zdoom/raze-gles
0
0
Fork 0
mirror of https://github.com/ZDoom/raze-gles.git synced 2024-12-25 03:00:46 +00:00
Code Issues Projects Releases Packages Wiki Activity
raze-gles/polymer/eduke32/build/src/quicklz.c
terminx ad2f6a6560 Update QuickLZ to 1.5.1 beta 7 
git-svn-id: https://svn.eduke32.com/eduke32@2662 1a8010ca-5511-0410-912e-c29ae57300e0
2012-05-17 21:36:50 +00:00

877 lines
24 KiB
C
Raw Blame History

// Fast data compression library
// Copyright (C) 2006-2011 Lasse Mikkel Reinhold
// lar@quicklz.com
//
// QuickLZ can be used for free under the GPL 1, 2 or 3 license (where anything
// released into public must be open source) or under a commercial license if such
// has been acquired (see http://www.quicklz.com/order.html). The commercial license
// does not cover derived or ported versions created by third parties under GPL.
// 1.5.1 BETA 7
#include "quicklz.h"
#if defined _MSC_VER
#include <intrin.h>
#endif
#if QLZ_VERSION_MAJOR != 1 || QLZ_VERSION_MINOR != 5 || QLZ_VERSION_REVISION != 1
#error quicklz.c and quicklz.h have different versions
#endif
#if (defined(__X86__) || defined(__i386__) || defined(i386) || defined(_M_IX86) || defined(__386__) || defined(__x86_64__) || defined(_M_X64))
#define X86X64
#endif
#define MINOFFSET 2
#define UNCONDITIONAL_MATCHLEN_COMPRESSOR 12
#define UNCONDITIONAL_MATCHLEN_DECOMPRESSOR 6
#define UNCOMPRESSED_END 4
#define CWORD_LEN 4
#if QLZ_COMPRESSION_LEVEL == 1 && defined QLZ_PTR_64 && QLZ_STREAMING_BUFFER == 0
#define OFFSET_BASE source
#define CAST (ui32)(size_t)
#else
#define OFFSET_BASE 0
#define CAST
#endif
#if defined(X86X64) && (defined(__GNUC__) || defined(__INTEL_COMPILER))
#define qlz_likely(x) __builtin_expect (x, 1)
#define qlz_unlikely(x) __builtin_expect (x, 0)
#else
#define qlz_likely(x) (x)
#define qlz_unlikely(x) (x)
#endif
int qlz_get_setting(int setting)
{
switch (setting)
{
case 0: return QLZ_COMPRESSION_LEVEL;
case 1: return sizeof(qlz_state_compress);
case 2: return sizeof(qlz_state_decompress);
case 3: return QLZ_STREAMING_BUFFER;
#ifdef QLZ_MEMORY_SAFE
case 6: return 1;
#else
case 6: return 0;
#endif
case 7: return QLZ_VERSION_MAJOR;
case 8: return QLZ_VERSION_MINOR;
case 9: return QLZ_VERSION_REVISION;
}
return -1;
}
#if QLZ_COMPRESSION_LEVEL == 1
static int same(const unsigned char *src, size_t n)
{
while (n > 0 && *(src + n) == *src)
n--;
return n == 0 ? 1 : 0;
}
#endif
static void reset_table_compress(qlz_state_compress *state)
{
int i;
for (i = 0; i < QLZ_HASH_VALUES; i++)
{
#if QLZ_COMPRESSION_LEVEL == 1
state->hash[i].offset = 0;
#else
state->hash_counter[i] = 0;
#endif
}
}
static void reset_table_decompress(qlz_state_decompress *state)
{
int i;
(void)state;
(void)i;
#if QLZ_COMPRESSION_LEVEL == 2
for (i = 0; i < QLZ_HASH_VALUES; i++)
{
state->hash_counter[i] = 0;
}
#endif
}
static __inline ui32 hash_func(ui32 i)
{
#if QLZ_COMPRESSION_LEVEL == 2
return ((i >> 9) ^(i >> 13) ^ i) & (QLZ_HASH_VALUES - 1);
#else
return ((i >> 12) ^ i) & (QLZ_HASH_VALUES - 1);
#endif
}
static __inline ui32 fast_read(void const *src, ui32 bytes)
{
#ifndef X86X64
unsigned char *p = (unsigned char *)src;
