[libpng15] Added LSR() macro to defend against buggy compilers that evaluate
non-taken code branches and complain about out-of-range shifts.
This commit is contained in:
Glenn Randers-Pehrson
parent
b2068640d1
commit
ef02d563a3
7
ANNOUNCE
7
ANNOUNCE
@ -1,5 +1,5 @@
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Libpng 1.5.6rc02 - October 26, 2011
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Libpng 1.5.6rc02 - October 27, 2011
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This is not intended to be a public release. It will be replaced
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within a few weeks by a public version or by another test version.
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@ -92,8 +92,9 @@ Version 1.5.6beta07 [October 21, 2011]
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Version 1.5.6rc01 [October 26, 2011]
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Changed misleading "Missing PLTE before cHRM" warning to "Out of place cHRM"
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Version 1.5.6rc02 [October 26, 2011]
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Version 1.5.6rc02 [October 27, 2011]
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Added LSR() macro to defend against buggy compilers that evaluate non-taken
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code branches and complain about out-of-range shifts.
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Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
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(subscription required; visit
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4
CHANGES
4
CHANGES
@ -3653,7 +3653,9 @@ Version 1.5.6beta07 [October 21, 2011]
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Version 1.5.6rc01 [October 26, 2011]
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Changed misleading "Missing PLTE before cHRM" warning to "Out of place cHRM"
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Version 1.5.6rc02 [October 26, 2011]
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Version 1.5.6rc02 [October 27, 2011]
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Added LSR() macro to defend against buggy compilers that evaluate non-taken
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code branches and complain about out-of-range shifts.
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Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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(subscription required; visit
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72
pngrutil.c
72
pngrutil.c
@ -301,7 +301,7 @@ png_inflate(png_structp png_ptr, png_bytep data, png_size_t size,
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{
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int ret, avail;
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/* The setting of 'avail_in' used to be outside the loop, by setting it
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/* The setting of 'avail_in' used to be outside the loop; by setting it
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* inside it is possible to chunk the input to zlib and simply rely on
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* zlib to advance the 'next_in' pointer. This allows arbitrary amounts o
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* data to be passed through zlib at the unavoidable cost of requiring a
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@ -2817,7 +2817,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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end_mask = (pixel_depth * row_width) & 7;
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if (end_mask != 0)
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{
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/* ep == NULL is a flag to say do nothing */
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/* end_ptr == NULL is a flag to say do nothing */
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end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
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end_byte = *end_ptr;
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# ifdef PNG_READ_PACKSWAP_SUPPORTED
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@ -2830,9 +2830,11 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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/* end_mask is now the bits to *keep* from the destination row */
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}
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/* This reduces to a memcpy for non-interlaced images and for the case where
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* interlacing isn't supported or isn't done (in that case the caller gets a
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* sequence of interlace pass rows.)
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/* For non-interlaced images this reduces to a png_memcpy(). A png_memcpy()
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* will also happen if interlacing isn't supported or if the application
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* does not call png_set_interlace_handling(). In the latter cases the
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* caller just gets a sequence of the unexpanded rows from each interlace
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* pass.
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*/
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#ifdef PNG_READ_INTERLACING_SUPPORTED
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if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE) &&
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@ -2848,9 +2850,9 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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if (pixel_depth < 8)
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{
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/* For pixel depths up to 4bpp the 8-pixel mask can be expanded to fit
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/* For pixel depths up to 4-bpp the 8-pixel mask can be expanded to fit
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* into 32 bits, then a single loop over the bytes using the four byte
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* values in the 32 bit mask can be used. For the 'display' option the
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* values in the 32-bit mask can be used. For the 'display' option the
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* expanded mask may also not require any masking within a byte. To
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* make this work the PACKSWAP option must be taken into account - it
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* simply requires the pixels to be reversed in each byte.
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@ -2869,15 +2871,25 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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*
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* The following defines allow generation of compile time constant bit
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* masks for each pixel depth and each possibility of swapped or not
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* swapped bytes. Pass is in the range 0..6, 'x', a pixel index, is in
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* the range 0..7, the result is 1 if the pixel is to be copied in the
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* pass, 0 if not. 'S' is for the sparkle method, 'B' for the block
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* method.
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* swapped bytes. Pass 'p' is in the range 0..6; 'x', a pixel index,
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* is in the range 0..7; and the result is 1 if the pixel is to be
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* copied in the pass, 0 if not. 'S' is for the sparkle method, 'B'
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* for the block method.
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*
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* With Microsoft Visual C and potentially other compilers the shifts
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* below to extract the relevant fields from a 64 bit value are faulted
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* if evaluated at compile time because the non-taken branch has an
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* invalid shift (negative or more than 31), hence the following.
