add otxn_param hook api

src/ripple/app/hook/Enum.h

@@ -545,6 +545,7 @@ namespace hook_api
         "otxn_generation",
         "otxn_id",
         "otxn_type",
+        "otxn_param",
         "rollback",
         "slot",
         "slot_clear",

src/ripple/app/hook/applyHook.h

@@ -199,6 +199,8 @@ namespace hook_api
     DECLARE_HOOK_FUNCTION(int64_t,	otxn_id,            uint32_t write_ptr, uint32_t write_len, uint32_t flags );
     DECLARE_HOOK_FUNCNARG(int64_t,	otxn_type           );
     DECLARE_HOOK_FUNCTION(int64_t,	otxn_slot,          uint32_t slot_no );
+    DECLARE_HOOK_FUNCTION(int64_t,  otxn_param,         uint32_t write_ptr, uint32_t write_len,
+                                                        uint32_t read_ptr,  uint32_t read_len);
 
     DECLARE_HOOK_FUNCTION(int64_t,  meta_slot,          uint32_t slot_no );
 
@@ -583,6 +585,8 @@ namespace hook
             ADD_HOOK_FUNCTION(otxn_id, ctx);
             ADD_HOOK_FUNCTION(otxn_type, ctx);
             ADD_HOOK_FUNCTION(otxn_slot, ctx);
+            ADD_HOOK_FUNCTION(otxn_param, ctx);
+
             ADD_HOOK_FUNCTION(hook_account, ctx);
             ADD_HOOK_FUNCTION(hook_hash, ctx);
             ADD_HOOK_FUNCTION(hook_again, ctx);

src/ripple/app/hook/impl/applyHook.cpp

@@ -4869,6 +4869,55 @@ DEFINE_HOOK_FUNCTION(
     return double_to_xfl(result);
 }
 
+DEFINE_HOOK_FUNCTION(
+    int64_t,
+    otxn_param,
+    uint32_t write_ptr, uint32_t write_len,
+    uint32_t read_ptr,  uint32_t read_len )
+{
+    HOOK_SETUP(); // populates memory_ctx, memory, memory_length, applyCtx, hookCtx on current stack
+
+    if (NOT_IN_BOUNDS(read_ptr, read_len, memory_length))
+        return OUT_OF_BOUNDS;
+
+    if (read_len < 1)
+        return TOO_SMALL;
+
+    if (read_len > 32)
+        return TOO_BIG;
+
+    if (!applyCtx.tx.isFieldPresent(sfHookParameters))
+        return DOESNT_EXIST;
+
+    std::vector<uint8_t> paramName { read_ptr + memory, read_ptr + read_len + memory }; 
+
+    auto const& params = applyCtx.tx.getFieldArray(sfHookParameters);
+
+    for (auto const& param: params)
+    {
+        if (!param.isFieldPresent(sfHookParameterName) || 
+            param.getFieldVL(sfHookParameterName) != paramName)
+            continue;
+        
+        if (!param.isFieldPresent(sfHookParameterValue))
+            return DOESNT_EXIST;
+
+        auto const& val = param.getFieldVL(sfHookParameterValue);
+        if (val.empty())
+            return DOESNT_EXIST;
+
+        if (val.size() < write_len)
+            return TOO_SMALL;
+        
+        WRITE_WASM_MEMORY_AND_RETURN(
+            write_ptr, write_len,
+            val.data(), val.size(),
+            memory, memory_length);
+    } 
+
+    return DOESNT_EXIST;
+}
+
 DEFINE_HOOK_FUNCTION(
     int64_t,
     hook_param,

src/test/app/SetHook_test.cpp

@@ -5146,6 +5146,11 @@ public:
         // RH TODO: test behaviour on emit failure
     }
 
+    void
+    test_otxn_param()
+    {
+    }
+    
     void
     test_slot()
     {
@@ -9703,6 +9708,7 @@ public:
         test_otxn_id();             //
         test_otxn_slot();           //
         test_otxn_type();           //
+        test_otxn_param();          
 
         test_slot();                //
         test_slot_clear();          //