nbt_treeops.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 <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

/* strdup isn't standard. GNU extension. */
static inline char* __strdup(const char* s)
{
    char* r = malloc(strlen(s) + 1);
    if(r == NULL) return NULL;

    strcpy(r, s);
    return r;
}

#define CHECKED_MALLOC(var, n, on_error) do { \
    if((var = malloc(n)) == NULL)             \
    {                                         \
        errno = NBT_EMEM;                     \
        on_error;                             \
    }                                         \
} while(0)

void nbt_free_list(struct tag_list* list)
{
    if (!list)
        return;

    struct list_head* current;
    struct list_head* temp;
    list_for_each_safe(current, temp, &list->entry)
    {
        struct tag_list* entry = list_entry(current, struct tag_list, entry);

        nbt_free(entry->data);
        free(entry);
    }

    free(list);
}

void nbt_free(nbt_node* tree)
{
    if(tree == NULL) return;

    if(tree->type == TAG_LIST || tree->type == TAG_COMPOUND)
        nbt_free_list(tree->payload.tag_list);

    else if(tree->type == TAG_BYTE_ARRAY)
        free(tree->payload.tag_byte_array.data);

    else if(tree->type == TAG_STRING)
        free(tree->payload.tag_string);

    free(tree->name);
    free(tree);
}

static struct tag_list* clone_list(struct tag_list* list)
{
    /* even empty lists are valid pointers! */
    assert(list);

    struct tag_list* ret;
    CHECKED_MALLOC(ret, sizeof *ret, goto clone_error);

    INIT_LIST_HEAD(&ret->entry);
    ret->data = NULL;

    struct list_head* pos;
    list_for_each(pos, &list->entry)
    {
        struct tag_list* current = list_entry(pos, struct tag_list, entry);
        struct tag_list* new;

        CHECKED_MALLOC(new, sizeof *new, goto clone_error);

        new->data = nbt_clone(current->data);

        if(new->data == NULL)
        {
            free(new);
            goto clone_error;
        }

        list_add_tail(&new->entry, &ret->entry);
    }

    return ret;

clone_error:
    nbt_free_list(ret);
    return NULL;
}

/* same as strdup, but handles NULL gracefully */
static inline char* safe_strdup(const char* s)
{
    return s ? __strdup(s) : NULL;
}

nbt_node* nbt_clone(nbt_node* tree)
{
    if(tree == NULL) return NULL;
    assert(tree->type != TAG_INVALID);

    nbt_node* ret;
    CHECKED_MALLOC(ret, sizeof *ret, return NULL);

    ret->type = tree->type;
    ret->name = safe_strdup(tree->name);

    if(tree->name && ret->name == NULL) goto clone_error;

    if(tree->type == TAG_STRING)
    {
        ret->payload.tag_string = __strdup(tree->payload.tag_string);
        if(ret->payload.tag_string == NULL) goto clone_error;
    }

    else if(tree->type == TAG_BYTE_ARRAY)
    {
        unsigned char* newbuf;
        CHECKED_MALLOC(newbuf, tree->payload.tag_byte_array.length, goto clone_error);

        memcpy(newbuf,
               tree->payload.tag_byte_array.data,
               tree->payload.tag_byte_array.length);

        ret->payload.tag_byte_array.data   = newbuf;
        ret->payload.tag_byte_array.length = tree->payload.tag_byte_array.length;
    }

    else if(tree->type == TAG_LIST || tree->type == TAG_COMPOUND)
    {
        ret->payload.tag_list = clone_list(tree->payload.tag_list);
        if(ret->payload.tag_list == NULL) goto clone_error;
    }
    else
    {
        ret->payload = tree->payload;
    }

    return ret;

clone_error:
    if(ret) free(ret->name);

    free(ret);
    return NULL;
}

bool nbt_map(nbt_node* tree, nbt_visitor_t v, void* aux)
{
    assert(v);

    if(tree == NULL)  return true;
    if(!v(tree, aux)) return false;

    /* And if the item is a list or compound, recurse through each of their elements. */
    if(tree->type == TAG_LIST || tree->type == TAG_COMPOUND)
    {
        struct list_head* pos;

        list_for_each(pos, &tree->payload.tag_list->entry)
            if(!nbt_map(list_entry(pos, struct tag_list, entry)->data, v, aux))
                return false;
    }

    return true;
}

/* Only returns NULL on error. An empty list is still a valid pointer */
static struct tag_list* filter_list(const struct tag_list* list, nbt_predicate_t predicate, void* aux)
{
    assert(list);

    struct tag_list* ret;
    CHECKED_MALLOC(ret, sizeof *ret, goto filter_error);

    ret->data = NULL;
    INIT_LIST_HEAD(&ret->entry);

    const struct list_head* pos;
    list_for_each(pos, &list->entry)
    {
        const struct tag_list* p = list_entry(pos, struct tag_list, entry);

        nbt_node* new_node = nbt_filter(p->data, predicate, aux);

        if(errno != NBT_OK)  goto filter_error;
        if(new_node == NULL) continue;

        struct tag_list* new_entry;
        CHECKED_MALLOC(new_entry, sizeof *new_entry, goto filter_error);

        new_entry->data = new_node;
        list_add_tail(&new_entry->entry, &ret->entry);
    }

    return ret;

filter_error:
    if(errno == NBT_OK)
        errno = NBT_EMEM;

    nbt_free_list(ret);
    return NULL;
}

nbt_node* nbt_filter(const nbt_node* tree, nbt_predicate_t filter, void* aux)
{
    assert(filter);

    errno = NBT_OK;

    if(tree == NULL)       return NULL;
    if(!filter(tree, aux)) return NULL;

    nbt_node* ret;
    CHECKED_MALLOC(ret, sizeof *ret, goto filter_error);

