[Python-checkins] cpython: Issue #14624: UTF-16 decoding is now 3x to 4x faster on various inputs.

Tue May 15 23:50:52 CEST 2012

http://hg.python.org/cpython/rev/cdcc816dea85
changeset: 76971:cdcc816dea85
user: Antoine Pitrou <solipsis at pitrou.net>
date: Tue May 15 23:48:04 2012 +0200
summary:
 Issue #14624: UTF-16 decoding is now 3x to 4x faster on various inputs.
Patch by Serhiy Storchaka.
files:
 Misc/NEWS | 3 +
 Objects/stringlib/codecs.h | 149 ++++++++++++-
 Objects/unicodeobject.c | 297 +++++++-----------------
 3 files changed, 240 insertions(+), 209 deletions(-)

diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #14624: UTF-16 decoding is now 3x to 4x faster on various inputs.
+ Patch by Serhiy Storchaka.
+
 - asdl_seq and asdl_int_seq are now Py_ssize_t sized.
 
 - Issue #14133 (PEP 415): Implement suppression of __context__ display with an
diff --git a/Objects/stringlib/codecs.h b/Objects/stringlib/codecs.h
--- a/Objects/stringlib/codecs.h
+++ b/Objects/stringlib/codecs.h
@@ -215,7 +215,6 @@
 goto Return;
 }
 
