mirrors/librempeg
1
0
Fork 0
mirror of https://github.com/librempeg/librempeg synced 2024-11-23 11:39:47 +00:00
Code Issues Packages Projects Releases Wiki Activity
d31c98bf80
librempeg/libswscale/swscale_altivec_template.c
Diego Biurrun 6e42e6c4b4 cosmetics attack, part I: Remove all tabs and prettyprint/reindent the code. 
Originally committed as revision 23158 to svn://svn.mplayerhq.hu/mplayer/trunk/libswscale
2007-04-28 11:44:49 +00:00

545 lines
22 KiB
C
Raw Blame History

/*
* AltiVec-enhanced yuv2yuvX
*
* Copyright (C) 2004 Romain Dolbeau <romain@dolbeau.org>
* based on the equivalent C code in "postproc/swscale.c"
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifdef CONFIG_DARWIN
#define AVV(x...) (x)
#else
#define AVV(x...) {x}
#endif
#define vzero vec_splat_s32(0)
static inline void
altivec_packIntArrayToCharArray(int *val, uint8_t* dest, int dstW) {
register int i;
vector unsigned int altivec_vectorShiftInt19 =
vec_add(vec_splat_u32(10),vec_splat_u32(9));
if ((unsigned long)dest % 16) {
/* badly aligned store, we force store alignement */
/* and will handle load misalignement on val w/ vec_perm */
vector unsigned char perm1;
vector signed int v1;
for (i = 0 ; (i < dstW) &&
(((unsigned long)dest + i) % 16) ; i++) {
int t = val[i] >> 19;
dest[i] = (t < 0) ? 0 : ((t > 255) ? 255 : t);
}
perm1 = vec_lvsl(i << 2, val);
v1 = vec_ld(i << 2, val);
for ( ; i < (dstW - 15); i+=16) {
int offset = i << 2;
vector signed int v2 = vec_ld(offset + 16, val);
vector signed int v3 = vec_ld(offset + 32, val);
vector signed int v4 = vec_ld(offset + 48, val);
vector signed int v5 = vec_ld(offset + 64, val);
vector signed int v12 = vec_perm(v1,v2,perm1);
vector signed int v23 = vec_perm(v2,v3,perm1);
vector signed int v34 = vec_perm(v3,v4,perm1);
vector signed int v45 = vec_perm(v4,v5,perm1);
vector signed int vA = vec_sra(v12, altivec_vectorShiftInt19);
vector signed int vB = vec_sra(v23, altivec_vectorShiftInt19);
vector signed int vC = vec_sra(v34, altivec_vectorShiftInt19);
vector signed int vD = vec_sra(v45, altivec_vectorShiftInt19);
vector unsigned short vs1 = vec_packsu(vA, vB);
vector unsigned short vs2 = vec_packsu(vC, vD);
vector unsigned char vf = vec_packsu(vs1, vs2);
vec_st(vf, i, dest);
v1 = v5;
}
} else { // dest is properly aligned, great
for (i = 0; i < (dstW - 15); i+=16) {
int offset = i << 2;
vector signed int v1 = vec_ld(offset, val);
vector signed int v2 = vec_ld(offset + 16, val);
vector signed int v3 = vec_ld(offset + 32, val);
vector signed int v4 = vec_ld(offset + 48, val);
vector signed int v5 = vec_sra(v1, altivec_vectorShiftInt19);
vector signed int v6 = vec_sra(v2, altivec_vectorShiftInt19);
vector signed int v7 = vec_sra(v3, altivec_vectorShiftInt19);
vector signed int v8 = vec_sra(v4, altivec_vectorShiftInt19);
vector unsigned short vs1 = vec_packsu(v5, v6);
vector unsigned short vs2 = vec_packsu(v7, v8);
vector unsigned char vf = vec_packsu(vs1, vs2);
vec_st(vf, i, dest);
}
}
for ( ; i < dstW ; i++) {
int t = val[i] >> 19;
