flat_xor_hd.c

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/*
 * Copyright 2014 Tushar Gohad
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice, this
 * list of conditions and the following disclaimer in the documentation and/or
 * other materials provided with the distribution.  THIS SOFTWARE IS PROVIDED BY
 * THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * liberasurecode flat_xor_hd backend
 *
 * vi: set noai tw=79 ts=4 sw=4:
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <xor_code.h>
 
#include "erasurecode.h"
#include "erasurecode_backend.h"
#include "erasurecode_helpers.h"
 
#define FLAT_XOR_LIB_MAJOR 1
#define FLAT_XOR_LIB_MINOR 0
#define FLAT_XOR_LIB_REV   0
#define FLAT_XOR_LIB_VER_STR "1.0"
#define FLAT_XOR_LIB_NAME "flat_xor_hd"
#if defined(__MACOS__) || defined(__MACOSX__) || defined(__OSX__) || defined(__APPLE__)
#define FLAT_XOR_SO_NAME "libXorcode" LIBERASURECODE_SO_SUFFIX ".dylib"
#else
#define FLAT_XOR_SO_NAME "libXorcode" LIBERASURECODE_SO_SUFFIX ".so.1"
#endif
#define DEFAULT_W 32
 
/* Forward declarations */
struct ec_backend_common backend_flat_xor_hd;
 
typedef xor_code_t* (*init_xor_hd_code_func)(int, int, int);
typedef void (*xor_code_encode_func)(xor_code_t *, char **, char **, int);
typedef int (*xor_code_decode_func)(xor_code_t *, char **, char **, int *, int, int);
typedef int (*xor_hd_fragments_needed_func)(xor_code_t *, int *, int *, int *);
 
struct flat_xor_hd_descriptor {
    xor_code_t *xor_desc;
    init_xor_hd_code_func init_xor_hd_code;
    xor_code_encode_func  xor_code_encode;
    xor_code_decode_func xor_code_decode;
    xor_hd_fragments_needed_func  xor_hd_fragments_needed;
};
 
static int flat_xor_hd_encode(void *desc,
                              char **data, char **parity, int blocksize)
{
    struct flat_xor_hd_descriptor *xdesc =
        (struct flat_xor_hd_descriptor *) desc;
 
    xor_code_t *xor_desc = (xor_code_t *) xdesc->xor_desc;
    xor_desc->encode(xor_desc, data, parity, blocksize);
    return 0;
}
 
static int flat_xor_hd_decode(void *desc,
                              char **data, char **parity, int *missing_idxs,
                              int blocksize)
{
    struct flat_xor_hd_descriptor *xdesc =
        (struct flat_xor_hd_descriptor *) desc;
 
    xor_code_t *xor_desc = (xor_code_t *) xdesc->xor_desc;
    return xor_desc->decode(xor_desc, data, parity, missing_idxs, blocksize, 1);
}
 
static int flat_xor_hd_reconstruct(void *desc,
                                   char **data, char **parity, int *missing_idxs,
                                   int destination_idx, int blocksize)
{
    struct flat_xor_hd_descriptor *xdesc =
        (struct flat_xor_hd_descriptor *) desc;
 
    xor_code_t *xor_desc = (xor_code_t *) xdesc->xor_desc;
    return xor_reconstruct_one(xor_desc, data, parity,
                               missing_idxs, destination_idx, blocksize);
}
 
static int flat_xor_hd_check_reconstruct_fragments(void *desc,
                                                   int *missing_idxs,
                                                   int destination_idx)
{
    struct flat_xor_hd_descriptor *xdesc =
        (struct flat_xor_hd_descriptor *) desc;
 
    xor_code_t *xor_desc = (xor_code_t *) xdesc->xor_desc;
 
    struct ec_bm missing_bm = NEW_BM;
    convert_list_to_bitmap(missing_idxs, &missing_bm);
    int num_available = xor_desc->k + xor_desc->m;
    for (int i = 0; i < EC_MAX_FRAGMENTS; i++)
        if (bm_get_value(&missing_bm, i))
            num_available--;
 
    if (xor_desc->hd == 3) {
        if (num_available < 2)
            return -EINSUFFFRAGS;
 
