Optimize account copies and use RefCell to handle duplicate accounts in BPF programs (#7958)

programs/bpf/c/src/dup_accounts/dup_accounts.c

@@ -0,0 +1,57 @@
+/**
+ * @brief Example C-based BPF program that exercises duplicate keyed ka
+ * passed to it
+ */
+#include <solana_sdk.h>
+
+/**
+ * Custom error for when input serialization fails
+ */
+
+extern uint32_t entrypoint(const uint8_t *input) {
+  #define FAILURE 1
+  #define INVALID_INPUT 2
+
+  SolKeyedAccount ka[4];
+  SolParameters params = (SolParameters) { .ka = ka };
+
+  if (!sol_deserialize(input, &params, SOL_ARRAY_SIZE(ka))) {
+    return INVALID_INPUT;
+  }
+
+  switch (params.data[0]) {
+      case(1):
+          sol_log("modify first account userdata");
+          ka[2].userdata[0] = 1;
+          break;
+      case(2):
+          sol_log("modify first account userdata");
+          ka[3].userdata[0] = 2;
+          break;
+      case(3):
+          sol_log("modify both account userdata");
+          ka[2].userdata[0] += 1;
+          ka[3].userdata[0] += 2;
+          break;
+      case(4):
+          sol_log("modify first account lamports");
+          *ka[1].lamports -= 1;
+          *ka[2].lamports += 1;
+          break;
+      case(5):
+          sol_log("modify first account lamports");
+          *ka[1].lamports -= 2;
+          *ka[3].lamports += 2;
+          break;
+      case(6):
+          sol_log("modify both account lamports");
+          *ka[1].lamports -= 3;
+          *ka[2].lamports += 1;
+          *ka[3].lamports += 2;
+          break;
+      default:
+          sol_log("Unrecognized command");
+          return FAILURE;
+  }
+  return SUCCESS;
+}