dest[i] = (t < 0) ? 0 : ((t > 255) ? 255 : t);
}
}
static inline void
yuv2yuvX_altivec_real(int16_t *lumFilter, int16_t **lumSrc, int lumFilterSize,
int16_t *chrFilter, int16_t **chrSrc, int chrFilterSize,
uint8_t *dest, uint8_t *uDest, uint8_t *vDest, int dstW, int chrDstW)
{
const vector signed int vini = {(1 << 18), (1 << 18), (1 << 18), (1 << 18)};
register int i, j;
{
int __attribute__ ((aligned (16))) val[dstW];
for (i = 0; i < (dstW -7); i+=4) {
vec_st(vini, i << 2, val);
}
for (; i < dstW; i++) {
val[i] = (1 << 18);
}
for (j = 0; j < lumFilterSize; j++) {
vector signed short l1, vLumFilter = vec_ld(j << 1, lumFilter);
vector unsigned char perm, perm0 = vec_lvsl(j << 1, lumFilter);
vLumFilter = vec_perm(vLumFilter, vLumFilter, perm0);
vLumFilter = vec_splat(vLumFilter, 0); // lumFilter[j] is loaded 8 times in vLumFilter
perm = vec_lvsl(0, lumSrc[j]);
l1 = vec_ld(0, lumSrc[j]);
for (i = 0; i < (dstW - 7); i+=8) {
int offset = i << 2;
vector signed short l2 = vec_ld((i << 1) + 16, lumSrc[j]);
vector signed int v1 = vec_ld(offset, val);
vector signed int v2 = vec_ld(offset + 16, val);
vector signed short ls = vec_perm(l1, l2, perm); // lumSrc[j][i] ... lumSrc[j][i+7]
vector signed int i1 = vec_mule(vLumFilter, ls);
vector signed int i2 = vec_mulo(vLumFilter, ls);
vector signed int vf1 = vec_mergeh(i1, i2);
vector signed int vf2 = vec_mergel(i1, i2); // lumSrc[j][i] * lumFilter[j] ... lumSrc[j][i+7] * lumFilter[j]
vector signed int vo1 = vec_add(v1, vf1);
vector signed int vo2 = vec_add(v2, vf2);
vec_st(vo1, offset, val);
vec_st(vo2, offset + 16, val);
l1 = l2;
}
for ( ; i < dstW; i++) {
val[i] += lumSrc[j][i] * lumFilter[j];
}
}
altivec_packIntArrayToCharArray(val,dest,dstW);
}
if (uDest != 0) {
int __attribute__ ((aligned (16))) u[chrDstW];
int __attribute__ ((aligned (16))) v[chrDstW];
for (i = 0; i < (chrDstW -7); i+=4) {
vec_st(vini, i << 2, u);
vec_st(vini, i << 2, v);
}
for (; i < chrDstW; i++) {
u[i] = (1 << 18);
v[i] = (1 << 18);
}
for (j = 0; j < chrFilterSize; j++) {
vector signed short l1, l1_V, vChrFilter = vec_ld(j << 1, chrFilter);
vector unsigned char perm, perm0 = vec_lvsl(j << 1, chrFilter);
vChrFilter = vec_perm(vChrFilter, vChrFilter, perm0);
vChrFilter = vec_splat(vChrFilter, 0); // chrFilter[j] is loaded 8 times in vChrFilter
perm = vec_lvsl(0, chrSrc[j]);
l1 = vec_ld(0, chrSrc[j]);
l1_V = vec_ld(2048 << 1, chrSrc[j]);
for (i = 0; i < (chrDstW - 7); i+=8) {
int offset = i << 2;
vector signed short l2 = vec_ld((i << 1) + 16, chrSrc[j]);
vector signed short l2_V = vec_ld(((i + 2048) << 1) + 16, chrSrc[j]);
vector signed int v1 = vec_ld(offset, u);
vector signed int v2 = vec_ld(offset + 16, u);
vector signed int v1_V = vec_ld(offset, v);
vector signed int v2_V = vec_ld(offset + 16, v);
vector signed short ls = vec_perm(l1, l2, perm); // chrSrc[j][i] ... chrSrc[j][i+7]
vector signed short ls_V = vec_perm(l1_V, l2_V, perm); // chrSrc[j][i+2048] ... chrSrc[j][i+2055]
vector signed int i1 = vec_mule(vChrFilter, ls);
vector signed int i2 = vec_mulo(vChrFilter, ls);
