Backport rred patches from my own sid branch to the 0.7.25 branch

* rewrite and refactor rred method to be able to handle even big (>30 MB)
  patches (Closes: #554349) and hardening the method itself by using more
  constants and a return value which can't be misinterpreted as linenumber
* Finally adope the patch from Morten Hustveit <morten@debian.org> to be
  able to optional use mmaps and iovec to increase patch speed -
  but as this increase memory usage we can always fall back to the "old"
  method which doesn't depend on mmaps.

debian/changelog

@@ -90,6 +90,10 @@ apt (0.7.25) UNRELEASED; urgency=low
     - add APT::FTPArchive::LongDescription to be able to disable them
   * apt-pkg/deb/debsrcrecords.cc:
     - use "diff" filetype for .debian.tar.* files (Closes: #554898)
+  * methods/rred.cc:
+    - rewrite to be able to handle even big patch files
+    - adopt optional mmap+iovec patch from Morten Hustveit
+      (Closes: #463354) which should speed up a bit. Thanks!
 
   [ Chris Leick ]
   * doc/ various manpages:

methods/rred.cc

@@ -1,202 +1,443 @@
+// Includes									/*{{{*/
 #include <apt-pkg/fileutl.h>
+#include <apt-pkg/mmap.h>
 #include <apt-pkg/error.h>
 #include <apt-pkg/acquire-method.h>
 #include <apt-pkg/strutl.h>
 #include <apt-pkg/hashes.h>
 
 #include <sys/stat.h>
+#include <sys/uio.h>
 #include <unistd.h>
 #include <utime.h>
 #include <stdio.h>
 #include <errno.h>
 #include <apti18n.h>
-
-/* this method implements a patch functionality similar to "patch --ed" that is
- * used by the "tiffany" incremental packages download stuff. it differs from 
- * "ed" insofar that it is way more restricted (and therefore secure). in the
- * moment only the "c", "a" and "d" commands of ed are implemented (diff 
- * doesn't output any other). additionally the records must be reverse sorted 
- * by line number and may not overlap (diff *seems* to produce this kind of 
- * output). 
+										/*}}}*/
+/** \brief RredMethod - ed-style incremential patch method			{{{
+ *
+ *  This method implements a patch functionality similar to "patch --ed" that is
+ *  used by the "tiffany" incremental packages download stuff. It differs from
+ *  "ed" insofar that it is way more restricted (and therefore secure).
+ *  The currently supported ed commands are "<em>c</em>hange", "<em>a</em>dd" and
+ *  "<em>d</em>elete" (diff doesn't output any other).
+ *  Additionally the records must be reverse sorted by line number and
+ *  may not overlap (diff *seems* to produce this kind of output).
  * */
+class RredMethod : public pkgAcqMethod {
+	bool Debug;
+	// the size of this doesn't really matter (except for performance)
+	const static int BUF_SIZE = 1024;
+	// the supported ed commands
+	enum Mode {MODE_CHANGED='c', MODE_DELETED='d', MODE_ADDED='a'};
+	// return values
+	enum State {ED_OK, ED_ORDERING, ED_PARSER, ED_FAILURE, MMAP_FAILED};
 
-const char *Prog;
+	State applyFile(FILE *ed_cmds, FILE *in_file, FILE *out_file,
+	             unsigned long &line, char *buffer, Hashes *hash) const;
+	void ignoreLineInFile(FILE *fin, char *buffer) const;
+	void copyLinesFromFileToFile(FILE *fin, FILE *fout, unsigned int lines,
+	                            Hashes *hash, char *buffer) const;
 