switch (bytes)
{
case 4:
return(*p | *(p + 1) << 8 | *(p + 2) << 16 | *(p + 3) << 24);
case 3:
return(*p | *(p + 1) << 8 | *(p + 2) << 16);
case 2:
return(*p | *(p + 1) << 8);
case 1:
return(*p);
}
return 0;
#else
if (bytes >= 1 && bytes <= 4)
return *((ui32 *)src);
else
return 0;
#endif
}
static __inline ui32 hashat(const unsigned char *src)
{
ui32 fetch, hash;
fetch = fast_read(src, 3);
hash = hash_func(fetch);
return hash;
}
static __inline void fast_write(ui32 f, void *dst, size_t bytes)
{
#ifndef X86X64
unsigned char *p = (unsigned char *)dst;
switch (bytes)
{
case 4:
*p = (unsigned char)f;
*(p + 1) = (unsigned char)(f >> 8);
*(p + 2) = (unsigned char)(f >> 16);
*(p + 3) = (unsigned char)(f >> 24);
return;
case 3:
*p = (unsigned char)f;
*(p + 1) = (unsigned char)(f >> 8);
*(p + 2) = (unsigned char)(f >> 16);
return;
case 2:
*p = (unsigned char)f;
*(p + 1) = (unsigned char)(f >> 8);
return;
case 1:
*p = (unsigned char)f;
return;
}
#else
switch (bytes)
{
case 4:
*((ui32 *)dst) = f;
return;
case 3:
*((ui32 *)dst) = f;
return;
case 2:
*((ui16 *)dst) = (ui16)f;
return;
case 1:
*((unsigned char *)dst) = (unsigned char)f;
return;
}
#endif
}
size_t qlz_size_decompressed(const char *source)
{
ui32 n, r;
n = (((*source) & 2) == 2) ? 4 : 1;
r = fast_read(source + 1 + n, n);
r = r & (0xffffffff >> ((4 - n)*8));
return r;
}
size_t qlz_size_compressed(const char *source)
{
ui32 n, r;
n = (((*source) & 2) == 2) ? 4 : 1;
r = fast_read(source + 1, n);
r = r & (0xffffffff >> ((4 - n)*8));
return r;
}
size_t qlz_size_header(const char *source)
{
size_t n = 2*((((*source) & 2) == 2) ? 4 : 1) + 1;
return n;
}
static __inline void memcpy_up(unsigned char *dst, const unsigned char *src, ui32 n)
{
// Caution if modifying memcpy_up! Overlap of dst and src must be special handled.
#ifndef X86X64
unsigned char *end = dst + n;
while (dst < end)
{
*dst = *src;
dst++;
src++;
}
#else
ui32 f = 0;
do
{
*(ui32 *)(dst + f) = *(ui32 *)(src + f);
f += MINOFFSET + 1;
}
while (f < n);
#endif
}
static __inline void update_hash(qlz_state_decompress *state, const unsigned char *s)
{
#if QLZ_COMPRESSION_LEVEL == 1
ui32 hash;
hash = hashat(s);
state->hash[hash].offset = s;
state->hash_counter[hash] = 1;
#elif QLZ_COMPRESSION_LEVEL == 2
ui32 hash;
unsigned char c;
hash = hashat(s);
c = state->hash_counter[hash];
state->hash[hash].offset[c & (QLZ_POINTERS - 1)] = s;
c++;
state->hash_counter[hash] = c;
#endif
(void)state;
(void)s;
}
#if QLZ_COMPRESSION_LEVEL <= 2
static void update_hash_upto(qlz_state_decompress *state, unsigned char **lh, const unsigned char *max)
{
while (*lh < max)
{
(*lh)++;
update_hash(state, *lh);
}
}
#endif
static size_t qlz_compress_core(const unsigned char *source, unsigned char *destination, size_t size, qlz_state_compress *state)
{
const unsigned char *last_byte = source + size - 1;
const unsigned char *src = source;
unsigned char *cword_ptr = destination;
unsigned char *dst = destination + CWORD_LEN;
ui32 cword_val = 1U << 31;
const unsigned char *last_matchstart = last_byte - UNCONDITIONAL_MATCHLEN_COMPRESSOR - UNCOMPRESSED_END;
ui32 fetch = 0;
