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[MP] Fix variant serialization after variant size change.

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The bit mask used for the type when compressing variants in the
Multiplayer API became too small to represent all variant types.

This commit expand the mask, which means we no longer have an extra bit
in the "meta" byte we use to store encoding information.

The extra bit was only used in case of booleans to store the value and
since booleans do not require extra encoding information we use those 2
bits to store the value instead.
This commit is contained in:
Fabio Alessandrelli 2022-08-24 19:26:10 +02:00
parent 8a1e598011
commit 75de626781
1 changed files with 11 additions and 11 deletions
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22
scene/main/multiplayer_api.cpp
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@ -59,18 +59,18 @@ Ref<MultiplayerAPI> MultiplayerAPI::create_default_interface() {
// The variant is compressed and encoded; The first byte contains all the meta
// information and the format is:
// - The first LSB 5 bits are used for the variant type.
// - The first LSB 6 bits are used for the variant type.
// - The next two bits are used to store the encoding mode.
// - The most significant is used to store the boolean value.
#define VARIANT_META_TYPE_MASK 0x1F
#define VARIANT_META_EMODE_MASK 0x60
// - Boolean values uses the encoding mode to store the value.
#define VARIANT_META_TYPE_MASK 0x3F
#define VARIANT_META_EMODE_MASK 0xC0
#define VARIANT_META_BOOL_MASK 0x80
#define ENCODE_8 0 << 5
#define ENCODE_16 1 << 5
#define ENCODE_32 2 << 5
#define ENCODE_64 3 << 5
#define ENCODE_8 0 << 6
#define ENCODE_16 1 << 6
#define ENCODE_32 2 << 6
#define ENCODE_64 3 << 6
Error MultiplayerAPI::encode_and_compress_variant(const Variant &p_variant, uint8_t *r_buffer, int &r_len, bool p_allow_object_decoding) {
// Unreachable because `VARIANT_MAX` == 27 and `ENCODE_VARIANT_MASK` == 31
// Unreachable because `VARIANT_MAX` == 38 and `ENCODE_VARIANT_MASK` == 77
CRASH_COND(p_variant.get_type() > VARIANT_META_TYPE_MASK);
uint8_t *buf = r_buffer;
@ -80,9 +80,9 @@ Error MultiplayerAPI::encode_and_compress_variant(const Variant &p_variant, uint
switch (p_variant.get_type()) {
case Variant::BOOL: {
if (buf) {
// We still have 1 free bit in the meta, so let's use it.
// We don't use encode_mode for booleans, so we can use it to store the value.
buf[0] = (p_variant.operator bool()) ? (1 << 7) : 0;
buf[0] |= encode_mode | p_variant.get_type();
buf[0] |= p_variant.get_type();
}
r_len += 1;
} break;