--- /dev/null
+/*-
+ * Copyright (c) 2013 Emil Mikulic <emikulic@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * [ http://www.openbsd.org/cgi-bin/cvsweb/src/share/misc/license.template ]
+ */
+
+// buftee: like tee(1) but buffers in memory.
+//
+// Read from stdin into memory all the time, so that the writer doesn't
+// block. Our memory usage is unbounded.
+//
+// Write to a number of file descriptors whenever we're able to.
+// Because write() can take a long time even with O_NONBLOCK set on the
+// fd, we have to do this from a separate kernel scheduling entity (we use
+// pthreads)
+//
+// We use a thread per output filedescriptor so that one slow output (e.g. disk)
+// doesn't block another (e.g. stdout to a terminal) (or vice-versa if you use
+// flow control on the terminal!)
+
+#define _GNU_SOURCE // for clock_gettime()
+
+#include <sys/queue.h>
+#include <sys/select.h>
+#include <sys/syscall.h>
+
+#include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#define READ_BUF_SIZE 4096
+#define SLOW_NSEC 4000
+
+// *** GLOBALS *****************************************************************
+
+// All queues are locked through one global mutex.
+static pthread_mutex_t shared_queue_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+// When a writer runs out of work to do, it sleeps on this global cond.
+static pthread_cond_t shared_wakeup_cond = PTHREAD_COND_INITIALIZER;
+
+// Asserted on receipt of SIGTERM, SIGINT.
+static volatile int stopping = 0;
+
+// *** (end globals) ***********************************************************
+
+static void signal_handler(int _ignored_ __attribute__((__unused__))) {
+ stopping = 1;
+}
+
+// Reference-counted buffer, contains data that was read in the main thread.
+struct buf {
+ char* data;
+ int len;
+ int refcount;
+};
+
+// Queue of buffers.
+struct buf_queue_elem {
+ struct buf* buf;
+ STAILQ_ENTRY(buf_queue_elem) entries;
+};
+STAILQ_HEAD(buf_queue, buf_queue_elem); // struct buf_queue
+
+// Context for a writer thread.
+struct writer_thread {
+ pthread_t thread;
+ int fd;
+
+ // Each writer has its own queue.
+ struct buf_queue queue;
+
+ STAILQ_ENTRY(writer_thread) entries;
+};
+
+// A list of writer threads.
+STAILQ_HEAD(writer_thread_list, writer_thread); // struct writer_thread_list
+
+static struct buf* alloc_buf(const char* const data, const int len) {
+ assert(len > 0);
+ struct buf* buf = malloc(sizeof(*buf));
+ buf->data = malloc((size_t)len);
+ memcpy(buf->data, data, (size_t)len);
+ buf->len = len;
+ buf->refcount = 0;
+ return buf;
+}
+
+static void unref_buf(struct buf* buf) {
+ assert(buf->refcount > 0);
+ if ((--buf->refcount) == 0) {
+ free(buf->data);
+ free(buf);
+ }
+}
+
+static void enqueue(struct buf_queue* restrict queue,
+ struct buf* restrict buf) {
+ struct buf_queue_elem* elem = malloc(sizeof(*elem));
+ elem->buf = buf;
+ buf->refcount++;
+ STAILQ_INSERT_TAIL(queue, elem, entries);
+}
+
+static struct buf* dequeue(struct buf_queue* const queue) {
+ assert(!STAILQ_EMPTY(queue));
+ struct buf_queue_elem* head;
+ head = STAILQ_FIRST(queue);
+ STAILQ_REMOVE_HEAD(queue, entries);
+ struct buf* buf = head->buf;
+ free(head);
+ return buf;
+}
+
+static void xpthread_create(pthread_t* thread,
+ void* (*start_routine)(void*),
+ void* arg) {
+ int ret = pthread_create(thread, NULL, start_routine, arg);
+ if (ret == 0) return;
+ errno = ret;
+ err(1, "pthread_create(%p) failed", thread);
+}
+
+static void set_nonblocking(const int fd) {
+ int flags;
+ if ((flags = fcntl(fd, F_GETFL)) == -1)
+ err(1, "fcntl(fd = %d, F_GETFL) failed", fd);
