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authoraxc <axc@yandex-team.ru>2022-02-10 16:47:35 +0300
committerDaniil Cherednik <dcherednik@yandex-team.ru>2022-02-10 16:47:35 +0300
commit1f5217043ad70f25dc35e75b3bd261a1e23d045e (patch)
tree11bf68c1fa5272d3d3446cbd5a0ff96ed9d75788 /contrib/tools/bison/gnulib/src/rawmemchr.c
parent69505a07cbb096113e85aa02e7d136cac4aa826c (diff)
downloadydb-1f5217043ad70f25dc35e75b3bd261a1e23d045e.tar.gz
Restoring authorship annotation for <axc@yandex-team.ru>. Commit 1 of 2.
Diffstat (limited to 'contrib/tools/bison/gnulib/src/rawmemchr.c')
-rw-r--r--contrib/tools/bison/gnulib/src/rawmemchr.c272
1 files changed, 136 insertions, 136 deletions
diff --git a/contrib/tools/bison/gnulib/src/rawmemchr.c b/contrib/tools/bison/gnulib/src/rawmemchr.c
index a0298ce64e..b0f4f4d044 100644
--- a/contrib/tools/bison/gnulib/src/rawmemchr.c
+++ b/contrib/tools/bison/gnulib/src/rawmemchr.c
@@ -1,136 +1,136 @@
-/* Searching in a string.
- Copyright (C) 2008-2013 Free Software Foundation, Inc.
-
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
-
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
-
-#include <config.h>
-
-/* Specification. */
-#include <string.h>
-
-/* Find the first occurrence of C in S. */
-void *
-rawmemchr (const void *s, int c_in)
-{
- /* On 32-bit hardware, choosing longword to be a 32-bit unsigned
- long instead of a 64-bit uintmax_t tends to give better
- performance. On 64-bit hardware, unsigned long is generally 64
- bits already. Change this typedef to experiment with
- performance. */
- typedef unsigned long int longword;
-
- const unsigned char *char_ptr;
- const longword *longword_ptr;
- longword repeated_one;
- longword repeated_c;
- unsigned char c;
-
- c = (unsigned char) c_in;
-
- /* Handle the first few bytes by reading one byte at a time.
- Do this until CHAR_PTR is aligned on a longword boundary. */
- for (char_ptr = (const unsigned char *) s;
- (size_t) char_ptr % sizeof (longword) != 0;
- ++char_ptr)
- if (*char_ptr == c)
- return (void *) char_ptr;
-
- longword_ptr = (const longword *) char_ptr;
-
- /* All these elucidatory comments refer to 4-byte longwords,
- but the theory applies equally well to any size longwords. */
-
- /* Compute auxiliary longword values:
- repeated_one is a value which has a 1 in every byte.
- repeated_c has c in every byte. */
- repeated_one = 0x01010101;
- repeated_c = c | (c << 8);
- repeated_c |= repeated_c << 16;
- if (0xffffffffU < (longword) -1)
- {
- repeated_one |= repeated_one << 31 << 1;
- repeated_c |= repeated_c << 31 << 1;
- if (8 < sizeof (longword))
- {
- size_t i;
-
- for (i = 64; i < sizeof (longword) * 8; i *= 2)
- {
- repeated_one |= repeated_one << i;
- repeated_c |= repeated_c << i;
- }
- }
- }
-
- /* Instead of the traditional loop which tests each byte, we will
- test a longword at a time. The tricky part is testing if *any of
- the four* bytes in the longword in question are equal to NUL or
- c. We first use an xor with repeated_c. This reduces the task
- to testing whether *any of the four* bytes in longword1 is zero.
-
- We compute tmp =
- ((longword1 - repeated_one) & ~longword1) & (repeated_one << 7).
- That is, we perform the following operations:
- 1. Subtract repeated_one.
- 2. & ~longword1.
- 3. & a mask consisting of 0x80 in every byte.
- Consider what happens in each byte:
- - If a byte of longword1 is zero, step 1 and 2 transform it into 0xff,
- and step 3 transforms it into 0x80. A carry can also be propagated
- to more significant bytes.
- - If a byte of longword1 is nonzero, let its lowest 1 bit be at
- position k (0 <= k <= 7); so the lowest k bits are 0. After step 1,
- the byte ends in a single bit of value 0 and k bits of value 1.
- After step 2, the result is just k bits of value 1: 2^k - 1. After
- step 3, the result is 0. And no carry is produced.
- So, if longword1 has only non-zero bytes, tmp is zero.
- Whereas if longword1 has a zero byte, call j the position of the least
- significant zero byte. Then the result has a zero at positions 0, ...,
- j-1 and a 0x80 at position j. We cannot predict the result at the more
- significant bytes (positions j+1..3), but it does not matter since we
- already have a non-zero bit at position 8*j+7.
-
- The test whether any byte in longword1 is zero is equivalent
- to testing whether tmp is nonzero.
