nbt_util.c

/*
 * -----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Lukas Niederbremer <webmaster@flippeh.de> and Clark Gaebel <cg.wowus.cg@gmail.com>
 * wrote this file. As long as you retain this notice you can do whatever you
 * want with this stuff. If we meet some day, and you think this stuff is worth
 * it, you can buy us a beer in return.
 * -----------------------------------------------------------------------------
 */
#include "nbt.h"

#include <string.h>

const char* nbt_type_to_string(nbt_type t)
{
#define DEF_CASE(name) case name: return #name;
    switch(t)
    {
        case 0: return "TAG_END";
        DEF_CASE(TAG_BYTE);
        DEF_CASE(TAG_SHORT);
        DEF_CASE(TAG_INT);
        DEF_CASE(TAG_LONG);
        DEF_CASE(TAG_FLOAT);
        DEF_CASE(TAG_DOUBLE);
        DEF_CASE(TAG_BYTE_ARRAY);
        DEF_CASE(TAG_STRING);
        DEF_CASE(TAG_LIST);
        DEF_CASE(TAG_COMPOUND);
    default:
        return "TAG_UNKNOWN";
    }
#undef DEF_CASE
}

const char* nbt_error_to_string(nbt_status s)
{
    switch(s)
    {
    case NBT_OK:
        return "No error.";
    case NBT_ERR:
        return "NBT tree is corrupt.";
    case NBT_EMEM:
        return "Out of memory. You should buy some RAM.";
    case NBT_EIO:
        return "IO Error. Nonexistant/corrupt file?";
    case NBT_EZ:
        return "Fatal zlib error. Corrupt file?";
    default:
        return "Unknown error.";
    }
}

/* Returns 1 if one is null and the other isn't. */
static int safe_strcmp(const char* a, const char* b)
{
    if(a == NULL)
        return b != NULL; /* a is NULL, b is not */

    if(b == NULL) /* b is NULL, a is not */
        return 1;

    return strcmp(a, b);
}

#ifndef min
#define min(a, b) ((a) < (b) ? (a) : (b))
#endif

#ifndef max
#define max(a, b) ((a) > (b) ? (a) : (b))
#endif

static inline bool floats_are_close(double a, double b)
{
    double epsilon = 0.000001;
    return (min(a, b) + epsilon) >= max(a, b);
}

bool nbt_eq(const nbt_node* restrict a, const nbt_node* restrict b)
{
    if(a->type != b->type)
        return false;

    if(safe_strcmp(a->name, b->name) != 0)
        return false;

    switch(a->type)
    {
    case TAG_BYTE:
        return a->payload.tag_byte == b->payload.tag_byte;
    case TAG_SHORT:
        return a->payload.tag_short == b->payload.tag_short;
    case TAG_INT:
        return a->payload.tag_int == b->payload.tag_int;
    case TAG_LONG:
        return a->payload.tag_long == b->payload.tag_long;
    case TAG_FLOAT:
        return floats_are_close((double)a->payload.tag_float, (double)b->payload.tag_float);
    case TAG_DOUBLE:
        return floats_are_close(a->payload.tag_double, b->payload.tag_double);
    case TAG_BYTE_ARRAY:
        if(a->payload.tag_byte_array.length != b->payload.tag_byte_array.length) return false;
        return memcmp(a->payload.tag_byte_array.data,
                      b->payload.tag_byte_array.data,
                      a->payload.tag_byte_array.length) == 0;
    case TAG_STRING:
        return strcmp(a->payload.tag_string, b->payload.tag_string) == 0;
    case TAG_LIST:
    case TAG_COMPOUND:
    {
        struct list_head *ai, *bi;
        struct tag_list *alist = a->type == TAG_LIST? a->payload.tag_list.list : a->payload.tag_compound;
        struct tag_list *blist = b->type == TAG_LIST? b->payload.tag_list.list : b->payload.tag_compound;

        for(ai = alist->entry.flink, bi = blist->entry.flink;
            ai != &alist->entry &&   bi != &blist->entry;
            ai = ai->flink,                        bi = bi->flink)
        {
            struct tag_list* ae = list_entry(ai, struct tag_list, entry);
            struct tag_list* be = list_entry(bi, struct tag_list, entry);

            if(!nbt_eq(ae->data, be->data))
                return false;
        }

        /* if there are still elements left in either list... */
        if(ai != &alist->entry || bi != &blist->entry)
            return false;

        return true;
    }

    default: /* wtf invalid type */
        return false;
    }
}