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 | #include "hdr/time_macros.h" |
11 | #include "src/__support/CPP/limits.h" |
12 | #include "src/__support/common.h" |
13 | #include "src/__support/libc_errno.h" |
14 | #include "src/__support/macros/config.h" |
15 | #include "src/__support/time/clock_gettime.h" |
16 | #include "src/__support/time/units.h" |
17 | |
18 | namespace LIBC_NAMESPACE_DECL { |
19 | |
20 | LLVM_LIBC_FUNCTION(clock_t, clock, ()) { |
21 | using namespace time_units; |
22 | struct timespec ts; |
23 | auto result = internal::clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts); |
24 | if (!result.has_value()) { |
25 | libc_errno = result.error(); |
26 | return -1; |
27 | } |
28 | |
29 | // The above syscall gets the CPU time in seconds plus nanoseconds. |
30 | // The standard requires that we return clock_t(-1) if we cannot represent |
31 | // clocks as a clock_t value. |
32 | constexpr clock_t CLOCK_SECS_MAX = |
33 | cpp::numeric_limits<clock_t>::max() / CLOCKS_PER_SEC; |
34 | if (ts.tv_sec > CLOCK_SECS_MAX) |
35 | return clock_t(-1); |
36 | if (ts.tv_nsec / 1_s_ns > CLOCK_SECS_MAX - ts.tv_sec) |
37 | return clock_t(-1); |
38 | |
39 | // For the integer computation converting tv_nsec to clocks to work |
40 | // correctly, we want CLOCKS_PER_SEC to be less than 1000000000. |
41 | static_assert(1_s_ns > CLOCKS_PER_SEC, |
42 | "Expected CLOCKS_PER_SEC to be less than 1'000'000'000." ); |
43 | return clock_t(ts.tv_sec * CLOCKS_PER_SEC + |
44 | ts.tv_nsec / (1_s_ns / CLOCKS_PER_SEC)); |
45 | } |
46 | |
47 | } // namespace LIBC_NAMESPACE_DECL |
48 | |