native: uart reconnect buffer replay

When using socket stdio, add option to replay what has been written to
stdout while not connected (`-r`).

The implementation is to simply use the existing log file (which is
implicitly created when the option is used), and read from it until
EOF upon reconnect.

closes #476

boards/native/drivers/native-uart0.c

@@ -45,6 +45,9 @@
 int _native_uart_sock;
 int _native_uart_conn;
 
+int _native_replay_enabled;
+FILE *_native_replay_buffer;
+
 fd_set _native_uart_rfds;
 
 /* uart API */
@@ -227,6 +230,34 @@ void handle_uart_sock(void)
     if (real_dup2(s, STDIN_FILENO) == -1) {
         err(EXIT_FAILURE, "handle_uart_sock: dup2()");
     }
+
+    /* play back log from last position */
+    if (_native_replay_enabled) {
+        warnx("handle_uart_sock: replaying buffer");
+        size_t nread;
+        char buf[200];
+        while ((nread = real_fread(buf, 1, sizeof(buf), _native_replay_buffer)) != 0) {
+            int nwritten;
+            int pos = 0;
+            while ((nwritten = real_write(STDOUT_FILENO, &buf[pos], nread)) != -1) {
+                nread -= nwritten;
+                pos += nwritten;
+                if (nread == 0) {
+                    break;
+                }
+            }
+            if (nwritten == -1) {
+                err(EXIT_FAILURE, "handle_uart_sock: write");
+            }
+        }
+        if (real_feof(_native_replay_buffer) != 0) {
+            real_clearerr(_native_replay_buffer);
+        }
+        else if (real_ferror(_native_replay_buffer) != 0) {
+            err(EXIT_FAILURE, "handle_uart_sock(): fread()");
+        }
+    }
+
     _native_syscall_leave();
 
     _native_uart_conn = s;
@@ -260,8 +291,18 @@ int _native_set_uart_fds(void)
 }
 #endif
 
-void _native_init_uart0(char *stdiotype, char *ioparam)
+void _native_init_uart0(char *stdiotype, char *ioparam, int replay)
 {
+    _native_replay_enabled = replay;
+
+    if (_native_replay_enabled) {
+        char stdout_logname[255];
+        snprintf(stdout_logname, sizeof(stdout_logname), "/tmp/riot.stdout.%d", _native_pid);
+        if ((_native_replay_buffer = real_fopen(stdout_logname, "r+")) == NULL) {
+            err(EXIT_FAILURE, "_native_init_uart0: fdopen(_native_null_out_file)");
+        }
+    }
+
     if (strcmp(stdiotype, "tcp") == 0) {
         _native_uart_sock = init_tcp_socket(ioparam);
     }

boards/native/include/board_internal.h

@@ -7,7 +7,7 @@ void _native_handle_uart0_input(void);
  * @param stdiotype: "stdio", "tcp", "udp" io redirection
  * @param ioparam: a string containing a port number if stdiotype is tcp
  */
-void _native_init_uart0(char *stdiotype, char *ioparam);
+void _native_init_uart0(char *stdiotype, char *ioparam, int replay);
 int _native_set_uart_fds(void);
 #endif
 

cpu/native/include/native_internal.h

@@ -13,6 +13,7 @@
 #define _NATIVE_INTERNAL_H
 
 #include <signal.h>
+#include <stdio.h>
 /* enable signal handler register access on different platforms
  * check here for more:
  * http://sourceforge.net/p/predef/wiki/OperatingSystems/
@@ -54,18 +55,23 @@ void _native_syscall_enter(void);
  */
 extern ssize_t (*real_read)(int fd, void *buf, size_t count);
 extern ssize_t (*real_write)(int fd, const void *buf, size_t count);
+extern size_t (*real_fread)(void *ptr, size_t size, size_t nmemb, FILE *stream);
 extern void* (*real_malloc)(size_t size);
+extern void (*real_clearerr)(FILE *stream);
 extern void (*real_free)(void *ptr);
 extern void* (*real_calloc)(size_t nmemb, size_t size);
 extern void* (*real_realloc)(void *ptr, size_t size);
 extern int (*real_getpid)(void);
 extern int (*real_pipe)(int[2]);
 extern int (*real_close)(int);
+extern int (*real_feof)(FILE *stream);
+extern int (*real_ferror)(FILE *stream);
 extern int (*real_fork)(void);
 extern int (*real_dup2)(int, int);
 extern int (*real_unlink)(const char *);
 extern int (*real_execve)(const char *, char *const[], char *const[]);
 extern int (*real_pause)(void);
+extern FILE* (*real_fopen)(const char *path, const char *mode);
 