-class RredMethod : public pkgAcqMethod
-{
-   bool Debug;
-   // the size of this doesn't really matter (except for performance)    
-   const static int BUF_SIZE = 1024;
-   // the ed commands
-   enum Mode {MODE_CHANGED, MODE_DELETED, MODE_ADDED};
-   // return values
-   enum State {ED_OK, ED_ORDERING, ED_PARSER, ED_FAILURE};
-   // this applies a single hunk, it uses a tail recursion to 
-   // reverse the hunks in the file
-   int ed_rec(FILE *ed_cmds, FILE *in_file, FILE *out_file, int line, 
-      char *buffer, unsigned int bufsize, Hashes *hash);
-   // apply a patch file
-   int ed_file(FILE *ed_cmds, FILE *in_file, FILE *out_file, Hashes *hash);
-   // the methods main method
-   virtual bool Fetch(FetchItem *Itm);
-   
-   public:
-   
-   RredMethod() : pkgAcqMethod("1.1",SingleInstance | SendConfig) {};
+	State patchFile(FileFd &Patch, FileFd &From, FileFd &out_file, Hashes *hash) const;
+	State patchMMap(FileFd &Patch, FileFd &From, FileFd &out_file, Hashes *hash) const;
+
+protected:
+	// the methods main method
+	virtual bool Fetch(FetchItem *Itm);
+
+public:
+	RredMethod() : pkgAcqMethod("1.1",SingleInstance | SendConfig) {};
 };
+										/*}}}*/
+/** \brief applyFile - in reverse order with a tail recursion			{{{
+ *
+ *  As it is expected that the commands are in reversed order in the patch file
+ *  we check in the first half if the command is valid, but doesn't execute it
+ *  and move a step deeper. After reaching the end of the file we apply the
+ *  patches in the correct order: last found command first.
+ *
+ *  \param ed_cmds patch file to apply
+ *  \param in_file base file we want to patch
+ *  \param out_file file to write the patched result to
+ *  \param line of command operation
+ *  \param buffer internal used read/write buffer
+ *  \param hash the created file for correctness
+ *  \return the success State of the ed command executor
+ */
+RredMethod::State RredMethod::applyFile(FILE *ed_cmds, FILE *in_file, FILE *out_file,
+			unsigned long &line, char *buffer, Hashes *hash) const {
+	// get the current command and parse it
+	if (fgets(buffer, BUF_SIZE, ed_cmds) == NULL) {
+		if (Debug == true)
+			std::clog << "rred: encounter end of file - we can start patching now." << std::endl;
+		line = 0;
+		return ED_OK;
+	}
 
