fake_log_device.c

来自「Android 一些工具」· C语言 代码 · 共 678 行 · 第 1/2 页

/*
 * Write a filtered log message to stderr.
 *
 * Log format parsing taken from the long-dead utils/Log.cpp.
 */
static void showLog(LogState *state,
        int logPrio, const char* tag, const char* msg)
{
#if defined(HAVE_LOCALTIME_R)
    struct tm tmBuf;
#endif
    struct tm* ptm;
    char timeBuf[32];
    char prefixBuf[128], suffixBuf[128];
    char priChar;
    time_t when;
    pid_t pid, tid;

    TRACE("LOG %d: %s %s", logPrio, tag, msg);

    priChar = getPriorityString(logPrio)[0];
    when = time(NULL);
    pid = tid = getpid();       // find gettid()?

    /*
     * Get the current date/time in pretty form
     *
     * It's often useful when examining a log with "less" to jump to
     * a specific point in the file by searching for the date/time stamp.
     * For this reason it's very annoying to have regexp meta characters
     * in the time stamp.  Don't use forward slashes, parenthesis,
     * brackets, asterisks, or other special chars here.
     */
#if defined(HAVE_LOCALTIME_R)
    ptm = localtime_r(&when, &tmBuf);
#else
    ptm = localtime(&when);
#endif
    //strftime(timeBuf, sizeof(timeBuf), "%Y-%m-%d %H:%M:%S", ptm);
    strftime(timeBuf, sizeof(timeBuf), "%m-%d %H:%M:%S", ptm);

    /*
     * Construct a buffer containing the log header and log message.
     */
    size_t prefixLen, suffixLen;

    switch (state->outputFormat) {
    case FORMAT_TAG:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "%c/%-8s: ", priChar, tag);
        strcpy(suffixBuf, "\n"); suffixLen = 1;
        break;
    case FORMAT_PROCESS:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "%c(%5d) ", priChar, pid);
        suffixLen = snprintf(suffixBuf, sizeof(suffixBuf),
            "  (%s)\n", tag);
        break;
    case FORMAT_THREAD:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "%c(%5d:%p) ", priChar, pid, (void*)tid);
        strcpy(suffixBuf, "\n"); suffixLen = 1;
        break;
    case FORMAT_RAW:
        prefixBuf[0] = 0; prefixLen = 0;
        strcpy(suffixBuf, "\n"); suffixLen = 1;
        break;
    case FORMAT_TIME:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "%s %-8s\n\t", timeBuf, tag);
        strcpy(suffixBuf, "\n"); suffixLen = 1;
        break;
    case FORMAT_THREADTIME:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "%s %5d %5d %c %-8s \n\t", timeBuf, pid, tid, priChar, tag);
        strcpy(suffixBuf, "\n"); suffixLen = 1;
        break;
    case FORMAT_LONG:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "[ %s %5d:%p %c/%-8s ]\n",
            timeBuf, pid, (void*)tid, priChar, tag);
        strcpy(suffixBuf, "\n\n"); suffixLen = 2;
        break;
    default:
        prefixLen = snprintf(prefixBuf, sizeof(prefixBuf),
            "%c/%-8s(%5d): ", priChar, tag, pid);
        strcpy(suffixBuf, "\n"); suffixLen = 1;
        break;
     }

    /*
     * Figure out how many lines there will be.
     */
    const char* end = msg + strlen(msg);
    size_t numLines = 0;
    const char* p = msg;
    while (p < end) {
        if (*p++ == '\n') numLines++;
    }
    if (p > msg && *(p-1) != '\n') numLines++;
    
    /*
     * Create an array of iovecs large enough to write all of
     * the lines with a prefix and a suffix.
     */
    const size_t INLINE_VECS = 6;
    struct iovec stackVec[INLINE_VECS];
    struct iovec* vec = stackVec;
    
    numLines *= 3;  // 3 iovecs per line.
    if (numLines > INLINE_VECS) {
        vec = (struct iovec*)malloc(sizeof(struct iovec)*numLines);
        if (vec == NULL) {
            msg = "LOG: write failed, no memory";
            numLines = 3;
        }
    }
    
    /*
     * Fill in the iovec pointers.
     */
    p = msg;
    struct iovec* v = vec;
    int totalLen = 0;
    while (p < end) {
        if (prefixLen > 0) {
            v->iov_base = prefixBuf;
            v->iov_len = prefixLen;
            totalLen += prefixLen;
            v++;
        }
        const char* start = p;
        while (p < end && *p != '\n') p++;
        if ((p-start) > 0) {
            v->iov_base = (void*)start;
            v->iov_len = p-start;
            totalLen += p-start;
            v++;
        }
        if (*p == '\n') p++;
        if (suffixLen > 0) {
            v->iov_base = suffixBuf;
            v->iov_len = suffixLen;
            totalLen += suffixLen;
            v++;
        }
    }
    
