case 227:
case 228:
case 229:
case 230:
case 231:
case 232:
case 233:
case 234:
case 235:
case 236:
case 237:
case 238:
case 239:
#endif
UPDATE_GOOD;
// "small literal": This opcode has no match, and encodes only a literal
// of length up to 15 bytes. The format is 1110LLLL LITERAL.
opc_len = 1;
L = (size_t)extract(opc, 0, 4);
goto copy_literal;
lrg_l:
#if !HAVE_LABELS_AS_VALUES
case 224:
#endif
UPDATE_GOOD;
// "large literal": This opcode has no match, and uses the previous match
// distance (i.e. it encodes only the match length). It is encoded in two
// bytes as 11100000 LLLLLLLL LITERAL. Because literals smaller than 16
// bytes can be represented by sml_l, there is an implicit bias of 16 on
// the literal length; the representable values are [16,271].
opc_len = 2;
if (src_len <= 2)
return; // source truncated
L = src_ptr[1] + 16;
goto copy_literal;
copy_literal:
// Check that the source buffer is large enough to hold the complete
// literal and at least the first byte of the next opcode. If so, advance
// the source pointer to point to the first byte of the literal and adjust
// the source length accordingly.
if (src_len <= opc_len + L)
return; // source truncated
PTR_LEN_INC(src_ptr, src_len, opc_len);
// Now we copy the literal from the source pointer to the destination.
if (dst_len >= L + 7 && src_len >= L + 7) {
// We are not near the end of the source or destination buffers; thus
// we can safely copy the literal using wide copies, without worrying
// about reading or writing past the end of either buffer.
for (size_t i = 0; i < L; i += 8)
store8(&dst_ptr[i], load8(&src_ptr[i]));
} else if (L <= dst_len) {
// We are too close to the end of either the input or output stream
// to be able to safely use an eight-byte copy. Instead we copy the
// literal byte-by-byte.
for (size_t i = 0; i < L; ++i)
dst_ptr[i] = src_ptr[i];
} else {
// Destination truncated: fill DST, and store partial match
// Copy partial literal
for (size_t i = 0; i < dst_len; ++i)
dst_ptr[i] = src_ptr[i];
// Save state
state->src = src_ptr + dst_len;
state->dst = dst_ptr + dst_len;
state->L = L - dst_len;
state->M = 0;
state->D = D;
return; // destination truncated
}
// Having completed the copy of the literal, we advance both the source
// and destination pointers by the number of literal bytes.
PTR_LEN_INC(dst_ptr, dst_len, L);
PTR_LEN_INC(src_ptr, src_len, L);
// Load the first byte of the next opcode, and jump to its implementation.
opc = src_ptr[0];
#if HAVE_LABELS_AS_VALUES
goto *opc_tbl[opc];
#else
break;
#endif
// ===============================================================
// Other opcodes
nop:
#if !HAVE_LABELS_AS_VALUES
case 6:
case 14:
#endif
UPDATE_GOOD;
opc_len = 1;
if (src_len <= opc_len)
return; // source truncated
PTR_LEN_INC(src_ptr, src_len, opc_len);
opc = src_ptr[0];
#if HAVE_LABELS_AS_VALUES
goto *opc_tbl[opc];
#else
break;
#endif
eos:
#if !HAVE_LABELS_AS_VALUES
case 22:
#endif
opc_len = 8;
if (src_len < opc_len)
return; // source truncated (here we don't need an extra byte for next op
// code)
PTR_LEN_INC(src_ptr, src_len, opc_len);
state->end_of_stream = 1;
UPDATE_GOOD;
return; // end-of-stream
// ===============================================================
// Return on error
udef:
#if !HAVE_LABELS_AS_VALUES
case 30:
case 38:
case 46:
case 54:
case 62:
case 112:
case 113:
case 114:
case 115:
case 116:
case 117:
case 118:
case 119:
case 120:
case 121:
case 122:
case 123:
case 124:
case 125:
case 126:
case 127:
case 208:
case 209:
case 210:
case 211:
case 212:
case 213:
case 214:
case 215:
case 216:
case 217:
case 218:
case 219:
case 220:
case 221:
case 222:
case 223:
#endif
invalid_match_distance:
return; // we already updated state
#if !HAVE_LABELS_AS_VALUES
}
}
#endif
}