-int RredMethod::ed_rec(FILE *ed_cmds, FILE *in_file, FILE *out_file, int line, 
-      char *buffer, unsigned int bufsize, Hashes *hash) {
-   int pos;
-   int startline;
-   int stopline;
-   int mode;
-   int written;
-   char *idx;
-
-   /* get the current command and parse it*/
-   if (fgets(buffer, bufsize, ed_cmds) == NULL) {
-      return line;
-   }
-   startline = strtol(buffer, &idx, 10);
-   if (startline < line) {
-      return ED_ORDERING;
-   }
-   if (*idx == ',') {
-      idx++;
-      stopline = strtol(idx, &idx, 10);
-   }
-   else {
-      stopline = startline;
-   }
-   if (*idx == 'c') {
-      mode = MODE_CHANGED;
-	   if (Debug == true) {
-		   std::clog << "changing from line " << startline 
-			     << " to " << stopline << std::endl;
-	   }
-   }
-   else if (*idx == 'a') {
-      mode = MODE_ADDED;
-	   if (Debug == true) {
-		   std::clog << "adding after line " << startline << std::endl;
-	   }
-   }
-   else if (*idx == 'd') {
-      mode = MODE_DELETED;
-	   if (Debug == true) {
-		   std::clog << "deleting from line " << startline 
-			     <<  " to " << stopline << std::endl;
-	   }
-   }
-   else {
-      return ED_PARSER;
-   }
-   /* get the current position */
-   pos = ftell(ed_cmds);
-   /* if this is add or change then go to the next full stop */
-   if ((mode == MODE_CHANGED) || (mode == MODE_ADDED)) {
-      do {
-         fgets(buffer, bufsize, ed_cmds);
-         while ((strlen(buffer) == (bufsize - 1)) 
-               && (buffer[bufsize - 2] != '\n')) {
-            fgets(buffer, bufsize, ed_cmds);
-            buffer[0] = ' ';
-         }
-      } while (strncmp(buffer, ".", 1) != 0);
-   }
-   /* do the recursive call */
-   line = ed_rec(ed_cmds, in_file, out_file, line, buffer, bufsize, 
-         hash);
-   /* pass on errors */
-   if (line < 0) {
-      return line;
-   }
-   /* apply our hunk */
-   fseek(ed_cmds, pos, SEEK_SET); 
-   /* first wind to the current position */
-   if (mode != MODE_ADDED) {
-      startline -= 1;
-   }
-   while (line < startline) {
-      fgets(buffer, bufsize, in_file);
-      written = fwrite(buffer, 1, strlen(buffer), out_file);
-      hash->Add((unsigned char*)buffer, written);
-      while ((strlen(buffer) == (bufsize - 1)) 
-            && (buffer[bufsize - 2] != '\n')) {
-         fgets(buffer, bufsize, in_file);
-         written = fwrite(buffer, 1, strlen(buffer), out_file);
-         hash->Add((unsigned char*)buffer, written);
-      }
-      line++;
-   }
-   /* include from ed script */
-   if ((mode == MODE_ADDED) || (mode == MODE_CHANGED)) {
-      do {
-         fgets(buffer, bufsize, ed_cmds);
-         if (strncmp(buffer, ".", 1) != 0) {
-            written = fwrite(buffer, 1, strlen(buffer), out_file);
-            hash->Add((unsigned char*)buffer, written);
-            while ((strlen(buffer) == (bufsize - 1)) 
-                  && (buffer[bufsize - 2] != '\n')) {
-               fgets(buffer, bufsize, ed_cmds);
-               written = fwrite(buffer, 1, strlen(buffer), out_file);
-               hash->Add((unsigned char*)buffer, written);
-            }
-         }
-         else {
-            break;
-         }
-      } while (1);
-   }
-   /* ignore the corresponding number of lines from input */
-   if ((mode == MODE_DELETED) || (mode == MODE_CHANGED)) {
-      while (line < stopline) {
-         fgets(buffer, bufsize, in_file);
-         while ((strlen(buffer) == (bufsize - 1)) 
-               && (buffer[bufsize - 2] != '\n')) {
-            fgets(buffer, bufsize, in_file);
-         }
-         line++;
-      }
-   }
-   return line;
-}
+	// parse in the effected linenumbers
+	char* idx;
+	errno=0;
+	unsigned long const startline = strtol(buffer, &idx, 10);
+	if (errno == ERANGE || errno == EINVAL) {
+		_error->Errno("rred", "startline is an invalid number");
+		return ED_PARSER;
+	}
+	if (startline > line) {
+		_error->Error("rred: The start line (%lu) of the next command is higher than the last line (%lu). This is not allowed.", startline, line);
+		return ED_ORDERING;
+	}
+	unsigned long stopline;
+	if (*idx == ',') {
+		idx++;
+		errno=0;
+		stopline = strtol(idx, &idx, 10);
+		if (errno == ERANGE || errno == EINVAL) {
+			_error->Errno("rred", "stopline is an invalid number");
+			return ED_PARSER;
+		}
+	}
+	else {
+		stopline = startline;
+	}
+	line = startline;
+
+	// which command to execute on this line(s)?
+	switch (*idx) {
+		case MODE_CHANGED:
+			if (Debug == true)
+				std::clog << "Change from line " << startline << " to " << stopline << std::endl;
+			break;
+		case MODE_ADDED:
+			if (Debug == true)
+				std::clog << "Insert after line " << startline << std::endl;
+			break;
+		case MODE_DELETED:
+			if (Debug == true)
+				std::clog << "Delete from line " << startline << " to " << stopline << std::endl;
+			break;
+		default:
+			_error->Error("rred: Unknown ed command '%c'. Abort.", *idx);
+			return ED_PARSER;
+	}
+	unsigned char mode = *idx;
+
+	// save the current position
+	unsigned const long pos = ftell(ed_cmds);
+
+	// if this is add or change then go to the next full stop
+	unsigned int data_length = 0;
+	if (mode == MODE_CHANGED || mode == MODE_ADDED) {
+		do {
+			ignoreLineInFile(ed_cmds, buffer);
+			data_length++;
+		}
+		while (strncmp(buffer, ".", 1) != 0);
+		data_length--; // the dot should not be copied
+	}
+
+	// do the recursive call - the last command is the one we need to execute at first
+	const State child = applyFile(ed_cmds, in_file, out_file, line, buffer, hash);
+	if (child != ED_OK) {
+		return child;
+	}
+
+	// change and delete are working on "line" - add is done after "line"
+	if (mode != MODE_ADDED)
+		line++;
+
+	// first wind to the current position and copy over all unchanged lines
+	if (line < startline) {
+		copyLinesFromFileToFile(in_file, out_file, (startline - line), hash, buffer);
+		line = startline;
+	}
 
