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jpeg: Optimise by replacing division with shifts.

This commit is contained in:
Vladimir Serbinenko 2015-02-26 21:27:32 +01:00
parent 18125877ee
commit 7213c1e028
1 changed files with 14 additions and 11 deletions
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25
grub-core/video/readers/jpeg.c
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@ -94,7 +94,7 @@ struct grub_jpeg_data
jpeg_data_unit_t crdu;
jpeg_data_unit_t cbdu;
unsigned vs, hs;
unsigned log_vs, log_hs;
int dri;
unsigned r1;
@ -315,11 +315,14 @@ grub_jpeg_decode_sof (struct grub_jpeg_data *data)
ss = grub_jpeg_get_byte (data); /* Sampling factor. */
if (!id)
{
data->vs = ss & 0xF; /* Vertical sampling. */
data->hs = ss >> 4; /* Horizontal sampling. */
if ((data->vs > 2) || (data->hs > 2) || (data->vs == 0) || (data->hs == 0))
grub_uint8_t vs, hs;
vs = ss & 0xF; /* Vertical sampling. */
hs = ss >> 4; /* Horizontal sampling. */
if ((vs > 2) || (hs > 2) || (vs == 0) || (hs == 0))
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"jpeg: sampling method not supported");
data->log_vs = (vs == 2);
data->log_hs = (hs == 2);
}
else if (ss != JPEG_SAMPLING_1x1)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
@ -616,10 +619,10 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
unsigned c1, vb, hb, nr1, nc1;
int rst = data->dri;
vb = data->vs * 8;
hb = data->hs * 8;
nr1 = (data->image_height + vb - 1) / vb;
nc1 = (data->image_width + hb - 1) / hb;
vb = 8 << data->log_vs;
hb = 8 << data->log_hs;
nr1 = (data->image_height + vb - 1) >> (3 + data->log_vs);
nc1 = (data->image_width + hb - 1) >> (3 + data->log_hs);
for (; data->r1 < nr1 && (!data->dri || rst);
data->r1++, data->bitmap_ptr += (vb * data->image_width - hb * nc1) * 3)
@ -629,8 +632,8 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
unsigned r2, c2, nr2, nc2;
grub_uint8_t *ptr2;
for (r2 = 0; r2 < data->vs; r2++)
for (c2 = 0; c2 < data->hs; c2++)
for (r2 = 0; r2 < (1U << data->log_vs); r2++)
for (c2 = 0; c2 < (1U << data->log_hs); c2++)
grub_jpeg_decode_du (data, 0, data->ydu[r2 * 2 + c2]);
if (data->color_components >= 3)
@ -652,7 +655,7 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
unsigned i0;
int yy;
i0 = (r2 / data->vs) * 8 + (c2 / data->hs);
i0 = (r2 >> data->log_vs) * 8 + (c2 >> data->log_hs);
yy = data->ydu[(r2 / 8) * 2 + (c2 / 8)][(r2 % 8) * 8 + (c2 % 8)];
if (data->color_components >= 3)