Mercurial > hg > octave-kai > gnulib-hg
changeset 9999:5f559abfabef
Add rawmemchr module, matching glibc.
* modules/string (Makefile.am): New indicator.
* m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): Set it.
* lib/string.in.h (rawmemchr): Declare when appropriate.
* modules/rawmemchr: New file.
* m4/rawmemchr.m4: Likewise.
* lib/rawmemchr.c: Likewise.
* modules/rawmemchr-tests: Likewise.
* tests/test-rawmemchr.c: Likewise.
* doc/glibc-functions/rawmemchr.texi (rawmemchr): Document
module.
* modules/strchrnul (Depends-on): Add rawmemchr.
* lib/strchrnul.c (strchrnul): Optimize a corner case.
Signed-off-by: Eric Blake <ebb9@byu.net>
author | Eric Blake <ebb9@byu.net> |
---|---|
date | Mon, 28 Apr 2008 17:08:43 -0600 |
parents | 3362dfd48604 |
children | 8095c13f76df |
files | ChangeLog doc/glibc-functions/rawmemchr.texi lib/rawmemchr.c lib/strchrnul.c lib/string.in.h m4/rawmemchr.m4 m4/string_h.m4 modules/rawmemchr modules/rawmemchr-tests modules/strchrnul modules/string tests/test-rawmemchr.c |
diffstat | 12 files changed, 318 insertions(+), 5 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,19 @@ 2008-04-28 Eric Blake <ebb9@byu.net> + Add rawmemchr module, matching glibc. + * modules/string (Makefile.am): New indicator. + * m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): Set it. + * lib/string.in.h (rawmemchr): Declare when appropriate. + * modules/rawmemchr: New file. + * m4/rawmemchr.m4: Likewise. + * lib/rawmemchr.c: Likewise. + * modules/rawmemchr-tests: Likewise. + * tests/test-rawmemchr.c: Likewise. + * doc/glibc-functions/rawmemchr.texi (rawmemchr): Document + module. + * modules/strchrnul (Depends-on): Add rawmemchr. + * lib/strchrnul.c (strchrnul): Optimize a corner case. + Whitespace cleanup. * tests/test-strchrnul.c: Reindent. * lib/strchrnul.c: Likewise.
--- a/doc/glibc-functions/rawmemchr.texi +++ b/doc/glibc-functions/rawmemchr.texi @@ -2,15 +2,15 @@ @subsection @code{rawmemchr} @findex rawmemchr -Gnulib module: --- +Gnulib module: rawmemchr Portability problems fixed by Gnulib: @itemize -@end itemize - -Portability problems not fixed by Gnulib: -@itemize @item This function is missing on all non-glibc platforms: MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin, mingw, Interix 3.5, BeOS. @end itemize + +Portability problems not fixed by Gnulib: +@itemize +@end itemize
new file mode 100644 --- /dev/null +++ b/lib/rawmemchr.c @@ -0,0 +1,136 @@ +/* Searching in a string. + Copyright (C) 2008 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; +}
--- a/lib/strchrnul.c +++ b/lib/strchrnul.c @@ -37,6 +37,8 @@ unsigned char c; c = (unsigned char) c_in; + if (!c) + return rawmemchr (s, 0); /* Handle the first few bytes by reading one byte at a time. Do this until CHAR_PTR is aligned on a longword boundary. */
--- a/lib/string.in.h +++ b/lib/string.in.h @@ -93,6 +93,22 @@ memrchr (a, b, c)) #endif +/* Find the first occurrence of C in S. More efficient than + memchr(S,C,N), at the expense of undefined behavior if C does not + occur within N bytes. */ +#if @GNULIB_RAWMEMCHR@ +# if ! @HAVE_RAWMEMCHR@ +extern void *rawmemchr (void const *__s, int __c_in) + __attribute__ ((__pure__)); +# endif +#elif defined GNULIB_POSIXCHECK +# undef rawmemchr +# define rawmemchr(a,b) \ + (GL_LINK_WARNING ("rawmemchr is unportable - " \ + "use gnulib module rawmemchr for portability"), \ + rawmemchr (a, b)) +#endif + /* Copy SRC to DST, returning the address of the terminating '\0' in DST. */ #if @GNULIB_STPCPY@ # if ! @HAVE_STPCPY@
new file mode 100644 --- /dev/null +++ b/m4/rawmemchr.m4 @@ -0,0 +1,21 @@ +# rawmemchr.m4 serial 1 +dnl Copyright (C) 2003, 2007, 2008 Free Software Foundation, Inc. +dnl This file is free software; the Free Software Foundation +dnl gives unlimited permission to copy and/or distribute it, +dnl with or without modifications, as long as this notice is preserved. + +AC_DEFUN([gl_FUNC_RAWMEMCHR], +[ + dnl Persuade glibc <string.h> to declare rawmemchr(). + AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS]) + + AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS]) + AC_REPLACE_FUNCS([rawmemchr]) + if test $ac_cv_func_rawmemchr = no; then + HAVE_RAWMEMCHR=0 + gl_PREREQ_RAWMEMCHR + fi +]) + +# Prerequisites of lib/strchrnul.c. +AC_DEFUN([gl_PREREQ_RAWMEMCHR], [:])
