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author | Thomas Martitz <kugel@rockbox.org> | 2012-01-07 19:56:09 +0100 |
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committer | Thomas Martitz <kugel@rockbox.org> | 2012-01-22 18:46:45 +0100 |
commit | a035261089403de259e74ce4dd196e2715138ed2 (patch) | |
tree | 440d75109a7ebfefef2a58076b38b1bfe9db8f63 /firmware/asm/strlen.c | |
parent | 8e8e978de6b6283b66a6829fa8c5e3b94674ce7d (diff) | |
download | rockbox-a035261089403de259e74ce4dd196e2715138ed2.tar.gz rockbox-a035261089403de259e74ce4dd196e2715138ed2.zip |
Move optimized memcpy and friends and strlen to firmware/asm,
using the new automatic-asm-picking infrastructure.
Diffstat (limited to 'firmware/asm/strlen.c')
-rw-r--r-- | firmware/asm/strlen.c | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/firmware/asm/strlen.c b/firmware/asm/strlen.c new file mode 100644 index 0000000000..649df6764b --- /dev/null +++ b/firmware/asm/strlen.c @@ -0,0 +1,93 @@ +/* +FUNCTION + <<strlen>>---character string length + +INDEX + strlen + +ANSI_SYNOPSIS + #include <string.h> + size_t strlen(const char *<[str]>); + +TRAD_SYNOPSIS + #include <string.h> + size_t strlen(<[str]>) + char *<[src]>; + +DESCRIPTION + The <<strlen>> function works out the length of the string + starting at <<*<[str]>>> by counting chararacters until it + reaches a <<NULL>> character. + +RETURNS + <<strlen>> returns the character count. + +PORTABILITY +<<strlen>> is ANSI C. + +<<strlen>> requires no supporting OS subroutines. + +QUICKREF + strlen ansi pure +*/ + +#include "config.h" +#include "_ansi.h" +#include <string.h> +#include <limits.h> + +#define LBLOCKSIZE (sizeof (long)) +#define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1)) + +#if LONG_MAX == 2147483647L +#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) +#else +#if LONG_MAX == 9223372036854775807L +/* Nonzero if X (a long int) contains a NULL byte. */ +#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) +#else +#error long int is not a 32bit or 64bit type. +#endif +#endif + +#ifndef DETECTNULL +#error long int is not a 32bit or 64bit byte +#endif + +size_t +_DEFUN (strlen, (str), + _CONST char *str) ICODE_ATTR; + +size_t +_DEFUN (strlen, (str), + _CONST char *str) +{ +#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) + _CONST char *start = str; + + while (*str) + str++; + + return str - start; +#else + _CONST char *start = str; + unsigned long *aligned_addr; + + if (!UNALIGNED (str)) + { + /* If the string is word-aligned, we can check for the presence of + a null in each word-sized block. */ + aligned_addr = (unsigned long*)str; + while (!DETECTNULL (*aligned_addr)) + aligned_addr++; + + /* Once a null is detected, we check each byte in that block for a + precise position of the null. */ + str = (char*)aligned_addr; + } + + while (*str) + str++; + return str - start; +#endif /* not PREFER_SIZE_OVER_SPEED */ +} |