From patchwork Sun May 31 19:10:33 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ondrej Bilka X-Patchwork-Id: 6991 Received: (qmail 83860 invoked by alias); 31 May 2015 19:11:13 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 83846 invoked by uid 89); 31 May 2015 19:11:12 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=2.1 required=5.0 tests=AWL, BAYES_99, BAYES_999, FREEMAIL_FROM, SPF_NEUTRAL autolearn=no version=3.3.2 X-HELO: popelka.ms.mff.cuni.cz Date: Sun, 31 May 2015 21:10:33 +0200 From: =?utf-8?B?T25kxZllaiBCw61sa2E=?= To: libc-alpha@sourceware.org Subject: Re: [PATCH v5] next iteration of strlen, strnlen, strchr, strchrnul, memchr, rawmemchr Message-ID: <20150531191033.GB8530@domone> References: <20150531190013.GA8530@domone> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20150531190013.GA8530@domone> User-Agent: Mutt/1.5.20 (2009-06-14) From now I will send these together, only questionable part there is assumption that searching nonascii chars with strchr happens rarely. Otherwise these are implemented by easy expression and using skeleton. I wait with memrchr as it needs to copy skeleton and reverse direction there. I want to do it once skeleton stabilizes. Comments on these functions? * string/strlen.c: Use string_skeleton. * string/strnlen.c: Likewise. * string/strchr.c: Likewise. * string/strchrnul.c: Likewise. * string/memchr.c: Likewise. * string/rawmemchr.c: Likewise. diff --git a/string/memchr.c b/string/memchr.c index 6896465..6835347 100644 --- a/string/memchr.c +++ b/string/memchr.c @@ -1,10 +1,5 @@ /* Copyright (C) 1991-2015 Free Software Foundation, Inc. This file is part of the GNU C Library. - Based on strlen implementation by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se) and - commentary by Jim Blandy (jimb@ai.mit.edu); - adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu), - and implemented by Roland McGrath (roland@ai.mit.edu). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -20,143 +15,36 @@ License along with the GNU C Library; if not, see . */ -#ifndef _LIBC -# include -#endif - #include +#include -#include +#undef __memchr +#undef memchr -#include +/* Return the length of the null-terminated string STR. Scan for + the null terminator quickly by testing four bytes at a time. */ -#undef __memchr -#ifdef _LIBC -# undef memchr -#endif +#include +#define EXPRESSION(p, c) (bytes_equal (p, c)) +#define EXPRESSION_NOCARRY(p, c) (bytes_equal_nocarry (p, c)) -#ifndef weak_alias -# define __memchr memchr -#endif +#define CHECK_N +#include #ifndef MEMCHR # define MEMCHR __memchr #endif -/* Search no more than N bytes of S for C. */ +#ifdef STATIC +static __always_inline +#endif void * -MEMCHR (void const *s, int c_in, size_t n) +MEMCHR (const void *str, int c, size_t n) { - /* 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; - n > 0 && (size_t) char_ptr % sizeof (longword) != 0; - --n, ++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 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. - - So, the test whether any byte in longword1 is zero is equivalent to - testing whether tmp is nonzero. */ - - while (n >= sizeof (longword)) - { - longword longword1 = *longword_ptr ^ repeated_c; - - if ((((longword1 - repeated_one) & ~longword1) - & (repeated_one << 7)) != 0) - break; - longword_ptr++; - n -= sizeof (longword); - } - - char_ptr = (const unsigned char *) longword_ptr; - - /* At this point, we know that either n < sizeof (longword), or 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. */ - - for (; n > 0; --n, ++char_ptr) - { - if (*char_ptr == c) - return (void *) char_ptr; - } - - return NULL; + return (void *) string_skeleton ((char *) str, c, n); } -#ifdef weak_alias + +#ifndef STATIC weak_alias (__memchr, memchr) -#endif libc_hidden_builtin_def (memchr) +#endif diff --git a/string/rawmemchr.c b/string/rawmemchr.c index 05b22be..6bc037d 100644 --- a/string/rawmemchr.c +++ b/string/rawmemchr.c @@ -1,10 +1,5 @@ /* Copyright (C) 1991-2015 Free Software Foundation, Inc. This file is part of the GNU C Library. - Based on strlen implementation by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se) and - commentary by Jim Blandy (jimb@ai.mit.edu); - adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu), - and implemented by Roland McGrath (roland@ai.mit.edu). