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82 lines
1.8 KiB
Go
82 lines
1.8 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package log
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/*
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#cgo LDFLAGS: -llog
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#include <stdlib.h>
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#include <android/log.h>
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*/
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import "C"
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import (
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"bufio"
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"log"
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"os"
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"runtime"
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"syscall"
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"unsafe"
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)
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// 1024 is the truncation limit from android/log.h, plus a \n.
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const logLineLimit = 1024
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var logTag = C.CString(appID)
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func init() {
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// Android's logcat already includes timestamps.
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log.SetFlags(log.Flags() &^ log.LstdFlags)
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log.SetOutput(new(androidLogWriter))
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// Redirect stdout and stderr to the Android logger.
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logFd(os.Stdout.Fd())
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logFd(os.Stderr.Fd())
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}
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type androidLogWriter struct {
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// buf has room for the maximum log line, plus a terminating '\0'.
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buf [logLineLimit + 1]byte
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}
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func (w *androidLogWriter) Write(data []byte) (int, error) {
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// Truncate the buffer, leaving space for the '\0'.
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if max := len(w.buf) - 1; len(data) > max {
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data = data[:max]
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}
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buf := w.buf[:len(data)+1]
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copy(buf, data)
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// Terminating '\0'.
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buf[len(data)] = 0
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C.__android_log_write(C.ANDROID_LOG_INFO, logTag, (*C.char)(unsafe.Pointer(&buf[0])))
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return len(data), nil
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}
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func logFd(fd uintptr) {
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r, w, err := os.Pipe()
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if err != nil {
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panic(err)
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}
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if err := syscall.Dup3(int(w.Fd()), int(fd), syscall.O_CLOEXEC); err != nil {
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panic(err)
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}
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go func() {
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lineBuf := bufio.NewReaderSize(r, logLineLimit)
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// The buffer to pass to C, including the terminating '\0'.
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buf := make([]byte, lineBuf.Size()+1)
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cbuf := (*C.char)(unsafe.Pointer(&buf[0]))
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for {
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line, _, err := lineBuf.ReadLine()
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if err != nil {
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break
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}
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copy(buf, line)
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buf[len(line)] = 0
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C.__android_log_write(C.ANDROID_LOG_INFO, logTag, cbuf)
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}
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// The garbage collector doesn't know that w's fd was dup'ed.
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// Avoid finalizing w, and thereby avoid its finalizer closing its fd.
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runtime.KeepAlive(w)
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}()
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}
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