.\"
.\"  LibXDiff by Davide Libenzi ( File Differential Library )
.\"  Copyright (C) 2003  Davide Libenzi
.\"
.\"  This library is free software; you can redistribute it and/or
.\"  modify it under the terms of the GNU Lesser General Public
.\"  License as published by the Free Software Foundation; either
.\"  version 2.1 of the License, or (at your option) any later version.
.\"
.\"  This library is distributed in the hope that it will be useful,
.\"  but WITHOUT ANY WARRANTY; without even the implied warranty of
.\"  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
.\"  Lesser General Public License for more details.
.\"
.\"  You should have received a copy of the GNU General Public License
.\"  along with this program; if not, write to the Free Software
.\"  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
.\"
.\"  Davide Libenzi <davidel@xmailserver.org>
.\"
.na
.TH LibXDiff 3 "0.23" "GNU" "File Differential Library"
.SH NAME

xdl_set_allocator, xdl_malloc, xdl_free, xdl_realloc, xdl_init_mmfile, xdl_free_mmfile,
xdl_mmfile_iscompact, xdl_seek_mmfile, xdl_read_mmfile, xdl_write_mmfile, xdl_writem_mmfile,
xdl_mmfile_writeallocate, xdl_mmfile_ptradd, xdl_mmfile_first, xdl_mmfile_next, xdl_mmfile_size, xdl_mmfile_cmp,
xdl_mmfile_compact, xdl_diff, xdl_patch, xdl_merge3, xdl_bdiff_mb, xdl_bdiff, xdl_rabdiff_mb, xdl_rabdiff,
xdl_bdiff_tgsize, xdl_bpatch \- File Differential Library support functions

.SH SYNOPSIS
.nf
.B #include <xdiff.h>
.sp
.BI "int xdl_set_allocator(memallocator_t const *" malt ");"
.nl
.BI "void *xdl_malloc(unsigned int " size ");"
.nl
.BI "void xdl_free(void *" ptr ");"
.nl
.BI "void *xdl_realloc(void *" ptr ", unsigned int " nsize ");"
.nl
.BI "int xdl_init_mmfile(mmfile_t *" mmf ", long " bsize ", unsigned long " flags ");"
.nl
.BI "void xdl_free_mmfile(mmfile_t *" mmf ");"
.nl
.BI "int xdl_mmfile_iscompact(mmfile_t *" mmf ");"
.nl
.BI "int xdl_seek_mmfile(mmfile_t *" mmf ", long " off ");"
.nl
.BI "long xdl_read_mmfile(mmfile_t *" mmf ", void *" data ", long " size ");"
.nl
.BI "long xdl_write_mmfile(mmfile_t *" mmf ", void const *" data ", long " size ");"
.nl
.BI "long xdl_writem_mmfile(mmfile_t *" mmf ", mmbuffer_t *" mb ", int " nbuf ");"
.nl
.BI "void *xdl_mmfile_writeallocate(mmfile_t *" mmf ", long " size ");"
.nl
.BI "long xdl_mmfile_ptradd(mmfile_t *" mmf ", char *" ptr ", long " size ", unsigned long " flags ");"
.nl
.BI "void *xdl_mmfile_first(mmfile_t *" mmf ", long *" size ");"
.nl
.BI "void *xdl_mmfile_next(mmfile_t *" mmf ", long *" size ");"
.nl
.BI "long xdl_mmfile_size(mmfile_t *" mmf ");"
.nl
.BI "int xdl_mmfile_cmp(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ");"
.nl
.BI "int xdl_mmfile_compact(mmfile_t *" mmfo ", mmfile_t *" mmfc ", long " bsize ", unsigned long " flags ");"
.nl
.BI "int xdl_diff(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", xpparam_t const *" xpp ", xdemitconf_t const *" xecfg ", xdemitcb_t *" ecb ");"
.nl
.BI "int xdl_patch(mmfile_t *" mmf ", mmfile_t *" mmfp ", int " mode ", xdemitcb_t *" ecb ", xdemitcb_t *" rjecb ");"
.nl
.BI "int xdl_merge3(mmfile_t *" mmfo ", mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", xdemitcb_t *" ecb ", xdemitcb_t *" rjecb ");"
.nl
.BI "int xdl_bdiff_mb(mmbuffer_t *" mmb1 ", mmbuffer_t *" mmb2 ", bdiffparam_t const *" bdp ", xdemitcb_t *" ecb ");"
.nl
.BI "int xdl_bdiff(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", bdiffparam_t const *" bdp ", xdemitcb_t *" ecb ");"
.nl
.BI "int xdl_rabdiff_mb(mmbuffer_t *" mmb1 ", mmbuffer_t *" mmb2 ", xdemitcb_t *" ecb ");"
.nl
.BI "int xdl_rabdiff(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", xdemitcb_t *" ecb ");"
.nl
.BI "long xdl_bdiff_tgsize(mmfile_t *" mmfp ");"
.nl
.BI "int xdl_bpatch(mmfile_t *" mmf ", mmfile_t *" mmfp ", xdemitcb_t *" ecb ");"