vector signed int i1_V = vec_mule(vChrFilter, ls_V);
vector signed int i2_V = vec_mulo(vChrFilter, ls_V);
vector signed int vf1 = vec_mergeh(i1, i2);
vector signed int vf2 = vec_mergel(i1, i2); // chrSrc[j][i] * chrFilter[j] ... chrSrc[j][i+7] * chrFilter[j]
vector signed int vf1_V = vec_mergeh(i1_V, i2_V);
vector signed int vf2_V = vec_mergel(i1_V, i2_V); // chrSrc[j][i] * chrFilter[j] ... chrSrc[j][i+7] * chrFilter[j]
vector signed int vo1 = vec_add(v1, vf1);
vector signed int vo2 = vec_add(v2, vf2);
vector signed int vo1_V = vec_add(v1_V, vf1_V);
vector signed int vo2_V = vec_add(v2_V, vf2_V);
vec_st(vo1, offset, u);
vec_st(vo2, offset + 16, u);
vec_st(vo1_V, offset, v);
vec_st(vo2_V, offset + 16, v);
l1 = l2;
l1_V = l2_V;
}
for ( ; i < chrDstW; i++) {
u[i] += chrSrc[j][i] * chrFilter[j];
v[i] += chrSrc[j][i + 2048] * chrFilter[j];
}
}
altivec_packIntArrayToCharArray(u,uDest,chrDstW);
altivec_packIntArrayToCharArray(v,vDest,chrDstW);
}
}
static inline void hScale_altivec_real(int16_t *dst, int dstW, uint8_t *src, int srcW, int xInc, int16_t *filter, int16_t *filterPos, int filterSize) {
register int i;
int __attribute__ ((aligned (16))) tempo[4];
if (filterSize % 4) {
for (i=0; i<dstW; i++) {
register int j;
register int srcPos = filterPos[i];
register int val = 0;
for (j=0; j<filterSize; j++) {
val += ((int)src[srcPos + j])*filter[filterSize*i + j];
}
dst[i] = av_clip(val>>7, 0, (1<<15)-1);
}
}
else
switch (filterSize) {
case 4:
{
for (i=0; i<dstW; i++) {
register int srcPos = filterPos[i];
vector unsigned char src_v0 = vec_ld(srcPos, src);
vector unsigned char src_v1, src_vF;
vector signed short src_v, filter_v;
vector signed int val_vEven, val_s;
if ((((int)src + srcPos)% 16) > 12) {
src_v1 = vec_ld(srcPos + 16, src);
}
src_vF = vec_perm(src_v0, src_v1, vec_lvsl(srcPos, src));
src_v = // vec_unpackh sign-extends...
(vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
// now put our elements in the even slots
src_v = vec_mergeh(src_v, (vector signed short)vzero);
filter_v = vec_ld(i << 3, filter);
// the 3 above is 2 (filterSize == 4) + 1 (sizeof(short) == 2)
// the neat trick : we only care for half the elements,
// high or low depending on (i<<3)%16 (it's 0 or 8 here),
// and we're going to use vec_mule, so we chose
// carefully how to "unpack" the elements into the even slots
if ((i << 3) % 16)
filter_v = vec_mergel(filter_v,(vector signed short)vzero);
else
filter_v = vec_mergeh(filter_v,(vector signed short)vzero);
val_vEven = vec_mule(src_v, filter_v);
val_s = vec_sums(val_vEven, vzero);
vec_st(val_s, 0, tempo);
dst[i] = av_clip(tempo[3]>>7, 0, (1<<15)-1);
}
}
break;
case 8:
{
for (i=0; i<dstW; i++) {
register int srcPos = filterPos[i];
vector unsigned char src_v0 = vec_ld(srcPos, src);
vector unsigned char src_v1, src_vF;
vector signed short src_v, filter_v;
vector signed int val_v, val_s;
if ((((int)src + srcPos)% 16) > 8) {
src_v1 = vec_ld(srcPos + 16, src);
}
src_vF = vec_perm(src_v0, src_v1, vec_lvsl(srcPos, src));
src_v = // vec_unpackh sign-extends...
(vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
filter_v = vec_ld(i << 4, filter);
// the 4 above is 3 (filterSize == 8) + 1 (sizeof(short) == 2)
val_v = vec_msums(src_v, filter_v, (vector signed int)vzero);
val_s = vec_sums(val_v, vzero);
vec_st(val_s, 0, tempo);
dst[i] = av_clip(tempo[3]>>7, 0, (1<<15)-1);
}
}
break;
case 16:
{
for (i=0; i<dstW; i++) {
register int srcPos = filterPos[i];
vector unsigned char src_v0 = vec_ld(srcPos, src);
vector unsigned char src_v1 = vec_ld(srcPos + 16, src);
vector unsigned char src_vF = vec_perm(src_v0, src_v1, vec_lvsl(srcPos, src));
vector signed short src_vA = // vec_unpackh sign-extends...
(vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
vector signed short src_vB = // vec_unpackh sign-extends...
(vector signed short)(vec_mergel((vector unsigned char)vzero, src_vF));
vector signed short filter_v0 = vec_ld(i << 5, filter);
vector signed short filter_v1 = vec_ld((i << 5) + 16, filter);
// the 5 above are 4 (filterSize == 16) + 1 (sizeof(short) == 2)
vector signed int val_acc = vec_msums(src_vA, filter_v0, (vector signed int)vzero);
vector signed int val_v = vec_msums(src_vB, filter_v1, val_acc);
vector signed int val_s = vec_sums(val_v, vzero);
vec_st(val_s, 0, tempo);
dst[i] = av_clip(tempo[3]>>7, 0, (1<<15)-1);
}
}
break;
default:
{
for (i=0; i<dstW; i++) {
register int j;
register int srcPos = filterPos[i];
vector signed int val_s, val_v = (vector signed int)vzero;
vector signed short filter_v0R = vec_ld(i * 2 * filterSize, filter);
vector unsigned char permF = vec_lvsl((i * 2 * filterSize), filter);
vector unsigned char src_v0 = vec_ld(srcPos, src);
vector unsigned char permS = vec_lvsl(srcPos, src);
for (j = 0 ; j < filterSize - 15; j += 16) {
vector unsigned char src_v1 = vec_ld(srcPos + j + 16, src);
vector unsigned char src_vF = vec_perm(src_v0, src_v1, permS);
vector signed short src_vA = // vec_unpackh sign-extends...
(vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
vector signed short src_vB = // vec_unpackh sign-extends...
(vector signed short)(vec_mergel((vector unsigned char)vzero, src_vF));
vector signed short filter_v1R = vec_ld((i * 2 * filterSize) + (j * 2) + 16, filter);
vector signed short filter_v2R = vec_ld((i * 2 * filterSize) + (j * 2) + 32, filter);
vector signed short filter_v0 = vec_perm(filter_v0R, filter_v1R, permF);
vector signed short filter_v1 = vec_perm(filter_v1R, filter_v2R, permF);
vector signed int val_acc = vec_msums(src_vA, filter_v0, val_v);
val_v = vec_msums(src_vB, filter_v1, val_acc);
filter_v0R = filter_v2R;
src_v0 = src_v1;
}
if (j < (filterSize-7)) {
// loading src_v0 is useless, it's already done above
//vector unsigned char src_v0 = vec_ld(srcPos + j, src);
vector unsigned char src_v1, src_vF;
vector signed short src_v, filter_v1R, filter_v;
if ((((int)src + srcPos)% 16) > 8) {
src_v1 = vec_ld(srcPos + j + 16, src);
}
src_vF = vec_perm(src_v0, src_v1, permS);
src_v = // vec_unpackh sign-extends...
