| 1 | //===-- Linux implementation of the clock function ------------------------===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #include "src/time/clock.h" |
| 10 | |
| 11 | #include "src/__support/CPP/limits.h" |
| 12 | #include "src/__support/OSUtil/syscall.h" // For internal syscall function. |
| 13 | #include "src/__support/common.h" |
| 14 | #include "src/errno/libc_errno.h" |
| 15 | #include "src/time/linux/clockGetTimeImpl.h" |
| 16 | |
| 17 | #include <sys/syscall.h> // For syscall numbers. |
| 18 | #include <time.h> |
| 19 | |
| 20 | namespace LIBC_NAMESPACE { |
| 21 | |
| 22 | LLVM_LIBC_FUNCTION(clock_t, clock, ()) { |
| 23 | struct timespec ts; |
| 24 | auto result = internal::clock_gettimeimpl(CLOCK_PROCESS_CPUTIME_ID, ts: &ts); |
| 25 | if (!result.has_value()) { |
| 26 | libc_errno = result.error(); |
| 27 | return -1; |
| 28 | } |
| 29 | |
| 30 | // The above syscall gets the CPU time in seconds plus nanoseconds. |
| 31 | // The standard requires that we return clock_t(-1) if we cannot represent |
| 32 | // clocks as a clock_t value. |
| 33 | constexpr clock_t CLOCK_SECS_MAX = |
| 34 | cpp::numeric_limits<clock_t>::max() / CLOCKS_PER_SEC; |
| 35 | if (ts.tv_sec > CLOCK_SECS_MAX) |
| 36 | return clock_t(-1); |
| 37 | if (ts.tv_nsec / 1000000000 > CLOCK_SECS_MAX - ts.tv_sec) |
| 38 | return clock_t(-1); |
| 39 | |
| 40 | // For the integer computation converting tv_nsec to clocks to work |
| 41 | // correctly, we want CLOCKS_PER_SEC to be less than 1000000000. |
| 42 | static_assert(1000000000 > CLOCKS_PER_SEC, |
| 43 | "Expected CLOCKS_PER_SEC to be less than 1000000000."); |
| 44 | return clock_t(ts.tv_sec * CLOCKS_PER_SEC + |
| 45 | ts.tv_nsec / (1000000000 / CLOCKS_PER_SEC)); |
| 46 | } |
| 47 | |
| 48 | } // namespace LIBC_NAMESPACE |
| 49 |