.SH DESCRIPTION
The
.B LibXDiff
library implements basic and yet complete functionalities to create
file differences/patches to both binary and text files. The library
uses memory files as file abstraction to achieve both performance and
portability. For binary files,
.B LibXDiff
implements both (with some modification) the algorithm described in
.IR "File System Support for Delta Compression" " by " "Joshua P. MacDonald" ,
and the method described in
.IR "Fingerprinting by Random Polynomials" " by " "Michael O. Rabin" "."
While for text files it follows directives described in
.IR "An O(ND) Difference Algorithm and Its Variations" " by " "Eugene W. Myers" .
Memory files used by the library are basically a collection of buffers
that store the file content. There are two different requirements for memory
files when passed to diff/patch functions. Text files for diff/patch functions
require that a single line do not have to spawn across two different memory
file blocks. Binary diff/patch functions require memory files to be compact.
A compact memory files is a file whose content is stored inside a single block.
Functionalities inside the library are available to satisfy these rules.
Using the
.B XDL_MMF_ATOMIC
memory file flag it is possible to make writes to not split the written
record across different blocks, while the functions
.BR xdl_mmfile_iscompact ()
,
.BR xdl_mmfile_compact ()
and
.BR xdl_mmfile_writeallocate ()
are usefull to test if the file is compact and to create a compacted version
of the file itself. The text file differential output uses the raw unified output
format, by omitting the file header since the result is always relative to
a single compare operation (between two files). The output format of the binary
patch file is proprietary (and binary) and it is basically a collection of
copy and insert commands, like described inside the MacDonald paper.


.SS Functions
The following functions are defined:
.TP
.BI "int xdl_set_allocator(memallocator_t const *" malt ");"

The
.B LibXDiff
library enable the user to set its own memory allocator, that will be used
for all the following memory requests. The allocator must be set before
to start calling the
.B LibXDiff
library with a call to
.BR xdl_set_allocator ().
The memory allocator structure contains the following members:
.nf

	typedef struct s_memallocator {
		void *priv;
		void *(*malloc)(void *priv, unsigned int size);
		void (*free)(void *priv, void *ptr);
		void *(*realloc)(void *priv, void *ptr, unsigned int nsize);
	} memallocator_t;

