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 relay on mmaps.

methods/rred.cc

@@ -1,11 +1,13 @@
 // 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>
@@ -29,7 +31,7 @@ class RredMethod : public pkgAcqMethod {
 	// the supported ed commands
 	enum Mode {MODE_CHANGED='c', MODE_DELETED='d', MODE_ADDED='a'};
 	// return values
-	enum State {ED_OK=0, ED_ORDERING=1, ED_PARSER=2, ED_FAILURE=3};
+	enum State {ED_OK, ED_ORDERING, ED_PARSER, ED_FAILURE, MMAP_FAILED};
 
 	State applyFile(FILE *ed_cmds, FILE *in_file, FILE *out_file,
 	             unsigned long &line, char *buffer, Hashes *hash) const;
@@ -37,7 +39,8 @@ class RredMethod : public pkgAcqMethod {
 	void copyLinesFromFileToFile(FILE *fin, FILE *fout, unsigned int lines,
 	                            Hashes *hash, char *buffer) const;
 
-	State patchFile(FILE *ed_cmds, FILE *in_file, FILE *out_file, Hashes *hash) const;
+	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
@@ -67,7 +70,7 @@ RredMethod::State RredMethod::applyFile(FILE *ed_cmds, FILE *in_file, FILE *out_
 	// 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::clog << "rred: encounter end of file - we can start patching now." << std::endl;
 		line = 0;
 		return ED_OK;
 	}
@@ -189,22 +192,240 @@ void RredMethod::ignoreLineInFile(FILE *fin, char *buffer) const {		/*{{{*/
 	}
 }
 										/*}}}*/
-RredMethod::State RredMethod::patchFile(FILE *ed_cmds, FILE *in_file, FILE *out_file,		/*{{{*/
-      Hashes *hash) const {
+RredMethod::State RredMethod::patchFile(FileFd &Patch, FileFd &From,		/*{{{*/
+					FileFd &out_file, Hashes *hash) const {
    char buffer[BUF_SIZE];
-   
+   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 */
    unsigned long line = -1; // assign highest possible value
-   State result = applyFile(ed_cmds, in_file, out_file, line, buffer, hash);
+   State const result = applyFile(fPatch, fFrom, fTo, line, buffer, hash);
    
    /* read the rest from infile */
    if (result == ED_OK) {
-      while (fgets(buffer, BUF_SIZE, in_file) != NULL) {
-         size_t const written = fwrite(buffer, 1, strlen(buffer), out_file);
+      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);
    }
    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);
+	FILE* fTo = fdopen(out_file.Fd(), "w");
+
+	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);
+
+			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);
+
+	fflush(fTo);
+
+	return ED_OK;
+#else
+	return MMAP_FAILED;
+#endif
 }
 										/*}}}*/
 bool RredMethod::Fetch(FetchItem *Itm)						/*{{{*/
@@ -234,19 +455,23 @@ 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 (patchFile(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->Errno("rred", _("Could not patch file %s"), Path.append(" (1)").c_str());
+      }
+   } else if (result != ED_OK) {
+      return _error->Errno("rred", _("Could not patch file %s"), Path.append(" (2)").c_str());
    }
 
    // write out the result
-   fflush(fFrom);
-   fflush(fPatch);
-   fflush(fTo);
    From.Close();
    Patch.Close();
    To.Close();