/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
#ident "$Id$"
#ident "Copyright (c) 2007-2012 Tokutek Inc.  All rights reserved."
#ident "The technology is licensed by the Massachusetts Institute of Technology, Rutgers State University of New Jersey, and the Research Foundation of State University of New York at Stony Brook under United States of America Serial No. 11/760379 and to the patents and/or patent applications resulting from it."

#include <ft-internal.h>
#include <db.h>

/*
 * ft-node-deserialize.c -
 *      This file contains functions used by deserializtion
 *  code paths in and out of the engine.  The functions can,
 *  essentially, be broken up into two types.  Some of these
 *  functions return error codes based expected values inside
 *  the fractal tree node, others merely read the specific 
 *  quantities of bytes out of the buffer.  It is expeceted
 *  that these will be called in the correct order by users
 *  of these functions/this API.
 *
 */

// Sets initial values for the given fractal tree node to be
// deserialized
void
initialize_ftnode(FTNODE node, BLOCKNUM blocknum)
{
    node->fullhash = 0xDEADBEEF; // <CER> Is this 'spoof' ok?
    node->thisnodename = blocknum;
    node->dirty = 0;
    node->bp = NULL;
    // <CER> Can we use this initialization as a correctness assert in
    // a later function?
    node->layout_version_read_from_disk = 0;
}

/************************
 * TODO: In other deserialization code, we check the rb size member.  We
 * verify that it is greater than or equal to 24.  Ignoring this magic
 * number for a moment, should we put this check in its own function? *
*************************/


// Read and check the 'magic' bytes on disk.  Returns an error if
// the magic does not match.
int
read_and_check_magic(struct rbuf *rb)
{
    int r = 0;
    bytevec magic;
    rbuf_literal_bytes(rb, &magic, 8);
    if (memcmp(magic, "tokuleaf", 8)!=0 &&
        memcmp(magic, "tokunode", 8)!=0) {
        r = DB_BADFORMAT; // TODO: Return more meaningful error.
    }

    return r;
}

// Read the version number from the given buffer
// and returns an error if the version is too old.
int
read_and_check_version(FTNODE node, struct rbuf *rb)
{
    int r = 0;
    int version = rbuf_int(rb);
    node->layout_version_read_from_disk = version;
    if (version < FT_LAYOUT_MIN_SUPPORTED_VERSION) {
        r = 1; // TODO: Better error reporting.
    }

    return r;
}

// Reads the basic version, build, and child info from
// the given buffer.
void
read_node_info(FTNODE node, struct rbuf *rb, int version)
{
    node->layout_version = version;
    node->layout_version_original = rbuf_int(rb);
    node->build_id = rbuf_int(rb);
    node->n_children = rbuf_int(rb);
}

// Allocates the partitions based on the given node's nubmer
// of children.  It then reads, out of the given buffer,
// the start and size of each child partition.
// TODO: Should these be two seperate functions?
void
allocate_and_read_partition_offsets(FTNODE node, struct rbuf *rb, FTNODE_DISK_DATA *ndd)
{
    XMALLOC_N(node->n_children, node->bp);
    // TODO: Fix this to use xmalloc_n
    XMALLOC_N(node->n_children, *ndd);
    // Read the partition locations.
    for (int i = 0; i < node->n_children; i++) {
        BP_START(*ndd, i) = rbuf_int(rb);
        BP_SIZE (*ndd, i) = rbuf_int(rb);
    }
}

// Compares checksum of stored (in the given buffer) checksum
// and the checksum of the buffer itself.  If these are NOT
// equal, this function returns an appropriate error code.
int
check_node_info_checksum(struct rbuf *rb)
{
    int r = 0;
    // Verify checksum of header stored.
    uint32_t checksum = x1764_memory(rb->buf, rb->ndone);
    uint32_t stored_checksum = rbuf_int(rb);

    if (stored_checksum != checksum) {
        // TODO: dump_bad_block(rb->buf, rb->size);
        r = TOKUDB_BAD_CHECKSUM;
    }

    return r;
}

// Reads node info from older (13 and 14) fractal tree nodes
// out of the given buffer.
void
read_legacy_node_info(FTNODE node, struct rbuf *rb, int version)
{
    (void)rbuf_int(rb); // 1. nodesize
    node->flags = rbuf_int(rb);    // 2. flags
    node->height = rbuf_int(rb);   // 3. height
    
    // If the version is less than 14, there are two extra ints here.
    // we would need to ignore them if they are there.
    if (version == FT_LAYOUT_VERSION_13) {
        (void) rbuf_int(rb);       // 4. rand4
        (void) rbuf_int(rb);       // 5. local
    }
}

// Assuming the given buffer is in the correct position,
// this checks to see if the stored checksum matches the
// checksum of the entire buffer.
int
check_legacy_end_checksum(struct rbuf *rb)
{
    int r = 0;
    uint32_t expected_xsum = rbuf_int(rb);
    uint32_t actual_xsum = x1764_memory(rb->buf, rb->size - 4);
    if (expected_xsum != actual_xsum) {
        r = TOKUDB_BAD_CHECKSUM;
    }
    
    return r;
}