.fi
The
.BR malloc ()
function pointer will be used by
.B LibXDiff
to request a memory block of
.I size
bytes. The
.BR free ()
function pointer will be called to free a previously allocated block
.I ptr
, while the
.BR realloc ()
will be used to resize the
.I ptr
to a new
.I nsize
size in bytes. The
.B priv
structure member will be passed to the
.BR malloc (), free (), realloc ()
functions as first parameter. The
.B LibXDiff
user must call
.BR xdl_set_allocator ()
before starting using the library, otherwise
.B LibXDiff
functions will fail due to the lack of memory allocation support.
A typical initialization sequence for
.B POSIX
systems will use the standard
.BR malloc (3),
.BR free (3),
.BR realloc (3)
and will look like:
.nf

	void *wrap_malloc(void *priv, unsigned int size) {
		return malloc(size);
	}

	void wrap_free(void *priv, void *ptr) {
		free(ptr);
	}

	void *wrap_realloc(void *priv, void *ptr, unsigned int size) {
		return realloc(ptr, size);
	}

	void my_init_xdiff(void) {
		memallocator_t malt;

		malt.priv = NULL;
		malt.malloc = wrap_malloc;
		malt.free = wrap_free;
		malt.realloc = wrap_realloc;
		xdl_set_allocator(&malt);
	}

.fi

.TP
.BI "void *xdl_malloc(unsigned int " size ");"

Allocates a memory block of
.I size
bytes using the
.B LibXDiff
memory allocator. The user can specify its own allocator using the
.BR xdl_set_allocator ()
function. The
.BR xdl_malloc ()
return a pointer to the newly allocated block, or
.B NULL
in case of failure.

.TP
.BI "void xdl_free(void *" ptr ");"

Free a previously allocated memory block pointed by
.IR ptr .
The
.I ptr
block must has been allocated using either
.BR xdl_malloc ()
or
.BR xdl_realloc ().

.TP
.BI "void *xdl_realloc(void *" ptr ", unsigned int " nsize ");"

Resizes the memory block pointed by
.I ptr
to a new size
.IR nsize .
Return the resized block if successful, or
.B NULL
in case the reallocation fails. After a successful reallocation, the old
.I ptr
block is to be considered no more valid.

.TP
.BI "int xdl_init_mmfile(mmfile_t *" mmf ", long " bsize ", unsigned long " flags ");"

Initialize the memory file
.I mmf
by requiring an internal block size of
.IR bsize .
The
.I flags
parameter is a combination of the following flags :
.br
.IP
.B XDL_MMF_ATOMIC
Writes on the memory file will be atomic. That is, the data will not be split
on two or more different blocks.

Once an
.BR xdl_init_mmfile ()
succeeded, a matching
.BR xdl_free_mmfile ()
must be called when the user has done using the memory file, otherwise serious
memory leaks will happen.
The function return 0 if succeed or -1 if an error is encountered.

.TP
.BI "void xdl_free_mmfile(mmfile_t *" mmf ");"

Free all the data associated with the
.I mmf
memory file.

.TP
.BI "int xdl_mmfile_iscompact(mmfile_t *" mmf ");"

Returns an integer different from 0 if the
.I mmf
memory file is compact, 0 otherwise. A compact memory file is one that have
the whole content stored inside a single block.

.TP
.BI "int xdl_seek_mmfile(mmfile_t *" mmf ", long " off ");"

Set the current data pointer of the memory file
.I mmf
to the specified offset
.I off
from the beginning of the file itself. Returns 0 if successful or -1 if an error
happened.

.TP
.BI "long xdl_read_mmfile(mmfile_t *" mmf ", void *" data ", long " size ");"

Request to read
.I size
bytes from the memory file
.I mmf
by storing the data inside the
.I data
buffer. Returns the number of bytes read into the
.I data
buffer. The amount of data read can be lower than the specified
.IR size .
The function returns -1 if an error happened.

.TP
.BI "long xdl_write_mmfile(mmfile_t *" mmf ", void const *" data ", long " size ");"

Request to write
.I size
bytes from the specified buffer
.I data
into the memory file
.IR mmf .
If the memory file has been created using the
.B XDL_MMF_ATOMIC
flag, the write request will not be split across different blocks.
Note that all write operations done on memory files do append data at the end
the file, and writes in the middle of it are allowed. This is because the library
memory file abstraction does not need this functionality to be available.
The function returns the number of bytes written or a number lower than
.I size
if an error happened.

