read_data: Handle the input data more gracefully

[log-plotter] / main.c

diff --git a/main.c b/main.c
index 6189b7be34b7048123c441f8ea1c33e96c258741..e116477dd5d77ba2d731dde0e404ea1f888ff435 100644 (file)
--- a/main.c
+++ b/main.c
@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <string.h>
 #include <sys/epoll.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -9,12 +10,67 @@
 #include "baud.h"
 #include "debug.h"
 
-int read_data(int infd, int outfd)
+/**
+ * Read data from a slow device
+ *
+ * return 1 when a complete NULL terminated line has been read
+ *
+ * return 0 when a partial line has been read and appended to the
+ *              buffer at @offset
+ *
+ * return negative on error
+ */
+static int read_log_line(int infd, char *buf, size_t bufsize, int *offset)
+{
+       int ret;
+       int i;
+
+       ret = read(infd, buf + *offset, bufsize - *offset - 1);
+       if (read < 0) {
+               pr_err("read: %m\n");
+               return -1;
+       }
+
+       if (ret == 0) {
+               pr_err("Read EOF, stopping\n");
+               return -1;
+       }
+       buf[*offset + ret] = 0;
+
+       for (i = 0; i < ret; i++) {
+               if (buf[i + *offset] == '\n' ||
+                   buf[i + *offset] == '\r') {
+                       /*
+                        * Got a complete line when there is a newline
+                        * at the end. Remove the newline and possible
+                        * other junk, such as '\r'
+                        */
+                       buf[i + *offset] = 0;
+                       *offset = 0;
+
+                       return 1;
+               }
+
+               /*
+                * Fixme! Nothing guarantees that there isn't actually
+                * more data (a part of a new log entry perhaps) after
+                * the newline. So in rare cases (we are prevented
+                * from reading the serial line in very long time) we
+                * might lose data from the stream..
+                */
+       }
+
+       *offset += ret;
+       return 0;
+}
+
+static int read_data(int infd, int outfd)
 {
        struct epoll_event ev;
        int epoll_fd;
        int ret;
        char buf[256];
+       int offset;
 
        epoll_fd = epoll_create(1);
        if (epoll_fd < 0) {
@@ -39,22 +95,28 @@ int read_data(int infd, int outfd)
                        return -1;
                }
 
-               ret = read(infd, buf, sizeof(buf));
-               if (read < 0) {
-                       pr_err("read: %m\n");
-                       break;
-               }
+               ret = read_log_line(infd, buf, sizeof(buf), &offset);
+               if (ret < 0)
+                       return ret;
 
-               if (ret == 0) {
-                       pr_err("Read EOF, stopping\n");
-                       break;
-               }
+               if (ret == 0)
+                       continue;
 
-               ret = write(outfd, buf, ret);
-               if (read < 0) {
-                       pr_err("write: %m\n");
-                       break;
+               if (outfd) {
+                       char newline = '\n';
+                       ret = write(outfd, buf, strlen(buf));
+                       if (read < 0) {
+                               pr_err("write: %m\n");
+                               break;
+                       }
+                       ret = write(outfd, &newline, 1);
+                       if (read < 0) {
+                               pr_err("write: %m\n");
+                               break;
+                       }
                }
+
+               pr_info("%s\n", buf);
        }
 
        return 0;
@@ -63,7 +125,7 @@ int read_data(int infd, int outfd)
 int main(int argc, char *argv[])
 {
        struct plotter_options options;
-       int fd, baud, ret = 0, out_fd = STDOUT_FILENO;
+       int fd, baud, ret = 0, out_fd = 0;
 
        if (read_args(argc, argv, &options))
                return 1;