implement block mining conditions

build_registries.js

@@ -1,6 +1,16 @@
 const fs = require("fs/promises");
 const path = require("path");
 
+// Overrides for block-to-item conversion
+const blockToItemOverrides = {
+  "grass_block": "dirt",
+  "stone": "cobblestone"
+};
+
+const biomes = [
+  "plains"
+];
+
 // Extract item and block data from registry dump
 async function extractItemsAndBlocks () {
 
@@ -48,12 +58,13 @@ async function extractItemsAndBlocks () {
   const exceptions = [ "air", "water", "lava" ];
 
   // While we're at it, map block IDs to item IDs
-  const mapping = [];
+  const mapping = [], mappingWithOverrides = [];
 
   for (const block in blocks) {
     if (!(block in items) && !exceptions.includes(block)) continue;
     palette[block] = blocks[block];
     mapping.push(items[block] || 0);
+    mappingWithOverrides.push(items[blockToItemOverrides[block]] || items[block] || 0);
     if (mapping.length === 256) break;
   }
 
@@ -64,7 +75,7 @@ async function extractItemsAndBlocks () {
     blockRegistry[block.replace("minecraft:", "")] = blockRegistrySource[block].protocol_id;
   }
 
-  return { blocks, items, palette, mapping, blockRegistry };
+  return { blocks, items, palette, mapping, mappingWithOverrides, blockRegistry };
 
 }
 
@@ -206,10 +217,6 @@ const requiredRegistries = [
   "damage_type"
 ];
 
-const biomes = [
-  "plains"
-];
-
 async function convert () {
 
   const inputPath = __dirname + "/notchian/generated/data/minecraft";
@@ -276,7 +283,7 @@ ${toCArray(tagBuffer)}
 // Block palette
 uint16_t block_palette[] = { ${Object.values(itemsAndBlocks.palette).join(", ")} };
 // Block-to-item mapping
-uint16_t B_to_I[] = { ${itemsAndBlocks.mapping.join(", ")} };
+uint16_t B_to_I[] = { ${itemsAndBlocks.mappingWithOverrides.join(", ")} };
 // Item-to-block mapping
 uint8_t I_to_B (uint16_t item) {
   switch (item) {

main.c

@@ -282,6 +282,14 @@ int main () {
           sc_keepAlive(client_fd);
           sc_updateTime(client_fd, world_time += 200);
           clock_gettime(CLOCK_REALTIME, &keepalive_last);
+          /**
+           * If the RNG seed ever hits 0, it'll never generate anything
+           * else. This is because the fast_rand function uses a simple
+           * XORshift. This isn't a common concern, so we only check for
+           * this periodically. If it does become zero, we reset it to
+           * the world seed as a good-enough fallback.
+           */
+          if (rng_seed == 0) rng_seed = world_seed;
         }
       }
 

src/globals.c

@@ -9,6 +9,7 @@ ssize_t recv_count;
 uint8_t recv_buffer[256] = {0};
 
 uint32_t world_seed = 0xA103DE6C;
+uint32_t rng_seed = 0xE2B9419;
 
 BlockChange block_changes[20000];
 int block_changes_count = 0;

src/globals.h

@@ -22,6 +22,7 @@ extern ssize_t recv_count;
 extern uint8_t recv_buffer[256];
 
 extern uint32_t world_seed;
+extern uint32_t rng_seed;
 
 #pragma pack(push, 1)
 

src/packets.c

@@ -386,14 +386,7 @@ int cs_playerAction (int client_fd) {
     // block was mined in survival
 
     uint8_t block = getBlockAt(x, y, z);
-    uint16_t item, tmp;
-
-    if (block == B_oak_leaves) {
-      if (sequence % 200 < 2) item = I_apple;
-      else if (sequence % 50 < 2) item = I_stick;
-      else if (sequence % 40 < 2) item = I_oak_sapling;
-      else item = 0;
-    } else item = B_to_I[block];
+    uint16_t tmp, item = getMiningResult(client_fd, block);
 
     makeBlockChange(x, y, z, 0);
 

src/tools.c

@@ -5,6 +5,7 @@
 #include <unistd.h>
 
 #include "globals.h"
+#include "registries.h"
 #include "varnum.h"
 #include "packets.h"
 #include "tools.h"
@@ -102,6 +103,13 @@ void readString (int client_fd) {
   recv_buffer[recv_count] = '\0';
 }
 
+uint32_t fast_rand () {
+  rng_seed ^= rng_seed << 13;
+  rng_seed ^= rng_seed >> 17;
+  rng_seed ^= rng_seed << 5;
+  return rng_seed;
+}
+
 int client_states[MAX_PLAYERS * 2];
 
 void setClientState (int client_fd, int new_state) {
@@ -275,3 +283,41 @@ void makeBlockChange (short x, short y, short z, uint8_t block) {
   block_changes_count ++;
 
 }
+
+// Returns the result of mining a block, taking into account the block type and tools
+// Probability numbers obtained with this formula: N = floor(P * 32 ^ 2)
+uint16_t getMiningResult (int client_fd, uint8_t block) {
+
+  switch (block) {
+
+    case B_oak_leaves:
+      uint32_t r = fast_rand();
+      printf("fast_rand: %u, in distribution: %.3f\n", r, (float)r / (4294967295.0f));
+      if (r < 21474836) return I_apple; // 0.5%
+      if (r < 85899345) return I_stick; // 2%
+      if (r < 214748364) return I_oak_sapling; // 5%
+      return 0;
+      break;
+
+    case B_stone:
+    case B_cobblestone:
+      // Check if player is holding a pickaxe
+      PlayerData *player;
+      if (getPlayerData(client_fd, &player)) return 0;
+      uint16_t held_item = player->inventory_items[player->hotbar];
+      if (
+        held_item != I_wooden_pickaxe &&
+        held_item != I_stone_pickaxe &&
+        held_item != I_iron_pickaxe &&
+        held_item != I_golden_pickaxe &&
+        held_item != I_diamond_pickaxe &&
+        held_item != I_netherite_pickaxe
+      ) return 0;
+      break;
+
+    default: break;
+  }
+
+  return B_to_I[block];
+
+}

src/tools.h

@@ -25,6 +25,8 @@ double readDouble (int client_fd);
 
 void readString (int client_fd);
 
+uint32_t fast_rand ();
+
 extern int client_states[MAX_PLAYERS * 2];
 
 void setClientState (int client_fd, int new_state);
@@ -42,4 +44,6 @@ uint8_t clientSlotToServerSlot (int window_id, uint8_t slot);
 uint8_t getBlockChange (short x, short y, short z);
 void makeBlockChange (short x, short y, short z, uint8_t block);
 
+uint16_t getMiningResult (int client_fd, uint8_t block);
+
 #endif