.TP
.BI "long xdl_writem_mmfile(mmfile_t *" mmf ", mmbuffer_t *" mb ", int " nbuf ");"

Request to sequentially write
.I nbuf
memory buffers passed inside the array
.I mb
into the memory file
.IR mmf .
The memory buffer structure is defined as :
.nf

	typedef struct s_mmbuffer {
		char *ptr;
		long size;
	} mmbuffer_t;

.fi
The
.I ptr
field is a pointer to the user data, whose size is specified inside the
.I size
structure field. The function returns the total number of bytes written
or a lower number if an error happened.

.TP
.BI "void *xdl_mmfile_writeallocate(mmfile_t *" mmf ", long " size ");"

The function request to allocate a write buffer of
.I size
bytes in the
.I mmf
memory file and returns the pointer to the allocated buffer. The user will
have the responsibility to store
.I size
bytes (no more, no less) inside the memory region pointed to by the returned pointer.
The files size will grow of
.I size
bytes as a consequence of this operation. The function will return
.B NULL
if an error happened.

.TP
.BI "long xdl_mmfile_ptradd(mmfile_t *" mmf ", char *" ptr ", long " size ", unsigned long " flags ");"

The function adds a user specified block to the end of the memory file
.IR mmf .
The block first byte is pointed to by
.I ptr
and its length is
.I size
bytes. The
.I flags
parameter can be used to specify attributes of the user memory block. Currently
supported attributes are:
.br
.IP
.B XDL_MMB_READONLY
Specify that the added memory block must be treated as read-only, and
every attempt to write on it should result in a failure of the memory file
writing functions.

The purpose of this function is basically to avoid copying memory around,
by helping the library to not drain the CPU cache. The function returns
.I size
in case of success, or -1 in case of error.

.TP
.BI "void *xdl_mmfile_first(mmfile_t *" mmf ", long *" size ");"

The function is used to return the first block of the
.I mmf
memory file block chain. The
.I size
parameter will receive the size of the block, while the function will return
the pointer the the first byte of the block itself. The function returns
.B NULL
if the file is empty.

.TP
.BI "void *xdl_mmfile_next(mmfile_t *" mmf ", long *" size ");"

The function is used to return the next block of the
.I mmf
memory file block chain. The
.I size
parameter will receive the size of the block, while the function will return
the pointer the the first byte of the block itself. The function returns
.B NULL
if the current block is the last one of the chain.

.TP
.BI "long xdl_mmfile_size(mmfile_t *" mmf ");"

The function returns the size of the specified memory file
.IR mmf .

.TP
.BI "int xdl_mmfile_cmp(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ");"

Request to compare two memory files
.IR mmf1 " and " mmf2
and returns 0 if files are identical, or a value different from 0 if
files are different.

.TP
.BI "int xdl_mmfile_compact(mmfile_t *" mmfo ", mmfile_t *" mmfc ", long " bsize ", unsigned long " flags ");"

Request to create a compact version of the memory file
.I mmfo
into the (uninitialized) memory file
.IR mmfc .
The
.I bsize
parameter specify the requested block size and
.I flags
specify flags to be used to create the new
.I mmfc
memory file (see
.BR xdl_init_mmfile ()
). The function returns 0 if succedded or -1 if an error happened.

.TP
.BI "int xdl_diff(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", xpparam_t const *" xpp ", xdemitconf_t const *" xecfg ", xdemitcb_t *" ecb ");"

Request to create the difference between the two text memory files
.IR mmf1 " and " mmf2 .
The
.I mmf1
memory files is considered the "old" file while
.I mmf2
is considered the "new" file. So the function will create a patch file
that once applied to
.I mmf1
will give
.I mmf2
as result. Files
.IR mmf1 " and " mmf2
must be atomic from a line point of view (or, as an extreme, compact), that
means that a single test line cannot spread among different memory file blocks.
The
.I xpp
parameter is a pointer to a structure :
.nf

	typedef struct s_xpparam {
		unsigned long flags;
	} xpparam_t;

.fi
that is used to specify parameters to be used by the file differential algorithm.
The
.I flags
field is a combination of the following flags :

.IP
.B XDF_NEED_MINIMAL
Requires the minimal edit script to be found by the algorithm (may be slow).

