nbt.c

#include <alloca.h>
#include <assert.h>
#include <string.h>
#include <clod/nbt.h>
 
constexpr size_t payload_zero_sizes[] = {
    [CLOD_NBT_INT8] = 1,
    [CLOD_NBT_INT16] = 2,
    [CLOD_NBT_INT32] = 4,
    [CLOD_NBT_INT64] = 8,
    [CLOD_NBT_FLOAT32] = 4,
    [CLOD_NBT_FLOAT64] = 8,
    [CLOD_NBT_INT8_ARRAY] = 4,
    [CLOD_NBT_INT32_ARRAY] = 4,
    [CLOD_NBT_INT64_ARRAY] = 4,
    [CLOD_NBT_STRING] = 2,
    [CLOD_NBT_LIST] = 5,
    [CLOD_NBT_COMPOUND] = 1
};
constexpr char payload_zero_sizes_len = sizeof(payload_zero_sizes) / sizeof(payload_zero_sizes[0]);
 
#define type_zero_size(type) (0 <= (type) && (type) < payload_zero_sizes_len ? payload_zero_sizes[(unsigned)type] : 0)
#define type_valid(type) (type_zero_size(type))
#define available(ptr, end) ((ptr) <= (char*)(end) ? (size_t)((char*)(end) - (ptr)) : 0)
 
size_t clod_nbt_payload_size(
    const char *restrict const payload,
    const void *const end,
    const char payload_type
) {
    switch (payload_type) {
        default: return 0;
        case CLOD_NBT_INT8: return 1;
        case CLOD_NBT_INT16: return 2;
        case CLOD_NBT_INT32: return 4;
        case CLOD_NBT_INT64: return 8;
        case CLOD_NBT_FLOAT32: return 4;
        case CLOD_NBT_FLOAT64: return 8;
        case CLOD_NBT_INT8_ARRAY: {
            if (available(payload, end) < 4) return 0;
            const size_t size = (size_t)bei32_dec(payload);
            if (available(payload, end) < 4 + size) return 0;
            return 4 + size;
        }
        case CLOD_NBT_INT32_ARRAY: {
            if (available(payload, end) < 4) return 0;
            const size_t size = (size_t)bei32_dec(payload) * 4;
            if (available(payload, end) < 4 + size) return 0;
            return 4 + size;
        }
        case CLOD_NBT_INT64_ARRAY: {
            if (available(payload, end) < 4) return 0;
            const size_t size = (size_t)bei32_dec(payload) * 8;
            if (available(payload, end) < 4 + size) return 0;
            return 4 + size;
        }
        case CLOD_NBT_STRING: {
            if (available(payload, end) < 2) return 0;
            const size_t size = (size_t)beu16_dec(payload);
            if (available(payload, end) < 2 + size) return 0;
            return 2 + size;
        }
        case CLOD_NBT_LIST: {
            if (available(payload, end) < 5) return 0;
            if (payload[0] == CLOD_NBT_ZERO) return 5;
            if (!type_valid(payload[0])) return 0;
            const size_t length = (size_t)bei32_dec(payload + 1);
            size_t size = 5;
            for (size_t i = 0; i < length; i++) {
                const size_t elem_size = clod_nbt_payload_size(payload + size, end, payload[0]);
                if (elem_size == 0) return 0;
                size += elem_size;
            }
            return size;
        }
        case CLOD_NBT_COMPOUND: {
            size_t size = 0;
            for (;;) {
                while (available(payload, end) >= size + 3) {
                    if (!type_valid(payload[size])) break;
                    const size_t name_size = beu16_dec(payload + size + 1);
                    if (available(payload, end) < size + 3 + name_size) return 0;
                    size += 3 + name_size + clod_nbt_payload_size(payload + size + 3 + name_size, end, payload[size]);
                }
 
                if (available(payload, end) < size + 1) return 0;
                if (payload[size] == CLOD_NBT_ZERO) return size + 1;
                return 0;
            }
        }
    }
}
 
size_t clod_nbt_tag_size(const char *restrict tag, const void *end) {
    if (available(tag, end) < 3) return 0;
    if (!type_valid(tag[0])) return 0;
    const size_t name_size = beu16_dec(tag + 1);
    if (available(tag, end) < 3 + name_size) return 0;
    return 3 + name_size + clod_nbt_payload_size(tag + 3 + name_size, end, tag[0]);
}
 
char *clod_nbt_tag_payload(const char *restrict tag, const void *end) {
    if (available(tag, end) < 3) return nullptr;
    if (!type_valid(tag[0])) return nullptr;
    const size_t name_size = beu16_dec(tag + 1);
    if (available(tag, end) < 3 + name_size) return nullptr;
    return (char*)tag + 3 + name_size;
}
 