-int RredMethod::ed_file(FILE *ed_cmds, FILE *in_file, FILE *out_file, 
-      Hashes *hash) {
+	if (mode != MODE_ADDED)
+		line--;
+
+	// include data from ed script
+	if (mode == MODE_CHANGED || mode == MODE_ADDED) {
+		fseek(ed_cmds, pos, SEEK_SET);
+		copyLinesFromFileToFile(ed_cmds, out_file, data_length, hash, buffer);
+	}
+
+	// ignore the corresponding number of lines from input
+	if (mode == MODE_CHANGED || mode == MODE_DELETED) {
+		while (line < stopline) {
+			ignoreLineInFile(in_file, buffer);
+			line++;
+		}
+	}
+	return ED_OK;
+}
+										/*}}}*/
+void RredMethod::copyLinesFromFileToFile(FILE *fin, FILE *fout, unsigned int lines,/*{{{*/
+					Hashes *hash, char *buffer) const {
+	while (0 < lines--) {
+		do {
+			fgets(buffer, BUF_SIZE, fin);
+			size_t const written = fwrite(buffer, 1, strlen(buffer), fout);
+			hash->Add((unsigned char*)buffer, written);
+		} while (strlen(buffer) == (BUF_SIZE - 1) &&
+		       buffer[BUF_SIZE - 2] != '\n');
+	}
+}
+										/*}}}*/
+void RredMethod::ignoreLineInFile(FILE *fin, char *buffer) const {		/*{{{*/
+	fgets(buffer, BUF_SIZE, fin);
+	while (strlen(buffer) == (BUF_SIZE - 1) &&
+	       buffer[BUF_SIZE - 2] != '\n') {
+		fgets(buffer, BUF_SIZE, fin);
+		buffer[0] = ' ';
+	}
+}
+										/*}}}*/
+RredMethod::State RredMethod::patchFile(FileFd &Patch, FileFd &From,		/*{{{*/
+					FileFd &out_file, Hashes *hash) const {
    char buffer[BUF_SIZE];
-   int result;
-   int written;
-   
+   FILE* fFrom = fdopen(From.Fd(), "r");
+   FILE* fPatch = fdopen(Patch.Fd(), "r");
+   FILE* fTo = fdopen(out_file.Fd(), "w");
+
    /* we do a tail recursion to read the commands in the right order */
-   result = ed_rec(ed_cmds, in_file, out_file, 0, buffer, BUF_SIZE, 
-         hash);
+   unsigned long line = -1; // assign highest possible value
+   State const result = applyFile(fPatch, fFrom, fTo, line, buffer, hash);
    
