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Close #14249: Use bit shifts instead of an union, it's more efficient. 

Patch written by Serhiy Storchaka
This commit is contained in:
Victor Stinner 2012-04-05 22:54:49 +02:00
parent 02184282c7
commit afb5205c48
2 changed files with 35 additions and 27 deletions
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1
Misc/ACKS
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@ -977,6 +977,7 @@ Richard Stoakley
Peter Stoehr
Casper Stoel
Michael Stone
Serhiy Storchaka
Ken Stox
Dan Stromberg
Daniel Stutzbach

61
Objects/unicodeobject.c
View File

@ -5393,9 +5393,11 @@ PyUnicode_DecodeUTF16(const char *s,
#if (SIZEOF_LONG == 8)
# define FAST_CHAR_MASK 0x8000800080008000L
# define SWAPPED_FAST_CHAR_MASK 0x0080008000800080L
# define STRIPPED_MASK 0x00FF00FF00FF00FFL
#elif (SIZEOF_LONG == 4)
# define FAST_CHAR_MASK 0x80008000L
# define SWAPPED_FAST_CHAR_MASK 0x00800080L
# define STRIPPED_MASK 0x00FF00FFL
#else
# error C 'long' size should be either 4 or 8!
#endif
@ -5496,39 +5498,31 @@ PyUnicode_DecodeUTF16Stateful(const char *s,
int kind = PyUnicode_KIND(unicode);
void *data = PyUnicode_DATA(unicode);
while (_q < aligned_end) {
union {
unsigned long as_long;
unsigned short units[sizeof(long) / sizeof(short)];
unsigned char bytes[sizeof(long)];
} block, block_copy;
unsigned long block = * (unsigned long *) _q;
Py_UCS4 maxch;
block.as_long = *(unsigned long *) _q;
if (native_ordering) {
/* Can use buffer directly */
if (block.as_long & FAST_CHAR_MASK)
if (block & FAST_CHAR_MASK)
break;
}
else {
/* Need to byte-swap */
block_copy = block;
if (block.as_long & SWAPPED_FAST_CHAR_MASK)
if (block & SWAPPED_FAST_CHAR_MASK)
break;
block.bytes[0] = block_copy.bytes[1];
block.bytes[1] = block_copy.bytes[0];
block.bytes[2] = block_copy.bytes[3];
block.bytes[3] = block_copy.bytes[2];
#if (SIZEOF_LONG == 8)
block.bytes[4] = block_copy.bytes[5];
block.bytes[5] = block_copy.bytes[4];
block.bytes[6] = block_copy.bytes[7];
block.bytes[7] = block_copy.bytes[6];
#endif
block = ((block >> 8) & STRIPPED_MASK) |
((block & STRIPPED_MASK) << 8);
}
maxch = Py_MAX(block.units[0], block.units[1]);
maxch = (Py_UCS2)(block & 0xFFFF);
#if SIZEOF_LONG == 8
maxch = Py_MAX(maxch, Py_MAX(block.units[2], block.units[3]));
ch = (Py_UCS2)((block >> 16) & 0xFFFF);
maxch = Py_MAX(maxch, ch);
ch = (Py_UCS2)((block >> 32) & 0xFFFF);
maxch = Py_MAX(maxch, ch);
ch = (Py_UCS2)(block >> 48);
maxch = Py_MAX(maxch, ch);
#else
ch = (Py_UCS2)(block >> 16);
maxch = Py_MAX(maxch, ch);
#endif
if (maxch > PyUnicode_MAX_CHAR_VALUE(unicode)) {
if (unicode_widen(&unicode, maxch) < 0)
@ -5536,11 +5530,24 @@ PyUnicode_DecodeUTF16Stateful(const char *s,
kind = PyUnicode_KIND(unicode);
data = PyUnicode_DATA(unicode);
}
PyUnicode_WRITE(kind, data, outpos++, block.units[0]);
PyUnicode_WRITE(kind, data, outpos++, block.units[1]);
#ifdef BYTEORDER_IS_LITTLE_ENDIAN
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)(block & 0xFFFF));
#if SIZEOF_LONG == 8
PyUnicode_WRITE(kind, data, outpos++, block.units[2]);
PyUnicode_WRITE(kind, data, outpos++, block.units[3]);
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)((block >> 16) & 0xFFFF));
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)((block >> 32) & 0xFFFF));
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)((block >> 48)));
#else
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)(block >> 16));
#endif
#else
#if SIZEOF_LONG == 8
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)((block >> 48)));
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)((block >> 32) & 0xFFFF));
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)((block >> 16) & 0xFFFF));
#else
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)(block >> 16));
#endif
PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)(block & 0xFFFF));
#endif
_q += SIZEOF_LONG;
}