Simplify string construction processes

calathea.c

@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include <string.h>
 #include <dirent.h>
 #include <math.h>
@@ -133,6 +134,32 @@ void page_list_free(struct PageList *list) {
 }
 
 /*** Templating ***/
+char * concat_strings(int n, ...) {
+  va_list list;
+  va_start(list, n);
+
+  int length = 0;
+  char **strings = malloc(n * sizeof(char *));
+  memset(strings, 0, n * sizeof(char *));
+
+  for (int i = 0; i < n; i++) {
+    strings[i] = va_arg(list, char *);
+    length += strlen(strings[i]);
+  }
+
+  char * joinedString = malloc((length + 1) * sizeof(char *));
+  memset(joinedString, 0, (length + 1) * sizeof(char *));
+
+  strcpy(joinedString, strings[0]);
+  for (int i = 1; i < n; i++) {
+    strcat(joinedString, strings[i]);
+  }
+
+  free(strings);
+  va_end(list);
+  return joinedString;
+}
+
 char * substitute_string(char dest[], char sub[], char *start, char *end) {
   int startIndex = start - dest;
 
@@ -242,22 +269,14 @@ int main(int argc, char *argv[]) {
     currentPage->incoming = page_list(initialInboundCapacity);
 
     // Build the page's permalink
-    currentPage->permalink = malloc(strlen(fileBasename) + 6);
-
-    strcpy(currentPage->permalink, fileBasename);
-    strcat(currentPage->permalink, ".html");
+    currentPage->permalink = concat_strings(2, fileBasename, ".html");
 
     // Construct the relative path
     // The two accounts for the slash and the terminal zero
-    char relativePath[strlen(pagesLocation) + filenameLength + 2];
-    memset(relativePath, 0, strlen(pagesLocation) + filenameLength + 2);
-
-    strcpy(relativePath, pagesLocation);
-    strcat(relativePath, "/");
-    strcat(relativePath,fileEntry->d_name);
-    relativePath[strlen(pagesLocation) + filenameLength + 1] = 0;
+    char *relativePath = concat_strings(3, pagesLocation, "/", fileEntry->d_name);
 
     char *buffer = read_file(relativePath);
+    free(relativePath);
 
     if (buffer == NULL) {
       fileEntry = readdir(pagesDir);
@@ -310,15 +329,8 @@ int main(int argc, char *argv[]) {
   }
 
   // Create the directory if it doesn't exist
-  char *createOutputDir = malloc(
-      (7 + strlen(outputDirectoryName)) * sizeof(char)
-  );
-
-  strcpy(createOutputDir, "mkdir \0");
-  strcat(createOutputDir, outputDirectoryName);
-
+  char *createOutputDir = concat_strings(2, "mkdir ", outputDirectoryName);
   system(createOutputDir);
-
   free(createOutputDir);
 
   /*** Link Processing ***/
@@ -346,22 +358,18 @@ int main(int argc, char *argv[]) {
 
       struct Page *linkedPage = map_get(pageMap, mapSize, title);
 
-      char *compiledLink;
+      char *compiledLink = NULL;
 
       if (linkedPage == NULL) {
         // i.e. the page does not exist
-        compiledLink = malloc(strlen(title) + 38);
-        strcpy(compiledLink, "<a class=\"calathea-404\" href=\"#\">");
-        strcat(compiledLink, title);
-        strcat(compiledLink, "</a>\0");
+        compiledLink = concat_strings(3,
+          "<a class=\"calathea-404\" href=\"#\">",
+          title,
+          "</a>"
+        );
       } else {
         page_list_insert(linkedPage->incoming, currentPage);
-        compiledLink = malloc(strlen(title) + strlen(linkedPage->permalink) + 5);
-        strcpy(compiledLink, "[");
-        strcat(compiledLink, title);
-        strcat(compiledLink, "](");
-        strcat(compiledLink, linkedPage->permalink);
-        strcat(compiledLink, ")\0");
+        compiledLink = concat_strings(5, "[", title, "](", linkedPage->permalink, ")");
       }
 
       char *newContent = substitute_string(
@@ -421,11 +429,15 @@ int main(int argc, char *argv[]) {
       strcpy(incomingLinksList, "<ul class=\"calathea-incoming\">\n");
       for (int i = 0; i < currentPage->incoming->length; i++) {
         struct Page *page = currentPage->incoming->pages[i];
-        strcat(incomingLinksList, "  <li><a href=\"");
-        strcat(incomingLinksList, page->permalink);
-        strcat(incomingLinksList, "\">");
-        strcat(incomingLinksList, page->title);
-        strcat(incomingLinksList, "</a></li>\n");
+        char *link = concat_strings(5,
+            "  <li><a href=\"",
+            page->permalink,
+            "\">",
+            page->title,
+            "</a></li>\n"
+        );
+        strcat(incomingLinksList, link);
+        free(link);
       }
       strcat(incomingLinksList, "</ul>\n");
 
@@ -441,13 +453,8 @@ int main(int argc, char *argv[]) {
     }
 
     // Output the page to the file
-    char *outputFileName = malloc(
-      (strlen(outputDirectoryName)
-       + strlen(currentPage->permalink)
-       + 2));
-    strcpy(outputFileName, outputDirectoryName);
-    strcat(outputFileName, "/\0");
-    strcat(outputFileName, currentPage->permalink);
+    char *outputFileName = concat_strings(3,
+        outputDirectoryName, "/", currentPage->permalink);
 
     FILE *outputFile = fopen(outputFileName, "w");