    /* read the rest from infile */
-   if (result >= 0) {
-      while (fgets(buffer, BUF_SIZE, in_file) != NULL) {
-         written = fwrite(buffer, 1, strlen(buffer), out_file);
+   if (result == ED_OK) {
+      while (fgets(buffer, BUF_SIZE, fFrom) != NULL) {
+         size_t const written = fwrite(buffer, 1, strlen(buffer), fTo);
          hash->Add((unsigned char*)buffer, written);
       }
+      fflush(fTo);
    }
-   else {
-      return ED_FAILURE;
-   }
-   return ED_OK;
+   return result;
 }
+										/*}}}*/
+struct EdCommand {								/*{{{*/
+  size_t data_start;
+  size_t data_end;
+  size_t data_lines;
+  size_t first_line;
+  size_t last_line;
+  char type;
+};
+#define IOV_COUNT 1024 /* Don't really want IOV_MAX since it can be arbitrarily large */
+										/*}}}*/
+RredMethod::State RredMethod::patchMMap(FileFd &Patch, FileFd &From,		/*{{{*/
+					FileFd &out_file, Hashes *hash) const {
+#ifdef _POSIX_MAPPED_FILES
+	MMap ed_cmds(Patch, MMap::ReadOnly);
+	MMap in_file(From, MMap::ReadOnly);
+
+	if (ed_cmds.Size() == 0 || in_file.Size() == 0)
+		return MMAP_FAILED;
+
+	EdCommand* commands = 0;
+	size_t command_count = 0;
+	size_t command_alloc = 0;
+
+	const char* begin = (char*) ed_cmds.Data();
+	const char* end = begin;
+	const char* ed_end = (char*) ed_cmds.Data() + ed_cmds.Size();
+
+	const char* input = (char*) in_file.Data();
+	const char* input_end = (char*) in_file.Data() + in_file.Size();
+
+	size_t i;
+
+	/* 1. Parse entire script.  It is executed in reverse order, so we cather it
+	 *    in the `commands' buffer first
+	 */
+
+	for(;;) {
+		EdCommand cmd;
+		cmd.data_start = 0;
+		cmd.data_end = 0;
+
+		while(begin != ed_end && *begin == '\n')
+			++begin;
+		while(end != ed_end && *end != '\n')
+			++end;
+		if(end == ed_end && begin == end)
+			break;
+
+		/* Determine command range */
+		const char* tmp = begin;
+
+		for(;;) {
+			/* atoll is safe despite lacking NUL-termination; we know there's an
+			 * alphabetic character at end[-1]
+			 */
+			if(tmp == end) {
+				cmd.first_line = atol(begin);
+				cmd.last_line = cmd.first_line;
+				break;
+			}
+			if(*tmp == ',') {
+				cmd.first_line = atol(begin);
+				cmd.last_line = atol(tmp + 1);
+				break;
+			}
+			++tmp;
+		}
+
+		// which command to execute on this line(s)?
+		switch (end[-1]) {
+			case MODE_CHANGED:
+				if (Debug == true)
+					std::clog << "Change from line " << cmd.first_line << " to " << cmd.last_line << std::endl;
+				break;
+			case MODE_ADDED:
+				if (Debug == true)
+					std::clog << "Insert after line " << cmd.first_line << std::endl;
+				break;
+			case MODE_DELETED:
+				if (Debug == true)
+					std::clog << "Delete from line " << cmd.first_line << " to " << cmd.last_line << std::endl;
+				break;
+			default:
+				_error->Error("rred: Unknown ed command '%c'. Abort.", end[-1]);
+				free(commands);
+				return ED_PARSER;
+		}
+		cmd.type = end[-1];
+
+		/* Determine the size of the inserted text, so we don't have to scan this
+		 * text again later.
+		 */
+		begin = end + 1;
+		end = begin;
+		cmd.data_lines = 0;
+
+		if(cmd.type == MODE_ADDED || cmd.type == MODE_CHANGED) {
+			cmd.data_start = begin - (char*) ed_cmds.Data();
+			while(end != ed_end) {
+				if(*end == '\n') {
+					if(end[-1] == '.' && end[-2] == '\n')
+						break;
+					++cmd.data_lines;
+				}
+				++end;
+			}
+			cmd.data_end = end - (char*) ed_cmds.Data() - 1;
+			begin = end + 1;
+			end = begin;
+		}
+		if(command_count == command_alloc) {
+			command_alloc = (command_alloc + 64) * 3 / 2;
+			commands = (EdCommand*) realloc(commands, command_alloc * sizeof(EdCommand));
+		}
+		commands[command_count++] = cmd;
+	}
+
+	struct iovec* iov = new struct iovec[IOV_COUNT];
+	size_t iov_size = 0;
+
+	size_t amount, remaining;
+	size_t line = 1;
+	EdCommand* cmd;
+
+	/* 2. Execute script.  We gather writes in a `struct iov' array, and flush
+	 *    using writev to minimize the number of system calls.  Data is read
+	 *    directly from the memory mappings of the input file and the script.
+	 */
+
+	for(i = command_count; i-- > 0; ) {
+		cmd = &commands[i];
+		if(cmd->type == MODE_ADDED)
+			amount = cmd->first_line + 1;
+		else
+			amount = cmd->first_line;
+
+		if(line < amount) {
+			begin = input;
+			while(line != amount) {
+				input = (const char*) memchr(input, '\n', input_end - input);
+				if(!input)
+					break;
+				++line;
+				++input;
+			}
 