-#undef LONG_PTR_MASK
 #undef ASCII_CHAR_MASK
 
 
@@ -415,4 +414,152 @@
 #undef MAX_SHORT_UNICHARS
 }
 
+/* The pattern for constructing UCS2-repeated masks. */
+#if SIZEOF_LONG == 8
+# define UCS2_REPEAT_MASK 0x0001000100010001ul
+#elif SIZEOF_LONG == 4
+# define UCS2_REPEAT_MASK 0x00010001ul
+#else
+# error C 'long' size should be either 4 or 8!
+#endif
+
+/* The mask for fast checking. */
+#if STRINGLIB_SIZEOF_CHAR == 1
+/* The mask for fast checking of whether a C 'long' contains a
+ non-ASCII or non-Latin1 UTF16-encoded characters. */
+# define FAST_CHAR_MASK (UCS2_REPEAT_MASK * (0xFFFFu & ~STRINGLIB_MAX_CHAR))
+#else
+/* The mask for fast checking of whether a C 'long' may contain
+ UTF16-encoded surrogate characters. This is an efficient heuristic,
+ assuming that non-surrogate characters with a code point >= 0x8000 are
+ rare in most input.
+*/
+# define FAST_CHAR_MASK (UCS2_REPEAT_MASK * 0x8000u)
+#endif
+/* The mask for fast byte-swapping. */
+#define STRIPPED_MASK (UCS2_REPEAT_MASK * 0x00FFu)
+/* Swap bytes. */
+#define SWAB(value) ((((value) >> 8) & STRIPPED_MASK) | \
+ (((value) & STRIPPED_MASK) << 8))
+
+Py_LOCAL_INLINE(Py_UCS4)
+STRINGLIB(utf16_decode)(const unsigned char **inptr, const unsigned char *e,
+ STRINGLIB_CHAR *dest, Py_ssize_t *outpos,
+ int native_ordering)
+{
+ Py_UCS4 ch;
+ const unsigned char *aligned_end =
+ (const unsigned char *) ((size_t) e & ~LONG_PTR_MASK);
+ const unsigned char *q = *inptr;
+ STRINGLIB_CHAR *p = dest + *outpos;
+ /* Offsets from q for retrieving byte pairs in the right order. */
+#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+ int ihi = !!native_ordering, ilo = !native_ordering;
+#else
+ int ihi = !native_ordering, ilo = !!native_ordering;
+#endif
+ --e;
+
+ while (q < e) {
+ Py_UCS4 ch2;
+ /* First check for possible aligned read of a C 'long'. Unaligned
+ reads are more expensive, better to defer to another iteration. */
+ if (!((size_t) q & LONG_PTR_MASK)) {
+ /* Fast path for runs of in-range non-surrogate chars. */
+ register const unsigned char *_q = q;
+ while (_q < aligned_end) {
+ unsigned long block = * (unsigned long *) _q;
+ if (native_ordering) {
+ /* Can use buffer directly */
+ if (block & FAST_CHAR_MASK)
+ break;
+ }
+ else {
+ /* Need to byte-swap */
+ if (block & SWAB(FAST_CHAR_MASK))
+ break;
+#if STRINGLIB_SIZEOF_CHAR == 1
+ block >>= 8;
+#else
+ block = SWAB(block);
+#endif
+ }
+#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+# if SIZEOF_LONG == 4
+ p[0] = (STRINGLIB_CHAR)(block & 0xFFFFu);
+ p[1] = (STRINGLIB_CHAR)(block >> 16);
+# elif SIZEOF_LONG == 8
+ p[0] = (STRINGLIB_CHAR)(block & 0xFFFFu);
+ p[1] = (STRINGLIB_CHAR)((block >> 16) & 0xFFFFu);
+ p[2] = (STRINGLIB_CHAR)((block >> 32) & 0xFFFFu);
+ p[3] = (STRINGLIB_CHAR)(block >> 48);
+# endif
+#else
+# if SIZEOF_LONG == 4
+ p[0] = (STRINGLIB_CHAR)(block >> 16);
+ p[1] = (STRINGLIB_CHAR)(block & 0xFFFFu);
+# elif SIZEOF_LONG == 8
+ p[0] = (STRINGLIB_CHAR)(block >> 48);
+ p[1] = (STRINGLIB_CHAR)((block >> 32) & 0xFFFFu);
+ p[2] = (STRINGLIB_CHAR)((block >> 16) & 0xFFFFu);
+ p[3] = (STRINGLIB_CHAR)(block & 0xFFFFu);
+# endif
+#endif
+ _q += SIZEOF_LONG;
+ p += SIZEOF_LONG / 2;
+ }
+ q = _q;
+ if (q >= e)
+ break;
+ }
+
+ ch = (q[ihi] << 8) | q[ilo];
+ q += 2;
+ if (!Py_UNICODE_IS_SURROGATE(ch)) {
+#if STRINGLIB_SIZEOF_CHAR < 2
+ if (ch > STRINGLIB_MAX_CHAR)
+ /* Out-of-range */
+ goto Return;
+#endif
+ *p++ = (STRINGLIB_CHAR)ch;
+ continue;
+ }
+
+ /* UTF-16 code pair: */
+ if (q >= e)
+ goto UnexpectedEnd;
+ if (!Py_UNICODE_IS_HIGH_SURROGATE(ch))
+ goto IllegalEncoding;
+ ch2 = (q[ihi] << 8) | q[ilo];
+ q += 2;
+ if (!Py_UNICODE_IS_LOW_SURROGATE(ch2))
+ goto IllegalSurrogate;
+ ch = Py_UNICODE_JOIN_SURROGATES(ch, ch2);
+#if STRINGLIB_SIZEOF_CHAR < 4
+ /* Out-of-range */
+ goto Return;
+#else
+ *p++ = (STRINGLIB_CHAR)ch;
+#endif
+ }
+ ch = 0;
+Return:
+ *inptr = q;
+ *outpos = p - dest;
+ return ch;
+UnexpectedEnd:
+ ch = 1;
+ goto Return;
+IllegalEncoding:
+ ch = 2;
+ goto Return;
+IllegalSurrogate:
+ ch = 3;
+ goto Return;
+}
+#undef UCS2_REPEAT_MASK
+#undef FAST_CHAR_MASK
+#undef STRIPPED_MASK
+#undef SWAB
+#undef LONG_PTR_MASK
 #endif /* STRINGLIB_IS_UNICODE */
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -5195,25 +5195,6 @@
 return PyUnicode_DecodeUTF16Stateful(s, size, errors, byteorder, NULL);
 }
 
-/* Two masks for fast checking of whether a C 'long' may contain
- UTF16-encoded surrogate characters. This is an efficient heuristic,
- assuming that non-surrogate characters with a code point >= 0x8000 are
- rare in most input.
- FAST_CHAR_MASK is used when the input is in native byte ordering,
- SWAPPED_FAST_CHAR_MASK when the input is in byteswapped ordering.
-*/
-#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
-
 PyObject *
 PyUnicode_DecodeUTF16Stateful(const char *s,
 Py_ssize_t size,
@@ -5226,30 +5207,15 @@
 Py_ssize_t endinpos;
 Py_ssize_t outpos;
 PyObject *unicode;
- const unsigned char *q, *e, *aligned_end;
+ const unsigned char *q, *e;
 int bo = 0; /* assume native ordering by default */
- int native_ordering = 0;
+ int native_ordering;
 const char *errmsg = "";
- /* Offsets from q for retrieving byte pairs in the right order. */
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
- int ihi = 1, ilo = 0;
-#else
- int ihi = 0, ilo = 1;
-#endif
 PyObject *errorHandler = NULL;
 PyObject *exc = NULL;
 
