From c7735c0ddc30c0d5de1890e17e915f4f947132cb Mon Sep 17 00:00:00 2001
From: mykola2312 <49044616+mykola2312@users.noreply.github.com>
Date: Fri, 16 Aug 2024 06:26:37 +0300
Subject: [PATCH] begin working on prefixes

---
 include/rtdisasm.h |  2 ++
 src/rtdisasm.c     | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/include/rtdisasm.h b/include/rtdisasm.h
index 6ca34b3..56dfe0b 100644
--- a/include/rtdisasm.h
+++ b/include/rtdisasm.h
@@ -1,4 +1,6 @@
 #ifndef __RTDISASM_H
 #define __RTDISASM_H
 
+#include <stdint.h>
+
 #endif
\ No newline at end of file
diff --git a/src/rtdisasm.c b/src/rtdisasm.c
index 1fd96c4..e9f5e91 100644
--- a/src/rtdisasm.c
+++ b/src/rtdisasm.c
@@ -1 +1,44 @@
-#include "rtdisasm.h"
\ No newline at end of file
+#include "rtdisasm.h"
+
+// prefix definitions. must be declared with macro in order
+// to be readable later in prefix table
+
+#define PREFIX_LOCK             0xF0
+#define PREFIX_REPNZ            0xF2 // also BND prefix
+#define PREFIX_REPZ             0xF3
+
+#define PREFIX_CS_OVERRIDE      0x2E // also branch-not-taken hint
+#define PREFIX_SS_OVERRIDE      0x36
+#define PREFIX_DS_OVERRIDE      0x3E // also branch-taken hint
+#define PREFIX_ES_OVERRIDE      0x26
+#define PREFIX_FS_OVERRIDE      0x64
+#define PREFIX_GS_OVERRIDE      0x65
+
+#define PREFIX_OPERAND_OVERRIDE 0x66
+#define PREFIX_ADDRESS_OVERRIDE 0x67
+
+static const uint8_t std_prefixes[] = {
+    PREFIX_LOCK,
+    PREFIX_REPNZ,
+    PREFIX_REPZ,
+
+    PREFIX_CS_OVERRIDE,
+    PREFIX_SS_OVERRIDE,
+    PREFIX_DS_OVERRIDE,
+    PREFIX_ES_OVERRIDE,
+    PREFIX_FS_OVERRIDE,
+    PREFIX_GS_OVERRIDE,
+
+    PREFIX_OPERAND_OVERRIDE,
+    PREFIX_ADDRESS_OVERRIDE
+};
+
+static const unsigned std_prefixes_len = sizeof(std_prefixes);
+
+static int is_std_prefix(const uint8_t prefix)
+{
+    for (unsigned i = 0; i < std_prefixes_len; i++)
+        if (prefix == std_prefixes[i]) return 1;
+    
+    return 0;
+}
\ No newline at end of file