From: Scott Worley Date: Sun, 7 May 2017 18:17:22 +0000 (-0700) Subject: Accept streams as input. Use a temp file X-Git-Url: http://git.scottworley.com/overonion/commitdiff_plain/a3915755b9992783e291b8921497ab7075557011 Accept streams as input. Use a temp file --- diff --git a/reverse.c b/reverse.c index 9bbf7b9..02a349f 100644 --- a/reverse.c +++ b/reverse.c @@ -2,14 +2,16 @@ #include #include +#include #include 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 4656356..20837ee 100644 --- a/reverse_lib.c +++ b/reverse_lib.c @@ -1,8 +1,10 @@ +#define _GNU_SOURCE #define _FILE_OFFSET_BITS 64 #include #include #include +#include #include #include #include @@ -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 9c0f05a..d8b0480 100644 --- 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 512edaa..30aff32 100644 --- 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; }