From 82fdb03c4cb9c76d151624352b5ecd86a3d6c94c Mon Sep 17 00:00:00 2001
From: Intel A80486DX2-66 <larry.holst@disroot.org>
Date: Tue, 19 Nov 2024 21:03:33 +0300
Subject: [PATCH] corrupter.c: extract `corrupt_byte`

---
 src/corrupter.c | 135 ++++++++++++++++++++++++++++--------------------
 1 file changed, 78 insertions(+), 57 deletions(-)

diff --git a/src/corrupter.c b/src/corrupter.c
index 1a013c0..c154fcc 100644
--- a/src/corrupter.c
+++ b/src/corrupter.c
@@ -1,5 +1,27 @@
 #include "corrupter.h"
 
+/* enums */
+enum Interoperation_Result {
+	INTEROPERATION_SUCCESS = false,
+	INTEROPERATION_ERROR = true
+};
+
+/* macros: definitions */
+#define Interoperation_Input_Vars                                             \
+    Corrupter_Param* param, Corrupter_Result* result, FILE* file,             \
+    file_offset_t i
+#define Interoperation_Share_Vars                                             \
+    param,                  result,                   file,                   \
+    i
+
+/* macros: lambdas */
+#define CORRUPT_BYTE_MACRO                                                    \
+    if (corrupt_byte(Interoperation_Share_Vars) == INTEROPERATION_ERROR) {    \
+        result->error = true;                                                 \
+        fclose(file);                                                         \
+        return result;                                                        \
+    }
+
 /* cached operations */
 const size_t UINT16_MAX_PLUS_1 = UINT16_MAX + 1;
 
@@ -21,6 +43,60 @@ static bool is_line_ending(byte c) {
 	return c == '\n' || c == '\r';
 }
 
+enum Interoperation_Result corrupt_byte(Interoperation_Input_Vars) {
+	uint8_t config = param->config;
+
+	FSEEK_MACRO(file, i, SEEK_SET);
+	byte byte_value;
+
+	if (fread(&byte_value, sizeof(byte), 1, file) != 1)
+		return INTEROPERATION_ERROR;
+
+	if (READ_CONFIG(C_PRINTABLE) && !isprint(byte_value))
+		return INTEROPERATION_SUCCESS;
+	else if (READ_CONFIG(C_LINE_ENDINGS) && is_line_ending(byte_value))
+		return INTEROPERATION_SUCCESS;
+
+	// generate bit mask
+	byte damage_left = param->threshold;
+	static bool bit_mask[CHAR_BIT];
+	uint8_t probability = param->probability;
+
+	for (byte bit = 0; bit < CHAR_BIT; bit++) {
+		if (get_chance(probability) && (damage_left > 0)) {
+			bit_mask[bit] = true;
+			damage_left--;
+		} else {
+			bit_mask[bit] = false;
+		}
+	}
+
+	bool damaged_byte = false;
+	file_offset_t threshold = (file_offset_t) param->threshold;
+
+	for (byte bit = 0; bit < threshold; bit++) {
+		if (bit_mask[bit] == false)
+			continue;
+
+		byte_value = FLIP_BIT(byte_value, bit);
+		result->hit_counter++;
+
+		damaged_byte = true;
+
+		// write the modified byte back to the file
+		FSEEK_MACRO(file, i, SEEK_SET);
+
+		if (fwrite(&byte_value, sizeof(byte), 1, file) != 1)
+			// on error
+			return INTEROPERATION_ERROR;
+	}
+
+	if (damaged_byte)
+		result->damaged_bytes++;
+
+	return INTEROPERATION_SUCCESS;
+}
+
 Corrupter_Result* corrupt_file(Corrupter_Param* param) {
 	Corrupter_Result* result = malloc(sizeof(Corrupter_Result));
 
@@ -29,9 +105,6 @@ Corrupter_Result* corrupt_file(Corrupter_Param* param) {
 
 	// copy and cast parameters
 	FILE* file = param->file;
-	uint8_t probability = param->probability;
-	file_offset_t threshold = (file_offset_t) param->threshold;
-	uint8_t config = param->config;
 
 	// refuse to operate on non-seekable streams
 	if (FSEEK_MACRO(file, FILE_OFFSET_C(0), SEEK_SET) != 0 ||
@@ -84,60 +157,8 @@ Corrupter_Result* corrupt_file(Corrupter_Param* param) {
 		rewind(file);
 
 		// iterate over the file contents
-		for (file_offset_t i = start; i < end; i++) {
-			FSEEK_MACRO(file, i, SEEK_SET);
-			byte byte_value;
-
-			if (fread(&byte_value, sizeof(byte), 1, file) != 1) {
-				result->error = true;
-				fclose(file);
-				return result;
-			}
-
-			if (READ_CONFIG(C_PRINTABLE) && !isprint(byte_value))
-				continue;
-			else if (READ_CONFIG(C_LINE_ENDINGS) && is_line_ending(byte_value))
-				continue;
-
-			// generate bit mask
-			byte damage_left = param->threshold;
-			static bool bit_mask[CHAR_BIT];
-
-			for (byte bit = 0; bit < CHAR_BIT; bit++) {
-				if (get_chance(probability) && (damage_left > 0)) {
-					bit_mask[bit] = true;
-					damage_left--;
-				} else {
-					bit_mask[bit] = false;
-				}
-			}
-
-			bool damaged_byte = false;
-
-			for (byte bit = 0; bit < threshold; bit++) {
-				if (bit_mask[bit] == false)
-					continue;
-
-				byte_value = FLIP_BIT(byte_value, bit);
-				result->hit_counter++;
-
-				damaged_byte = true;
-
-				// write the modified byte back to the file
-				FSEEK_MACRO(file, i, SEEK_SET);
-
-				if (fwrite(&byte_value, sizeof(byte), 1, file) == 1)
-					continue;
-
-				// on error
-				result->error = true;
-				fclose(file);
-				return result;
-			}
-
-			if (damaged_byte)
-				result->damaged_bytes++;
-		}
+		for (file_offset_t i = start; i < end; i++)
+			CORRUPT_BYTE_MACRO;
 
 		puts(" [OK]");
 	}