| //===-- Linux implementation of the clock function ------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "src/time/clock.h" |
| #include "hdr/time_macros.h" |
| #include "src/__support/CPP/limits.h" |
| #include "src/__support/common.h" |
| #include "src/__support/time/linux/clock_gettime.h" |
| #include "src/__support/time/units.h" |
| #include "src/errno/libc_errno.h" |
| |
| namespace LIBC_NAMESPACE { |
| |
| LLVM_LIBC_FUNCTION(clock_t, clock, ()) { |
| using namespace time_units; |
| struct timespec ts; |
| auto result = internal::clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts); |
| if (!result.has_value()) { |
| libc_errno = result.error(); |
| return -1; |
| } |
| |
| // The above syscall gets the CPU time in seconds plus nanoseconds. |
| // The standard requires that we return clock_t(-1) if we cannot represent |
| // clocks as a clock_t value. |
| constexpr clock_t CLOCK_SECS_MAX = |
| cpp::numeric_limits<clock_t>::max() / CLOCKS_PER_SEC; |
| if (ts.tv_sec > CLOCK_SECS_MAX) |
| return clock_t(-1); |
| if (ts.tv_nsec / 1_s_ns > CLOCK_SECS_MAX - ts.tv_sec) |
| return clock_t(-1); |
| |
| // For the integer computation converting tv_nsec to clocks to work |
| // correctly, we want CLOCKS_PER_SEC to be less than 1000000000. |
| static_assert(1_s_ns > CLOCKS_PER_SEC, |
| "Expected CLOCKS_PER_SEC to be less than 1'000'000'000."); |
| return clock_t(ts.tv_sec * CLOCKS_PER_SEC + |
| ts.tv_nsec / (1_s_ns / CLOCKS_PER_SEC)); |
| } |
| |
| } // namespace LIBC_NAMESPACE |