        if (xor_desc->m == 5) {
            if ((xor_desc->k == 8 || xor_desc->k == 9) && num_available < 3)
                return -EINSUFFFRAGS;
            if (xor_desc->k == 10 && num_available < 4)
                return -EINSUFFFRAGS;
        } else if (xor_desc->m == 6) {
            if (xor_desc->k >= 9 && xor_desc->k <= 11 && num_available < 3)
                return -EINSUFFFRAGS;
            if (xor_desc->k >= 12 && xor_desc->k <= 14 && num_available < 4)
                return -EINSUFFFRAGS;
            if (xor_desc->k == 15 && num_available < 5)
                return -EINSUFFFRAGS;
        }
    } else { /* hd == 4 */
        if (num_available < 3)
            return -EINSUFFFRAGS;
 
        if (xor_desc->m == 5) {
            if ((xor_desc->k == 7 || xor_desc->k == 8) && num_available < 4)
                return -EINSUFFFRAGS;
            if (xor_desc->k + xor_desc->m - num_available > 9)
                return -EINSUFFFRAGS;
        } else if (xor_desc->m == 6) {
            if (num_available < (xor_desc->k + xor_desc->m) / 2 - 3)
                return -EINSUFFFRAGS;
        }
    }
    return 0;
}
 
static int flat_xor_hd_min_fragments(void *desc,
                                     int *missing_idxs, int *fragments_to_exclude,
                                     int *fragments_needed)
{
    struct flat_xor_hd_descriptor *xdesc =
        (struct flat_xor_hd_descriptor *) desc;
 
    xor_code_t *xor_desc = (xor_code_t *) xdesc->xor_desc;
    xor_desc->fragments_needed(xor_desc, missing_idxs, fragments_to_exclude, fragments_needed);
    return 0;
}
 
static int
flar_xor_hd_element_size(void* desc)
{
    return DEFAULT_W;
}
 
static void * flat_xor_hd_init(struct ec_backend_args *args, void *sohandle)
{
    int k = args->uargs.k;
    int m = args->uargs.m;
    int hd = args->uargs.hd;
 
    xor_code_t *xor_desc = NULL;
    struct flat_xor_hd_descriptor *bdesc = NULL;
 
    /* store w back in args so upper layer can get to it */
    args->uargs.w = DEFAULT_W;
 
    /* init xor_code_t descriptor */
    xor_desc = init_xor_hd_code(k, m, hd);
    if (NULL == xor_desc) {
        return NULL;
    }
 
    /* fill in flat_xor_hd_descriptor */
    bdesc = (struct flat_xor_hd_descriptor *)
        malloc(sizeof(struct flat_xor_hd_descriptor));
    if (NULL == bdesc) {
        free (xor_desc);
        return NULL;
    }
 
    bdesc->xor_desc = xor_desc;
 
    return (void *) bdesc;
}
 
static int flat_xor_hd_exit(void *desc)
{
    struct flat_xor_hd_descriptor *bdesc =
        (struct flat_xor_hd_descriptor *) desc;
 
    free (bdesc->xor_desc);
    free (bdesc);
    return 0;
}
 
/*
 * For the time being, we only claim compatibility with versions that
 * match exactly
 */
static bool flat_xor_is_compatible_with(uint32_t version) {
    return version == backend_flat_xor_hd.ec_backend_version;
}
 
static struct ec_backend_op_stubs flat_xor_hd_op_stubs = {
    .INIT                       = flat_xor_hd_init,
    .EXIT                       = flat_xor_hd_exit,
    .ISSYSTEMATIC               = 1,
    .ENCODE                     = flat_xor_hd_encode,
    .DECODE                     = flat_xor_hd_decode,
    .FRAGSNEEDED                = flat_xor_hd_min_fragments,
    .RECONSTRUCT                = flat_xor_hd_reconstruct,
    .ELEMENTSIZE                = flar_xor_hd_element_size,
    .ISCOMPATIBLEWITH           = flat_xor_is_compatible_with,
    .GETMETADATASIZE            = get_backend_metadata_size_zero,
    .GETENCODEOFFSET            = get_encode_offset_zero,
    .CHECKRECONSTRUCTFRAGMENTS  = flat_xor_hd_check_reconstruct_fragments,
};
 
__attribute__ ((visibility ("internal")))
struct ec_backend_common backend_flat_xor_hd = {
    .id                         = EC_BACKEND_FLAT_XOR_HD,
    .name                       = FLAT_XOR_LIB_NAME,
    .soname                     = FLAT_XOR_SO_NAME,
    .soversion                  = FLAT_XOR_LIB_VER_STR,
    .ops                        = &flat_xor_hd_op_stubs,
    .ec_backend_version         = _VERSION(FLAT_XOR_LIB_MAJOR,
                                           FLAT_XOR_LIB_MINOR,
                                           FLAT_XOR_LIB_REV),
};