initial upload

src/eval/eval_decode.c

@@ -0,0 +1,50 @@
+// Copyright (c) 2024 Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+////////////////////////////////
+// NOTE(allen): Eval Decode Function
+
+internal void
+eval_print_decode_from_bytecode(FILE *out, String8 bytecode){
+  U8 *ptr = bytecode.str;
+  U8 *opl = bytecode.str + bytecode.size;
+  
+  for (;ptr < opl;){
+    // consume opcode
+    SYMS_EvalOp op = (SYMS_EvalOp)*ptr;
+    if (op >= SYMS_EvalOp_COUNT){
+      fprintf(out, "decode error: undefined op code\n");
+      goto done;
+    }
+    U8 ctrlbits = syms_eval_opcode_ctrlbits[op];
+    ptr += 1;
+    
+    // decode
+    U64 imm = 0;
+    U32 decode_size = (ctrlbits >> SYMS_EvalOpCtrlBits_DecodeShft)&SYMS_EvalOpCtrlBits_DecodeMask;
+    {
+      U8 *next_ptr = ptr + decode_size;
+      if (next_ptr > opl){
+        fprintf(out, "decode error: expected constant goes past the end of bytecode\n");
+        goto done;
+      }
+      // TODO(allen): to improve this:
+      //  gaurantee 8 bytes padding after the end of serialized bytecode
+      //  read 8 bytes and mask
+      switch (decode_size){
+        case 1: imm = *ptr; break;
+        case 2: imm = *(U16*)ptr; break;
+        case 4: imm = *(U32*)ptr; break;
+        case 8: imm = *(U64*)ptr; break;
+      }
+      ptr = next_ptr;
+    }
+    
+    // op string & control bits
+    SYMS_String8 op_string = syms_eval_opcode_strings[op];
+    
+    // print
+    fprintf(out, "%.*s 0x%llx\n", str8_varg(op_string), imm);
+  }
+  done:;
+}