The
.I xecfg
parameter point to a structure :
.nf

	typedef struct s_xdemitconf {
		long ctxlen;
	} xdemitconf_t;

.fi
that is used to configure the algorithm responsible of the creation the the
differential file from an edit script. The
.I ctxlen
field is used to specify the amount of context to be emitted inside the
differential file (the value 3 is suggested for normal operations).
The parameter
.I ecb
is a pointer to a structure :
.nf

	typedef struct s_xdemitcb {
		void *priv;
		int (*outf)(void *, mmbuffer_t *, int);
	} xdemitcb_t;

.fi
that is used by the differential file creation algorithm to emit the created
data. The
.I priv
field is an opaque pointer to a user specified data, while the
.I outf
field point to a callback function that is called internally to emit algorithm
generated data rappresenting the differential file. The first parameter of the
callback is the same
.I priv
field specified inside the
.B xdemitcb_t
structure. The second parameter point to an array of
.B mmbuffer_t
(see above for a definition of the structure) whose element count is specified
inside the last parameter of the callback itself. The callback will always be
called with entire records (lines) and never a record (line) will be emitted
using two different callback calls. This is important because if the called will
use another memory file to store the result, by creating the target memory file with
.B XDL_MMF_ATOMIC
will guarantee the "atomicity" of the memory file itself.
The function returns 0 if succeeded or -1 if an error occurred.

.TP
.BI "int xdl_patch(mmfile_t *" mmf ", mmfile_t *" mmfp ", int " mode ", xdemitcb_t *" ecb ", xdemitcb_t *" rjecb ");"

Request to patch the memory file
.I mmf
using the patch file stored in
.IR mmfp .
The
.I mmf
memory file
.B is not
changed during the operation and can be considered as read only.
The
.I mode
parameter can be one of the following values :
.IP
.B XDL_PATCH_NORMAL
Perform standard patching like if the patch memory file
.I mmfp
has been created using
.I mmf
as "old" file.
.IP
.B XDL_PATCH_REVERSE
Apply the reverse patch. That means that the
.I mmf
memory file has to be considered as if it was specified as "new" file during
the differential operation (
.BR xdl_diff ()
). The result of the operation will then be the file content that was used
as "old" file during the differential operation.

The following flags can be specified (by or-ing them) to one of the above:
.IP
.B XDL_PATCH_IGNOREBSPACE
Ignore the whitespace at the beginning and the end of the line.

The
.I ecb
will be used by the patch algorithm to create the result file while the
.I rjecb
will be used to emit all differential chunks that cannot be applied.
Like explained above, callbacks are always called with entire records to guarantee
atomicity of the resulting output.
The function returns 0 if succeeded without performing any fuzzy hunk detection,
a positive value if it secceeded with fuzzy hunk detection or -1 if an error occurred
during the patch operation.

.TP
.BI "int xdl_merge3(mmfile_t *" mmfo ", mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", xdemitcb_t *" ecb ", xdemitcb_t *" rjecb ");"

Merges three files together. The
.I mmfo
file is the original one, while
.IR mmf1 " and " mmf2
are two modified versions of
.IR mmfo .
The function works by creating a differential between
.IR mmfo " and " mmf2
and by applying the resulting patch to
.IR mmf1 .
Because of this sequence,
.I mmf1
changes will be privileged against the ones of
.IR mmf2 .
The
.I ecb
will be used by the patch algorithm to create the result file while the
.I rjecb
will be used to emit all differential chunks that cannot be applied.
Like explained above, callbacks are always called with entire records to guarantee
atomicity of the resulting output.
The function returns 0 if succeeded or -1 if an error occurred during the patch operation.