unsigned int lits = 0;
(void) lits;
if (src <= last_matchstart)
fetch = fast_read(src, 3);
while (qlz_likely(src <= last_matchstart))
{
if (qlz_unlikely((cword_val & 1) == 1))
{
// store uncompressed if compression ratio is too low
if (src > source + (size >> 1) && dst - destination > src - source - ((src - source) >> 5))
return 0;
fast_write((cword_val >> 1) | (1U << 31), cword_ptr, CWORD_LEN);
cword_ptr = dst;
dst += CWORD_LEN;
cword_val = 1U << 31;
fetch = fast_read(src, 3);
}
#if QLZ_COMPRESSION_LEVEL == 1
{
const unsigned char *o;
ui32 hash, cached;
hash = hash_func(fetch);
cached = fetch ^ state->hash[hash].cache;
state->hash[hash].cache = fetch;
o = state->hash[hash].offset + OFFSET_BASE;
state->hash[hash].offset = CAST(src - OFFSET_BASE);
#ifdef X86X64
if ((cached & 0xffffff) == 0 && o != OFFSET_BASE && (src - o > MINOFFSET || (src == o + 1 && lits >= 3 && src > source + 3 && same(src - 3, 6))))
{
#else
if (cached == 0 && o != OFFSET_BASE && (src - o > MINOFFSET || (src == o + 1 && lits >= 3 && src > source + 3 && same(src - 3, 6))))
{
#endif
size_t matchlen = 3;
hash <<= 4;
cword_val = (cword_val >> 1) | (1U << 31);
#if defined X86X64 && defined QLZ_PTR_64
{
#ifdef __GNUC__
unsigned long long a = *(unsigned long long *)(src + matchlen);
unsigned long long b = *(unsigned long long *)(o + matchlen);
unsigned long long c = a^b;
#else
unsigned int a = *(unsigned int *)(src + matchlen);
unsigned int b = *(unsigned int *)(o + matchlen);
unsigned int c = a^b;
#endif
if (qlz_unlikely(c == 0))
{
size_t q = last_byte - UNCOMPRESSED_END - src + 1;
size_t remaining = q > 255 ? 255 : q;
matchlen += sizeof(c);
while (src[matchlen] == o[matchlen] && matchlen < remaining)
matchlen++;
}
else
{
#if defined _MSC_VER || defined __INTEL_COMPILER
unsigned int index = 0;
_BitScanForward((unsigned long *)&index, c);
matchlen += index >> 3;
#else
matchlen += __builtin_ctzll(c) >> 3;
#endif
}
}
#else
if (src[matchlen] == o[matchlen])
{
size_t q = last_byte - UNCOMPRESSED_END - src + 1;
size_t remaining = q > 255 ? 255 : q;
matchlen ++;
while (src[matchlen] == o[matchlen] && matchlen < remaining)
matchlen++;
}
#endif
src += matchlen;
if (qlz_likely(matchlen < 18))
{
fast_write((ui32)(matchlen - 2) | hash, dst, 2);
dst += 2;
}
else
{
fast_write((ui32)(matchlen << 16) | hash, dst, 3);
dst += 3;
}
fetch = fast_read(src, 3);
lits = 0;
}
else
{
lits++;
*dst = *src;
src++;
dst++;
cword_val = (cword_val >> 1);
#ifdef X86X64
fetch = fast_read(src, 3);
#else
fetch = (fetch >> 8 & 0xffff) | (*(src + 2) << 16);
#endif
}
}
#elif QLZ_COMPRESSION_LEVEL >= 2
{
const unsigned char *o, *offset2;
ui32 hash, matchlen, k, m, best_k = 0;
unsigned char c;
size_t remaining = (last_byte - UNCOMPRESSED_END - src + 1) > 255 ? 255 : (last_byte - UNCOMPRESSED_END - src + 1);
(void)best_k;
fetch = fast_read(src, 3);
hash = hash_func(fetch);
c = state->hash_counter[hash];
offset2 = state->hash[hash].offset[0];
if (offset2 < src - MINOFFSET && c > 0 && ((fast_read(offset2, 3) ^ fetch) & 0xffffff) == 0)
{
matchlen = 3;
if (*(offset2 + matchlen) == *(src + matchlen))
{
matchlen = 4;