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -20,166 +15,25 @@ License along with the GNU C Library; if not, see . */ -#ifdef HAVE_CONFIG_H -#include -#endif +#include +#include -#undef __ptr_t -#define __ptr_t void * +#undef rawmemchr +#undef __rawmemchr -#if defined (_LIBC) -# include -# include -# include -#endif -#if defined (HAVE_LIMITS_H) || defined (_LIBC) -# include -#endif +#include +#define EXPRESSION(p, c) (bytes_equal (p, c)) +#define EXPRESSION_NOCARRY(p, c) (bytes_equal_nocarry (p, c)) -#define LONG_MAX_32_BITS 2147483647 +#include -#ifndef LONG_MAX -#define LONG_MAX LONG_MAX_32_BITS -#endif - -#include - -#undef memchr - -#ifndef RAWMEMCHR -# define RAWMEMCHR __rawmemchr -#endif - -/* Find the first occurrence of C in S. */ -__ptr_t -RAWMEMCHR (s, c_in) - const __ptr_t s; - int c_in; +void * +__rawmemchr (const void *s, int c) { - const unsigned char *char_ptr; - const unsigned long int *longword_ptr; - unsigned long int longword, magic_bits, charmask; - unsigned char c; - - c = (unsigned char) c_in; - - /* Handle the first few characters by reading one character at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ - for (char_ptr = (const unsigned char *) s; - ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == c) - return (__ptr_t) char_ptr; - - /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ - - longword_ptr = (unsigned long int *) char_ptr; - - /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits - the "holes." Note that there is a hole just to the left of - each byte, with an extra at the end: - - bits: 01111110 11111110 11111110 11111111 - bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD - - The 1-bits make sure that carries propagate to the next 0-bit. - The 0-bits provide holes for carries to fall into. */ - - if (sizeof (longword) != 4 && sizeof (longword) != 8) - abort (); - -#if LONG_MAX <= LONG_MAX_32_BITS - magic_bits = 0x7efefeff; -#else - magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff; -#endif - - /* Set up a longword, each of whose bytes is C. */ - charmask = c | (c << 8); - charmask |= charmask << 16; -#if LONG_MAX > LONG_MAX_32_BITS - charmask |= charmask << 32; -#endif - - /* Instead of the traditional loop which tests each character, - 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 zero. */ - while (1) - { - /* We tentatively exit the loop if adding MAGIC_BITS to - LONGWORD fails to change any of the hole bits of LONGWORD. - - 1) Is this safe? Will it catch all the zero bytes? - Suppose there is a byte with all zeros. Any carry bits - propagating from its left will fall into the hole at its - least significant bit and stop. Since there will be no - carry from its most significant bit, the LSB of the - byte to the left will be unchanged, and the zero will be - detected. - - 2) Is this worthwhile? Will it ignore everything except - zero bytes? Suppose every byte of LONGWORD has a bit set - somewhere. There will be a carry into bit 8. If bit 8 - is set, this will carry into bit 16. If bit 8 is clear, - one of bits 9-15 must be set, so there will be a carry - into bit 16. Similarly, there will be a carry into bit - 24. If one of bits 24-30 is set, there will be a carry - into bit 31, so all of the hole bits will be changed. - - The one misfire occurs when bits 24-30 are clear and bit - 31 is set; in this case, the hole at bit 31 is not - changed. If we had access to the processor carry flag, - we could close this loophole by putting the fourth hole - at bit 32! - - So it ignores everything except 128's, when they're aligned - properly. - - 3) But wait! Aren't we looking for C, not zero? - Good point. So what we do is XOR LONGWORD with a longword, - each of whose bytes is C. This turns each byte that is C - into a zero. */ - - longword = *longword_ptr++ ^ charmask; - - /* Add MAGIC_BITS to LONGWORD. */ - if ((((longword + magic_bits) - - /* Set those bits that were unchanged by the addition. */ - ^ ~longword) - - /* Look at only the hole bits. If any of the hole bits - are unchanged, most likely one of the bytes was a - zero. */ - & ~magic_bits) != 0) - { - /* Which of the bytes was C? If none of them were, it was - a misfire; continue the search. */ - - const unsigned char *cp = (const unsigned char *) (longword_ptr - 1); - - if (cp[0] == c) - return (__ptr_t) cp; - if (cp[1] == c) - return (__ptr_t) &cp[1]; - if (cp[2] == c) - return (__ptr_t) &cp[2]; - if (cp[3] == c) - return (__ptr_t) &cp[3]; -#if LONG_MAX > 2147483647 - if (cp[4] == c) - return (__ptr_t) &cp[4]; - if (cp[5] == c) - return (__ptr_t) &cp[5]; - if (cp[6] == c) - return (__ptr_t) &cp[6]; - if (cp[7] == c) - return (__ptr_t) &cp[7]; -#endif - } - } + return (void *) string_skeleton (s, c, 0); } + libc_hidden_def (__rawmemchr) weak_alias (__rawmemchr, rawmemchr) + diff --git a/string/strchr.c b/string/strchr.c index 5f90075..e7c2e4c 100644 --- a/string/strchr.c +++ b/string/strchr.c @@ -1,10 +1,5 @@ /* Copyright (C) 1991-2015 Free Software Foundation, Inc. This file is part of the GNU C Library. - Based on strlen implementation by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se) and - bug fix and commentary by Jim Blandy (jimb@ai.mit.edu); - adaptation to strchr suggested by Dick Karpinski (dick@cca.ucsf.edu), - and implemented by Roland McGrath (roland@ai.mit.edu). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -21,166 +16,21 @@ . */ #include -#include - #undef strchr +#undef index + +#define AS_STRCHR +#define STRCHRNUL strchrnul_static +#include "string/strchrnul.c" + -/* Find the first occurrence of C in S. */ char * strchr (const char *s, int c_in) { - const unsigned char *char_ptr; - const unsigned long int *longword_ptr; - unsigned long int longword, magic_bits, charmask; - unsigned char c; - - c = (unsigned char) c_in; - - /* Handle the first few characters by reading one character at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ - for (char_ptr = (const unsigned char *) s; - ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == c) - return (void *) char_ptr; - else if (*char_ptr == '\0') - return NULL; - - /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ - - longword_ptr = (unsigned long int *) char_ptr; - - /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits - the "holes." Note that there is a hole just to the left of - each byte, with an extra at the end: - - bits: 01111110 11111110 11111110 11111111 - bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD - - The 1-bits make sure that carries propagate to the next 0-bit. - The 0-bits provide holes for carries to fall into. */ - switch (sizeof (longword)) - { - case 4: magic_bits = 0x7efefeffL; break; - case 8: magic_bits = ((0x7efefefeL << 16) << 16) | 0xfefefeffL; break; - default: - abort (); - } - - /* Set up a longword, each of whose bytes is C. */ - charmask = c | (c << 8); - charmask |= charmask << 16; - if (sizeof (longword) > 4) - /* Do the shift in two steps to avoid a warning if long has 32 bits. */ - charmask |= (charmask << 16) << 16; - if (sizeof (longword) > 8) - abort (); - - /* Instead of the traditional loop which tests each character, - 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 zero. */ - for (;;) - { - /* We tentatively exit the loop if adding MAGIC_BITS to - LONGWORD fails to change any of the hole bits of LONGWORD. - - 1) Is this safe? Will it catch all the zero bytes? - Suppose there is a byte with all zeros. Any carry bits - propagating from its left will fall into the hole at its - least significant bit and stop. Since there will be no - carry from its most significant bit, the LSB of the - byte to the left will be unchanged, and the zero will be - detected. - - 2) Is this worthwhile? Will it ignore everything except - zero bytes? Suppose every byte of LONGWORD has a bit