.TP
.BI "int xdl_bdiff(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", bdiffparam_t const *" bdp ", xdemitcb_t *" ecb ");"

Request to create the difference between the two text memory files
.IR mmf1 " and " mmf2 .
The
.I mmf1
memory files is considered the "old" file while
.I mmf2
is considered the "new" file. So the function will create a patch file
that once applied to
.I mmf1
will give
.I mmf2
as result. Files
.IR mmf1 " and " mmf2
must be compact to make it easy and faster to perform the difference operation.
Functions are available to check for compactness (
.BR xdl_mmfile_iscompact ()
) and to make compact a non-compact file (
.BR xdl_mmfile_compact ()
). An example of how to create a compact memory file (described inside the test
subdirectory) is :
.nf

	int xdlt_load_mmfile(char const *fname, mmfile_t *mf, int binmode) {
		char cc;
		int fd;
		long size, bsize;
		char *blk;

		if (xdl_init_mmfile(mf, XDLT_STD_BLKSIZE, XDL_MMF_ATOMIC) < 0)
			return -1;
		if ((fd = open(fname, O_RDONLY)) == -1) {
			perror(fname);
			xdl_free_mmfile(mf);
			return -1;
		}
		if ((size = bsize = lseek(fd, 0, SEEK_END)) > 0 && !binmode) {
			if (lseek(fd, -1, SEEK_END) != (off_t) -1 &&
			    read(fd, &cc, 1) && cc != '\\n')
				bsize++;
		}
		lseek(fd, 0, SEEK_SET);
		if (!(blk = (char *) xdl_mmfile_writeallocate(mf, bsize))) {
			xdl_free_mmfile(mf);
			close(fd);
			return -1;
		}
		if (read(fd, blk, (size_t) size) != (size_t) size) {
			perror(fname);
			xdl_free_mmfile(mf);
			close(fd);
			return -1;
		}
		close(fd);
		if (bsize > size)
			blk[size] = '\\n';
		return 0;
	}

.fi
The
.I bdp
parameter points to a structure :
.nf

	typedef struct s_bdiffparam {
		long bsize;
	} bdiffparam_t;

.fi
that is used to pass information to the binary file differential algorithm.
The
.I bsize
parameter specify the size of the block that will be used to decompose
.I mmf1
during the block classification phase of the algorithm (see MacDonald paper).
Suggested values go from 16 to 64, with a preferred power of two characteristic.
The
.I ecb
parameter is used to pass the emission callback to the algorithm responsible
of the output file creation.
The function returns 0 if succeede or -1 if an error is occurred.

.TP
.BI "int xdl_bdiff_mb(mmbuffer_t *" mmb1 ", mmbuffer_t *" mmb2 ", bdiffparam_t const *" bdp ", xdemitcb_t *" ecb ");"

Same as
.BR xdl_bdiff ()
but it works on memory buffer directly. The
.BR xdl_bdiff ()
is implemented internally with a
.BR xdl_bdiff_mb ()
after having setup the two memory buffers from the passed memory files (that must be compact,
as described above). The memory buffer structure is defined as :
.nf

	typedef struct s_mmbuffer {
		char *ptr;
		long size;
	} mmbuffer_t;

.fi
An empty memory buffer is specified by setting the
.I ptr
member as
.B NULL
and the
.I size
member as zero. The reason of having this function is to avoid the memory file
preparation, that might involve copying memory from other sources. Using
the
.BR xdl_bdiff_mb (),
the caller can setup the two memory buffer by using, for example,
.BR mmap (2),
and hence avoiding unnecessary memory copies. The other parameters and the return value
of the function
.BR xdl_bdiff_mb ()
are the same as the ones already described in
.BR xdl_bdiff ().