while (*(offset2 + matchlen) == *(src + matchlen) && matchlen < remaining)
matchlen++;
}
}
else
matchlen = 0;
for (k = 1; k < QLZ_POINTERS && c > k; k++)
{
o = state->hash[hash].offset[k];
#if QLZ_COMPRESSION_LEVEL == 3
if (((fast_read(o, 3) ^ fetch) & 0xffffff) == 0 && o < src - MINOFFSET)
#elif QLZ_COMPRESSION_LEVEL == 2
if (*(src + matchlen) == *(o + matchlen) && ((fast_read(o, 3) ^ fetch) & 0xffffff) == 0 && o < src - MINOFFSET)
#endif
{
m = 3;
while (*(o + m) == *(src + m) && m < remaining)
m++;
#if QLZ_COMPRESSION_LEVEL == 3
if ((m > matchlen) || (m == matchlen && o > offset2))
#elif QLZ_COMPRESSION_LEVEL == 2
if (m > matchlen)
#endif
{
offset2 = o;
matchlen = m;
best_k = k;
}
}
}
o = offset2;
state->hash[hash].offset[c & (QLZ_POINTERS - 1)] = src;
c++;
state->hash_counter[hash] = c;
#if QLZ_COMPRESSION_LEVEL == 3
if (matchlen > 2 && src - o < 131071)
{
ui32 u;
size_t offset = src - o;
for (u = 1; u < matchlen; u++)
{
hash = hashat(src + u);
c = state->hash_counter[hash]++;
state->hash[hash].offset[c & (QLZ_POINTERS - 1)] = src + u;
}
cword_val = (cword_val >> 1) | (1U << 31);
src += matchlen;
if (matchlen == 3 && offset <= 63)
{
*dst = (unsigned char)(offset << 2);
dst++;
}
else if (matchlen == 3 && offset <= 16383)
{
ui32 f = (ui32)((offset << 2) | 1);
fast_write(f, dst, 2);
dst += 2;
}
else if (matchlen <= 18 && offset <= 1023)
{
ui32 f = ((matchlen - 3) << 2) | ((ui32)offset << 6) | 2;
fast_write(f, dst, 2);
dst += 2;
}
else if (matchlen <= 33)
{
ui32 f = ((matchlen - 2) << 2) | ((ui32)offset << 7) | 3;
fast_write(f, dst, 3);
dst += 3;
}
else
{
ui32 f = ((matchlen - 3) << 7) | ((ui32)offset << 15) | 3;
fast_write(f, dst, 4);
dst += 4;
}
}
else
{
*dst = *src;
src++;
dst++;
cword_val = (cword_val >> 1);
}
#elif QLZ_COMPRESSION_LEVEL == 2
if (matchlen > 2)
{
cword_val = (cword_val >> 1) | (1U << 31);
src += matchlen;
if (matchlen < 10)
{
ui32 f = best_k | ((matchlen - 2) << 2) | (hash << 5);
fast_write(f, dst, 2);
dst += 2;
}
else
{
ui32 f = best_k | (matchlen << 16) | (hash << 5);
fast_write(f, dst, 3);
dst += 3;
}
}
else
{
*dst = *src;
src++;
dst++;
cword_val = (cword_val >> 1);
}
#endif
}
#endif
}
while (src <= last_byte)
{
if ((cword_val & 1) == 1)
{
fast_write((cword_val >> 1) | (1U << 31), cword_ptr, CWORD_LEN);
cword_ptr = dst;
dst += CWORD_LEN;
cword_val = 1U << 31;
}
#if QLZ_COMPRESSION_LEVEL < 3
if (src <= last_byte - 3)
{
#if QLZ_COMPRESSION_LEVEL == 1
ui32 hash, fetch;
fetch = fast_read(src, 3);
hash = hash_func(fetch);
state->hash[hash].offset = CAST(src - OFFSET_BASE);
state->hash[hash].cache = fetch;
#elif QLZ_COMPRESSION_LEVEL == 2
ui32 hash;
unsigned char c;
hash = hashat(src);
c = state->hash_counter[hash];
state->hash[hash].offset[c & (QLZ_POINTERS - 1)] = src;
c++;
state->hash_counter[hash] = c;
#endif
}
#endif
*dst = *src;
src++;
dst++;
cword_val = (cword_val >> 1);
}
while ((cword_val & 1) != 1)
cword_val = (cword_val >> 1);
fast_write((cword_val >> 1) | (1U << 31), cword_ptr, CWORD_LEN);
// min. size must be 9 bytes so that the qlz_size functions can take 9 bytes as argument
return dst - destination < 9 ? 9 : dst - destination;