clod_sstr clod_nbt_tag_name(const char *restrict tag, const void *end) {
    if (available(tag, end) < 3) return CLOD_SSTR_NULL;
    if (!type_valid(tag[0])) return CLOD_SSTR_NULL;
    const size_t name_size = beu16_dec(tag + 1);
    if (available(tag, end) < 3 + name_size) return CLOD_SSTR_NULL;
    return clod_sstr(tag + 3, name_size);
}
 
bool clod_nbt_iter_next(
    const char *const restrict payload,
    const void *const end,
    const char payload_type,
    struct clod_nbt_iter *iter
) {
    switch (payload_type) {
    case CLOD_NBT_COMPOUND: {
        if (iter->payload == nullptr) {
            memset(iter, 0, sizeof(*iter));
            iter->tag = (char*)payload;
        } else {
            iter->tag += iter->size;
            iter->index++;
        }
 
        if (available(iter->tag, end) < 1) goto iter_fail;
        if (iter->tag[0] == CLOD_NBT_ZERO) {
            iter->tag++;
            iter->payload = nullptr;
            iter->size = 0;
            iter->type = CLOD_NBT_ZERO;
            return false;
        }
 
        char *tag_payload = clod_nbt_tag_payload(iter->tag, end);
        if (!tag_payload) goto iter_fail;
        const size_t payload_size = clod_nbt_payload_size(tag_payload, end, iter->tag[0]);
        if (payload_size == 0) goto iter_fail;
 
        iter->payload = tag_payload;
        iter->size = (size_t)(tag_payload - iter->tag) + payload_size;
        iter->type = iter->tag[0];
        return true;
    }
    case CLOD_NBT_LIST: {
        if (iter->payload == nullptr) {
            if (available(payload, end) < 5) goto iter_fail;
            memset(iter, 0, sizeof(*iter));
            iter->payload = (char*)payload;
            iter->type = payload[0];
        } else {
            iter->payload += iter->size;
            iter->index++;
        }
 
        if (iter->index >= (uint32_t)bei32_dec(payload + 1)) {
            iter->tag = iter->payload;
            iter->payload = nullptr;
            iter->size = 0;
            iter->type = CLOD_NBT_ZERO;
            return false;
        }
 
        const size_t payload_size = clod_nbt_payload_size(iter->payload, end, payload[0]);
        if (payload_size == 0) goto iter_fail;
        iter->size = payload_size;
        return true;
    }
    case CLOD_NBT_STRING: {
        if (iter->payload == nullptr) {
            if (available(payload, end) < 2) goto iter_fail;
            memset(iter, 0, sizeof(*iter));
            iter->payload = (char*)payload;
            iter->size = 1;
            iter->type = CLOD_NBT_INT8;
        } else {
            iter->payload++;
            iter->index++;
        }
 
        if (iter->index >= beu16_dec(payload)) {
            iter->tag = iter->payload;
            iter->payload = nullptr;
            iter->size = 0;
            iter->type = CLOD_NBT_ZERO;
            return false;
        }
        return true;
    }
    case CLOD_NBT_INT8_ARRAY: {
        if (iter->payload == nullptr) {
            if (available(payload, end) < 4) goto iter_fail;
            memset(iter, 0, sizeof(*iter));
            iter->payload = (char*)payload;
            iter->size = 1;
            iter->type = CLOD_NBT_INT8;
        } else {
            iter->payload++;
            iter->index++;
        }
 
        if (iter->index >= (uint32_t)bei32_dec(payload)) {
            iter->tag = iter->payload;
            iter->payload = nullptr;
            iter->size = 0;
            iter->type = CLOD_NBT_ZERO;
            return false;
        }
        return true;
    }
    case CLOD_NBT_INT32_ARRAY: {
        if (iter->payload == nullptr) {
            if (available(payload, end) < 4) goto iter_fail;
            memset(iter, 0, sizeof(*iter));
            iter->payload = (char*)payload;
            iter->size = 4;
            iter->type = CLOD_NBT_INT32;
        } else {
            iter->payload += 4;
            iter->index++;
        }
 
        if (iter->index >= (uint32_t)bei32_dec(payload)) {
            iter->tag = iter->payload;
            iter->payload = nullptr;
            iter->size = 0;
            iter->type = CLOD_NBT_ZERO;
            return false;
        }
        return true;
    }
    case CLOD_NBT_INT64_ARRAY: {
        if (iter->payload == nullptr) {
            if (available(payload, end) < 4) goto iter_fail;
            memset(iter, 0, sizeof(*iter));
            iter->payload = (char*)payload;
            iter->size = 8;
            iter->type = CLOD_NBT_INT64;
        } else {
            iter->payload += 8;
            iter->index++;
        }
 
        if (iter->index >= (uint32_t)bei32_dec(payload)) {
            iter->tag = iter->payload;
            iter->payload = nullptr;
            iter->size = 0;
            iter->type = CLOD_NBT_ZERO;
            return false;
        }
        return true;
    }
    default: return false;
    }
 