+ if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
+ err(1, "fcntl(fd = %d, F_SETFL, O_NONBLOCK) failed", fd);
+}
+
+static int make_file(const char* filename) {
+ int fd = open(filename, O_CREAT | O_EXCL | O_NONBLOCK | O_WRONLY, 0666);
+ if (fd == -1)
+ err(1, "failed to open(\"%s\")", filename);
+ return fd;
+}
+
+static void get_mono_time(struct timespec* t) {
+ if (clock_gettime(CLOCK_MONOTONIC, t) == -1)
+ err(1, "clock_gettime(CLOCK_MONOTONIC) failed");
+}
+
+static void time_diff(const struct timespec* restrict start,
+ const struct timespec* restrict end,
+ struct timespec* restrict out) {
+ out->tv_sec = end->tv_sec - start->tv_sec;
+ out->tv_nsec = end->tv_nsec - start->tv_nsec;
+ if (out->tv_nsec < 0) {
+ out->tv_sec -= 1;
+ out->tv_nsec += 1000000000;
+ }
+ assert(out->tv_sec >= 0);
+ assert(out->tv_nsec >= 0);
+ assert(out->tv_nsec < 1000000000);
+}
+
+static void warn_time(const char* desc,
+ const struct timespec* restrict start,
+ const struct timespec* restrict end) {
+ struct timespec diff;
+ time_diff(start, end, &diff);
+ if (diff.tv_sec > 0 || diff.tv_nsec > SLOW_NSEC) {
+ char buf[128];
+ extern char *__progname; // This is where glibc stashes argv[0].
+ snprintf(buf, sizeof(buf), "%d: %s: %s took %d.%09d secs\n",
+ (int)getpid(), __progname, desc,
+ (int)diff.tv_sec, (int)diff.tv_nsec);
+ // Best effort write to a non-blocking stderr.
+ (void)write(STDERR_FILENO, buf, strlen(buf));
+ }
+}
+
+static int xread(const int fd, char* const restrict buf, const int count) {
+ ssize_t read_ret;
+ int saved_errno;
+ struct timespec t0;
+ struct timespec t1;
+
+ get_mono_time(&t0);
+ read_ret = read(fd, buf, (size_t)count);
+ saved_errno = errno;
+ get_mono_time(&t1);
+ warn_time("read()", &t0, &t1);
+
+ errno = saved_errno;
+ if (read_ret == -1)
+ err(1, "read(fd = %d, count = %d) failed", fd, count);
+ //FIXME: EAGAIN?
+
+ assert(read_ret >= 0);
+ return (int)read_ret;
+}
+
+static int xwrite(const int fd, struct buf* const buf) {
+ ssize_t write_ret;
+ int saved_errno;
+ struct timespec t0;
+ struct timespec t1;
+
+ get_mono_time(&t0);
+ write_ret = write(fd, buf->data, (size_t)buf->len);
+ saved_errno = errno;
+ get_mono_time(&t1);
+ warn_time("write()", &t0, &t1);
+
+ errno = saved_errno;
+ if (write_ret == -1)
+ err(1, "write(fd = %d, count = %d) failed", fd, buf->len);
+ //FIXME: EAGAIN?
+ if (write_ret == 0)
+ return 0;
+ assert(write_ret >= 0);
+ if (write_ret < buf->len)
+ err(1, "write(fd = %d, count = %d) stopped short (returned %d)",
+ fd, buf->len, (int)write_ret);
+ // FIXME: handle this
+ assert(write_ret == buf->len);
+ return (int)write_ret;
+}
+
+static int max(const int a, const int b) { return (a > b) ? a : b; }
+
+static void wait_until_readable(const int fd) {
+ int select_ret;
+ fd_set read_fds;
+ FD_ZERO(&read_fds);
+ FD_SET(fd, &read_fds);
+ if ((select_ret = select(fd + 1, &read_fds, NULL, NULL, NULL)) == -1)
+ err(1, "select() failed");
+ if (!FD_ISSET(fd, &read_fds))
+ errx(1, "select() did not return readable fd = %d", fd);
+}
+
+static void lock(pthread_mutex_t* mutex) {
+ int ret = pthread_mutex_lock(mutex);
+ if (ret == 0) return;
+ errno = ret;
+ err(1, "pthread_mutex_lock(%p) failed", mutex);
+}
+
+static void unlock(pthread_mutex_t* mutex) {
+ int ret = pthread_mutex_unlock(mutex);
+ if (ret == 0) return;
+ errno = ret;
+ err(1, "pthread_mutex_unlock(%p) failed", mutex);
+}
+
+static void* writer_routine(void *arg) {
+ struct writer_thread* my = arg;
+ for (;;) {
+ // FIXME: less locking
+ struct buf* buf = NULL;
+
+ lock(&shared_queue_mutex);
+ while (!stopping && STAILQ_EMPTY(&my->queue)) {
+ // Sleep.
