73 lines
2.5 KiB
C
73 lines
2.5 KiB
C
#ifndef VLIBC_SYS_TIMES_H
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#define VLIBC_SYS_TIMES_H
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/*
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* vlibc — <sys/times.h>.
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*
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* Process CPU-time accounting in clock ticks. times() and struct tms are
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* XSI [CX] in POSIX.1-2008 (glibc gates them behind _XOPEN_SOURCE, not
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* _POSIX_C_SOURCE), so the whole surface sits at level 2 — nothing here is
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* POSIX.1-2008 base:
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*
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* Level 2 (muslmimic): times, struct tms.
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*
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* clock_t is the scalar tick type owned by <sys/types.h> (typedef long
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* clock_t; <time.h> pulls it from the same place for clock()); this header
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* includes that one rather than re-typedefing clock_t. The unit of every
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* times() figure is the tick: CLK_TCK per second, the fixed x86_64 USER_HZ
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* constant of 100 that todo 32's sysconf(_SC_CLK_TCK) reports (defined
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* once, in src/misc/sysconf.c).
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*
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* struct tms mirrors the x86_64 kernel's __kernel_tms exactly: four longs
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* in the same order (tms_utime, tms_stime, tms_cutime, tms_cstime), which
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* is why src/sys/times.c hands the struct straight to SYS_times. The kernel
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* writes all four words on every successful call, so no field is optional.
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*
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* The declaration carries no intent attribute: times() performs a syscall
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* with side effects and reports failures through errno, so const/pure
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* would be unsound (see the rationale in <sys/time.h>).
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*/
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#include <vlibc/features.h>
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#include <sys/types.h> /* clock_t */
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#ifdef __cplusplus
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extern "C" {
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#endif
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#if VLIBC_LEVEL_GE(2)
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/* Level 2 (muslmimic): XSI process-CPU-time accounting. */
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/*
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* CPU-time accounting for the calling process and its waited-for children,
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* measured in clock ticks (CLK_TCK per second). tms_utime and tms_stime
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* are the user and system CPU time of the calling process; tms_cutime and
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* tms_cstime are the user and system CPU time consumed by children that
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* have been waited for (all four zeroed before any child is waited on).
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*/
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struct tms
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{
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clock_t tms_utime; /* user CPU time of the calling process */
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clock_t tms_stime; /* system CPU time of the calling process */
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clock_t tms_cutime; /* user CPU time of waited-for children */
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clock_t tms_cstime; /* system CPU time of waited-for children */
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};
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/*
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* Store the process CPU-time accounting through buf and return the number
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* of clock ticks since an arbitrary fixed point in the past (the Linux
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* kernel reports ticks since boot). Return (clock_t)-1 with errno set when
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* buf points outside the address space.
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*/
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clock_t
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times(struct tms *buf);
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#endif /* VLIBC_LEVEL_GE(2) */
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#ifdef __cplusplus
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}
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#endif
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#endif /* VLIBC_SYS_TIMES_H */
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