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mtr ver 0.92

    1: /*
    2:     mtr  --  a network diagnostic tool
    3:     Copyright (C) 2016  Matt Kimball
    4: 
    5:     This program is free software; you can redistribute it and/or modify
    6:     it under the terms of the GNU General Public License version 2 as
    7:     published by the Free Software Foundation.
    8: 
    9:     This program is distributed in the hope that it will be useful,
   10:     but WITHOUT ANY WARRANTY; without even the implied warranty of
   11:     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   12:     GNU General Public License for more details.
   13: 
   14:     You should have received a copy of the GNU General Public License
   15:     along with this program; if not, write to the Free Software
   16:     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   17: */
   18: 
   19: #include "command.h"
   20: 
   21: #include <errno.h>
   22: #include <fcntl.h>
   23: #include <string.h>
   24: #include <stdio.h>
   25: #include <stdlib.h>
   26: #include <unistd.h>
   27: 
   28: /*
   29:     Initialize the command buffer and put the command stream in
   30:     non-blocking mode.
   31: */
   32: void init_command_buffer(
   33:     struct command_buffer_t *command_buffer,
   34:     int command_stream)
   35: {
   36:     int flags;
   37: 
   38:     memset(command_buffer, 0, sizeof(struct command_buffer_t));
   39:     command_buffer->command_stream = command_stream;
   40: 
   41:     /*  Get the current command stream flags  */
   42:     flags = fcntl(command_stream, F_GETFL, 0);
   43:     if (flags == -1) {
   44:         perror("Unexpected command stream error");
   45:         exit(EXIT_FAILURE);
   46:     }
   47: 
   48:     /*  Set the O_NONBLOCK bit  */
   49:     if (fcntl(command_stream, F_SETFL, flags | O_NONBLOCK)) {
   50:         perror("Unexpected command stream error");
   51:         exit(EXIT_FAILURE);
   52:     }
   53: }
   54: 
   55: /*  Read currently available data from the command stream  */
   56: int read_commands(
   57:     struct command_buffer_t *buffer)
   58: {
   59:     int space_remaining =
   60:         COMMAND_BUFFER_SIZE - buffer->incoming_read_position - 1;
   61:     char *read_position =
   62:         &buffer->incoming_buffer[buffer->incoming_read_position];
   63:     int read_count;
   64:     int command_stream = buffer->command_stream;
   65: 
   66:     read_count = read(command_stream, read_position, space_remaining);
   67: 
   68:     /*  If the command stream has been closed, read will return zero.  */
   69:     if (read_count == 0) {
   70:         errno = EPIPE;
   71:         return -1;
   72:     }
   73: 
   74:     if (read_count > 0) {
   75:         /*  Account for the newly read data  */
   76:         buffer->incoming_read_position += read_count;
   77:     }
   78: 
   79:     if (read_count < 0) {
   80:         /*  EAGAIN simply means there is no available data to read  */
   81:         /*  EINTR indicates we received a signal during read  */
   82:         if (errno != EINTR && errno != EAGAIN) {
   83:             perror("Unexpected command buffer read error");
   84:             exit(EXIT_FAILURE);
   85:         }
   86:     }
   87: 
   88:     return 0;
   89: }