git.ozlabs.org Git - ccan/blob - ccan/io/_info

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include "config.h"
   4
   5 /**
   6  * io - simple library for asynchronous io handling.
   7  *
   8  * io provides a mechanism to write I/O servers with multiple
   9  * connections.  Each callback indicates what I/O they plan next
  10  * (eg. read, write).  It is also possible to write custom I/O
  11  * plans.
  12  *
  13  * When compiled with DEBUG, control flow is changed so that rather
  14  * than returning to the main io_loop(), plans are executed sequentially
  15  * providing a backtrace showing what has occurred on that connection.
  16  * Which connection(s) do this depends on the user-specified io_debug
  17  * function.
  18  *
  19  * Example:
  20  * // Given tr A-Z a-z outputs tr a-z a-z
  21  * #include <ccan/io/io.h>
  22  * #include <ccan/err/err.h>
  23  * #include <assert.h>
  24  * #include <stdlib.h>
  25  * #include <signal.h>
  26  * #include <sys/types.h>
  27  * #include <sys/wait.h>
  28  *
  29  * struct buffer {
  30  *      size_t max, off, rlen;
  31  *      char *buf;
  32  * };
  33  *
  34  * struct stdin_buffer {
  35  *      struct io_conn *reader, *writer;
  36  *      size_t len;
  37  *      char inbuf[4096];
  38  * };
  39  *
  40  * // This reads from stdin.
  41  * static struct io_plan wake_writer(struct io_conn *, struct stdin_buffer *);
  42  * // This writes the stdin buffer to the child.
  43  * static struct io_plan wake_reader(struct io_conn *, struct stdin_buffer *);
  44  *
  45  * static struct io_plan wake_writer(struct io_conn *c, struct stdin_buffer *b)
  46  * {
  47  *      assert(c == b->reader);
  48  *      io_wake(b->writer, io_write(b->inbuf, b->len, wake_reader, b));
  49  *      return io_idle();
  50  * }
  51  *
  52  * static void reader_exit(struct io_conn *c, struct stdin_buffer *b)
  53  * {
  54  *      assert(c == b->reader);
  55  *      io_wake(b->writer, io_close());
  56  *      b->reader = NULL;
  57  * }
  58  *
  59  * static struct io_plan wake_reader(struct io_conn *c, struct stdin_buffer *b)
  60  * {
  61  *      assert(c == b->writer);
  62  *      if (!b->reader)
  63  *              return io_close();
  64  *      b->len = sizeof(b->inbuf);
  65  *      io_wake(b->reader, io_read_partial(b->inbuf, &b->len, wake_writer, b));
  66  *      return io_idle();
  67  * }
  68  *
  69  * static void fail_child_write(struct io_conn *conn, struct stdin_buffer *b)
  70  * {
  71  *      if (b->reader)
  72  *              err(1, "Failed writing to child.");
  73  * }
  74  *
  75  * // This reads from the child and saves it into buffer.
  76  * static struct io_plan read_from_child(struct io_conn *conn,
  77  *                                       struct buffer *b)
  78  * {
  79  *      b->off += b->rlen;
  80  *
  81  *      if (b->off == b->max)
  82  *              b->buf = realloc(b->buf, b->max *= 2);
  83  *
  84  *      b->rlen = b->max - b->off;
  85  *      return io_read_partial(b->buf + b->off, &b->rlen, read_from_child, b);
  86  * }
  87  *
  88  * // Feed a program our stdin, gather its stdout, print that at end.
  89  * int main(int argc, char *argv[])
  90  * {
  91  *      int tochild[2], fromchild[2];
  92  *      struct buffer out;
  93  *      struct stdin_buffer sbuf;
  94  *      int status;
  95  *      size_t off;
  96  *      ssize_t ret;
  97  *      struct io_conn *from_child;
  98  *
  99  *      if (argc == 1)
 100  *              errx(1, "Usage: runner <cmdline>...");
 101  *
 102  *      if (pipe(tochild) != 0 || pipe(fromchild) != 0)
 103  *              err(1, "Creating pipes");
 104  *
 105  *      if (!fork()) {
 106  *              // Child runs command.
 107  *              close(tochild[1]);
 108  *              close(fromchild[0]);
 109  *
 110  *              dup2(tochild[0], STDIN_FILENO);
 111  *              dup2(fromchild[1], STDOUT_FILENO);
 112  *              execvp(argv[1], argv + 1);
 113  *              exit(127);
 114  *      }
 115  *
 116  *      close(tochild[0]);
 117  *      close(fromchild[1]);
 118  *      signal(SIGPIPE, SIG_IGN);
 119  *
 120  *      sbuf.len = sizeof(sbuf.inbuf);
 121  *      sbuf.reader = io_new_conn(STDIN_FILENO,
 122  *                                io_read_partial(sbuf.inbuf, &sbuf.len,
 123  *                                                wake_writer, &sbuf));
 124  *      sbuf.writer = io_new_conn(tochild[1], io_idle());
 125  *
 126  *      out.max = 128;
 127  *      out.off = 0;
 128  *      out.rlen = 128;
 129  *      out.buf = malloc(out.max);
 130  *      from_child = io_new_conn(fromchild[0],
 131  *                               io_read_partial(out.buf, &out.rlen,
 132  *                                               read_from_child, &out));
 133  *      if (!sbuf.reader || !sbuf.writer || !from_child)
 134  *              err(1, "Allocating connections");
 135  *
 136  *      io_set_finish(sbuf.reader, reader_exit, &sbuf);
 137  *      io_set_finish(sbuf.writer, fail_child_write, &sbuf);
 138  *
 139  *      io_loop();
 140  *      wait(&status);
 141  *
 142  *      for (off = 0; off < out.off; off += ret) {
 143  *              ret = write(STDOUT_FILENO, out.buf+off, out.off-off);
 144  *              if (ret < 0)
 145  *                      err(1, "Writing stdout");
 146  *      }
 147  *      free(out.buf);
 148  *
 149  *      return WIFEXITED(status) ? WEXITSTATUS(status) : 2;
 150  * }
 151  *
 152  * License: LGPL (v2.1 or any later version)
 153  * Author: Rusty Russell <rusty@rustcorp.com.au>
 154  */
 155 int main(int argc, char *argv[])
 156 {
 157         if (argc != 2)
 158                 return 1;
 159
 160         if (strcmp(argv[1], "depends") == 0) {
 161                 printf("ccan/time\n");
 162                 printf("ccan/timer\n");
 163                 return 0;
 164         }
 165
 166         return 1;
 167 }