(vector signed short)(vec_mergeh((vector unsigned char)vzero, src_vF));
// loading filter_v0R is useless, it's already done above
//vector signed short filter_v0R = vec_ld((i * 2 * filterSize) + j, filter);
filter_v1R = vec_ld((i * 2 * filterSize) + (j * 2) + 16, filter);
filter_v = vec_perm(filter_v0R, filter_v1R, permF);
val_v = vec_msums(src_v, filter_v, val_v);
}
val_s = vec_sums(val_v, vzero);
vec_st(val_s, 0, tempo);
dst[i] = av_clip(tempo[3]>>7, 0, (1<<15)-1);
}
}
}
}
static inline int yv12toyuy2_unscaled_altivec(SwsContext *c, uint8_t* src[], int srcStride[], int srcSliceY,
int srcSliceH, uint8_t* dstParam[], int dstStride_a[]) {
uint8_t *dst=dstParam[0] + dstStride_a[0]*srcSliceY;
// yv12toyuy2( src[0],src[1],src[2],dst,c->srcW,srcSliceH,srcStride[0],srcStride[1],dstStride[0] );
uint8_t *ysrc = src[0];
uint8_t *usrc = src[1];
uint8_t *vsrc = src[2];
const int width = c->srcW;
const int height = srcSliceH;
const int lumStride = srcStride[0];
const int chromStride = srcStride[1];
const int dstStride = dstStride_a[0];
const vector unsigned char yperm = vec_lvsl(0, ysrc);
const int vertLumPerChroma = 2;
register unsigned int y;
if (width&15) {
yv12toyuy2( ysrc, usrc, vsrc, dst,c->srcW,srcSliceH, lumStride, chromStride, dstStride);
return srcSliceH;
}
/* this code assume:
1) dst is 16 bytes-aligned
2) dstStride is a multiple of 16
3) width is a multiple of 16
4) lum&chrom stride are multiple of 8
*/
for (y=0; y<height; y++) {
int i;
for (i = 0; i < width - 31; i+= 32) {
const unsigned int j = i >> 1;
vector unsigned char v_yA = vec_ld(i, ysrc);
vector unsigned char v_yB = vec_ld(i + 16, ysrc);
vector unsigned char v_yC = vec_ld(i + 32, ysrc);
vector unsigned char v_y1 = vec_perm(v_yA, v_yB, yperm);
vector unsigned char v_y2 = vec_perm(v_yB, v_yC, yperm);
vector unsigned char v_uA = vec_ld(j, usrc);
vector unsigned char v_uB = vec_ld(j + 16, usrc);
vector unsigned char v_u = vec_perm(v_uA, v_uB, vec_lvsl(j, usrc));
vector unsigned char v_vA = vec_ld(j, vsrc);
vector unsigned char v_vB = vec_ld(j + 16, vsrc);
vector unsigned char v_v = vec_perm(v_vA, v_vB, vec_lvsl(j, vsrc));
vector unsigned char v_uv_a = vec_mergeh(v_u, v_v);
vector unsigned char v_uv_b = vec_mergel(v_u, v_v);
vector unsigned char v_yuy2_0 = vec_mergeh(v_y1, v_uv_a);
vector unsigned char v_yuy2_1 = vec_mergel(v_y1, v_uv_a);
vector unsigned char v_yuy2_2 = vec_mergeh(v_y2, v_uv_b);
vector unsigned char v_yuy2_3 = vec_mergel(v_y2, v_uv_b);
vec_st(v_yuy2_0, (i << 1), dst);
vec_st(v_yuy2_1, (i << 1) + 16, dst);
vec_st(v_yuy2_2, (i << 1) + 32, dst);
vec_st(v_yuy2_3, (i << 1) + 48, dst);
}
if (i < width) {
const unsigned int j = i >> 1;
vector unsigned char v_y1 = vec_ld(i, ysrc);
vector unsigned char v_u = vec_ld(j, usrc);
vector unsigned char v_v = vec_ld(j, vsrc);
vector unsigned char v_uv_a = vec_mergeh(v_u, v_v);
vector unsigned char v_yuy2_0 = vec_mergeh(v_y1, v_uv_a);
vector unsigned char v_yuy2_1 = vec_mergel(v_y1, v_uv_a);
vec_st(v_yuy2_0, (i << 1), dst);
