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In the PNG reader inner loop, collapse the two ReadFull calls into one.

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R=rsc,r
APPROVED=rsc
DELTA=29  (2 added, 4 deleted, 23 changed)
OCL=35460
CL=35565
This commit is contained in:
Nigel Tao 2009-10-09 22:44:40 -07:00
parent fb1bcd47c6
commit 6e4f935369
2 changed files with 22 additions and 24 deletions
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44
src/pkg/image/png/reader.go
View File

@ -209,46 +209,44 @@ func (d *decoder) idatReader(idat io.Reader) os.Error {
nrgba = d.image.(*image.NRGBA);
}
// cr and pr are the bytes for the current and previous row.
cr := make([]uint8, bpp * d.width);
pr := make([]uint8, bpp * d.width);
// The +1 is for the per-row filter type, which is at cr[0].
cr := make([]uint8, 1 + bpp * d.width);
pr := make([]uint8, 1 + bpp * d.width);
var filter [1]uint8;
for y := 0; y < d.height; y++ {
// Read the decompressed bytes.
n, err := io.ReadFull(r, filter[0:1]);
if err != nil {
return err;
}
n, err = io.ReadFull(r, cr);
_, err := io.ReadFull(r, cr);
if err != nil {
return err;
}
// Apply the filter.
switch filter[0] {
cdat := cr[1:len(cr)];
pdat := pr[1:len(pr)];
switch cr[0] {
case ftNone:
// No-op.
case ftSub:
for i := bpp; i < n; i++ {
cr[i] += cr[i-bpp];
for i := bpp; i < len(cdat); i++ {
cdat[i] += cdat[i-bpp];
}
case ftUp:
for i := 0; i < n; i++ {
cr[i] += pr[i];
for i := 0; i < len(cdat); i++ {
cdat[i] += pdat[i];
}
case ftAverage:
for i := 0; i < bpp; i++ {
cr[i] += pr[i]/2;
cdat[i] += pdat[i]/2;
}
for i := bpp; i < n; i++ {
cr[i] += uint8((int(cr[i-bpp])+int(pr[i]))/2);
for i := bpp; i < len(cdat); i++ {
cdat[i] += uint8((int(cdat[i-bpp])+int(pdat[i]))/2);
}
case ftPaeth:
for i := 0; i < bpp; i++ {
cr[i] += paeth(0, pr[i], 0);
cdat[i] += paeth(0, pdat[i], 0);
}
for i := bpp; i < n; i++ {
cr[i] += paeth(cr[i-bpp], pr[i], pr[i-bpp]);
for i := bpp; i < len(cdat); i++ {
cdat[i] += paeth(cdat[i-bpp], pdat[i], pdat[i-bpp]);
}
default:
return FormatError("bad filter type");
@ -258,18 +256,18 @@ func (d *decoder) idatReader(idat io.Reader) os.Error {
switch d.colorType {
case ctTrueColor:
for x := 0; x < d.width; x++ {
rgba.Set(x, y, image.RGBAColor{cr[3*x + 0], cr[3*x + 1], cr[3*x + 2], 0xff});
rgba.Set(x, y, image.RGBAColor{cdat[3*x + 0], cdat[3*x + 1], cdat[3*x + 2], 0xff});
}
case ctPaletted:
for x := 0; x < d.width; x++ {
if cr[x] > maxPalette {
if cdat[x] > maxPalette {
return FormatError("palette index out of range");
}
paletted.SetColorIndex(x, y, cr[x]);
paletted.SetColorIndex(x, y, cdat[x]);
}
case ctTrueColorAlpha:
for x := 0; x < d.width; x++ {
nrgba.Set(x, y, image.NRGBAColor{cr[4*x + 0], cr[4*x + 1], cr[4*x + 2], cr[4*x + 3]});
nrgba.Set(x, y, image.NRGBAColor{cdat[4*x + 0], cdat[4*x + 1], cdat[4*x + 2], cdat[4*x + 3]});
}
}

2
src/pkg/image/png/writer.go
View File

@ -148,7 +148,7 @@ func writeImage(w io.Writer, m image.Image, ct uint8) os.Error {
case ctTrueColorAlpha:
bpp = 4;
}
// The bytes for the current and previous row.
// cr and pr are the bytes for the current and previous row.
// The +1 is for the per-row filter type, which is at cr[0].
cr := make([]uint8, 1 + bpp * m.Width());
pr := make([]uint8, 1 + bpp * m.Width());