set - somewhere. There will be a carry into bit 8. If bit 8 - is set, this will carry into bit 16. If bit 8 is clear, - one of bits 9-15 must be set, so there will be a carry - into bit 16. Similarly, there will be a carry into bit - 24. If one of bits 24-30 is set, there will be a carry - into bit 31, so all of the hole bits will be changed. - - The one misfire occurs when bits 24-30 are clear and bit - 31 is set; in this case, the hole at bit 31 is not - changed. If we had access to the processor carry flag, - we could close this loophole by putting the fourth hole - at bit 32! - - So it ignores everything except 128's, when they're aligned - properly. - - 3) But wait! Aren't we looking for C as well as zero? - Good point. So what we do is XOR LONGWORD with a longword, - each of whose bytes is C. This turns each byte that is C - into a zero. */ - - longword = *longword_ptr++; - - /* Add MAGIC_BITS to LONGWORD. */ - if ((((longword + magic_bits) - - /* Set those bits that were unchanged by the addition. */ - ^ ~longword) - - /* Look at only the hole bits. If any of the hole bits - are unchanged, most likely one of the bytes was a - zero. */ - & ~magic_bits) != 0 || - - /* That caught zeroes. Now test for C. */ - ((((longword ^ charmask) + magic_bits) ^ ~(longword ^ charmask)) - & ~magic_bits) != 0) - { - /* Which of the bytes was C or zero? - If none of them were, it was a misfire; continue the search. */ - - const unsigned char *cp = (const unsigned char *) (longword_ptr - 1); - - if (*cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (sizeof (longword) > 4) - { - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - if (*++cp == c) - return (char *) cp; - else if (*cp == '\0') - return NULL; - } - } - } - - return NULL; + unsigned char c = (unsigned char) c_in; + unsigned char *r = (unsigned char *) STRCHRNUL (s, c); + return (*r == c) ? (char *) r : NULL; } -#ifdef weak_alias -#undef index weak_alias (strchr, index) -#endif libc_hidden_builtin_def (strchr) diff --git a/string/strchrnul.c b/string/strchrnul.c index 2678f1d..933f37e 100644 --- a/string/strchrnul.c +++ b/string/strchrnul.c @@ -1,10 +1,5 @@ /* Copyright (C) 1991-2015 Free Software Foundation, Inc. This file is part of the GNU C Library. - Based on strlen implementation by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se) and - bug fix and commentary by Jim Blandy (jimb@ai.mit.edu); - adaptation to strchr suggested by Dick Karpinski (dick@cca.ucsf.edu), - and implemented by Roland McGrath (roland@ai.mit.edu). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -21,153 +16,69 @@ . */ #include -#include #include -#undef __strchrnul #undef strchrnul +#undef __strchrnul -#ifndef STRCHRNUL -# define STRCHRNUL __strchrnul -#endif - -/* Find the first occurrence of C in S or the final NUL byte. */ -char * -STRCHRNUL (s, c_in) - const char *s; - int c_in; -{ - const unsigned char *char_ptr; - const unsigned long int *longword_ptr; - unsigned long int longword, magic_bits, charmask; - unsigned char c; - - c = (unsigned char) c_in; +/* Return the length of the null-terminated string STR. Scan for + the null terminator quickly by testing four bytes at a time. */ - /* Handle the first few characters by reading one character at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ - for (char_ptr = (const unsigned char *) s; - ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == c || *char_ptr == '\0') - return (void *) char_ptr; +/* Here idea is still use the result of expression + contains_zero (*p) | contains_zero (*p ^ cmask) + but we can optimize it by using commutativity of operations. */ - /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ +#include +#define EXPRESSION(s, cmask) ((((s) - ones) | (((s) ^ cmask) - ones)) \ + & high_bits & (~s)) - longword_ptr = (unsigned long int *) char_ptr; +/* TODO simplify. */ +#define EXPRESSION_NOCARRY(s, cmask) contains_zero_nocarry (s) \ + | bytes_equal_nocarry (s, cmask) - /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits - the "holes." Note