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author | Timo Teräs <timo.teras@iki.fi> | 2020-03-04 11:27:01 +0200 |
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committer | Rich Felker <dalias@aerifal.cx> | 2020-03-14 21:23:37 -0400 |
commit | 8343334d7b9cd4338bdac80e17be079cbc675ec3 (patch) | |
tree | f5d9d39d0ae60519f92022e25620e06e26ea9560 /src/errno | |
parent | 2b2c8aafce9d80f9d58652643538f4d58e82b856 (diff) | |
download | musl-8343334d7b9cd4338bdac80e17be079cbc675ec3.tar.gz musl-8343334d7b9cd4338bdac80e17be079cbc675ec3.tar.bz2 musl-8343334d7b9cd4338bdac80e17be079cbc675ec3.tar.xz musl-8343334d7b9cd4338bdac80e17be079cbc675ec3.zip |
improve strerror speed
change the current O(n) lookup to O(1) based on the machinery
described in "How To Write Shared Libraries" (Appendix B).
Diffstat (limited to 'src/errno')
-rw-r--r-- | src/errno/__strerror.h | 13 | ||||
-rw-r--r-- | src/errno/strerror.c | 41 |
2 files changed, 32 insertions, 22 deletions
diff --git a/src/errno/__strerror.h b/src/errno/__strerror.h index 2f04d400..2d992da5 100644 --- a/src/errno/__strerror.h +++ b/src/errno/__strerror.h @@ -1,8 +1,9 @@ -/* This file is sorted such that 'errors' which represent exceptional - * conditions under which a correct program may fail come first, followed - * by messages that indicate an incorrect program or system failure. The - * macro E() along with double-inclusion is used to ensure that ordering - * of the strings remains synchronized. */ +/* The first entry is a catch-all for codes not enumerated here. + * This file is included multiple times to declare and define a structure + * with these messages, and then to define a lookup table translating + * error codes to offsets of corresponding fields in the structure. */ + +E(0, "No error information") E(EILSEQ, "Illegal byte sequence") E(EDOM, "Domain error") @@ -101,5 +102,3 @@ E(EDQUOT, "Quota exceeded") E(ENOMEDIUM, "No medium found") E(EMEDIUMTYPE, "Wrong medium type") E(EMULTIHOP, "Multihop attempted") - -E(0, "No error information") diff --git a/src/errno/strerror.c b/src/errno/strerror.c index e3ed771a..7f926432 100644 --- a/src/errno/strerror.c +++ b/src/errno/strerror.c @@ -1,30 +1,41 @@ #include <errno.h> +#include <stddef.h> #include <string.h> #include "locale_impl.h" -#define E(a,b) ((unsigned char)a), -static const unsigned char errid[] = { +/* mips has one error code outside of the 8-bit range due to a + * historical typo, so we just remap it. */ +#if EDQUOT==1133 +#define EDQUOT_ORIG 1133 +#undef EDQUOT +#define EDQUOT 109 +#endif + +static const struct errmsgstr_t { +#define E(n, s) char str##n[sizeof(s)]; +#include "__strerror.h" +#undef E +} errmsgstr = { +#define E(n, s) s, #include "__strerror.h" +#undef E }; -#undef E -#define E(a,b) b "\0" -static const char errmsg[] = +static const unsigned short errmsgidx[] = { +#define E(n, s) [n] = offsetof(struct errmsgstr_t, str##n), #include "__strerror.h" -; +#undef E +}; char *__strerror_l(int e, locale_t loc) { const char *s; - int i; - /* mips has one error code outside of the 8-bit range due to a - * historical typo, so we just remap it. */ - if (EDQUOT==1133) { - if (e==109) e=-1; - else if (e==EDQUOT) e=109; - } - for (i=0; errid[i] && errid[i] != e; i++); - for (s=errmsg; i; s++, i--) for (; *s; s++); +#ifdef EDQUOT_ORIG + if (e==EDQUOT) e=0; + else if (e==EDQUOT_ORIG) e=EDQUOT; +#endif + if (e >= sizeof errmsgidx / sizeof *errmsgidx) e = 0; + s = (char *)&errmsgstr + errmsgidx[e]; return (char *)LCTRANS(s, LC_MESSAGES, loc); } |