Append new primes to the end of a file.

src/files.c

@@ -21,17 +21,17 @@ int inputPrimes(char *file, List *list) {
 	return 0;
 }
 
-int outputPrimes(char *file, List *list) {
+int outputPrimes(char *file, List *list, size_t startPos) {
 	// Assert safeguards
 	assert(file);
 	assert(list);
 
-	FILE *out = fopen(file, "w");
+	FILE *out = fopen(file, "a");
 	if(!out) return 1;
 
 	printf("Saving primes to `%s'...\n", file);
 	puts("0%");
-	for(size_t i = 0; i < list->end; ++i) {
+	for(size_t i = startPos; i < list->end; ++i) {
 		if(!mpz_out_raw(out, list->list[i])) return 3;
 		if(i == list->end / 4) puts("25%");
 		else if(i == list->end / 2) puts("50%");

src/files.h

@@ -21,10 +21,12 @@ int inputPrimes(char *file, List *list);
  * @brief Output primes from a List into an Indivisible file.
  * @param file File to output primes to.
  * @param list List to read primes from.
+ * @param startPos The position in the List of primes at which to append
+ * to the file.
  * @returns If 0 then load was successful, if 1 then failed to open,
  * if 2 failed to close, if 3 failed when writing.
  */
-int outputPrimes(char *file, List *list);
+int outputPrimes(char *file, List *list, size_t startPos);
 
 /**
  * @brief Export primes from a List to a plain text file.

src/main.c

@@ -128,6 +128,8 @@ int main(int argc, char *argv[]) {
 		struct stat s;
 		if(stat(dfile, &s) == 0) newFile = false;
 	}
+	// Last position added from file
+	size_t startPos = 0;
 
 	int exitCode = 0;
 
@@ -169,6 +171,7 @@ int main(int argc, char *argv[]) {
 	} else {
 		// Load primes from file
 		int err = inputPrimes(dfile, &primes);
+		startPos = primes.end;
 
 		if(err == 0) {
 			printf("Loaded %zu primes.\n", primes.end);
@@ -244,7 +247,7 @@ int main(int argc, char *argv[]) {
 	printf("Found %zu primes.\n", primes.end);
 
 	if(dfile) {
-		int err = outputPrimes(dfile, &primes);
+		int err = outputPrimes(dfile, &primes, startPos);
 		if(err == 0) {
 			puts("Successfully saved primes.");
 		} else {