/**
* mds — A micro-display server
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "util.h"
#include "config.h"
#include "macros.h"
#include <alloca.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <errno.h>
#include <ctype.h>
/**
* Read an environment variable, but handle it as undefined if empty
*
* @param var The environment variable's name
* @return The environment variable's value, `NULL` if empty or not defined
*/
char* getenv_nonempty(const char* var)
{
char* rc = getenv(var);
if ((rc == NULL) || (*rc == '\0'))
return NULL;
return rc;
}
/**
* Re-exec the server.
* This function only returns on failure.
*
* @param argc The number of elements in `argv`
* @param argv The command line arguments
* @param reexeced Whether the server has previously been re-exec:ed
*/
void reexec_server(int argc, char** argv, int reexeced)
{
char readlink_buf[PATH_MAX];
ssize_t readlink_ptr;
char** reexec_args;
char** reexec_args_;
int i;
/* Re-exec the server. */
readlink_ptr = readlink(SELF_EXE, readlink_buf, (sizeof(readlink_buf) / sizeof(char)) - 1);
if (readlink_ptr < 0)
return;
/* ‘readlink() does not append a null byte to buf.’ */
readlink_buf[readlink_ptr] = '\0';
reexec_args = alloca(((size_t)argc + 2) * sizeof(char*));
reexec_args_ = reexec_args;
if (reexeced == 0)
{
*reexec_args_++ = *argv;
*reexec_args_ = strdup("--re-exec");
if (*reexec_args_ == NULL)
return;
for (i = 1; i < argc; i++)
reexec_args_[i] = argv[i];
}
else /* Don't let the --re-exec:s accumulate. */
*reexec_args_ = *argv;
for (i = 1; i < argc; i++)
reexec_args_[i] = argv[i];
reexec_args_[argc] = NULL;
execv(readlink_buf, reexec_args);
}
/**
* Set up a signal trap.
* This function should only be used for common mds
* signals, and this function may choose to add
* additional behaviour depending on the signal, such
* as blocking other signals.
*
* @param signo The signal to trap
* @param function The function to run when the signal is caught
* @return Zero on success, -1 on error
*/
int xsigaction(int signo, void (*function)(int signo))
{
struct sigaction action;
sigset_t sigset;
sigemptyset(&sigset);
action.sa_handler = function;
action.sa_mask = sigset;
action.sa_flags = 0;
return sigaction(signo, &action, NULL);
}
/**
* Send a message over a socket
*
* @param socket The file descriptor of the socket
* @param message The message to send
* @param length The length of the message
* @return The number of bytes that have been sent (even on error)
*/
size_t send_message(int socket, const char* message, size_t length)
{
size_t block_size = length;
size_t sent = 0;
ssize_t just_sent;
errno = 0;
while (length > 0)
if ((just_sent = send(socket, message + sent, min(block_size, length), MSG_NOSIGNAL)) < 0)
{
if (errno == EMSGSIZE)
{
block_size >>= 1;
if (block_size == 0)
return sent;
}
else
return sent;
}
else
{
sent += (size_t)just_sent;
length -= (size_t)just_sent;
}
return sent;
}
/**
* A version of `atoi` that is strict about the syntax and bounds
*
* @param str The text to parse
* @param value Slot in which to store the value
* @param min The minimum accepted value
* @param max The maximum accepted value
* @return Zero on success, -1 on syntax error
*/
int strict_atoi(const char* str, int* value, int min, int max)
{
long long int r;
char* endptr;
r = strtoll(str, &endptr, 10);
if ((*str == '\0') || isspace(*str) ||
(endptr - str != (ssize_t)strlen(str)) ||
(r < (long long int)min) ||
(r > (long long int)max))
return -1;
*value = (int)r;
return 0;
}
/**
* Send a buffer into a file and ignore interruptions
*
* @param fd The file descriptor
* @param buffer The buffer
* @param length The length of the buffer
* @return Zero on success, -1 on error
*/
int full_write(int fd, const char* buffer, size_t length)
{
ssize_t wrote;
while (length > 0)
{
errno = 0;
wrote = write(fd, buffer, length);
if (errno && (errno != EINTR))
return -1;
length -= (size_t)max(wrote, 0);
buffer += (size_t)max(wrote, 0);
}
return 0;
}
/**
* Read a file completly and ignore interruptions
*
* @param fd The file descriptor
* @return The content of the file, you will need to free it. `NULL` on error.
*/
char* full_read(int fd)
{
size_t state_buf_size = 8 << 10;
size_t state_buf_ptr = 0;
char* state_buf;
ssize_t got;
/* Allocate buffer for data. */
if (xmalloc(state_buf, state_buf_size, char))
return NULL;
/* Read the file. */
for (;;)
{
/* Grow buffer if it is too small. */
if (state_buf_size == state_buf_ptr)
{
char* old_buf = state_buf;
if (xrealloc(state_buf, state_buf_size <<= 1, char))
{
free(old_buf);
return NULL;
}
}
/* Read from the file into the buffer. */
got = read(fd, state_buf + state_buf_ptr, state_buf_size - state_buf_ptr);
if ((got < 0) && (errno != EINTR))
{
free(state_buf);
return NULL;
}
if (got == 0)
break;
state_buf_ptr += (size_t)got;
}
return state_buf;
}
/**
* Check whether a string begins with a specific string,
* where neither of the strings are necessarily NUL-terminated
*
* @param haystack The string that should start with the other string
* @param needle The string the first string should start with
* @param haystack_n The length of `haystack`
* @param needle_n The length of `needle`
* @return Whether the `haystack` begins with `needle`
*/
int startswith_n(const char* haystack, const char* needle, size_t haystack_n, size_t needle_n)
{
size_t i;
if (haystack_n < needle_n)
return 0;
for (i = 0; i < needle_n; i++)
if (haystack[i] != needle[i])
return 0;
return 1;
}