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*/
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# define S_COPY(p,x) (((p)<4 ? 0x80088822 >> ((3-(p))*8+(7-(x))) :\
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0xaa55ff00 >> ((7-(p))*8+(7-(x)))) & 1)
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# define B_COPY(p,x) (((p)<4 ? 0xff0fff33 >> ((3-(p))*8+(7-(x))) :\
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0xff55ff00 >> ((7-(p))*8+(7-(x)))) & 1)
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# if defined PNG_USE_COMPILE_TIME_MASKS && defined _MSC_VER
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# define LSR(x,s) ((x)>>((s) & 0x1f))
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# else
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# define LSR(x,s) ((x)>>(s))
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# endif
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# define S_COPY(p,x) (((p)<4 ? LSR(0x80088822,(3-(p))*8+(7-(x))) :\
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LSR(0xaa55ff00,(7-(p))*8+(7-(x)))) & 1)
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# define B_COPY(p,x) (((p)<4 ? LSR(0xff0fff33,(3-(p))*8+(7-(x))) :\
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LSR(0xff55ff00,(7-(p))*8+(7-(x)))) & 1)
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/* Return a mask for pass 'p' pixel 'x' at depth 'd'. The mask is
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* little endian - the first pixel is at bit 0 - however the extra
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@ -2892,9 +2904,9 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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# define S_MASKx(p,x,d,s) (S_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
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# define B_MASKx(p,x,d,s) (B_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
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/* Combine 8 of these to get the full mask. For the 1 and 2 bpp cases
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* the result needs replicating, for the 4bpp case the above generates
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* a full 32 bits.
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/* Combine 8 of these to get the full mask. For the 1-bpp and 2-bpp
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* cases the result needs replicating, for the 4-bpp case the above
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* generates a full 32 bits.
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*/
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# define MASK_EXPAND(m,d) ((m)*((d)==1?0x01010101:((d)==2?0x00010001:1)))
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@ -2972,7 +2984,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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png_uint_32 m;
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/* It doesn't matter in the following if png_uint_32 has more than
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* 32 bits because the high bits always match those in m<<24, it is,
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* 32 bits because the high bits always match those in m<<24; it is,
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* however, essential to use OR here, not +, because of this.
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*/
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m = mask;
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@ -2988,7 +3000,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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}
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/* NOTE: this may overwrite the last byte with garbage if the image
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* is not an exact number of bytes wide, libpng has always done
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* is not an exact number of bytes wide; libpng has always done
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* this.
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*/
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if (row_width <= pixels_per_byte)
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@ -3044,7 +3056,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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bytes_to_jump = PNG_PASS_COL_OFFSET(pass) * pixel_depth;
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/* And simply copy these bytes. Some optimization is possible here,
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* depending on the value of 'bytes_to_copy'. Speical case the low
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* depending on the value of 'bytes_to_copy'. Special case the low
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* byte counts, which we know to be frequent.
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*
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* Notice that these cases all 'return' rather than 'break' - this
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@ -3067,7 +3079,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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}
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case 2:
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/* There is a possibility of a partial copy at the end here, this
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/* There is a possibility of a partial copy at the end here; this
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* slows the code down somewhat.
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*/
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do
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@ -3105,12 +3117,12 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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default:
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#if PNG_ALIGN_TYPE != PNG_ALIGN_NONE
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/* Check for double byte alignment and, if possible, use a 16
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* bit copy. Don't attempt this for narrow images - ones that
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/* Check for double byte alignment and, if possible, use a
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* 16-bit copy. Don't attempt this for narrow images - ones that
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* are less than an interlace panel wide. Don't attempt it for
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* wide bytes-to-copy either - use the memcpy there.
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* wide bytes-to-copy either - use the png_memcpy there.
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*/
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if (bytes_to_copy < 16 /*else use memcpy*/ &&
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if (bytes_to_copy < 16 /*else use png_memcpy*/ &&
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png_isaligned(dp, png_uint_16) &&
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png_isaligned(sp, png_uint_16) &&
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bytes_to_copy % sizeof (png_uint_16) == 0 &&
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@ -3150,7 +3162,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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/* Get to here when the row_width truncates the final copy.
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* There will be 1-3 bytes left to copy, so don't try the
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* 16bit loop below.
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* 16-bit loop below.
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*/
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dp = (png_bytep)dp32;
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sp = (png_const_bytep)sp32;
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@ -3160,7 +3172,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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return;
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}
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/* Else do it in 16 bit quantities, but only if the size is
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/* Else do it in 16-bit quantities, but only if the size is
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* not too large.
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*/
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else
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@ -3200,7 +3212,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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}
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#endif /* PNG_ALIGN_ code */
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/* The true default - use a memcpy: */
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/* The true default - use a png_memcpy: */
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for (;;)
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{
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png_memcpy(dp, sp, bytes_to_copy);
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@ -3224,7 +3236,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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else
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#endif
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/* If here then the switch above wasn't used so just memcpy the whole row
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/* If here then the switch above wasn't used so just png_memcpy the whole row
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* from the temporary row buffer (notice that this overwrites the end of the
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* destination row if it is a partial byte.)
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*/
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