}
static size_t qlz_decompress_core(const unsigned char *source, unsigned char *destination, size_t size, qlz_state_decompress *state, const unsigned char *history)
{
const unsigned char *src = source + qlz_size_header((const char *)source);
unsigned char *dst = destination;
const unsigned char *last_destination_byte = destination + size - 1;
ui32 cword_val = 1;
const unsigned char *last_matchstart = last_destination_byte - UNCONDITIONAL_MATCHLEN_DECOMPRESSOR - UNCOMPRESSED_END;
unsigned char *last_hashed = destination - 1;
const unsigned char *last_source_byte = source + qlz_size_compressed((const char *)source) - 1;
static const ui32 bitlut[16] = {4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0};
(void) last_source_byte;
(void) last_hashed;
(void) state;
(void) history;
for (;;)
{
ui32 fetch;
if (cword_val == 1)
{
#ifdef QLZ_MEMORY_SAFE
if (src + CWORD_LEN - 1 > last_source_byte)
return 0;
#endif
cword_val = fast_read(src, CWORD_LEN);
src += CWORD_LEN;
}
#ifdef QLZ_MEMORY_SAFE
if (src + 4 - 1 > last_source_byte)
return 0;
#endif
fetch = fast_read(src, 4);
if ((cword_val & 1) == 1)
{
ui32 matchlen;
const unsigned char *offset2;
#if QLZ_COMPRESSION_LEVEL == 1
ui32 hash;
cword_val = cword_val >> 1;
hash = (fetch >> 4) & 0xfff;
offset2 = (const unsigned char *)(size_t)state->hash[hash].offset;
if ((fetch & 0xf) != 0)
{
matchlen = (fetch & 0xf) + 2;
src += 2;
}
else
{
matchlen = *(src + 2);
src += 3;
}
#elif QLZ_COMPRESSION_LEVEL == 2
ui32 hash;
unsigned char c;
cword_val = cword_val >> 1;
hash = (fetch >> 5) & 0x7ff;
c = (unsigned char)(fetch & 0x3);
offset2 = state->hash[hash].offset[c];
if ((fetch & (28)) != 0)
{
matchlen = ((fetch >> 2) & 0x7) + 2;
src += 2;
}
else
{
matchlen = *(src + 2);
src += 3;
}
#elif QLZ_COMPRESSION_LEVEL == 3
ui32 offset;
cword_val = cword_val >> 1;
if ((fetch & 3) == 0)
{
offset = (fetch & 0xff) >> 2;
matchlen = 3;
src++;
}
else if ((fetch & 2) == 0)
{
offset = (fetch & 0xffff) >> 2;
matchlen = 3;
src += 2;
}
else if ((fetch & 1) == 0)
{
offset = (fetch & 0xffff) >> 6;
matchlen = ((fetch >> 2) & 15) + 3;
src += 2;
}
else if ((fetch & 127) != 3)
{
offset = (fetch >> 7) & 0x1ffff;
matchlen = ((fetch >> 2) & 0x1f) + 2;
src += 3;
}
else
{
offset = (fetch >> 15);
matchlen = ((fetch >> 7) & 255) + 3;
src += 4;
}
offset2 = dst - offset;
#endif
#ifdef QLZ_MEMORY_SAFE
if (offset2 < history || offset2 > dst - MINOFFSET - 1)
return 0;
if (matchlen > (ui32)(last_destination_byte - dst - UNCOMPRESSED_END + 1))
return 0;
#endif
memcpy_up(dst, offset2, matchlen);
dst += matchlen;
#if QLZ_COMPRESSION_LEVEL <= 2
update_hash_upto(state, &last_hashed, dst - matchlen);
last_hashed = dst - 1;
#endif
}
else
{
if (dst < last_matchstart)
{
unsigned int n = bitlut[cword_val & 0xf];
#ifdef X86X64
*(ui32 *)dst = *(ui32 *)src;
#else
memcpy_up(dst, src, 4);
#endif
cword_val = cword_val >> n;
dst += n;
src += n;
#if QLZ_COMPRESSION_LEVEL <= 2
update_hash_upto(state, &last_hashed, dst - 3);
#endif
}
else
{
while (dst <= last_destination_byte)
{
if (cword_val == 1)
{
src += CWORD_LEN;
cword_val = 1U << 31;
}
#ifdef QLZ_MEMORY_SAFE
