95 lines
2.4 KiB
Go
95 lines
2.4 KiB
Go
// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build faketime && !windows
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// +build faketime,!windows
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// Faketime isn't currently supported on Windows. This would require
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// modifying syscall.Write to call syscall.faketimeWrite,
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// translating the Stdout and Stderr handles into FDs 1 and 2.
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// (See CL 192739 PS 3.)
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package runtime
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import "unsafe"
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// faketime is the simulated time in nanoseconds since 1970 for the
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// playground.
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var faketime int64 = 1257894000000000000
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var faketimeState struct {
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lock mutex
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// lastfaketime is the last faketime value written to fd 1 or 2.
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lastfaketime int64
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// lastfd is the fd to which lastfaketime was written.
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//
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// Subsequent writes to the same fd may use the same
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// timestamp, but the timestamp must increase if the fd
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// changes.
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lastfd uintptr
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}
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//go:nosplit
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func nanotime() int64 {
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return faketime
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}
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//go:linkname time_now time.now
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func time_now() (sec int64, nsec int32, mono int64) {
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return faketime / 1e9, int32(faketime % 1e9), faketime
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}
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func write(fd uintptr, p unsafe.Pointer, n int32) int32 {
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if !(fd == 1 || fd == 2) {
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// Do an ordinary write.
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return write1(fd, p, n)
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}
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// Write with the playback header.
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// First, lock to avoid interleaving writes.
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lock(&faketimeState.lock)
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// If the current fd doesn't match the fd of the previous write,
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// ensure that the timestamp is strictly greater. That way, we can
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// recover the original order even if we read the fds separately.
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t := faketimeState.lastfaketime
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if fd != faketimeState.lastfd {
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t++
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faketimeState.lastfd = fd
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}
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if faketime > t {
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t = faketime
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}
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faketimeState.lastfaketime = t
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// Playback header: 0 0 P B <8-byte time> <4-byte data length> (big endian)
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var buf [4 + 8 + 4]byte
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buf[2] = 'P'
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buf[3] = 'B'
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tu := uint64(t)
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buf[4] = byte(tu >> (7 * 8))
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buf[5] = byte(tu >> (6 * 8))
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buf[6] = byte(tu >> (5 * 8))
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buf[7] = byte(tu >> (4 * 8))
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buf[8] = byte(tu >> (3 * 8))
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buf[9] = byte(tu >> (2 * 8))
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buf[10] = byte(tu >> (1 * 8))
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buf[11] = byte(tu >> (0 * 8))
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nu := uint32(n)
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buf[12] = byte(nu >> (3 * 8))
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buf[13] = byte(nu >> (2 * 8))
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buf[14] = byte(nu >> (1 * 8))
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buf[15] = byte(nu >> (0 * 8))
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write1(fd, unsafe.Pointer(&buf[0]), int32(len(buf)))
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// Write actual data.
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res := write1(fd, p, n)
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unlock(&faketimeState.lock)
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return res
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}
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