+			iov[iov_size].iov_base = (void*) begin;
+			iov[iov_size].iov_len = input - begin;
+			hash->Add((const unsigned char*) begin, input - begin);
 
-bool RredMethod::Fetch(FetchItem *Itm)
+			if(++iov_size == IOV_COUNT) {
+				writev(out_file.Fd(), iov, IOV_COUNT);
+				iov_size = 0;
+			}
+		}
+
+		if(cmd->type == MODE_DELETED || cmd->type == MODE_CHANGED) {
+			remaining = (cmd->last_line - cmd->first_line) + 1;
+			line += remaining;
+			while(remaining) {
+				input = (const char*) memchr(input, '\n', input_end - input);
+				if(!input)
+					break;
+				--remaining;
+				++input;
+			}
+		}
+
+		if(cmd->type == MODE_CHANGED || cmd->type == MODE_ADDED) {
+			if(cmd->data_end != cmd->data_start) {
+				iov[iov_size].iov_base = (void*) ((char*)ed_cmds.Data() + cmd->data_start);
+				iov[iov_size].iov_len = cmd->data_end - cmd->data_start;
+				hash->Add((const unsigned char*) ((char*)ed_cmds.Data() + cmd->data_start),
+				iov[iov_size].iov_len);
+
+				if(++iov_size == IOV_COUNT) {
+					writev(out_file.Fd(), iov, IOV_COUNT);
+					iov_size = 0;
+				}
+			}
+		}
+	}
+
+	if(input != input_end) {
+		iov[iov_size].iov_base = (void*) input;
+		iov[iov_size].iov_len = input_end - input;
+		hash->Add((const unsigned char*) input, input_end - input);
+		++iov_size;
+	}
+
+	if(iov_size) {
+		writev(out_file.Fd(), iov, iov_size);
+		iov_size = 0;
+	}
+
+	for(i = 0; i < iov_size; i += IOV_COUNT) {
+		if(iov_size - i < IOV_COUNT)
+			writev(out_file.Fd(), iov + i, iov_size - i);
+		else
+			writev(out_file.Fd(), iov + i, IOV_COUNT);
+	}
+
+	delete [] iov;
+	free(commands);
+
+	return ED_OK;
+#else
+	return MMAP_FAILED;
+#endif
+}
+										/*}}}*/
+bool RredMethod::Fetch(FetchItem *Itm)						/*{{{*/
 {
-   Debug = _config->FindB("Debug::pkgAcquire::RRed",false);
+   Debug = _config->FindB("Debug::pkgAcquire::RRed", false);
    URI Get = Itm->Uri;
    string Path = Get.Host + Get.Path; // To account for relative paths
-   // Path contains the filename to patch
+
    FetchResult Res;
    Res.Filename = Itm->DestFile;
-   URIStart(Res);
-   // Res.Filename the destination filename
+   if (Itm->Uri.empty() == true) {
+      Path = Itm->DestFile;
+      Itm->DestFile.append(".result");
+   } else
+      URIStart(Res);
 
    if (Debug == true) 
       std::clog << "Patching " << Path << " with " << Path 
@@ -211,19 +452,27 @@ bool RredMethod::Fetch(FetchItem *Itm)
       return false;
    
