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