that there is a hole just to the left of - each byte, with an extra at the end: - bits: 01111110 11111110 11111110 11111111 - bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD +#include - The 1-bits make sure that carries propagate to the next 0-bit. - The 0-bits provide holes for carries to fall into. */ - switch (sizeof (longword)) - { - case 4: magic_bits = 0x7efefeffL; break; - case 8: magic_bits = ((0x7efefefeL << 16) << 16) | 0xfefefeffL; break; - default: - abort (); - } +#ifndef STRCHRNUL +# define STRCHRNUL __strchrnul +#endif - /* Set up a longword, each of whose bytes is C. */ - charmask = c | (c << 8); - charmask |= charmask << 16; - if (sizeof (longword) > 4) - /* Do the shift in two steps to avoid a warning if long has 32 bits. */ - charmask |= (charmask << 16) << 16; - if (sizeof (longword) > 8) - abort (); - - /* Instead of the traditional loop which tests each character, - 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 zero. */ - for (;;) +#ifdef AS_STRCHR +static __always_inline +#endif +char * +STRCHRNUL (const char *s_in, int c_in) +{ + char *s_aligned; + vector_int mask; + const vector_int *lptr; + char *s = (char *) s_in; + unsigned char c = (unsigned char) c_in; + vector_int cmask = broadcast (c); + if (__glibc_unlikely (c > 127)) { - /* We tentatively exit the loop if adding MAGIC_BITS to - LONGWORD fails to change any of the hole bits of LONGWORD. - - 1) Is this safe? Will it catch all the zero bytes? - Suppose there is a byte with all zeros. Any carry bits - propagating from its left will fall into the hole at its - least significant bit and stop. Since there will be no - carry from its most significant bit, the LSB of the - byte to the left will be unchanged, and the zero will be - detected. - - 2) Is this worthwhile? Will it ignore everything except - zero bytes? Suppose every byte of LONGWORD has a bit set - somewhere. There will be a carry into bit 8. If bit 8 - is set, this will carry into bit 16. If bit 8 is clear, - one of bits 9-15 must be set, so there will be a carry - into bit 16. Similarly, there will be a carry into bit - 24. If one of bits 24-30 is set, there will be a carry - into bit 31, so all of the hole bits will be changed. - - The one misfire occurs when bits 24-30 are clear and bit - 31 is set; in this case, the hole at bit 31 is not - changed. If we had access to the processor carry flag, - we could close this loophole by putting the fourth hole - at bit 32! - - So it ignores everything except 128's, when they're aligned - properly. - - 3) But wait! Aren't we looking for C as well as zero? - Good point. So what we do is XOR LONGWORD with a longword, - each of whose bytes is C. This turns each byte that is C - into a zero. */ - - longword = *longword_ptr++; - - /* Add MAGIC_BITS to LONGWORD. */ - if ((((longword + magic_bits) - - /* Set those bits that were unchanged by the addition. */ - ^ ~longword) - - /* Look at only the hole bits. If any of the hole bits - are unchanged, most likely one of the bytes was a - zero. */ - & ~magic_bits) != 0 || - - /* That caught zeroes. Now test for C. */ - ((((longword ^ charmask) + magic_bits) ^ ~(longword ^ charmask)) - & ~magic_bits) != 0) - { - /* Which of the bytes was C or zero? - If none of them were, it was a misfire; continue the search. */ - - const unsigned char *cp = (const unsigned char *) (longword_ptr - 1); - - if (*cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (sizeof (longword) > 4) - { - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - } - } + s_aligned = PTR_ALIGN_DOWN (s, LSIZE); + lptr = (const vector_int *) s_aligned; + mask = SHIFT_BYTES (contains_zero_nocarry (*lptr) + | bytes_equal_nocarry (*lptr, cmask), + s - s_aligned); + + if (mask) + return s + first_nonzero_byte (mask); + + while (1) + { + s_aligned += LSIZE; + lptr = (const vector_int *) s_aligned; + mask = contains_zero(*lptr) | bytes_equal (*lptr, cmask); + if (mask) + return s_aligned + first_nonzero_byte (mask); + } } - - /* This should never happen. */ - return NULL; + else + return string_skeleton (s, c, 0); } +#ifndef AS_STRCHR weak_alias (__strchrnul, strchrnul) +#endif diff --git a/string/strlen.c b/string/strlen.c index d066bde..a472e0c 100644 --- a/string/strlen.c +++ b/string/strlen.c @@ -1,8 +1,5 @@ /* Copyright (C) 1991-2015 Free Software Foundation, Inc. This file is part of the GNU C Library. - Written by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se); - commentary by Jim Blandy (jimb@ai.mit.edu). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -25,81 +22,16 @@ /* Return the length of the null-terminated string STR. Scan for the null terminator quickly by testing four bytes at a time. */ + +#include +#define EXPRESSION(p, c) (contains_zero (p)) +#define EXPRESSION_NOCARRY(p, c) (contains_zero_nocarry (p)) +#include + size_t strlen (const char *str) { - const char *char_ptr; - const unsigned long int *longword_ptr; - unsigned long int longword, himagic, lomagic; - - /* Handle the first few characters by reading one character at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ - for (char_ptr = str; ((unsigned long int) char_ptr - & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == '\0') - return char_ptr - str; - - /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ - - longword_ptr = (unsigned long int *) char_ptr; - - /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits - the "holes." Note that there is a hole just to the left of - each byte, with an extra at the end: - - bits: 01111110 11111110 11111110 11111111 - bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD - - The 1-bits make sure that carries propagate to the next 0-bit. - The 0-bits provide holes for carries to fall into. */ - himagic = 0x80808080L; - lomagic = 0x01010101L; - if (sizeof (longword) > 4) - { - /* 64-bit version of the magic. */ - /* Do the shift in two steps to avoid a warning if long has 32 bits. */ - himagic = ((himagic << 16) << 16) | himagic; - lomagic = ((lomagic << 16) << 16) | lomagic; - } - if (sizeof (longword) > 8) - abort (); - - /* Instead of the traditional loop which tests each character, - 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 zero. */ - for (;;) - { - longword = *longword_ptr++; - - if (((longword - lomagic) & ~longword & himagic) != 0) - { - /* Which of the bytes was the zero? If none of them were, it was - a misfire; continue the search. */ - - const char *cp = (const char *) (longword_ptr - 1); - - if (cp[0] == 0) - return cp - str; - if (cp[1] == 0) - return cp - str + 1; - if (cp[2] == 0) - return cp - str + 2; - if (cp[3] == 0) - return cp - str + 3; - if (sizeof (longword) > 4) - { - if (cp[4] == 0) - return cp - str + 4; - if (cp[5] == 0) - return cp - str + 5; - if (cp[6] == 0) - return cp - str + 6; - if (cp[7] == 0) - return cp - str + 7; - } - } - } + return string_skeleton (str, 0, 0) - str; } + libc_hidden_builtin_def (strlen) diff --git a/string/strnlen.c b/string/strnlen.c index 803d78b..9a71e4d 100644 --- a/string/strnlen.c +++ b/string/strnlen.c @@ -1,15 +1,10 @@ -/* Find the length of STRING, but scan at most MAXLEN characters. - Copyright (C) 1991-2015 Free Software Foundation, Inc. - Contributed by Jakub Jelinek . - - Based on strlen written by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se); - commentary by Jim Blandy (jimb@ai.mit.edu). +/* Copyright (C) 1991-2015 Free Software Foundation, Inc. + This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public License as - published by the Free Software Foundation; either version 2.1 of the - License, or (at your option) any later version. + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of @@ -17,149 +12,27 @@ Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; see the file COPYING.LIB. If - not, see . */ + License along with the GNU C Library; if not, see + . */ #include #include -/* Find the length of S, but scan at most MAXLEN characters. If no - '\0' terminator is found in that many characters, return MAXLEN. */ +#undef strlen + +/* Return the length of the null-terminated string STR. Scan