 /**
  * data structures

cpu/native/startup.c

@@ -161,7 +161,7 @@ void usage_exit(void)
 #endif
 
 #ifdef MODULE_UART0
-    real_printf(" [-t <port>|-u [path]]");
+    real_printf(" [-t <port>|-u [path]] [-r]");
 #endif
 
     real_printf(" [-i <id>] [-d] [-e|-E] [-o]\n");
@@ -175,7 +175,9 @@ void usage_exit(void)
     real_printf("\
 -t <port>   redirect stdio to TCP socket listening on <port>\n\
 -u <path>   redirect stdio to UNIX socket (<path> if given,\n\
-            /tmp/riot.tty.PID otherwise)\n");
+            /tmp/riot.tty.PID otherwise)\n\
+-r          replay missed output when (re-)attaching to socket\n\
+            (implies -o)\n");
 #endif
     real_printf("\
 -i <id>     specify instance id (set by config module)\n\
@@ -209,6 +211,11 @@ __attribute__((constructor)) static void startup(int argc, char **argv)
     *(void **)(&real_unlink) = dlsym(RTLD_NEXT, "unlink");
     *(void **)(&real_execve) = dlsym(RTLD_NEXT, "execve");
     *(void **)(&real_pause) = dlsym(RTLD_NEXT, "pause");
+    *(void **)(&real_fopen) = dlsym(RTLD_NEXT, "fopen");
+    *(void **)(&real_fread) = dlsym(RTLD_NEXT, "fread");
+    *(void **)(&real_feof) = dlsym(RTLD_NEXT, "feof");
+    *(void **)(&real_ferror) = dlsym(RTLD_NEXT, "ferror");
+    *(void **)(&real_clearerr) = dlsym(RTLD_NEXT, "clearerr");
 
     _native_argv = argv;
     _progname = argv[0];
@@ -223,6 +230,7 @@ __attribute__((constructor)) static void startup(int argc, char **argv)
     char *stdiotype = "stdio";
 #ifdef MODULE_UART0
     char *ioparam = NULL;
+    int replay = 0;
 #endif
 
 #ifdef MODULE_NATIVENET
@@ -274,6 +282,10 @@ __attribute__((constructor)) static void startup(int argc, char **argv)
             stdouttype = "file";
         }
 #ifdef MODULE_UART0
+        else if (strcmp("-r", arg) == 0) {
+            stdouttype = "file";
+            replay = 1;
+        }
         else if (strcmp("-t", arg) == 0) {
             stdiotype = "tcp";
             if (argp + 1 < argc) {
@@ -314,7 +326,7 @@ __attribute__((constructor)) static void startup(int argc, char **argv)
     _native_null_in(stdiotype);
 
 #ifdef MODULE_UART0
-    _native_init_uart0(stdiotype, ioparam);
+    _native_init_uart0(stdiotype, ioparam, replay);
 #endif
 
     native_hwtimer_pre_init();

cpu/native/syscalls.c

@@ -50,7 +50,9 @@ extern volatile tcb_t *sched_active_thread;
 
 ssize_t (*real_read)(int fd, void *buf, size_t count);
 ssize_t (*real_write)(int fd, const void *buf, size_t count);
+size_t (*real_fread)(void *ptr, size_t size, size_t nmemb, FILE *stream);
 void* (*real_malloc)(size_t size);
+void (*real_clearerr)(FILE *stream);
 void (*real_free)(void *ptr);
 void* (*real_calloc)(size_t nmemb, size_t size);
 void* (*real_realloc)(void *ptr, size_t size);
@@ -60,7 +62,10 @@ int (*real_fork)(void);
 int (*real_dup2)(int, int);
 int (*real_unlink)(const char *);
 int (*real_execve)(const char *, char *const[], char *const[]);
+int (*real_feof)(FILE *stream);
+int (*real_ferror)(FILE *stream);
 int (*real_pause)(void);
+FILE* (*real_fopen)(const char *path, const char *mode);
 
 void _native_syscall_enter(void)
 {