1 files changed, 239 insertions, 0 deletions
diff --git a/ext2ed/disk.c b/ext2ed/disk.c
new file mode 100644
index 0000000..4612d00
--- /dev/null
+++ b/ext2ed/disk.c
@@ -0,0 +1,239 @@
+/*
+
+/usr/src/ext2ed/disk.c
+
+A part of the extended file system 2 disk editor.
+
+-------------------------------------------------
+The filesystem's disk activity pass through here.
+-------------------------------------------------
+
+This file is acting as a filter - Before we pass an actual read or write request to the operating system, we
+double check the various permissions and possible errors here.
+
+The major update which needs to be done here is switching to the use of the llseek system call, so that we will
+be able to support ext2 filesystems up to 4 TB. Currently, due to the standard fseek usage, we can't handle
+filesystems bigger than 4 GB. The limit is actually 2 GB because I used long rather than unsigned long long at too
+many places in the program. To conclude - This upgrade needs to be done carefully; There are many places to change.
+
+First written on: April 9 1995
+
+Copyright (C) 1995 Gadi Oxman
+
+*/
+
+#include "config.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include "ext2ed.h"
+
+int write_access;
+
+int low_read (unsigned char *buffer,unsigned long length,unsigned long offset)
+
+/*
+
+This function is used when we need to read something from the filesystem.
+
+*/
+
+{
+
+#ifdef DEBUG
+
+	char temp [80];
+
+	if (device_handle==NULL) {					/* Check that a device is indeed open */
+		internal_error ("No device opened yet read requested","disk","low_read");
+		return (0);
+	}
+	if (offset > file_system_info.file_system_size) {		/* Check that the offset is within limits */
+		sprintf (temp,"Seek offset %ld is out of range",offset);
+		internal_error (temp,"disk","low_read");
+		return (0);
+	}
+
+#endif
+
+	if ( (fseek (device_handle,offset,SEEK_SET))==-1) {		/* Seek to the required offset */
+		wprintw (command_win,"Error - Failed to seek to offset %ld in device %s\n",offset,device_name);
+		refresh_command_win ();
+		return (0);
+	};
+
+	if ( (fread (buffer,1,length,device_handle))==-1) {		/* And do the actual reading */
+		wprintw (command_win,"Error - Failed to read from offset %ld in device %s\n",offset,device_name);
+		refresh_command_win ();return (0);
+	};
+
+	return (1);
+}
+
+int low_write (unsigned char *buffer,unsigned long length,unsigned long offset)
+
+/*
+
+This is used to change something in the filesystem.
+write_access is checked to see if we are allowed to do the actual writing.
+As a double safety measure, AllowChanges is rechecked here.
+If logging is enabled, we log the change before writing it to the device.
+
+*/
+{
+	char temp [80];
+
+	if (!write_access) {
+		wprintw (command_win,"Error - Write access not available (use enablewrite)\n");
+		return (0);
+	}
+
+#ifdef DEBUG
+
+	if (!AllowChanges) {
+		internal_error ("AllowChanges=0 yet enablewrite succeeded","disk","low_write");
+		return (0);
+	}
+
+	if (device_handle==NULL) {
+		internal_error ("No device opened yet read requested","disk","low_write");
+		return (0);
+	}
+
+	if (offset > file_system_info.file_system_size) {
+		sprintf (temp,"Seek offset %ld is out of range",offset);
+		internal_error (temp,"disk","low_write");
+		return (0);
+	}
+
+#endif
+
+	if (LogChanges)
+		if (!log_changes (buffer,length,offset))
+			return (0);
+
+	if ( (fseek (device_handle,offset,SEEK_SET))==-1) {
+		wprintw (command_win,"Error - Failed to seek to offset %ld in device %s\n",offset,device_name);
+		refresh_command_win ();return (0);
+	};
+
+
+	if ( (fwrite (buffer,1,length,device_handle))==-1) {
+		wprintw (command_win,"Error - Failed to write to offset %ld in device %s\n",offset,device_name);
+		refresh_command_win ();return (0);
+	};
+
+	wprintw (command_win,"Data written");refresh_command_win ();
+	return (1);
+}
+
+int log_changes (unsigned char *buffer,unsigned long length,unsigned long offset)
+
+/*
+
+Log the change in a primitive form - An hex dump of the data before the change and after the change.
+The hex bytes are converted to text, so that they will be readable with a standard text editor.
+
+*/
+
+{
+	unsigned char *original;
+
+	int i;
+	time_t current_time;
+	FILE *fp;
+
+	if ((fp=fopen (LogFile,"a+"))==NULL) {
+		wprintw (command_win,"Error - Unable to open log file %s\n",LogFile);
+		refresh_command_win ();return (0);
+	};
+
+	current_time=time (NULL);
+
+	fprintf (fp,"\n----- EXT2ED log begin -----\n\n");
+	fprintf (fp,"Time: %s\nDevice: %s\n",ctime ((time_t *) &current_time),device_name);
+	fprintf (fp,"Offset: %lu\nLength: %lu\n",offset,length);
+
+	original=(unsigned char *) malloc (length*sizeof (unsigned char));
+
+	if (original==NULL) {
+		wprintw (command_win,"Fatal error - Can\'t allocate %lu bytes!");
+		refresh_command_win ();fclose (fp);return (0);
+	}
+
+	if (!low_read (original,length,offset)) {
+		fclose (fp);return (0);
+	}
+
+	fprintf (fp,"\nOriginal data:\n\n");
+
+	for (i=0;i<length;i++) {
+		if (i%16==0 && i!=0) fprintf (fp,"\n");
+		fprintf (fp,"%02x ",original [i]);
+	}
+
+	fprintf (fp,"\n\nNew data:\n\n");
+
+	for (i=0;i<length;i++) {
+		if (i%16==0 && i!=0) fprintf (fp,"\n");
+		fprintf (fp,"%02x ",buffer [i]);
+	}
+
+	fprintf (fp,"\n----- EXT2ED log end  -----\n");
+
+	fclose (fp);
+	return (1);
+}
+
+int load_type_data (void)
+
+/*
+
+Just read from the current position into type data.
+
+*/
+
+{
+	if (device_handle==NULL) {
+		printf ("Error - No device opened\n");
+		return (0);
+	}
+
+	if (device_offset==-1) {
+		printf ("Error - No offset set\n");
+		return (0);
+	}
+
+	if (low_read (type_data.u.buffer,EXT2_MAX_BLOCK_SIZE,device_offset)==0)
+		return (0);
+
+	if (current_type!=NULL)
+		if (strcmp (current_type->name,"ext2_dir_entry")==0)
+			current_type->length=type_data.u.t_ext2_dir_entry.rec_len;
+
+	return (1);
+}
+
+int write_type_data (void)
+
+{
+	if (device_handle==NULL) {
+		wprintw (command_win,"Error - No device opened\n");
+		refresh_command_win ();
+		return (0);
+	}
+
+	if (device_offset==-1) {
+		wprintw (command_win,"Error - No offset set\n");
+		refresh_command_win ();
+		return (0);
+	}
+
+	if (low_write (type_data.u.buffer,file_system_info.block_size,device_offset)==0)
+		return (0);
+
+	return (1);
+}
+