.TP
.BI "int xdl_rabdiff(mmfile_t *" mmf1 ", mmfile_t *" mmf2 ", xdemitcb_t *" ecb ");"

Request to create the difference between the two text memory files
.IR mmf1 " and " mmf2
using the Rabin's polynomial fingerprinting algorithm. This algorithm typically
performs faster and produces smaller deltas, when compared to the XDelta-like one.
The
.I mmf1
memory files is considered the "old" file while
.I mmf2
is considered the "new" file. So the function will create a patch file
that once applied to
.I mmf1
will give
.I mmf2
as result. Files
.IR mmf1 " and " mmf2
must be compact to make it easy and faster to perform the difference operation.
Functions are available to check for compactness (
.BR xdl_mmfile_iscompact ()
) and to make compact a non-compact file (
.BR xdl_mmfile_compact ()
). The
.I ecb
parameter is used to pass the emission callback to the algorithm responsible
of the output file creation.
The function returns 0 if succeede or -1 if an error is occurred.

.TP
.BI "int xdl_rabdiff_mb(mmbuffer_t *" mmb1 ", mmbuffer_t *" mmb2 ", xdemitcb_t *" ecb ");"

Same as
.BR xdl_rabdiff ()
but it works on memory buffer directly. The memory buffer structure is defined as :
.nf

	typedef struct s_mmbuffer {
		char *ptr;
		long size;
	} mmbuffer_t;

.fi
An empty memory buffer is specified by setting the
.I ptr
member as
.B NULL
and the
.I size
member as zero. The reason of having this function is to avoid the memory file
preparation, that might involve copying memory from other sources. Using
the
.BR xdl_rabdiff_mb (),
the caller can setup the two memory buffer by using, for example,
.BR mmap (2),
and hence avoiding unnecessary memory copies. The other parameters and the return value
of the function
.BR xdl_rabdiff_mb ()
are the same as the ones already described in
.BR xdl_rabdiff ().

.TP
.BI "long xdl_bdiff_tgsize(mmfile_t *" mmfp ");"

Given a binary memory file patch, it returns the size that the result file
will have once the patch is applied to the target file. It can be used to
pre-allocate (or write-allocate) a memory block to store the patch result
so that a compact file will be available at the end of the operation. The
function returns the requested size, or -1 if an error occurred during the operation.

.TP
.BI "int xdl_bpatch(mmfile_t *" mmf ", mmfile_t *" mmfp ", xdemitcb_t *" ecb ");"

Request to patch the binary memory file
.I mmf
using the binary patch file stored in
.IR mmfp .
The
.I mmf
memory file
.B is not
changed during the operation and can be considered as read only. The binary
patch algorithm has no notion of context, so the patch operation cannot be
partial (either success or failure). The
.I ecb
parameter contain the callabck (see above for description) used by the binary
patch algorithm to emit the result file. The function returns 0 if succeeded
or -1 if an error occurred during the patch operation.

.SH SEE ALSO
Two papers drove the content of this library and these are :
.br
.IP o
.IR "File System Support for Delta Compression" " by " "Joshua P. MacDonald"
.BR http://www.xmailserver.org/xdfs.pdf
.br
.IP o
.IR "Fingerprinting by Random Polynomials" " by " "Michael O. Rabin"
.BR http://www.xmailserver.org/rabin.pdf
.br
.IP o
.IR "An O(ND) Difference Algorithm and Its Variations" " by " "Eugene W. Myers"
.BR http://www.xmailserver.org/diff2.pdf
.PP

Also usefull information can be looked up inside the
.B diffutil
GNU package :

.BR http://www.gnu.org/software/diffutils/diffutils.html

.SH LICENSE
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
A copy of the license is available at :

.BR http://www.gnu.org/copyleft/lesser.html

.SH AUTHOR
Developed by Davide Libenzi
.RB < davidel@xmailserver.org >

.SH AVAILABILITY
The latest version of
.B LibXDiff
can be found at :

.BR http://www.xmailserver.org/xdiff-lib.html

.SH BUGS
There are no known bugs.  Bug reports and comments to Davide Libenzi
.RB < davidel@xmailserver.org >