if (src >= last_source_byte + 1)
return 0;
#endif
*dst = *src;
dst++;
src++;
cword_val = cword_val >> 1;
}
#if QLZ_COMPRESSION_LEVEL <= 2
update_hash_upto(state, &last_hashed, last_destination_byte - 3); // todo, use constant
#endif
return size;
}
}
}
}
size_t qlz_compress(const void *source, char *destination, size_t size, qlz_state_compress *state)
{
size_t r;
ui32 compressed;
size_t base;
if (size == 0 || size > 0xffffffff - 400)
return 0;
if (size < 216)
base = 3;
else
base = 9;
#if QLZ_STREAMING_BUFFER > 0
if (state->stream_counter + size - 1 >= QLZ_STREAMING_BUFFER)
#endif
{
reset_table_compress(state);
r = base + qlz_compress_core((const unsigned char *)source, (unsigned char *)destination + base, size, state);
#if QLZ_STREAMING_BUFFER > 0
reset_table_compress(state);
#endif
if (r == base)
{
memcpy(destination + base, source, size);
r = size + base;
compressed = 0;
}
else
{
compressed = 1;
}
state->stream_counter = 0;
}
#if QLZ_STREAMING_BUFFER > 0
else
{
unsigned char *src = state->stream_buffer + state->stream_counter;
memcpy(src, source, size);
r = base + qlz_compress_core(src, (unsigned char *)destination + base, size, state);
if (r == base)
{
memcpy(destination + base, src, size);
r = size + base;
compressed = 0;
reset_table_compress(state);
}
else
{
compressed = 1;
}
state->stream_counter += size;
}
#endif
if (base == 3)
{
*destination = (unsigned char)(0 | compressed);
*(destination + 1) = (unsigned char)r;
*(destination + 2) = (unsigned char)size;
}
else
{
*destination = (unsigned char)(2 | compressed);
fast_write((ui32)r, destination + 1, 4);
fast_write((ui32)size, destination + 5, 4);
}
*destination |= (QLZ_COMPRESSION_LEVEL << 2);
*destination |= (1 << 6);
*destination |= ((QLZ_STREAMING_BUFFER == 0 ? 0 : (QLZ_STREAMING_BUFFER == 100000 ? 1 : (QLZ_STREAMING_BUFFER == 1000000 ? 2 : 3))) << 4);
// 76543210
// 01SSLLHC
return r;
}
size_t qlz_decompress(const char *source, void *destination, qlz_state_decompress *state)
{
size_t dsiz = qlz_size_decompressed(source);
size_t csiz = qlz_size_compressed(source);
#if QLZ_STREAMING_BUFFER > 0
if (state->stream_counter + qlz_size_decompressed(source) - 1 >= QLZ_STREAMING_BUFFER)
#endif
{
if ((*source & 1) == 1)
{
reset_table_decompress(state);
dsiz = qlz_decompress_core((const unsigned char *)source, (unsigned char *)destination, dsiz, state, (const unsigned char *)destination);
}
else
{
if (csiz != dsiz + qlz_size_header(source))
return 0;
memcpy(destination, source + qlz_size_header(source), dsiz);
}
state->stream_counter = 0;
reset_table_decompress(state);
}
#if QLZ_STREAMING_BUFFER > 0
else
{
unsigned char *dst = state->stream_buffer + state->stream_counter;
if ((*source & 1) == 1)
{
dsiz = qlz_decompress_core((const unsigned char *)source, dst, dsiz, state, (const unsigned char *)state->stream_buffer);
}
else
{
// if(csiz != dsiz + qlz_size_header(source))
// return 0;
memcpy(dst, source + qlz_size_header(source), dsiz);
reset_table_decompress(state);
}
memcpy(destination, dst, dsiz);
state->stream_counter += dsiz;
}
#endif
return dsiz;
}
Reference in a new issue View git blame Copy permalink