ext.h

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#pragma once
/*
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** 'compositing' using talloc structures
 *
 * These allow multiple variable length memory areas to be appended to
 * talloced structures.  Extensions can either contain a header in which
 * case the exact length is recorded, or they can be of a fixed size.
 *
 * The structure being extended must be padded to a multiple of FR_EXT_ALIGNMENT.
 * i.e. CC_HINT(aligned(FR_EXT_ALIGNMENT)).
 *
 * It is strongly recommended that extended structures are allocated in a
 * talloc_pool() to avoid the overhead of multiple reallocs.
 *
 * @file src/lib/util/ext.h
 *
 * @copyright 2020 The FreeRADIUS server project
 * @copyright 2020 Arran Cudbard-Bell <a.cudbardb@freeradius.org>
 */
RCSIDH(ext_h, "$Id: 8f485ee92039de1ea8fb6df5deaf0d960e8544e1 $")
 
#include <freeradius-devel/util/table.h>
#include <limits.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
/** The alignment of object extension structures
 *
 */
#ifdef __WORD_SIZE
#  if __WORD_SIZE < 4
#    define FR_EXT_ALIGNMENT    sizeof(uint32_t)
#  else
#    define FR_EXT_ALIGNMENT    __WORD_SIZE             /* From limits.h */
#  endif
#else
#  define FR_EXT_ALIGNMENT      sizeof(uint64_t)
#endif
 
typedef struct fr_ext_s fr_ext_t;
 
/** Function for pre-allocating extension memory for extensions before they're copied
 *
 * @param[in] def               Extension definitions.
 * @param[in,out] dst_chunk_p   to add extensions to.
 * @param[in] ext               that's being copied.
 * @param[in] src_ext_ptr       Pointer for the src extension.
 * @param[in] src_ext_len       Length of the src extension.
 * @return
 *      - NULL on error.
 *      - Pointer to the new extension on success.
 */
typedef void *(* fr_ext_alloc_t)(fr_ext_t const *def, TALLOC_CTX **dst_chunk_p,
                                 int ext, void *src_ext_ptr, size_t src_ext_len);
 
/** Function for re-populating extensions after they're copied
 *
 * @param[in] ext               that's being copied.
 * @param[in] dst_chunk         Talloc chunk we're copying to.
 * @param[in] dst_ext_ptr       Pointer to the dst extension to populate.
 * @param[in] dst_ext_len       The length of the dst extension.
 * @param[in] src_chunk         Talloc chunk we're copying from.
 * @param[in] src_ext_ptr       Pointer for the src extension.
 * @param[in] src_ext_len       Length of the src extension.
 * @return
 *      - NULL on error.
 *      - Pointer to the new extension on success.
 */
typedef int (* fr_ext_copy_t)(int ext,
                              TALLOC_CTX *dst_chunk,
                              void *dst_ext_ptr, size_t dst_ext_len,
                              TALLOC_CTX const *src_chunk,
                              void *src_ext_ptr, size_t src_ext_len);
 
/** Function for re-establishing internal consistency on realloc
 *
 * In some cases the chunk may cache a pointer to an extension.
 * On realloc this pointer may be invalidated.  This provides a
 * callback to fixup consistency issues after a realloc.
 *
 * @param[in] ext               that's being copied.
 * @param[in] chunk             Talloc chunk.
 * @param[in] ext_ptr           Pointer to the extension to fixup.
 * @param[in] ext_len           The length of the extension to fixup.
 * @return
 *      - NULL on error.
 *      - Pointer to the new extension on success.
 */
typedef int (* fr_ext_fixup_t)(int ext, TALLOC_CTX *chunk,
                               void *ext_ptr, size_t ext_len);
 
/** Additional information for a given extension
 */
typedef struct {
        size_t                  min;                    //!< Minimum size of extension.
        bool                    has_hdr;                //!< Additional metadata should be allocated before
                                                        ///< the extension data to record the exact length
                                                        ///< of the extension.
        bool                    can_copy;               //!< Copying this extension between structs is allowed.
 
        fr_ext_alloc_t          alloc;                  //!< Override the normal alloc operation with a callback.
        fr_ext_copy_t           copy;                   //!< Override the normal copy operation with a callback.
        fr_ext_fixup_t          fixup;                  //!< Callback for fixing up internal consistency issues.
} fr_ext_info_t;
 
/** Structure to define a set of extensions
 *
 */
struct fr_ext_s {
        size_t                  offset_of_exts;         //!< Where in the extended struct the extensions array starts.
        fr_table_num_ordered_t const    *name_table;    //!< String identifiers for the extensions.
        size_t                  *name_table_len;        //!< How many extensions there are in the table.
        int                     max;                    //!< The highest extension value.
        fr_ext_info_t const     *info;                  //!< Additional information about each extension.
};
 
/** Optional extension header struct
 *
 */
typedef struct {
        size_t                  len;                    //!< Length of extension data.
        uint8_t                 data[];                 //!< Extension data
} CC_HINT(aligned(FR_EXT_ALIGNMENT)) fr_ext_hdr_t;
 
static inline CC_HINT(always_inline) uint8_t *fr_ext_offsets(fr_ext_t const *def, TALLOC_CTX const *chunk)
{
        return (uint8_t *)(((uintptr_t)chunk) + def->offset_of_exts);
}
 
/** Return a pointer to an extension in a chunk
 *
 */
static inline CC_HINT(always_inline) void *fr_ext_ptr(TALLOC_CTX const *chunk, size_t offset, bool has_hdr)
{
        uintptr_t out;
 
        out = (uintptr_t)chunk;                                 /* chunk start */
        out += offset * FR_EXT_ALIGNMENT;                       /* offset described by the extension */
        out += sizeof(fr_ext_hdr_t) * (has_hdr == true);        /* data field offset by length header */
 
        return (void *)out;
}
 
void    *fr_ext_alloc_size(fr_ext_t const *def, TALLOC_CTX **chunk_p, int ext, size_t ext_len);
 
size_t  fr_ext_len(fr_ext_t const *def, TALLOC_CTX const *chunk_in, int ext);
 
void    *fr_ext_copy(fr_ext_t const *def, TALLOC_CTX **chunk_out, TALLOC_CTX  const *chunk_in, int ext);
 
int     fr_ext_copy_all(fr_ext_t const *def, TALLOC_CTX **chunk_out, TALLOC_CTX  const *chunk_in);
 
void    fr_ext_debug(fr_ext_t const *def, char const *name, TALLOC_CTX const *chunk);
 
#ifdef __cplusplus
}
#endif