- /* Note: size will always be longer than the resulting Unicode
- character count */
- unicode = PyUnicode_New(size, 127);
- if (!unicode)
- return NULL;
- if (size == 0)
- return unicode;
- outpos = 0;
-
 q = (unsigned char *)s;
- e = q + size - 1;
+ e = q + size;
 
 if (byteorder)
 bo = *byteorder;
@@ -5258,155 +5224,98 @@
 byte order setting accordingly. In native mode, the leading BOM
 mark is skipped, in all other modes, it is copied to the output
 stream as-is (giving a ZWNBSP character). */
- if (bo == 0) {
- if (size >= 2) {
- const Py_UCS4 bom = (q[ihi] << 8) | q[ilo];
+ if (bo == 0 && size >= 2) {
+ const Py_UCS4 bom = (q[1] << 8) | q[0];
+ if (bom == 0xFEFF) {
+ q += 2;
+ bo = -1;
+ }
+ else if (bom == 0xFFFE) {
+ q += 2;
+ bo = 1;
+ }
+ if (byteorder)
+ *byteorder = bo;
+ }
+
+ if (q == e) {
+ if (consumed)
+ *consumed = size;
+ Py_INCREF(unicode_empty);
+ return unicode_empty;
+ }
+
 #ifdef BYTEORDER_IS_LITTLE_ENDIAN
- if (bom == 0xFEFF) {
- q += 2;
- bo = -1;
- }
- else if (bom == 0xFFFE) {
- q += 2;
- bo = 1;
- }
+ native_ordering = bo <= 0;
 #else
- if (bom == 0xFEFF) {
- q += 2;
- bo = 1;
- }
- else if (bom == 0xFFFE) {
- q += 2;
- bo = -1;
- }
-#endif
- }
- }
-
- if (bo == -1) {
- /* force LE */
- ihi = 1;
- ilo = 0;
- }
- else if (bo == 1) {
- /* force BE */
- ihi = 0;
- ilo = 1;
- }
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
- native_ordering = ilo < ihi;
-#else
- native_ordering = ilo > ihi;
-#endif
-
- aligned_end = (const unsigned char *) ((size_t) e & ~LONG_PTR_MASK);
- while (q < e) {
- Py_UCS4 ch;
- /* First check for possible aligned read of a C 'long'. Unaligned
- reads are more expensive, better to defer to another iteration. */
- if (!((size_t) q & LONG_PTR_MASK)) {
- /* Fast path for runs of non-surrogate chars. */
- register const unsigned char *_q = q;
+ native_ordering = bo >= 0;
+#endif
+
+ /* Note: size will always be longer than the resulting Unicode
+ character count */
+ unicode = PyUnicode_New((e - q + 1) / 2, 127);
+ if (!unicode)
+ return NULL;
+
+ outpos = 0;
+ while (1) {
+ Py_UCS4 ch = 0;
+ if (e - q >= 2) {
 int kind = PyUnicode_KIND(unicode);
- void *data = PyUnicode_DATA(unicode);
- while (_q < aligned_end) {
- unsigned long block = * (unsigned long *) _q;
- Py_UCS4 maxch;
- if (native_ordering) {
- /* Can use buffer directly */
- if (block & FAST_CHAR_MASK)
- break;
- }
- else {
- /* Need to byte-swap */
- if (block & SWAPPED_FAST_CHAR_MASK)
- break;
- block = ((block >> 8) & STRIPPED_MASK) |
- ((block & STRIPPED_MASK) << 8);
- }
- maxch = (Py_UCS2)(block & 0xFFFF);
-#if SIZEOF_LONG == 8
- ch = (Py_UCS2)((block >> 16) & 0xFFFF);
- maxch = MAX_MAXCHAR(maxch, ch);
- ch = (Py_UCS2)((block >> 32) & 0xFFFF);
- maxch = MAX_MAXCHAR(maxch, ch);
- ch = (Py_UCS2)(block >> 48);
- maxch = MAX_MAXCHAR(maxch, ch);
-#else
- ch = (Py_UCS2)(block >> 16);
- maxch = MAX_MAXCHAR(maxch, ch);
-#endif
- if (maxch > PyUnicode_MAX_CHAR_VALUE(unicode)) {
- if (unicode_widen(&unicode, outpos, maxch) < 0)
- goto onError;
- kind = PyUnicode_KIND(unicode);
- data = PyUnicode_DATA(unicode);
- }
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
- PyUnicode_WRITE(kind, data, outpos++, (Py_UCS2)(block & 0xFFFF));
-#if SIZEOF_LONG == 8
- 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;
- }
- q = _q;
- if (q >= e)
- break;
- }
- ch = (q[ihi] << 8) | q[ilo];
-
- q += 2;
-
- if (!Py_UNICODE_IS_SURROGATE(ch)) {
+ if (kind == PyUnicode_1BYTE_KIND) {
+ if (PyUnicode_IS_ASCII(unicode))
+ ch = asciilib_utf16_decode(&q, e,
+ PyUnicode_1BYTE_DATA(unicode), &outpos,
+ native_ordering);
+ else
+ ch = ucs1lib_utf16_decode(&q, e,
+ PyUnicode_1BYTE_DATA(unicode), &outpos,
+ native_ordering);
+ } else if (kind == PyUnicode_2BYTE_KIND) {
+ ch = ucs2lib_utf16_decode(&q, e,
+ PyUnicode_2BYTE_DATA(unicode), &outpos,
+ native_ordering);
+ } else {
+ assert(kind == PyUnicode_4BYTE_KIND);
+ ch = ucs4lib_utf16_decode(&q, e,
+ PyUnicode_4BYTE_DATA(unicode), &outpos,
+ native_ordering);
+ }
+ }
+
+ switch (ch)
+ {
+ case 0:
+ /* remaining byte at the end? (size should be even) */
+ if (q == e || consumed)
+ goto End;
+ errmsg = "truncated data";
+ startinpos = ((const char *)q) - starts;
+ endinpos = ((const char *)e) - starts;
+ break;
+ /* The remaining input chars are ignored if the callback
+ chooses to skip the input */
+ case 1:
+ errmsg = "unexpected end of data";
+ startinpos = ((const char *)q) - 2 - starts;
+ endinpos = ((const char *)e) - starts;
+ break;
+ case 2:
+ errmsg = "illegal encoding";
+ startinpos = ((const char *)q) - 2 - starts;
+ endinpos = startinpos + 2;
+ break;
+ case 3:
+ errmsg = "illegal UTF-16 surrogate";
+ startinpos = ((const char *)q) - 4 - starts;
+ endinpos = startinpos + 2;
+ break;
+ default:
 if (unicode_putchar(&unicode, &outpos, ch) < 0)
 goto onError;
 continue;
 }
 