--- a/m4/string_h.m4 +++ b/m4/string_h.m4 @@ -35,6 +35,7 @@ GNULIB_MEMMEM=0; AC_SUBST([GNULIB_MEMMEM]) GNULIB_MEMPCPY=0; AC_SUBST([GNULIB_MEMPCPY]) GNULIB_MEMRCHR=0; AC_SUBST([GNULIB_MEMRCHR]) + GNULIB_RAWMEMCHR=0; AC_SUBST([GNULIB_RAWMEMCHR]) GNULIB_STPCPY=0; AC_SUBST([GNULIB_STPCPY]) GNULIB_STPNCPY=0; AC_SUBST([GNULIB_STPNCPY]) GNULIB_STRCHRNUL=0; AC_SUBST([GNULIB_STRCHRNUL]) @@ -66,6 +67,7 @@ HAVE_DECL_MEMMEM=1; AC_SUBST([HAVE_DECL_MEMMEM]) HAVE_MEMPCPY=1; AC_SUBST([HAVE_MEMPCPY]) HAVE_DECL_MEMRCHR=1; AC_SUBST([HAVE_DECL_MEMRCHR]) + HAVE_RAWMEMCHR=1; AC_SUBST([HAVE_RAWMEMCHR]) HAVE_STPCPY=1; AC_SUBST([HAVE_STPCPY]) HAVE_STPNCPY=1; AC_SUBST([HAVE_STPNCPY]) HAVE_STRCHRNUL=1; AC_SUBST([HAVE_STRCHRNUL])
new file mode 100644 --- /dev/null +++ b/modules/rawmemchr @@ -0,0 +1,25 @@ +Description: +rawmemchr() function: Find the first occurrence of C in S. + +Files: +lib/rawmemchr.c +m4/rawmemchr.m4 + +Depends-on: +extensions +string + +configure.ac: +gl_FUNC_RAWMEMCHR +gl_STRING_MODULE_INDICATOR([rawmemchr]) + +Makefile.am: + +Include: +<string.h> + +License: +LGPL + +Maintainer: +FSF
new file mode 100644 --- /dev/null +++ b/modules/rawmemchr-tests @@ -0,0 +1,10 @@ +Files: +tests/test-rawmemchr.c + +Depends-on: + +configure.ac: + +Makefile.am: +TESTS += test-rawmemchr +check_PROGRAMS += test-rawmemchr
--- a/modules/strchrnul +++ b/modules/strchrnul @@ -9,6 +9,7 @@ Depends-on: extensions string +rawmemchr configure.ac: gl_FUNC_STRCHRNUL
--- a/modules/string +++ b/modules/string @@ -40,6 +40,7 @@ -e 's|@''GNULIB_MEMMEM''@|$(GNULIB_MEMMEM)|g' \ -e 's|@''GNULIB_MEMPCPY''@|$(GNULIB_MEMPCPY)|g' \ -e 's|@''GNULIB_MEMRCHR''@|$(GNULIB_MEMRCHR)|g' \ + -e 's|@''GNULIB_RAWMEMCHR''@|$(GNULIB_RAWMEMCHR)|g' \ -e 's|@''GNULIB_STPCPY''@|$(GNULIB_STPCPY)|g' \ -e 's|@''GNULIB_STPNCPY''@|$(GNULIB_STPNCPY)|g' \ -e 's|@''GNULIB_STRCHRNUL''@|$(GNULIB_STRCHRNUL)|g' \ @@ -56,6 +57,7 @@ -e 's|@''HAVE_DECL_MEMMEM''@|$(HAVE_DECL_MEMMEM)|g' \ -e 's|@''HAVE_MEMPCPY''@|$(HAVE_MEMPCPY)|g' \ -e 's|@''HAVE_DECL_MEMRCHR''@|$(HAVE_DECL_MEMRCHR)|g' \ + -e 's|@''HAVE_RAWMEMCHR''@|$(HAVE_RAWMEMCHR)|g' \ -e 's|@''HAVE_STPCPY''@|$(HAVE_STPCPY)|g' \ -e 's|@''HAVE_STPNCPY''@|$(HAVE_STPNCPY)|g' \ -e 's|@''HAVE_STRCHRNUL''@|$(HAVE_STRCHRNUL)|g' \
new file mode 100644 --- /dev/null +++ b/tests/test-rawmemchr.c @@ -0,0 +1,84 @@ +/* + * Copyright (C) 2008 Free Software Foundation + * Written by Eric Blake and Bruno Haible + * + * 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> + +#include <string.h> + +#include <stdio.h> +#include <stdlib.h> + +#define ASSERT(expr) \ + do \ + { \ + if (!(expr)) \ + { \ + fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \ + fflush (stderr); \ + abort (); \ + } \ + } \ + while (0) + +/* Calculating void * + int is not portable, so this wrapper converts + to char * to make the tests easier to write. */ +#define RAWMEMCHR (char *) rawmemchr + +int +main () +{ + size_t n = 0x100000; + char *input = malloc (n + 1); + ASSERT (input); + + input[0] = 'a'; + input[1] = 'b'; + memset (input + 2, 'c', 1024); + memset (input + 1026, 'd', n - 1028); + input[n - 2] = 'e'; + input[n - 1] = 'a'; + input[n] = '\0'; + + /* Basic behavior tests. */ + ASSERT (RAWMEMCHR (input, 'a') == input); + ASSERT (RAWMEMCHR (input, 'b') == input + 1); + ASSERT (RAWMEMCHR (input, 'c') == input + 2); + ASSERT (RAWMEMCHR (input, 'd') == input + 1026); + + ASSERT (RAWMEMCHR (input + 1, 'a') == input + n - 1); + ASSERT (RAWMEMCHR (input + 1, 'e') == input + n - 2); + + ASSERT (RAWMEMCHR (input, '\0') == input + n); + + /* Alignment tests. */ + { + int i, j; + for (i = 0; i < 32; i++) + { + for (j = 0; j < 256; j++) + input[i + j] = j; + for (j = 0; j < 256; j++) + { + ASSERT (RAWMEMCHR (input + i, j) == input + i + j); + } + } + } + + free (input); + + return 0; +}