for + the null terminator quickly by testing four bytes at a time. */ -#ifdef STRNLEN -# define __strnlen STRNLEN -#endif +#define STATIC +#define MEMCHR memchr_static +#include "string/memchr.c" size_t -__strnlen (const char *str, size_t maxlen) +__strnlen (const char *str, size_t n) { - const char *char_ptr, *end_ptr = str + maxlen; - const unsigned long int *longword_ptr; - unsigned long int longword, himagic, lomagic; - - if (maxlen == 0) - return 0; - - if (__glibc_unlikely (end_ptr < str)) - end_ptr = (const char *) ~0UL; - - /* Handle the first few characters by reading one character at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ - for (char_ptr = str; ((unsigned long int) char_ptr - & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == '\0') - { - if (char_ptr > end_ptr) - char_ptr = end_ptr; - return char_ptr - str; - } - - /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ - - longword_ptr = (unsigned long int *) char_ptr; - - /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits - the "holes." Note that there is a hole just to the left of - each byte, with an extra at the end: - - bits: 01111110 11111110 11111110 11111111 - bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD - - The 1-bits make sure that carries propagate to the next 0-bit. - The 0-bits provide holes for carries to fall into. */ - himagic = 0x80808080L; - lomagic = 0x01010101L; - if (sizeof (longword) > 4) - { - /* 64-bit version of the magic. */ - /* Do the shift in two steps to avoid a warning if long has 32 bits. */ - himagic = ((himagic << 16) << 16) | himagic; - lomagic = ((lomagic << 16) << 16) | lomagic; - } - if (sizeof (longword) > 8) - abort (); - - /* Instead of the traditional loop which tests each character, - 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 zero. */ - while (longword_ptr < (unsigned long int *) end_ptr) - { - /* We tentatively exit the loop if adding MAGIC_BITS to - LONGWORD fails to change any of the hole bits of LONGWORD. - - 1) Is this safe? Will it catch all the zero bytes? - Suppose there is a byte with all zeros. Any carry bits - propagating from its left will fall into the hole at its - least significant bit and stop. Since there will be no - carry from its most significant bit, the LSB of the - byte to the left will be unchanged, and the zero will be - detected. - - 2) Is this worthwhile? Will it ignore everything except - zero bytes? Suppose every byte of LONGWORD has a bit set - somewhere. There will be a carry into bit 8. If bit 8 - is set, this will carry into bit 16. If bit 8 is clear, - one of bits 9-15 must be set, so there will be a carry - into bit 16. Similarly, there will be a carry into bit - 24. If one of bits 24-30 is set, there will be a carry - into bit 31, so all of the hole bits will be changed. - - The one misfire occurs when bits 24-30 are clear and bit - 31 is set; in this case, the hole at bit 31 is not - changed. If we had access to the processor carry flag, - we could close this loophole by putting the fourth hole - at bit 32! - - So it ignores everything except 128's, when they're aligned - properly. */ - - longword = *longword_ptr++; - - if ((longword - lomagic) & himagic) - { - /* Which of the bytes was the zero? If none of them were, it was - a misfire; continue the search. */ - - const char *cp = (const char *) (longword_ptr - 1); - - char_ptr = cp; - if (cp[0] == 0) - break; - char_ptr = cp + 1; - if (cp[1] == 0) - break; - char_ptr = cp + 2; - if (cp[2] == 0) - break; - char_ptr = cp + 3; - if (cp[3] == 0) - break; - if (sizeof (longword) > 4) - { - char_ptr = cp + 4; - if (cp[4] == 0) - break; - char_ptr = cp + 5; - if (cp[5] == 0) - break; - char_ptr = cp + 6; - if (cp[6] == 0) - break; - char_ptr = cp + 7; - if (cp[7] == 0) - break; - } - } - char_ptr = end_ptr; - } - - if (char_ptr > end_ptr) - char_ptr = end_ptr; - return char_ptr - str; + char *ret = MEMCHR (str, 0, n); + return ret ? ret - str : n; } -#ifndef STRNLEN + weak_alias (__strnlen, strnlen) -#endif libc_hidden_def (strnlen)