-
- This test can read beyond the end of a string, depending on where
- C_IN is encountered. However, this is considered safe since the
- initialization phase ensured that the read will be aligned,
- therefore, the read will not cross page boundaries and will not
- cause a fault. */
-
- while (1)
- {
- longword longword1 = *longword_ptr ^ repeated_c;
-
- if ((((longword1 - repeated_one) & ~longword1)
- & (repeated_one << 7)) != 0)
- break;
- longword_ptr++;
- }
-
- char_ptr = (const unsigned char *) longword_ptr;
-
- /* At this point, we know that one of the sizeof (longword) bytes
- starting at char_ptr is == c. On little-endian machines, we
- could determine the first such byte without any further memory
- accesses, just by looking at the tmp result from the last loop
- iteration. But this does not work on big-endian machines.
- Choose code that works in both cases. */
-
- char_ptr = (unsigned char *) longword_ptr;
- while (*char_ptr != c)
- char_ptr++;
- return (void *) char_ptr;
-}
+/* Searching in a string.
+ Copyright (C) 2008-2013 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+/* Specification. */
+#include <string.h>
+
+/* Find the first occurrence of C in S. */
+void *
+rawmemchr (const void *s, int c_in)
+{
+ /* On 32-bit hardware, choosing longword to be a 32-bit unsigned
+ long instead of a 64-bit uintmax_t tends to give better
+ performance. On 64-bit hardware, unsigned long is generally 64
+ bits already. Change this typedef to experiment with
+ performance. */
+ typedef unsigned long int longword;
+
+ const unsigned char *char_ptr;
+ const longword *longword_ptr;
+ longword repeated_one;
+ longword repeated_c;
+ unsigned char c;
+
+ c = (unsigned char) c_in;
+
+ /* Handle the first few bytes by reading one byte at a time.
+ Do this until CHAR_PTR is aligned on a longword boundary. */
+ for (char_ptr = (const unsigned char *) s;
+ (size_t) char_ptr % sizeof (longword) != 0;
+ ++char_ptr)
+ if (*char_ptr == c)
+ return (void *) char_ptr;
+
+ longword_ptr = (const longword *) char_ptr;
+
+ /* All these elucidatory comments refer to 4-byte longwords,
+ but the theory applies equally well to any size longwords. */
+
+ /* Compute auxiliary longword values:
+ repeated_one is a value which has a 1 in every byte.
+ repeated_c has c in every byte. */
+ repeated_one = 0x01010101;
+ repeated_c = c | (c << 8);
+ repeated_c |= repeated_c << 16;
+ if (0xffffffffU < (longword) -1)
+ {
+ repeated_one |= repeated_one << 31 << 1;
+ repeated_c |= repeated_c << 31 << 1;
+ if (8 < sizeof (longword))
+ {
+ size_t i;
+
+ for (i = 64; i < sizeof (longword) * 8; i *= 2)
+ {
+ repeated_one |= repeated_one << i;
+ repeated_c |= repeated_c << i;
+ }
+ }
+ }
+
+ /* Instead of the traditional loop which tests each byte, we will
+ test a longword at a time. The tricky part is testing if *any of
+ the four* bytes in the longword in question are equal to NUL or
+ c. We first use an xor with repeated_c. This reduces the task
+ to testing whether *any of the four* bytes in longword1 is zero.
+
+ We compute tmp =
+ ((longword1 - repeated_one) & ~longword1) & (repeated_one << 7).
+ That is, we perform the following operations:
+ 1. Subtract repeated_one.
+ 2. & ~longword1.
+ 3. & a mask consisting of 0x80 in every byte.
+ Consider what happens in each byte:
+ - If a byte of longword1 is zero, step 1 and 2 transform it into 0xff,
+ and step 3 transforms it into 0x80. A carry can also be propagated
+ to more significant bytes.
+ - If a byte of longword1 is nonzero, let its lowest 1 bit be at
+ position k (0 <= k <= 7); so the lowest k bits are 0. After step 1,
+ the byte ends in a single bit of value 0 and k bits of value 1.
+ After step 2, the result is just k bits of value 1: 2^k - 1. After
+ step 3, the result is 0. And no carry is produced.
+ So, if longword1 has only non-zero bytes, tmp is zero.
+ Whereas if longword1 has a zero byte, call j the position of the least
+ significant zero byte. Then the result has a zero at positions 0, ...,
+ j-1 and a 0x80 at position j. We cannot predict the result at the more
+ significant bytes (positions j+1..3), but it does not matter since we
+ already have a non-zero bit at position 8*j+7.
+
+ The test whether any byte in longword1 is zero is equivalent
+ to testing whether tmp is nonzero.
+
+ This test can read beyond the end of a string, depending on where
+ C_IN is encountered. However, this is considered safe since the
+ initialization phase ensured that the read will be aligned,
+ therefore, the read will not cross page boundaries and will not
+ cause a fault. */
+
+ while (1)
+ {
+ longword longword1 = *longword_ptr ^ repeated_c;
+
+ if ((((longword1 - repeated_one) & ~longword1)
+ & (repeated_one << 7)) != 0)
+ break;
+ longword_ptr++;
+ }
+
+ char_ptr = (const unsigned char *) longword_ptr;
+
+ /* At this point, we know that one of the sizeof (longword) bytes
+ starting at char_ptr is == c. On little-endian machines, we
+ could determine the first such byte without any further memory
+ accesses, just by looking at the tmp result from the last loop
+ iteration. But this does not work on big-endian machines.
+ Choose code that works in both cases. */
+
+ char_ptr = (unsigned char *) longword_ptr;
+ while (*char_ptr != c)
+ char_ptr++;
+ return (void *) char_ptr;
+}