iter_fail:
    memset(iter, 0, sizeof(*iter));
    return false;
}
 
char *clod_nbt_compound_get(
    const char *restrict compound,
    const void *end,
    const clod_sstr name
) {
    struct clod_nbt_iter iter = CLOD_NBT_ITER_ZERO;
    while (clod_nbt_iter_next(compound, end, CLOD_NBT_COMPOUND, &iter)) {
        if (clod_sstr_eq(clod_nbt_tag_name(iter.tag, end), name)) return iter.tag;
    }
    return nullptr;
}
 
char *clod_nbt_compound_add(
    char *restrict compound,
    const void **end,
    ptrdiff_t *free,
    const clod_sstr name,
    const char type
) {
    if (!type_valid(type)) return nullptr;
    const size_t elem_size = 3 + name.size + type_zero_size(type);
    if (!compound) {
        *free -= (ptrdiff_t)elem_size;
        return nullptr;
    }
 
    struct clod_nbt_iter iter = CLOD_NBT_ITER_ZERO;
    while (clod_nbt_iter_next(compound, *end, CLOD_NBT_COMPOUND, &iter)) {
        if (clod_sstr_eq(clod_nbt_tag_name(iter.tag, *end), name)) return iter.tag;
    }
 
    if (!iter.tag) return nullptr;
    *free -= (ptrdiff_t)elem_size;
    if (*free < 0) {
        // Out of space.
        return nullptr;
    }
 
    memmove(iter.tag + elem_size, iter.tag, available(iter.tag, *end) - elem_size);
 
    iter.tag[0] = type;
    beu16_enc(iter.tag + 1, (uint16_t)name.size);
    memcpy(iter.tag + 3, name.ptr, name.size);
    memset(iter.tag + 3 + name.size, 0, type_zero_size(type));
 
    *end = *(char**)end + elem_size;
    return iter.tag;
}
 
bool clod_nbt_compound_del(
    char *restrict compound,
    const void **end,
    ptrdiff_t *free,
    const clod_sstr name
) {
    struct clod_nbt_iter iter = CLOD_NBT_ITER_ZERO;
    while (clod_nbt_iter_next(compound, *end, CLOD_NBT_COMPOUND, &iter)) {
        if (clod_sstr_eq(clod_nbt_tag_name(iter.tag, *end), name)) {
            memmove(iter.tag, iter.tag + iter.size, available(iter.tag, *end) - iter.size);
            *end = *(char**)end - iter.size;
            *free += (ptrdiff_t)iter.size;
            return true;
        }
    }
    return false;
}
 
bool clod_nbt_list_resize(
    char *restrict list,
    const char **end,
    ptrdiff_t *free,
    char type,
    const uint32_t length
) {
    if (!list) {
        *free -= (ptrdiff_t)(length * type_zero_size(type));
        return false;
    }
    if (available(list, *end) < 5) return false;
 
    if (list[0] != type) {
        const size_t old_size = clod_nbt_payload_size(list, *end, CLOD_NBT_LIST);
        const size_t new_size = 5 + length * type_zero_size(type);
        if (old_size == 0) return false;
 
        const ptrdiff_t delta = (ptrdiff_t)new_size - (ptrdiff_t)old_size;
        *free -= delta;
        if (*free < 0) return false;
 
        memmove(list + new_size, list + old_size, available(list, *end) - old_size);
        memset(list, 0, new_size);
        list[0] = type;
        bei32_enc(list + 1, (int32_t)length);
        *end = *(char**)end + delta;
        return true;
    }
 
    const uint32_t old_length = (uint32_t)bei32_dec(list + 1);
 
    if (old_length < length) {
        const size_t old_size = clod_nbt_payload_size(list, *end, CLOD_NBT_LIST);
        const size_t append_size = type_zero_size(list[0]) * (length - old_length);
 
        *free -= (ptrdiff_t)append_size;
        if (*free < 0) return false;
 
        memmove(list + old_size + append_size, list + old_size, available(list, *end) - old_size - append_size);
        memset(list + old_size, 0, append_size);
        bei32_enc(list + 1, (int32_t)length);
 
        *end = *(char**)end + append_size;
        return true;
    }
 
    if (old_length > length) {
        struct clod_nbt_iter iter = CLOD_NBT_ITER_ZERO;
        char *truncate = nullptr;
        while (clod_nbt_iter_next(list, *end, CLOD_NBT_LIST, &iter))
            if (iter.index == length) truncate = iter.payload;
 
        if (!iter.tag || !truncate) return false;
 
        memmove(truncate, iter.tag, available(iter.tag, *end));
        bei32_enc(list + 1, (int32_t)length);
        *free += iter.tag - truncate;
        *end = *(char**)end - (iter.tag - truncate);
        return true;
    }
 
    return true;
}