    /*
     * Write the entire message to the log file with a single writev() call.
     * We need to use this rather than a collection of printf()s on a FILE*
     * because of multi-threading and multi-process issues.
     *
     * If the file was not opened with O_APPEND, this will produce interleaved
     * output when called on the same file from multiple processes.
     *
     * If the file descriptor is actually a network socket, the writev()
     * call may return with a partial write.  Putting the writev() call in
     * a loop can result in interleaved data.  This can be alleviated
     * somewhat by wrapping the writev call in the Mutex.
     */

    for(;;) {
        int cc = writev(fileno(stderr), vec, v-vec);

        if (cc == totalLen) break;
        
        if (cc < 0) {
            if(errno == EINTR) continue;
            
                /* can't really log the failure; for now, throw out a stderr */
            fprintf(stderr, "+++ LOG: write failed (errno=%d)\n", errno);
            break;
        } else {
                /* shouldn't happen when writing to file or tty */
            fprintf(stderr, "+++ LOG: write partial (%d of %d)\n", cc, totalLen);
            break;
        }
    }

    /* if we allocated storage for the iovecs, free it */
    if (vec != stackVec)
        free(vec);
}


/*
 * Receive a log message.  We happen to know that "vector" has three parts:
 *
 *  priority (1 byte)
 *  tag (N bytes -- null-terminated ASCII string)
 *  message (N bytes -- null-terminated ASCII string)
 */
static ssize_t logWritev(int fd, const struct iovec* vector, int count)
{
    LogState* state;

    /* Make sure that no-one frees the LogState while we're using it.
     * Also guarantees that only one thread is in showLog() at a given
     * time (if it matters).
     */
    lock();

    state = fdToLogState(fd);
    if (state == NULL) {
        errno = EBADF;
        goto error;
    }

    if (state->isBinary) {
        TRACE("%s: ignoring binary log\n", state->debugName);
        goto bail;
    }

    if (count != 3) {
        TRACE("%s: writevLog with count=%d not expected\n",
            state->debugName, count);
        goto error;
    }

    /* pull out the three fields */
    int logPrio = *(const char*)vector[0].iov_base;
    const char* tag = (const char*) vector[1].iov_base;
    const char* msg = (const char*) vector[2].iov_base;

    /* see if this log tag is configured */
    int i;
    int minPrio = state->globalMinPriority;
    for (i = 0; i < kTagSetSize; i++) {
        if (state->tagSet[i].minPriority == ANDROID_LOG_UNKNOWN)
            break;      /* reached end of configured values */

        if (strcmp(state->tagSet[i].tag, tag) == 0) {
            //TRACE("MATCH tag '%s'\n", tag);
            minPrio = state->tagSet[i].minPriority;
            break;
        }
    }

    if (logPrio >= minPrio) {
        showLog(state, logPrio, tag, msg);
    } else {
        //TRACE("+++ NOLOG(%d): %s %s", logPrio, tag, msg);
    }

bail:
    unlock();
    return vector[0].iov_len + vector[1].iov_len + vector[2].iov_len;
error:
    unlock();
    return -1;
}

/*
 * Free up our state and close the fake descriptor.
 */
static int logClose(int fd)
{
    deleteFakeFd(fd);
    return 0;
}

/*
 * Open a log output device and return a fake fd.
 */
static int logOpen(const char* pathName, int flags)
{
    LogState *logState;
    int fd = -1;

    lock();

    logState = createLogState();
    if (logState != NULL) {
        configureInitialState(pathName, logState);
        fd = logState->fakeFd;
    } else  {
        errno = ENFILE;
    }

    unlock();

    return fd;
}


/*
 * Runtime redirection.  If this binary is running in the simulator,
 * just pass log messages to the emulated device.  If it's running
 * outside of the simulator, write the log messages to stderr.
 */

static int (*redirectOpen)(const char *pathName, int flags) = NULL;
static int (*redirectClose)(int fd) = NULL;
static ssize_t (*redirectWritev)(int fd, const struct iovec* vector, int count)
        = NULL;

static void setRedirects()
{
    const char *ws;

    /* Wrapsim sets this environment variable on children that it's
     * created using its LD_PRELOAD wrapper.
     */
    ws = getenv("ANDROID_WRAPSIM");
    if (ws != NULL && strcmp(ws, "1") == 0) {
        /* We're running inside wrapsim, so we can just write to the device. */
        redirectOpen = (int (*)(const char *pathName, int flags))open;
        redirectClose = close;
        redirectWritev = writev;
    } else {
        /* There's no device to delegate to; handle the logging ourselves. */
        redirectOpen = logOpen;
        redirectClose = logClose;
        redirectWritev = logWritev;
    }
}

int fakeLogOpen(const char *pathName, int flags)
{
    if (redirectOpen == NULL) {
        setRedirects();
    }
    return redirectOpen(pathName, flags);
}

int fakeLogClose(int fd)
{
    /* Assume that open() was called first. */
    return redirectClose(fd);
}

ssize_t fakeLogWritev(int fd, const struct iovec* vector, int count)
{
    /* Assume that open() was called first. */
    return redirectWritev(fd, vector, count);
}