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Fixing a very rare 1-bit overflow in ETC1S SSE optimized colorspace error calculations (which are 32-bit vs. the plain C++ code's 64-bit). Ultimately the output would still be correct and transcodable, but this could cause a compressor assertion check to fail. Found during compressor fuzz testing.

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This commit is contained in:
Richard Geldreich
2025-11-18 17:27:51 -05:00
parent 6e54503437
commit 5a1ae5d65d
4 changed files with 280 additions and 95 deletions
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128
encoder/basisu_enc.cpp
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@@ -3987,5 +3987,133 @@ namespace basisu
return true;
}
static void rasterize_line(image& dst, int xs, int ys, int xe, int ye, int pred, int inc_dec, int e, int e_inc, int e_no_inc, const color_rgba& color)
{
int start, end, var;
if (pred)
{
start = ys; end = ye; var = xs;
for (int i = start; i <= end; i++)
{
dst.set_clipped(var, i, color);
if (e < 0)
e += e_no_inc;
else
{
var += inc_dec;
e += e_inc;
}
}
}
else
{
start = xs; end = xe; var = ys;
for (int i = start; i <= end; i++)
{
dst.set_clipped(i, var, color);
if (e < 0)
e += e_no_inc;
else
{
var += inc_dec;
e += e_inc;
}
}
}
}
void draw_line(image& dst, int xs, int ys, int xe, int ye, const color_rgba& color)
{
if (xs > xe)
{
std::swap(xs, xe);
std::swap(ys, ye);
}
int dx = xe - xs, dy = ye - ys;
if (!dx)
{
if (ys > ye)
std::swap(ys, ye);
for (int i = ys; i <= ye; i++)
dst.set_clipped(xs, i, color);
}
else if (!dy)
{
for (int i = xs; i < xe; i++)
dst.set_clipped(i, ys, color);
}
else if (dy > 0)
{
if (dy <= dx)
{
int e = 2 * dy - dx, e_no_inc = 2 * dy, e_inc = 2 * (dy - dx);
rasterize_line(dst, xs, ys, xe, ye, 0, 1, e, e_inc, e_no_inc, color);
}
else
{
int e = 2 * dx - dy, e_no_inc = 2 * dx, e_inc = 2 * (dx - dy);
rasterize_line(dst, xs, ys, xe, ye, 1, 1, e, e_inc, e_no_inc, color);
}
}
else
{
dy = -dy;
if (dy <= dx)
{
int e = 2 * dy - dx, e_no_inc = 2 * dy, e_inc = 2 * (dy - dx);
rasterize_line(dst, xs, ys, xe, ye, 0, -1, e, e_inc, e_no_inc, color);
}
else
{
int e = 2 * dx - dy, e_no_inc = (2 * dx), e_inc = 2 * (dx - dy);
rasterize_line(dst, xe, ye, xs, ys, 1, -1, e, e_inc, e_no_inc, color);
}
}
}
// Used for generating random test data
void draw_circle(image& dst, int cx, int cy, int r, const color_rgba& color)
{
assert(r >= 0);
if (r < 0)
return;
int x = r;
int y = 0;
int err = 1 - x;
while (x >= y)
{
dst.set_clipped(cx + x, cy + y, color);
dst.set_clipped(cx + y, cy + x, color);
dst.set_clipped(cx - y, cy + x, color);
dst.set_clipped(cx - x, cy + y, color);
dst.set_clipped(cx - x, cy - y, color);
dst.set_clipped(cx - y, cy - x, color);
dst.set_clipped(cx + y, cy - x, color);
dst.set_clipped(cx + x, cy - y, color);
++y;
if (err < 0)
{
err += 2 * y + 1;
}
else
{
--x;
err += 2 * (y - x) + 1;
}
}
}
void set_image_alpha(image& img, uint32_t a)
{
for (uint32_t y = 0; y < img.get_height(); y++)
for (uint32_t x = 0; x < img.get_width(); x++)
img(x, y).a = (uint8_t)a;
}
} // namespace basisu