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Fix problems with >8 bit input

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Enforce bit depth promised by --input-bitdepth to avoid crashes when
larger values are provided.

Do endianess byte swap for all bytes when the buffer gets extended
to multiple of 8 pixels, and not just the number of input pixels.

Don't swap bytes on a little-endian system.
This commit is contained in:
Ari Koivula 2016-11-11 21:04:56 +02:00
parent 2c005cda25
commit b8a618e666
1 changed files with 34 additions and 12 deletions
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46
src/yuv_io.c
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@ -79,12 +79,14 @@ static void swap_16b_buffer_bytes(kvz_pixel* input, int size)
static void shift_to_bitdepth(kvz_pixel* input, int size, int from_bitdepth, int to_bitdepth)
{
int shift = to_bitdepth - from_bitdepth;
kvz_pixel bitdepth_mask = (1 << from_bitdepth) - 1;
for (int i = 0; i < size; ++i) {
// Shifting by a negative number is undefined.
if (shift > 0) {
input[i] <<= shift;
input[i] = (input[i] & bitdepth_mask) << shift;
} else {
input[i] >>= shift;
input[i] = (input[i] & bitdepth_mask) >> shift;
}
}
}
@ -99,6 +101,7 @@ static void shift_to_bitdepth_and_spread(kvz_pixel *input,
assert(sizeof(kvz_pixel) > 1);
int shift = to_bitdepth - from_bitdepth;
unsigned char *byte_buf = (unsigned char *)input;
kvz_pixel bitdepth_mask = (1 << from_bitdepth) - 1;
// Starting from the back of the 1-byte samples, copy each sample to it's
// place in the 2-byte per sample array, overwriting the bytes that have
@ -109,20 +112,33 @@ static void shift_to_bitdepth_and_spread(kvz_pixel *input,
for (int i = size - 1; i >= 0; --i) {
// Shifting by a negative number is undefined.
if (shift > 0) {
input[i] = byte_buf[i] << shift;
input[i] = (byte_buf[i] & bitdepth_mask) << shift;
} else {
input[i] = byte_buf[i] >> shift;
input[i] = (byte_buf[i] & bitdepth_mask) >> shift;
}
}
}
bool machine_is_big_endian()
static bool machine_is_big_endian()
{
// Big and little endianess refers to which end of the egg you prefer to eat
// first. Therefore in big endian system, the most significant bits are in
// the first address.
uint16_t number = 1;
char first_byte = *(char*)&number;
return (first_byte != 0);
return (first_byte == 0);
}
static void mask_to_bitdepth(kvz_pixel *buf, unsigned length, unsigned bitdepth)
{
kvz_pixel bitdepth_mask = (1 << bitdepth) - 1;
for (int i = 0; i < length; ++i) {
buf[i] = buf[i] & bitdepth_mask;
}
}
@ -133,8 +149,8 @@ static int yuv_io_read_plane(
kvz_pixel *out_buf)
{
unsigned bytes_per_sample = in_bitdepth > 8 ? 2 : 1;
unsigned buf_length = in_width * in_height;
unsigned buf_bytes = buf_length * bytes_per_sample;
unsigned buf_bytes = in_width * in_height * bytes_per_sample;
unsigned out_length = out_width * out_height;
if (in_width == out_width) {
// No need to extend pixels.
@ -151,17 +167,23 @@ static int yuv_io_read_plane(
}
if (in_bitdepth > 8) {
// Assume little endian input.
if (machine_is_big_endian()) {
swap_16b_buffer_bytes(out_buf, buf_length);
swap_16b_buffer_bytes(out_buf, out_length);
}
}
// Shift the data to the correct bitdepth.
// Ignore any bits larger than in_bitdepth to guarantee ouput data will be
// in the correct range.
if (in_bitdepth <= 8 && out_bitdepth > 8) {
shift_to_bitdepth_and_spread(out_buf, buf_length, in_bitdepth, out_bitdepth);
shift_to_bitdepth_and_spread(out_buf, out_length, in_bitdepth, out_bitdepth);
} else if (in_bitdepth != out_bitdepth) {
shift_to_bitdepth(out_buf, buf_length, in_bitdepth, out_bitdepth);
shift_to_bitdepth(out_buf, out_length, in_bitdepth, out_bitdepth);
} else if (in_bitdepth % 8 != 0) {
mask_to_bitdepth(out_buf, out_length, out_bitdepth);
}
return 1;
}