    ret->type = tree->type;
    ret->name = safe_strdup(tree->name);

    if(tree->name && ret->name == NULL) goto filter_error;

    if(tree->type == TAG_STRING)
    {
        ret->payload.tag_string = __strdup(tree->payload.tag_string);
        if(ret->payload.tag_string == NULL) goto filter_error;
    }

    else if(tree->type == TAG_BYTE_ARRAY)
    {
        CHECKED_MALLOC(ret->payload.tag_byte_array.data,
                       tree->payload.tag_byte_array.length,
                       goto filter_error);

        memcpy(ret->payload.tag_byte_array.data,
               tree->payload.tag_byte_array.data,
               tree->payload.tag_byte_array.length);

        ret->payload.tag_byte_array.length = tree->payload.tag_byte_array.length;
    }

    /* Okay, we want to keep this node, but keep traversing the tree! */
    else if(tree->type == TAG_LIST || tree->type == TAG_COMPOUND)
    {
        ret->payload.tag_list = filter_list(tree->payload.tag_list, filter, aux);
        if(ret->payload.tag_list == NULL) goto filter_error;
    }
    else
    {
        ret->payload = tree->payload;
    }

    return ret;

filter_error:
    if(errno == NBT_OK)
        errno = NBT_EMEM;

    if(ret) free(ret->name);

    free(ret);
    return NULL;
}

nbt_node* nbt_filter_inplace(nbt_node* tree, nbt_predicate_t filter, void* aux)
{
    assert(filter);

    if(tree == NULL)               return                 NULL;
    if(!filter(tree, aux))         return nbt_free(tree), NULL;
    if(tree->type != TAG_LIST &&
       tree->type != TAG_COMPOUND) return tree;

    struct list_head* pos;
    struct list_head* n;

    list_for_each_safe(pos, n, &tree->payload.tag_list->entry)
    {
        struct tag_list* cur = list_entry(pos, struct tag_list, entry);

        cur->data = nbt_filter_inplace(cur->data, filter, aux);

        if(cur->data == NULL)
        {
            list_del(pos);
            free(cur);
        }
    }

    return tree;
}

nbt_node* nbt_find(nbt_node* tree, nbt_predicate_t predicate, void* aux)
{
    if(tree == NULL)                  return NULL;
    if(predicate(tree, aux))          return tree;
    if(tree->type != TAG_LIST &&
       tree->type != TAG_COMPOUND)    return NULL;

    struct list_head* pos;
    list_for_each(pos, &tree->payload.tag_list->entry)
    {
        struct tag_list* p = list_entry(pos, struct tag_list, entry);
        struct nbt_node* found;

        if((found = nbt_find(p->data, predicate, aux)))
            return found;
    }

    return NULL;
}

static bool names_are_equal(const nbt_node* node, void* vname)
{
    const char* name = vname;

    assert(node);

    if(name == NULL && node->name == NULL)
        return true;

    if(name == NULL || node->name == NULL)
        return false;

    return strcmp(node->name, name) == 0;
}

nbt_node* nbt_find_by_name(nbt_node* tree, const char* name)
{
    return nbt_find(tree, &names_are_equal, (void*)name);
}

/*
 * Returns the index of the first occurence of `c' in `s', or the index of the
 * NULL-terminator. Whichever comes first.
 */
static size_t index_of(const char* s, char c)
{
    const char* p = s;

    for(; *p; p++)
        if(*p == c)
            return p - s;

    return p - s;
}

/*
 * Pretends that s1 ends after `len' bytes, and does a strcmp.
 */
static int partial_strcmp(const char* s1, size_t len, const char* s2)
{
    assert(s1);

    if(s2 == NULL) return len != 0;

    int r;
    if((r = strncmp(s1, s2, len)) != 0)
        return r;

    /* at this point, the first `len' characters match. Check for NULL. */
    return s2[len] != '\0';
}

/*
 * Format:
 *   current_name.[other shit]
 * OR
 *   current_name'\0'
 *
 * where current_name can be empty.
 */
nbt_node* nbt_find_by_path(nbt_node* tree, const char* path)
{
    assert(tree);
    assert(path);

    /* The end of the "current_name" piece. */
    size_t e = index_of(path, '.');

    bool names_match = partial_strcmp(path, e, tree->name) == 0;

    /* Names don't match. These aren't the droids you're looking for. */
    if(!names_match)                                         return NULL;

    /* We're a leaf node, and the names match. Wooo found it. */
    if(path[e] == '\0')                                     return tree;

    /*
     * Initial names match, but the string isn't at the end. We're expecting a
     * list, but haven't hit one.
     */
    if(tree->type != TAG_LIST && tree->type != TAG_COMPOUND) return NULL;

    /* At this point, the inital names match, and we're not at a leaf node. */

    struct list_head* pos;
    list_for_each(pos, &tree->payload.tag_list->entry)
    {
        struct tag_list* elem = list_entry(pos, struct tag_list, entry);
        nbt_node* r;

        if((r = nbt_find_by_path(elem->data, path + e + 1)) != NULL)
            return r;
    }

    /* Wasn't found in the list (or the current node isn't a list). Give up. */
    return NULL;
}

/* Gets the length of the list, plus the length of all its children. */
static inline size_t nbt_full_list_length(struct tag_list* list)
{
    size_t accum = 0;

    struct list_head* pos;
    list_for_each(pos, &list->entry)
        accum += nbt_size(list_entry(pos, const struct tag_list, entry)->data);

    return accum;
}

size_t nbt_size(const nbt_node* tree)
{
    if(tree == NULL)
        return 0;

    if(tree->type == TAG_LIST || tree->type == TAG_COMPOUND)
        return nbt_full_list_length(tree->payload.tag_list) + 1;

    return 1;
}