Add skip= and count= options to the NSH hexdump command. From Ken Pettit

ChangeLog.txt

@@ -716,4 +716,6 @@
 	  (2013-10-30).
 	* apps/platform/mikroe-stm32f4: Now supports storage of configuration
 	  data.  From Ken Pettit (2013-10-30).
+	* apps/nshlib/nsh_dbgcmds.c and others:  Add skip= and count=
+	  options to the hexdump command.  From Ken Pettit (2013-11-1).
 

nshlib/Kconfig

@@ -238,6 +238,10 @@ config NSH_CODECS_BUFSIZE
 	int "File buffer size used by CODEC commands"
 	default 128
 
+config NSH_CMDOPT_HEXDUMP
+	bool "hexdump: Enable 'skip' and 'count' parameters"
+	default n
+
 endmenu
 
 config NSH_FILEIOSIZE

nshlib/nsh_dbgcmds.c

@@ -369,10 +369,16 @@ int cmd_hexdump(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
 {
   uint8_t buffer[IOBUFFERSIZE];
   char msg[32];
-  int position;
+  off_t position;
   int fd;
   int ret = OK;
-  
+#ifdef CONFIG_NSH_CMDOPT_HEXDUMP
+  off_t skip = 0;
+  off_t count = 0xfffffff;
+  off_t dumpbytes;
+  int x;
+#endif
+
   /* Open the file for reading */
 
   fd = open(argv[1], O_RDONLY);
@@ -381,33 +387,101 @@ int cmd_hexdump(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
       nsh_output(vtbl, g_fmtcmdfailed, "hexdump", "open", NSH_ERRNO);
       return ERROR;
     }
-  
+
+#ifdef CONFIG_NSH_CMDOPT_HEXDUMP
+  for (x = 2; x < argc; x++)
+    {
+      if (strncmp(argv[x], "skip=", 5) == 0)
+        {
+          skip = atoi(&argv[x][5]);
+        }
+      else if (strncmp(argv[x], "count=", 6) == 0)
+        {
+          count = atoi(&argv[x][6]);
+        }
+    }
+#endif
+
   position = 0;
   for (;;)
-  {
-    int nbytesread = read(fd, buffer, IOBUFFERSIZE);
+    {
+      int nbytesread = read(fd, buffer, IOBUFFERSIZE);
 
-    /* Check for read errors */
+      /* Check for read errors */
+
+      if (nbytesread < 0)
+        {
+          int errval = errno;
+          nsh_output(vtbl, g_fmtcmdfailed, "hexdump", "read",
+                     NSH_ERRNO_OF(errval));
+          ret = ERROR;
+          break;
+        }
+      else if (nbytesread > 0)
+        {
+#ifdef CONFIG_NSH_CMDOPT_HEXDUMP
+          if (position < skip)
+            {
+              /* Skip bytes until we reach the skip point */
+
+              position += nbytesread;
+              if (position > skip)
+                {
+                  dumpbytes = position - skip;
+                  if (dumpbytes > count)
+                    {
+                      dumpbytes = count;
+                    }
+
+                  snprintf(msg, sizeof(msg), "%s at %08x", argv[1], skip);
+                  nsh_dumpbuffer(vtbl, msg,
+                                 &buffer[nbytesread - (position-skip)],
+                                 dumpbytes);
+
+                  if (count > dumpbytes)
+                    {
+                      count -= dumpbytes;
+                    }
+                  else
+                    {
+                      break;
+                    }
+                }
+
+              /* Don't print if we are in skip mode */
+
+              continue;
+            }
+
+          /* Limit dumpbuffer to count if less than a full buffer needed */
+
+          if (nbytesread > count)
+            {
+              nbytesread = count;
+            }
+#endif
+
+          snprintf(msg, sizeof(msg), "%s at %08x", argv[1], position);
+          nsh_dumpbuffer(vtbl, msg, buffer, nbytesread);
+          position += nbytesread;
+
+#ifdef CONFIG_NSH_CMDOPT_HEXDUMP
+          if (count > nbytesread)
+            {
+              count -= nbytesread;
+            }
+          else
+            {
+              break;
+            }
+#endif
+        }
+      else
+        {
+          break; // EOF
+        }
+    }
 
-    if (nbytesread < 0)
-      {
-        int errval = errno;
-        nsh_output(vtbl, g_fmtcmdfailed, "hexdump", "read", NSH_ERRNO_OF(errval));
-        ret = ERROR;
-        break;
-      }
-    else if (nbytesread > 0)
-      {
-        snprintf(msg, sizeof(msg), "%s at %08x", argv[1], position);
-        nsh_dumpbuffer(vtbl, msg, buffer, nbytesread);
-        position += nbytesread;
-      }
-    else
-      {
-        break; // EOF
-      }
-  }
-  
   (void)close(fd);
   return ret;
 }

nshlib/nsh_parse.c

@@ -245,7 +245,11 @@ static const struct cmdmap_s g_cmdmap[] =
 
 #if CONFIG_NFILE_DESCRIPTORS > 0
 #ifndef CONFIG_NSH_DISABLE_HEXDUMP
+#ifndef CONFIG_NSH_CMDOPT_HEXDUMP
   { "hexdump",  cmd_hexdump,  2, 2, "<file or device>" },
+#else
+  { "hexdump",  cmd_hexdump,  2, 4, "<file or device> [skip=<bytes>] [count=<bytes>]" },
+#endif
 #endif
 #endif