- /* UTF-16 code pair: */
- if (q > e) {
- errmsg = "unexpected end of data";
- startinpos = (((const char *)q) - 2) - starts;
- endinpos = ((const char *)e) + 1 - starts;
- goto utf16Error;
- }
- if (Py_UNICODE_IS_HIGH_SURROGATE(ch)) {
- Py_UCS4 ch2 = (q[ihi] << 8) | q[ilo];
- q += 2;
- if (Py_UNICODE_IS_LOW_SURROGATE(ch2)) {
- if (unicode_putchar(&unicode, &outpos,
- Py_UNICODE_JOIN_SURROGATES(ch, ch2)) < 0)
- goto onError;
- continue;
- }
- else {
- errmsg = "illegal UTF-16 surrogate";
- startinpos = (((const char *)q)-4)-starts;
- endinpos = startinpos+2;
- goto utf16Error;
- }
-
- }
- errmsg = "illegal encoding";
- startinpos = (((const char *)q)-2)-starts;
- endinpos = startinpos+2;
- /* Fall through to report the error */
-
- utf16Error:
 if (unicode_decode_call_errorhandler(
 errors,
 &errorHandler,
@@ -5421,33 +5330,8 @@
 &outpos))
 goto onError;
 }
- /* remaining byte at the end? (size should be even) */
- if (e == q) {
- if (!consumed) {
- errmsg = "truncated data";
- startinpos = ((const char *)q) - starts;
- endinpos = ((const char *)e) + 1 - starts;
- if (unicode_decode_call_errorhandler(
- errors,
- &errorHandler,
- "utf16", errmsg,
- &starts,
- (const char **)&e,
- &startinpos,
- &endinpos,
- &exc,
- (const char **)&q,
- &unicode,
- &outpos))
- goto onError;
- /* The remaining input chars are ignored if the callback
- chooses to skip the input */
- }
- }
-
- if (byteorder)
- *byteorder = bo;
-
+
+End:
 if (consumed)
 *consumed = (const char *)q-starts;
 
@@ -5466,9 +5350,6 @@
 return NULL;
 }
 
-#undef FAST_CHAR_MASK
-#undef SWAPPED_FAST_CHAR_MASK
-
 PyObject *
 _PyUnicode_EncodeUTF16(PyObject *str,
 const char *errors,
-- 
Repository URL: http://hg.python.org/cpython
