change message size cap (was 128) to INT64_MAX

caesarcrypt.vcxproj

@@ -13,12 +13,14 @@
   <ItemGroup>
     <ClCompile Include="src\caesarcrypt.c" />
     <ClCompile Include="src\crypt.c" />
+    <ClCompile Include="src\dyninput.c" />
   </ItemGroup>
   <ItemGroup>
     <None Include="caesarcrypt.licenseheader" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="src\crypt.h" />
+    <ClInclude Include="src\dyninput.h" />
   </ItemGroup>
   <PropertyGroup Label="Globals">
     <VCProjectVersion>16.0</VCProjectVersion>

caesarcrypt.vcxproj.filters

@@ -21,6 +21,9 @@
     <ClCompile Include="src\crypt.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="src\dyninput.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <None Include="caesarcrypt.licenseheader" />
@@ -29,5 +32,8 @@
     <ClInclude Include="src\crypt.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="src\dyninput.h">
+      <Filter>Source Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

src/caesarcrypt.c

@@ -9,11 +9,11 @@
 */
 
 #include "crypt.h"
+#include "dyninput.h"
 
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
-#include <string.h>
-#include <stdbool.h>
 
 
 int main()
@@ -25,13 +25,17 @@ int main()
 		,stdout
 	);
 	char buf[4];
+	int64_t maxsize = INT64_MAX;
 	fgets(buf, 3, stdin);
 	int choice = strtol(buf, NULL, 10);
-	
-	char* msg = calloc(128, sizeof(char));
 
 	fputs("Enter your message text: ", stdout);
-	if (msg) fgets(msg, 128, stdin);
+	char* msg = dyninput_str(maxsize);
+	if (!msg)
+	{
+		puts("ERROR: String input failed! Exiting...");
+		return -1;
+	}
 
 	fputs("Enter your key (shift value): ", stdout);
 	fgets(buf, 4, stdin);
@@ -39,22 +43,24 @@ int main()
 
 	if (choice == 1)
 	{
-		caesar_encrypt(msg, 128, key);
+		caesar_encrypt(msg, maxsize, key);
 		puts("\nYour encrypted message is:");
-		for (int i = 0; i < 128 && msg[i]; i++)
+		for (int i = 0; i < maxsize && msg[i]; i++)
 		{
 			putchar(msg[i]);
 		}
 	}
 	else if (choice == 2)
 	{
-		caesar_decrypt(msg, 128, key);
+		caesar_decrypt(msg, maxsize, key);
 		puts("\nYour decrypted message is:");
-		for (int i = 0; i < 128 && msg[i]; i++)
+		for (int i = 0; i < maxsize && msg[i]; i++)
 		{
 			putchar(msg[i]);
 		}
 	}
 
+	free(msg);
+	msg = NULL;
 	return 0;
 }

src/crypt.c

@@ -10,16 +10,62 @@
 
 #include "crypt.h"
 
+#include <stdbool.h>
+#include <stdint.h>
 
-void caesar_encrypt(char* str, int size, int key)
+
+/* 
+  * For built in C mod operator (%) -1 % 26 == -1
+  * For the requirements of this algorithm -1 mod 26 == 25 is required
+  * The below functions accomplish this
+*/
+
+// Which of the two below functions is faster (find out!)
+inline int mod(int a, int b)
 {
-	for (int i = 0; i < size && str[i] != '\n'; i++)
-		if (str[i] != ' ') str[i] += key % 26;
+	return (a % b + b) % b;
 }
 
 
-void caesar_decrypt(char* str, int size, int key)
+inline int fast_mod(int a, int b)
 {
-	for (int i = 0; i < size && str[i] != '\n'; i++)
-		if (str[i] != ' ') str[i] -= key % 26;
+	const int result = a % b;
+	return result >= 0 ? result : result + b;
+}
+
+
+/*
+  * 65 - 90	 = ASCII 'A' - 'Z'
+  * 97 - 122 = ASCII 'a' - 'z'
+*/
+
+inline bool isupper(char c)
+{
+	return c >= 'A' && c <= 'Z';
+}
+
+
+void caesar_encrypt(char* str, int64_t size, int key)
+{
+	for (int64_t i = 0; i < size && str[i] != '\n'; i++)
+		if (str[i] != ' ')
+		{
+			bool upper = isupper(str[i]);
+			str[i] += (char)key - (upper ? 65 : 97);
+			str[i] %= 26;
+			str[i] += (upper ? 65 : 97);
+		}
+}
+
+
+void caesar_decrypt(char* str, int64_t size, int key)
+{
+	for (int64_t i = 0; i < size && str[i] != '\n'; i++)
+		if (str[i] != ' ')
+		{
+			bool upper = isupper(str[i]);
+			str[i] = str[i] - (char)key - (upper ? 65 : 97);
+			str[i] = (char)mod(str[i], 26);
+			str[i] += (upper ? 65 : 97);
+		}
 }

src/crypt.h

@@ -9,8 +9,9 @@
 */
 
 #pragma once
+#include <stdint.h>
 
 
-void caesar_encrypt(char* str, int size, int key);
+void caesar_encrypt(char* str, int64_t size, int key);
 
-void caesar_decrypt(char* str, int size, int key);
+void caesar_decrypt(char* str, int64_t size, int key);

src/dyninput.c

@@ -0,0 +1,58 @@
+/*
+  * Filename: dyninput.c
+  * Authors(s): Roland (Roland@example.com)
+  * Description: Short description here
+  *
+  * This Source Code Form is subject to the terms of the Mozilla Public
+  * License, v. 2.0. If a copy of the MPL was not distributed with this
+  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+
+char* dyninput_str(int_least64_t maxsize)
+{
+	char* str = malloc(3 * sizeof(char));
+	if (!str)
+	{
+		puts("\nError allocating memory!");
+		return NULL;
+	}
+
+	int_least64_t size = 3, i = 0;
+	char c = 0;
+
+	do
+	{
+		if (size == maxsize)
+		{
+			printf("Character limit of %lld reached!\n", maxsize);
+			break;
+		}
+
+		c = (char)getchar();
+		if (i + 1 == size)
+		{
+			char* tmp = realloc(str, size + 1);
+			if (!tmp)
+			{
+				puts("Error (re)allocating memory!");
+				return NULL;
+			}
+			str = tmp;
+			size++;
+		}
+
+		str[i] = c;
+		i++;
+	} while (c && c != '\n');
+	if (str[i - 1] != '\n') str[i - 1] = '\n';
+	str[i] = '\0';
+
+	// Sanitise stdin
+	while (c != '\n') c = (char)getchar();
+	return str;
+}

src/dyninput.h

@@ -0,0 +1,16 @@
+/*
+  * Filename: dyninput.h
+  * Authors(s): Roland (r.weirhowell@gmail.com)
+  * Description: Header file for dyninput.c
+  *
+  * This Source Code Form is subject to the terms of the Mozilla Public
+  * License, v. 2.0. If a copy of the MPL was not distributed with this
+  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include <stdint.h>
+
+
+char* dyninput_str(int_least64_t maxsize);