+#include "reverse_lib.h"
+#include "temp_file.h"
+
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+/* Reverse input_file. Dump the result in a temporary file. Return the temp
+ * file's name. The caller must free the filename. */
+char* reverse_to_temp_file(const char* input_file) {
+ char* temp_filename;
+ FILE* f;
+ make_temporary_file(&temp_filename, &f);
+ reverse_file(input_file, f);
+ if (fclose(f) == EOF) err(EX_IOERR, "Couldn't close temporary file");
+ return temp_filename;
+}
+
+/* Compare the contents of two files. Terminate with a diagnostic if they
+ * differ. */
+void compare(const char* filename1, const char* filename2) {
+ FILE* f1 = fopen(filename1, "r");
+ if (f1 == NULL) err(EX_IOERR, "Couldn't open file %s", filename1);
+ FILE* f2 = fopen(filename2, "r");
+ if (f2 == NULL) err(EX_IOERR, "Couldn't open file %s", filename2);
+
+ for (int pos = 0; ; pos++) {
+ int c1 = fgetc(f1);
+ int c2 = fgetc(f2);
+ if (c1 == EOF && ferror(f1)) err(EX_IOERR, "Error reading file %s", filename1);
+ if (c2 == EOF && ferror(f2)) err(EX_IOERR, "Error reading file %s", filename2);
+ if (c1 != c2) {
+ errx(EX_SOFTWARE, "Unexpected difference found at offset %d after reversing twice. "
+ "Expected %d but found %d", pos, c1, c2);
+ }
+ if (c1 == EOF) break;
+ }
+
+ if (fclose(f1) != 0) err(EX_IOERR, "Couldn't close file %s", filename1);
+ if (fclose(f2) != 0) err(EX_IOERR, "Couldn't close file %s", filename2);
+}
+
+void test_reverse_twice_from_files_is_the_same(const char* test_filename) {
+ char* intermediate = reverse_to_temp_file(test_filename);
+ char* back_to_normal = reverse_to_temp_file(intermediate);
+
+ compare(test_filename, back_to_normal);
+
+ if (unlink(intermediate) == -1) err(EX_IOERR, "Couldn't remove intermediate temp file");
+ if (unlink(back_to_normal) == -1) err(EX_IOERR, "Couldn't remove twice-reversed temp file");
+ free(intermediate);
+ free(back_to_normal);
+}
+
+void test_reverse_from_file_then_from_stream_is_the_same(const char* test_filename) {
+ int pipefd[2];
+ if (pipe(pipefd) == -1) err(EX_OSERR, "Couldn't create pipe");
+
+ pid_t pid = fork();
+ if (pid == -1) err(EX_OSERR, "Couldn't fork");
+ if (pid == 0) {
+ if (close(pipefd[0]) == -1) err(EX_OSERR, "Couldn't close unneeded pipe descriptor");
+ FILE* to_second = fdopen(pipefd[1], "w");
+ if (to_second == NULL) err(EX_IOERR, "Couldn't open pipe for writing");
+ reverse_file(test_filename, to_second);
+ exit(0);
+ }
+ if (close(pipefd[1]) == -1) err(EX_OSERR, "Couldn't close unneeded pipe descriptor");
+ FILE* from_first = fdopen(pipefd[0], "r");
+ if (from_first == NULL) err(EX_IOERR, "Couldn't open pipe for reading");
+ char* out_temp_filename;
+ FILE* out_file;
+ make_temporary_file(&out_temp_filename, &out_file);
+ reverse_stream(from_first, out_file);
+ if (fclose(out_file) == EOF) err(EX_IOERR, "Couldn't close temporary file");
+
+ compare(test_filename, out_temp_filename);
+
+ if (unlink(out_temp_filename) == -1) err(EX_IOERR, "Couldn't remove temp output file");
+ free(out_temp_filename);
+}
+
+int main(int argc, char** argv) {
+ char* test_filename = "reverse.c";
+ if (argc > 2) {
+ errx(EX_USAGE, "usage: reverse_test [datafile]");
+ } else if (argc == 2) {
+ test_filename = argv[1];
+ }
+
+ test_reverse_twice_from_files_is_the_same(test_filename);
+ test_reverse_from_file_then_from_stream_is_the_same(test_filename);
+
+ puts("PASS");
+ return 0;
+}