--- /dev/null
+reverse
+reverse_test
+*.o
+deps.makefile
+deps.makefile.bak
--- /dev/null
+CC = gcc
+CFLAGS = -Wall -Wextra -pedantic -Wstrict-overflow
+
+all: reverse
+
+clean:
+ -rm *.o reverse reverse_test
+
+distclean: clean
+ -rm deps.makefile deps.makefile.bak
+
+depend: *.c
+ makedepend -f- $^ > deps.makefile
+
+test: reverse_test
+ ./reverse_test
+
+.PHONY: clean distclean depend test
+
+reverse: reverse.o reverse_lib.o temp_file.o
+reverse_test: reverse_test.o reverse_lib.o temp_file.o
+ $(CC) -o $@ $^ $(CFLAGS)
+
+%.o: %.c
+ $(CC) -c -o $@ $< $(CFLAGS)
+
+-include deps.makefile
--- /dev/null
+#include "reverse_lib.h"
+
+#include <err.h>
+#include <stdio.h>
+#include <string.h>
+#include <sysexits.h>
+
+int main(int argc, char** argv) {
+ 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");
+ }
+ return 0;
+}
--- /dev/null
+#define _FILE_OFFSET_BITS 64
+
+#include "temp_file.h"
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+static off_t ceil_div(off_t dividend, off_t divisor) {
+ return (dividend - 1) / divisor + 1;
+}
+
+void reverse_file(const char* input_filename, FILE* output_stream) {
+ const off_t mmap_chunk_size = 512 << 20;
+
+ int fd = open(input_filename, O_RDONLY);
+ if (fd == -1) err(EX_NOINPUT, "Could not open specified file");
+
+ struct stat stats;
+ if (fstat(fd, &stats) == -1) err(EX_NOINPUT, "Could not stat input");
+
+ long page_size = sysconf(_SC_PAGE_SIZE);
+ off_t num_chunks = ceil_div(stats.st_size, mmap_chunk_size);
+ for (off_t chunk = num_chunks - 1; chunk >= 0; chunk--) {
+ off_t start_offset = chunk * mmap_chunk_size;
+ off_t end_offset = (chunk + 1) * mmap_chunk_size;
+ if (end_offset > stats.st_size) {
+ end_offset = stats.st_size;
+ }
+ off_t pages = ceil_div(end_offset - start_offset, page_size);
+ long map_size = pages * page_size;
+ char *m = mmap(NULL, map_size, PROT_READ, MAP_SHARED, fd, start_offset);
+ if (m == MAP_FAILED) err(EX_NOINPUT, "Could not mmap chunk %lld of %lld", chunk, num_chunks);
+
+ for (off_t p = (end_offset - start_offset) - 1; p >= 0; p--) {
+ if (fputc(m[p], output_stream) == EOF) errx(EX_IOERR, "Could not write");
+ }
+
+ if (munmap(m, map_size) == -1) err(EX_IOERR, "Could not unmap chunk %lld of %lld", chunk, num_chunks);
+ }
+
+ if (close(fd) == -1) err(EX_IOERR, "Could not close input");
+}
+
+/* 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);
+}
--- /dev/null
+#ifndef _OVERONION_REVERSE_LIB_H
+#define _OVERONION_REVERSE_LIB_H
+
+#include <stdio.h>
+
+/* Copy the contents of input_filename to output_stream backwards.
+ * 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 */
--- /dev/null
+#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;
+}
--- /dev/null
+#define _GNU_SOURCE
+
+#include "temp_file.h"
+
+#include <err.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sysexits.h>
+
+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");
+}
--- /dev/null
+#ifndef _OVERONION_TEMP_FILE_H
+#define _OVERONION_TEMP_FILE_H
+
+#include <stdio.h>
+
+/* 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. */
+void make_temporary_file(char** temp_filename, FILE** temp_file);
+
+#endif /* _OVERONION_TEMP_FILE_H */
projects / overonion / commitdiff