vec_st(v_yuy2_1, (i << 1) + 16, dst);
}
if ( (y&(vertLumPerChroma-1))==(vertLumPerChroma-1) ) {
usrc += chromStride;
vsrc += chromStride;
}
ysrc += lumStride;
dst += dstStride;
}
return srcSliceH;
}
static inline int yv12touyvy_unscaled_altivec(SwsContext *c, uint8_t* src[], int srcStride[], int srcSliceY,
int srcSliceH, uint8_t* dstParam[], int dstStride_a[]) {
uint8_t *dst=dstParam[0] + dstStride_a[0]*srcSliceY;
// yv12toyuy2( src[0],src[1],src[2],dst,c->srcW,srcSliceH,srcStride[0],srcStride[1],dstStride[0] );
uint8_t *ysrc = src[0];
uint8_t *usrc = src[1];
uint8_t *vsrc = src[2];
const int width = c->srcW;
const int height = srcSliceH;
const int lumStride = srcStride[0];
const int chromStride = srcStride[1];
const int dstStride = dstStride_a[0];
const int vertLumPerChroma = 2;
const vector unsigned char yperm = vec_lvsl(0, ysrc);
register unsigned int y;
if (width&15) {
yv12touyvy( ysrc, usrc, vsrc, dst,c->srcW,srcSliceH, lumStride, chromStride, dstStride);
return srcSliceH;
}
/* this code assume:
1) dst is 16 bytes-aligned
2) dstStride is a multiple of 16
3) width is a multiple of 16
4) lum&chrom stride are multiple of 8
*/
for (y=0; y<height; y++) {
int i;
for (i = 0; i < width - 31; i+= 32) {
const unsigned int j = i >> 1;
vector unsigned char v_yA = vec_ld(i, ysrc);
vector unsigned char v_yB = vec_ld(i + 16, ysrc);
vector unsigned char v_yC = vec_ld(i + 32, ysrc);
vector unsigned char v_y1 = vec_perm(v_yA, v_yB, yperm);
vector unsigned char v_y2 = vec_perm(v_yB, v_yC, yperm);
vector unsigned char v_uA = vec_ld(j, usrc);
vector unsigned char v_uB = vec_ld(j + 16, usrc);
vector unsigned char v_u = vec_perm(v_uA, v_uB, vec_lvsl(j, usrc));
vector unsigned char v_vA = vec_ld(j, vsrc);
vector unsigned char v_vB = vec_ld(j + 16, vsrc);
vector unsigned char v_v = vec_perm(v_vA, v_vB, vec_lvsl(j, vsrc));
vector unsigned char v_uv_a = vec_mergeh(v_u, v_v);
vector unsigned char v_uv_b = vec_mergel(v_u, v_v);
vector unsigned char v_uyvy_0 = vec_mergeh(v_uv_a, v_y1);
vector unsigned char v_uyvy_1 = vec_mergel(v_uv_a, v_y1);
vector unsigned char v_uyvy_2 = vec_mergeh(v_uv_b, v_y2);
vector unsigned char v_uyvy_3 = vec_mergel(v_uv_b, v_y2);
vec_st(v_uyvy_0, (i << 1), dst);
vec_st(v_uyvy_1, (i << 1) + 16, dst);
vec_st(v_uyvy_2, (i << 1) + 32, dst);
vec_st(v_uyvy_3, (i << 1) + 48, dst);
}
if (i < width) {
const unsigned int j = i >> 1;
vector unsigned char v_y1 = vec_ld(i, ysrc);
vector unsigned char v_u = vec_ld(j, usrc);
vector unsigned char v_v = vec_ld(j, vsrc);
vector unsigned char v_uv_a = vec_mergeh(v_u, v_v);
vector unsigned char v_uyvy_0 = vec_mergeh(v_uv_a, v_y1);
vector unsigned char v_uyvy_1 = vec_mergel(v_uv_a, v_y1);
vec_st(v_uyvy_0, (i << 1), dst);
vec_st(v_uyvy_1, (i << 1) + 16, dst);
}
if ( (y&(vertLumPerChroma-1))==(vertLumPerChroma-1) ) {
usrc += chromStride;
vsrc += chromStride;
}
ysrc += lumStride;
dst += dstStride;
}
return srcSliceH;
}
Reference in New Issue View Git Blame Copy Permalink