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Annotation of embedaddon/mtr/packet/command_cygwin.c, revision 1.1

1.1     ! misho       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 <io.h>
        !            23: #include <stdio.h>
        !            24: 
        !            25: /*
        !            26:     A completion routine to be called by Windows when a read from
        !            27:     the command stream has completed.
        !            28: */
        !            29: static
        !            30: void CALLBACK finish_read_command(
        !            31:     DWORD status,
        !            32:     DWORD size_read,
        !            33:     OVERLAPPED * overlapped)
        !            34: {
        !            35:     struct command_buffer_t *buffer;
        !            36:     char *read_position;
        !            37: 
        !            38:     /*
        !            39:        hEvent is unusuaed by ReadFileEx, so we use it to pass
        !            40:        our command_buffer structure.
        !            41:      */
        !            42:     buffer = (struct command_buffer_t *) overlapped->hEvent;
        !            43: 
        !            44:     if (status) {
        !            45:         /*  When the stream is closed ERROR_BROKEN_PIPE will be the result  */
        !            46:         if (status == ERROR_BROKEN_PIPE) {
        !            47:             buffer->platform.pipe_open = false;
        !            48:             return;
        !            49:         }
        !            50: 
        !            51:         fprintf(stderr, "ReadFileEx completion failure %d\n", status);
        !            52:         exit(EXIT_FAILURE);
        !            53:     }
        !            54: 
        !            55:     /*  Copy from the overlapped I/O buffer to the incoming command buffer  */
        !            56:     read_position =
        !            57:         &buffer->incoming_buffer[buffer->incoming_read_position];
        !            58:     memcpy(read_position, buffer->platform.overlapped_buffer, size_read);
        !            59: 
        !            60:     /*  Account for the newly read data  */
        !            61:     buffer->incoming_read_position += size_read;
        !            62:     buffer->platform.read_active = false;
        !            63: }
        !            64: 
        !            65: /*
        !            66:     An APC which does nothing, to be used only to wake from the current
        !            67:     alertable wait.
        !            68: */
        !            69: static
        !            70: void CALLBACK empty_apc(
        !            71:     ULONG * param)
        !            72: {
        !            73: }
        !            74: 
        !            75: /*  Wake from the next alertable wait without waiting for newly read data  */
        !            76: static
        !            77: void queue_empty_apc(
        !            78:     void)
        !            79: {
        !            80:     if (QueueUserAPC((PAPCFUNC) empty_apc, GetCurrentThread(), 0) == 0) {
        !            81:         fprintf(stderr, "Unexpected QueueUserAPC failure %d\n",
        !            82:                 GetLastError());
        !            83:         exit(EXIT_FAILURE);
        !            84:     }
        !            85: }
        !            86: 
        !            87: /*  Start a new overlapped I/O read from the command stream  */
        !            88: void start_read_command(
        !            89:     struct command_buffer_t *buffer)
        !            90: {
        !            91:     HANDLE command_stream = (HANDLE) get_osfhandle(buffer->command_stream);
        !            92:     int space_remaining =
        !            93:         COMMAND_BUFFER_SIZE - buffer->incoming_read_position - 1;
        !            94:     int err;
        !            95: 
        !            96:     /*  If a read is already active, or the pipe is closed, do nothing  */
        !            97:     if (!buffer->platform.pipe_open || buffer->platform.read_active) {
        !            98:         return;
        !            99:     }
        !           100: 
        !           101:     memset(&buffer->platform.overlapped, 0, sizeof(OVERLAPPED));
        !           102:     buffer->platform.overlapped.hEvent = (HANDLE) buffer;
        !           103: 
        !           104:     if (!ReadFileEx
        !           105:         (command_stream, buffer->platform.overlapped_buffer,
        !           106:          space_remaining, &buffer->platform.overlapped,
        !           107:          finish_read_command)) {
        !           108: 
        !           109:         err = GetLastError();
        !           110: 
        !           111:         if (err == ERROR_BROKEN_PIPE) {
        !           112:             /*  If the command stream has been closed, we need to wake from
        !           113:                the next altertable wait to exit the main loop  */
        !           114:             buffer->platform.pipe_open = false;
        !           115:             queue_empty_apc();
        !           116: 
        !           117:             return;
        !           118:         } else if (err != WAIT_IO_COMPLETION) {
        !           119:             fprintf(stderr, "Unexpected ReadFileEx failure %d\n",
        !           120:                     GetLastError());
        !           121:             exit(EXIT_FAILURE);
        !           122:         }
        !           123:     }
        !           124: 
        !           125:     /*  Remember that we have started an overlapped read already  */
        !           126:     buffer->platform.read_active = true;
        !           127: }
        !           128: 
        !           129: /*  Initialize the command buffer, and start the first overlapped read  */
        !           130: void init_command_buffer(
        !           131:     struct command_buffer_t *command_buffer,
        !           132:     int command_stream)
        !           133: {
        !           134:     memset(command_buffer, 0, sizeof(struct command_buffer_t));
        !           135:     command_buffer->command_stream = command_stream;
        !           136:     command_buffer->platform.pipe_open = true;
        !           137: }
        !           138: 
        !           139: /*
        !           140:     Return with errno EPIPE if the command stream has been closed.
        !           141:     Otherwise, not much to do for Cygwin, since we are using Overlapped I/O
        !           142:     to read commands.
        !           143: */
        !           144: int read_commands(
        !           145:     struct command_buffer_t *buffer)
        !           146: {
        !           147:     if (!buffer->platform.pipe_open) {
        !           148:         errno = EPIPE;
        !           149:         return -1;
        !           150:     }
        !           151: 
        !           152:     return 0;
        !           153: }