Accept streams as input. Use a temp file

diff --git a/reverse.c b/reverse.c
index 9bbf7b93076e4a61870f3f01c2e2010ed8ada58e..02a349fc33009860caa43dea115fbc27fdc86b19 100644 (file)
--- a/reverse.c
+++ b/reverse.c
@@ -2,14 +2,16 @@
 
 #include <err.h>
 #include <stdio.h>
+#include <string.h>
 #include <sysexits.h>
 
 int main(int argc, char** argv) {
-  if (argc != 2) {
+  if (argc == 1 || (argc == 2 && strcmp(argv[1], "-") == 0)) {
+    reverse_stream(stdin, stdout);
+  } else if (argc == 2) {
+    reverse_file(argv[1], stdout);
+  } else {
     errx(EX_USAGE, "Usage: reverse filename");
   }
-
-  reverse_file(argv[1], stdout);
-
   return 0;
 }

diff --git a/reverse_lib.c b/reverse_lib.c
index 46563562f3b3833d44a67b0809e5887c2abb949e..20837ee5f65fe95b237436b0d1685fd2d497a69d 100644 (file)
--- a/reverse_lib.c
+++ b/reverse_lib.c
@@ -1,8 +1,10 @@
+#define _GNU_SOURCE
 #define _FILE_OFFSET_BITS 64
 
 #include <err.h>
 #include <fcntl.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -29,3 +31,47 @@ void reverse_file(const char* input_filename, FILE* output_stream) {
   if (munmap(m, map_size) == -1) err(EX_IOERR, "Could not unmap input");
   if (close(fd) == -1) err(EX_IOERR, "Could not close input");
 }
+
+/* Create a temporary file in $TMPDIR, or /tmp if TMPDIR is not set.
+ * Caller must free temp_filename and fclose temp_file.  Succeeds or terminates
+ * the process. */
+static void make_temporary_file(char** temp_filename, FILE** temp_file) {
+  char* TMPDIR = getenv("TMPDIR");
+  if (TMPDIR == NULL) {
+    TMPDIR = "/tmp";
+  }
+  if (asprintf(temp_filename, "%s/reverse.XXXXXX", TMPDIR) == -1) {
+    errx(EX_OSERR, "Could not assemble temporary filename");
+  }
+  int fd = mkstemp(*temp_filename);
+  if (fd == -1) err(EX_IOERR, "Could not make a temporary file");
+  *temp_file = fdopen(fd, "w");
+  if (*temp_file == NULL) err(EX_IOERR, "Could not open temporary file");
+}
+
+/* Copy data from input to output until EOF is reached. */
+static void copy(FILE* input, FILE* output) {
+  for (;;) {
+    int c = fgetc(input);
+    if (c == EOF) {
+      if (ferror(input)) errx(EX_IOERR, "Could not read");
+      if (!feof(input)) errx(EX_IOERR, "Unexpected end of file");
+      break;
+    }
+    if (fputc(c, output) == EOF) errx(EX_IOERR, "Could not write");
+  }
+}
+
+void reverse_stream(FILE* input_stream, FILE* output_stream) {
+  char* temp_filename;
+  FILE* temp_file;
+  make_temporary_file(&temp_filename, &temp_file);
+
+  copy(input_stream, temp_file);
+  if (fclose(temp_file) != 0) err(EX_IOERR, "Could not close temporary file");
+
+  reverse_file(temp_filename, output_stream);
+
+  if (unlink(temp_filename) == -1) err(EX_IOERR, "Could not remove temporary file");
+  free(temp_filename);
+}

diff --git a/reverse_lib.h b/reverse_lib.h
index 9c0f05ae2eaa9d75d1894ff4da8a0eb3c55eecfd..d8b04802b607c6d07170b88a2b429b4163a1f79c 100644 (file)
--- a/reverse_lib.h
+++ b/reverse_lib.h
@@ -7,4 +7,9 @@
  * input_filename must be a real file, not a pipe. */
 void reverse_file(const char* input_filename, FILE* output_stream);
 
+/* Save the contents of input_stream to a temporary file.  On EOF,
+ * emit them backwards to output_stream.  Temporary files go in
+ * $TMPDIR if set, /tmp otherwise. */
+void reverse_stream(FILE* input_stream, FILE* output_stream);
+
 #endif /* _OVERONION_REVERSE_LIB_H */

diff --git a/reverse_test.c b/reverse_test.c
index 512edaa7477b77d9d8a193bf40ca2b66ff985302..30aff32d4d4153231ce510eadd83e5c9105d755c 100644 (file)
--- a/reverse_test.c
+++ b/reverse_test.c
@@ -9,6 +9,8 @@
 
 static const char test_file[] = "reverse.c";
 
+/* 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 = strdup("/tmp/reverse_test.XXXXXX");
   int fd = mkstemp(temp_filename);
@@ -20,20 +22,19 @@ char* reverse_to_temp_file(const char* input_file) {
   return temp_filename;
 }
 
-void test_reverse_twice_is_the_same() {
-  char* intermediate = reverse_to_temp_file(test_file);
-  char* back_to_normal = reverse_to_temp_file(intermediate);
-
-  FILE* f1 = fopen(test_file, "r");
-  if (f1 == NULL) err(EX_IOERR, "Couldn't open test file");
-  FILE* f2 = fopen(back_to_normal, "r");
-  if (f2 == NULL) err(EX_IOERR, "Couldn't open twice-reversed temp file");
+/* 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 test file");
-    if (c2 == EOF && ferror(f2)) err(EX_IOERR, "Error reading twice-reversed temp file");
+    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);
@@ -41,16 +42,55 @@ void test_reverse_twice_is_the_same() {
     if (c1 == EOF) break;
   }
 
-  if (fclose(f1) != 0) err(EX_IOERR, "Couldn't close test file");
-  if (fclose(f2) != 0) err(EX_IOERR, "Couldn't close twice-reversed temp file");
+  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() {
+  char* intermediate = reverse_to_temp_file(test_file);
+  char* back_to_normal = reverse_to_temp_file(intermediate);
+
+  compare(test_file, 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() {
+  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_file, 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 = strdup("/tmp/reverse_test.XXXXXX");
+  int out_fd = mkstemp(out_temp_filename);
+  if (out_fd == -1) err(EX_IOERR, "Couldn't make a temporary file");
+  FILE* out_file = fdopen(out_fd, "w");
+  if (out_file == NULL) err(EX_IOERR, "Couldn't open temporary file");
+  reverse_stream(from_first, out_file);
+  if (fclose(out_file) == EOF) err(EX_IOERR, "Couldn't close temporary file");
+
+  compare(test_file, out_temp_filename);
+
+  if (unlink(out_temp_filename) == -1) err(EX_IOERR, "Couldn't remove temp output file");
+  free(out_temp_filename);
+}
+
 int main() {
-  test_reverse_twice_is_the_same();
+  test_reverse_twice_from_files_is_the_same();
+  test_reverse_from_file_then_from_stream_is_the_same();
   puts("PASS");
   return 0;
 }