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Callback on include #727

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37 changes: 33 additions & 4 deletions docs/capi.rst
Original file line number Diff line number Diff line change
Expand Up @@ -69,10 +69,14 @@ However, if you want to fetch the imported rules from another source (eg: from a
database or remote service), a callback function can be set with
:c:func:`yr_compiler_set_include_callback`.
The callback receives the following parameters:
*``include_name``: name of the requested file.
*``calling_rule_filename``: the requesting file name (NULL if not a file).
*``calling_rule_namespace``: namespace (NULL if undefined).
And should return the requested file as a string.
* ``include_name``: name of the requested file.
* ``calling_rule_filename``: the requesting file name (NULL if not a file).
* ``calling_rule_namespace``: namespace (NULL if undefined).
* ``user_data`` pointer is the same you passed to
:c:func:`yr_compiler_set_include_callback`.
It should return the requested file's content as a string. The memory for this string
should be allocated by the callback function (yr_malloc can be used) but will
be automatically freed by the yara compiler.

The callback function has the following prototype:

Expand Down Expand Up @@ -695,6 +699,31 @@ Functions
Enables the specified rule. After being disabled with :c:func:`yr_rule_disable`
a rule can be enabled again by using this function.

.. c:function:: void* yr_calloc(size_t count, size_t size);
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Instead of exposing all these functions as part of the API I would do something simpler but even more flexible. Add an argument to yr_compiler_set_include_callback which is a pointer to the free function that YARA should use to deallocate the memory returned by the callback. This way the program can use whatever allocator it wants, as long as the program provides the appropriate free function. The program could even use a statically allocated buffer and pass YARA a NULL instead of a pointer to the free function, indicating the buffer don't need to be de-allocated at all. For example:

typedef  void (*YR_COMPILER_INCLUDE_FREE_FUNC) (void*)

YR_API void yr_compiler_set_include_callback(
     YR_COMPILER* compiler,
     YR_COMPILER_INCLUDE_CALLBACK_FUNC include_callback,
     YR_COMPILER_INCLUDE_FREE_FUNC include_free,
     void* user_data)


Cross-platform wrapper for HeapAlloc on Windows and calloc on other platforms.

.. c:function:: void* yr_malloc(size_t size);

Cross-platform wrapper for HeapAlloc on Windows and malloc on other platforms.

.. c:function:: void* yr_realloc(void* ptr, size_t size);

Cross-platform wrapper for HeapReAlloc on Windows and realloc on other platforms.

.. c:function:: void yr_free(void* ptr);

Cross-platform wrapper for HeapFree on Windows and free on other platforms.

.. c:function:: char* yr_strdup(const char *str);

Allocates a new buffer the same size as str and copies str to the new buffer.

.. c:function:: char* yr_strdup(const char *str, size_t n);

Allocates a new buffer of size n and copies the n first character of str.


Error codes
-----------

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2 changes: 1 addition & 1 deletion libyara/compiler.c
Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,7 @@ YR_API void yr_compiler_set_include_callback(
void* user_data)
{
compiler->include_callback = include_callback;
compiler->user_data = user_data;
compiler->incl_clbk_user_data = user_data;
}


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1 change: 1 addition & 0 deletions libyara/include/yara.h
Original file line number Diff line number Diff line change
Expand Up @@ -39,5 +39,6 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "yara/error.h"
#include "yara/stream.h"
#include "yara/hash.h"
#include "yara/mem.h"

#endif
1 change: 1 addition & 0 deletions libyara/include/yara/compiler.h
Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,7 @@ typedef struct _YR_COMPILER

char include_base_dir[MAX_PATH];
void* user_data;
void* incl_clbk_user_data;

YR_COMPILER_CALLBACK_FUNC callback;
YR_COMPILER_INCLUDE_CALLBACK_FUNC include_callback;
Expand Down
13 changes: 7 additions & 6 deletions libyara/include/yara/mem.h
Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#define YR_MEM_H

#include <stdio.h>
#include <yara/utils.h>

#ifdef DMALLOC

Expand All @@ -45,24 +46,24 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#else

void* yr_calloc(
YR_API void* yr_calloc(
size_t count,
size_t size);

void* yr_malloc(
YR_API void* yr_malloc(
size_t size);

void* yr_realloc(
YR_API void* yr_realloc(
void* ptr,
size_t size);

void yr_free(
YR_API void yr_free(
void *ptr);

char* yr_strdup(
YR_API char* yr_strdup(
const char *str);

char* yr_strndup(
YR_API char* yr_strndup(
const char *str, size_t n);

#endif
Expand Down
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