+ pthread_cond_wait(&shared_wakeup_cond, &shared_queue_mutex);
+ }
+ if (!STAILQ_EMPTY(&my->queue))
+ buf = dequeue(&my->queue);
+ unlock(&shared_queue_mutex);
+
+ if (stopping) break;
+ assert(buf != NULL);
+
+ // Write.
+ int write_ret = xwrite(my->fd, buf);
+ if (write_ret == 0) {
+ errx(1, "fd %d hit EOF", my->fd);
+ }
+ assert(write_ret == buf->len);
+
+ // Unreference buffer, freeing it if we have to.
+ lock(&shared_queue_mutex);
+ unref_buf(buf);
+ unlock(&shared_queue_mutex);
+ }
+ warnx("thread exiting cleanly");
+ return NULL;
+}
+
+static void add_writer_thread(struct writer_thread_list* list, const int fd) {
+ set_nonblocking(fd);
+ struct writer_thread* writer = malloc(sizeof(*writer));
+ writer->fd = fd;
+ STAILQ_INIT(&(writer->queue));
+ STAILQ_INSERT_TAIL(list, writer, entries);
+ xpthread_create(&(writer->thread), writer_routine, writer);
+}
+
+static void xpthread_cond_broadcast(pthread_cond_t* cond) {
+ int ret = pthread_cond_broadcast(cond);
+ if (ret == 0) return;
+ errno = ret;
+ err(1, "pthread_cond_broadcast(%p) failed", cond);
+}
+
+static void xpthread_join(pthread_t thread) {
+ int ret = pthread_join(thread, NULL);
+ if (ret == 0) return;
+ errno = ret;
+ err(1, "pthread_join(%lu) failed", thread);
+}
+
+int main(int argc, char **argv) {
+ struct writer_thread_list writers;
+ STAILQ_INIT(&writers);
+
+ if (signal(SIGINT, signal_handler) == SIG_ERR) err(1, "signal() failed");
+ if (signal(SIGTERM, signal_handler) == SIG_ERR) err(1, "signal() failed");
+ //if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) err(1, "signal() failed");
+ set_nonblocking(STDERR_FILENO);
+
+ // On Linux, making STDOUT non-blocking has the side-effect of
+ // also making STDIN nonblocking.
+ add_writer_thread(&writers, STDOUT_FILENO);
+
+ // Process cmdline args.
+ for (int i = 1; i < argc; i++) {
+ add_writer_thread(&writers, make_file(argv[i]));
+ }
+
+ // Reader loop.
+ while (!stopping) {
+ wait_until_readable(STDIN_FILENO);
+ if (stopping) {
+ warnx("stopping after select()");
+ break;
+ }
+
+ // Read.
+ char data[READ_BUF_SIZE];
+ int read_ret = xread(STDIN_FILENO, data, sizeof(data));
+ if (read_ret == 0) {
+ warnx("stdin hit EOF");
+ break;
+ }
+ struct buf* buf = alloc_buf(data, read_ret);
+
+ // Enqueue.
+ lock(&shared_queue_mutex);
+ struct writer_thread* writer;
+ STAILQ_FOREACH(writer, &writers, entries) enqueue(&(writer->queue), buf);
+ xpthread_cond_broadcast(&shared_wakeup_cond);
+ unlock(&shared_queue_mutex);
+ }
+
+ // Wake and join threads.
+ stopping = 1;
+ lock(&shared_queue_mutex);
+ xpthread_cond_broadcast(&shared_wakeup_cond);
+ unlock(&shared_queue_mutex);
+ {
+ struct writer_thread* writer;
+ STAILQ_FOREACH(writer, &writers, entries) xpthread_join(writer->thread);
+ }
+
+ // Free writer list.
+ while (!STAILQ_EMPTY(&writers)) {
+ struct writer_thread* writer = STAILQ_FIRST(&writers);
+ STAILQ_REMOVE_HEAD(&writers, entries);
+ // FIXME: free its queue?
+ free(writer);
+ }
+
+ warnx("exiting cleanly");
+ return 0;
+}
+// vim:set ts=2 sw=2 tw=80 et:
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