    Hashes Hash;
-   FILE* fFrom = fdopen(From.Fd(), "r");
-   FILE* fPatch = fdopen(Patch.Fd(), "r");
-   FILE* fTo = fdopen(To.Fd(), "w");
    // now do the actual patching
-   if (ed_file(fPatch, fFrom, fTo, &Hash) != ED_OK) {
-     _error->Errno("rred", _("Could not patch file"));  
-      return false;
+   State const result = patchMMap(Patch, From, To, &Hash);
+   if (result == MMAP_FAILED) {
+      // retry with patchFile
+      lseek(Patch.Fd(), 0, SEEK_SET);
+      lseek(From.Fd(), 0, SEEK_SET);
+      To.Open(Itm->DestFile,FileFd::WriteEmpty);
+      if (_error->PendingError() == true)
+         return false;
+      if (patchFile(Patch, From, To, &Hash) != ED_OK) {
+	 return _error->WarningE("rred", _("Could not patch %s with mmap and with file operation usage - the patch seems to be corrupt."), Path.c_str());
+      } else if (Debug == true) {
+	 std::clog << "rred: finished file patching of " << Path  << " after mmap failed." << std::endl;
+      }
+   } else if (result != ED_OK) {
+      return _error->Errno("rred", _("Could not patch %s with mmap (but no mmap specific fail) - the patch seems to be corrupt."), Path.c_str());
+   } else if (Debug == true) {
+      std::clog << "rred: finished mmap patching of " << Path << std::endl;
    }
 
    // write out the result
-   fflush(fFrom);
-   fflush(fPatch);
-   fflush(fTo);
    From.Close();
    Patch.Close();
    To.Close();
@@ -250,13 +499,44 @@ bool RredMethod::Fetch(FetchItem *Itm)
 
    return true;
 }
-
-int main(int argc, char *argv[])
-{
-   RredMethod Mth;
-
-   Prog = strrchr(argv[0],'/');
-   Prog++;
-   
-   return Mth.Run();
+										/*}}}*/
+/** \brief Wrapper class for testing rred */					/*{{{*/
+class TestRredMethod : public RredMethod {
+public:
+	/** \brief Run rred in debug test mode
+	 *
+	 *  This method can be used to run the rred method outside
+	 *  of the "normal" acquire environment for easier testing.
+	 *
+	 *  \param base basename of all files involved in this rred test
+	 */
+	bool Run(char const *base) {
+		_config->CndSet("Debug::pkgAcquire::RRed", "true");
+		FetchItem *test = new FetchItem;
+		test->DestFile = base;
+		return Fetch(test);
+	}
+};
+										/*}}}*/
+/** \brief Starter for the rred method (or its test method)			{{{
+ *
+ *  Used without parameters is the normal behavior for methods for
+ *  the APT acquire system. While this works great for the acquire system
+ *  it is very hard to test the method and therefore the method also
+ *  accepts one parameter which will switch it directly to debug test mode:
+ *  The test mode expects that if "Testfile" is given as parameter
+ *  the file "Testfile" should be ed-style patched with "Testfile.ed"
+ *  and will write the result to "Testfile.result".
+ */
+int main(int argc, char *argv[]) {
+	if (argc <= 1) {
+		RredMethod Mth;
+		return Mth.Run();
+	} else {
+		TestRredMethod Mth;
+		bool result = Mth.Run(argv[1]);
+		_error->DumpErrors();
+		return result;
+	}
 }
+										/*}}}*/