From 4e189721b2691ed552f1098caea76b62bab26213 Mon Sep 17 00:00:00 2001
From: flobernd <flobernd@users.noreply.github.com>
Date: Mon, 5 Feb 2018 23:49:50 +0100
Subject: [PATCH] Minor changes to the operand formatter hooks

`ZYDIS_FORMATTER_HOOK_PRE_OPERAND` and `ZYDIS_FORMATTER_HOOK_POST_OPERAND` can be used to omit a specific operand, if you return a status-code different to `ZYDIS_STATUS_SUCCESS`.
---
 src/Formatter.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/Formatter.c b/src/Formatter.c
index 476de9c..9cdb076 100644
--- a/src/Formatter.c
+++ b/src/Formatter.c
@@ -88,13 +88,16 @@ static ZydisStatus ZydisFormatInstrIntel(const ZydisFormatter* formatter, ZydisS
             ZYDIS_CHECK(ZydisStringAppendC(string, ", "));
         }
 
+        const ZydisUSize strLenPreOperand = string->length;
         if (formatter->funcPreOperand)
         {
-            formatter->funcPreOperand(formatter, string, instruction, &instruction->operands[i], 
-                userData);
+            if (!ZYDIS_SUCCESS(formatter->funcPreOperand(formatter, string, instruction, 
+                &instruction->operands[i], userData)))
+            {
+                goto SkipOperand;
+            }
         }
 
-        const ZydisUSize strLenPreOperand = string->length;
         switch (instruction->operands[i].type)
         {
         case ZYDIS_OPERAND_TYPE_REGISTER:
@@ -125,9 +128,19 @@ static ZydisStatus ZydisFormatInstrIntel(const ZydisFormatter* formatter, ZydisS
         default:
             return ZYDIS_STATUS_INVALID_PARAMETER;
         }
+
+        if (formatter->funcPostOperand)
+        {
+            if (!ZYDIS_SUCCESS(formatter->funcPostOperand(formatter, string, instruction, 
+                &instruction->operands[i], userData)))
+            {
+                goto SkipOperand;
+            }
+        }
         
         if (strLenPreOperand == string->length)
         {
+SkipOperand:
             // Omit whole operand, if the string did not change during the formatting-callback
             string->length = strLenRestore;
 
@@ -140,12 +153,6 @@ static ZydisStatus ZydisFormatInstrIntel(const ZydisFormatter* formatter, ZydisS
             continue;
         }
 
-        if (formatter->funcPostOperand)
-        {
-            formatter->funcPostOperand(formatter, string, instruction, &instruction->operands[i], 
-                userData);
-        }
-
         if ((instruction->encoding == ZYDIS_INSTRUCTION_ENCODING_EVEX) ||
             (instruction->encoding == ZYDIS_INSTRUCTION_ENCODING_MVEX))
         {
@@ -902,6 +909,10 @@ ZydisStatus ZydisFormatterInit(ZydisFormatter* formatter, ZydisFormatterStyle st
     switch (style)
     {
     case ZYDIS_FORMATTER_STYLE_INTEL:
+        formatter->funcPreInstruction       = ZYDIS_NULL;
+        formatter->funcPostInstruction      = ZYDIS_NULL;
+        formatter->funcPreOperand           = ZYDIS_NULL;
+        formatter->funcPostOperand          = ZYDIS_NULL;
         formatter->funcFormatInstruction    = &ZydisFormatInstrIntel;
         formatter->funcFormatOperandReg     = &ZydisFormatOperandRegIntel;
         formatter->funcFormatOperandMem     = &ZydisFormatOperandMemIntel;