Implement pipe support (resolves #13)

src/imgcat.c

@@ -14,18 +14,20 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* Feature-test macro for fileno(3). */
-#define _XOPEN_SOURCE
+/* Feature-test macro for fileno(3), fdopen(3), and mkstemp(3). */
+#define _XOPEN_SOURCE 500
 #include <assert.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
+#include <err.h>
 
 #include <getopt.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
+#include <errno.h>
 #include <sysexits.h>
 
 #include <term.h>
@@ -62,6 +64,10 @@ static struct {
     .optimum_format = F_8_COLOR
 };
 
+/* Global temporary filename for dumping stdin into.  */
+#define MAX_TEMPFILE_NAME 128
+static char tempfile_name[MAX_TEMPFILE_NAME + 1];
+
 /* Long options */
 static struct option long_options[] = {
     /* Options affecting output colour depth. */
@@ -86,28 +92,35 @@ static struct option long_options[] = {
 };
 
 
-/* Returns index of first positional argument. */
-static int parse_args(int argc, char **argv);
+/** Returns the filename of the image to open. */
+static const char* parse_args(int argc, char **argv);
 static void bad_usage(const char *msg, ...) __attribute__((noreturn));
+static void fatal_error(int code, const char *msg, ...) __attribute__((noreturn));
 static void determine_terminal_capabilities();
 static void usage(FILE *dest);
+static const char *dump_stdin_into_tempfile();
 
 /* Set first thing in main(). */
 static char const* program_name;
 
 
 int main(int argc, char **argv) {
-    int width, image_name_index;
+    int width;
     bool status;
     const char *image_name;
     Format color_format = F_UNSET;
     program_name = argv[0];
 
-    image_name_index = parse_args(argc, argv);
-
-    /* No image file specified. */
-    if (image_name_index == argc) {
-        bad_usage("Must specify an image file.");
+    image_name = parse_args(argc, argv);
+    if (image_name == NULL) {
+        if (isatty(fileno(stdin))) {
+            /* No image is specified on the command line, and there's nothing
+             * redirected to stdin. */
+            bad_usage("Must specify an image file.");
+        } else {
+            /* There's an image redirected to stdin. */
+            image_name = dump_stdin_into_tempfile();
+        }
     }
 
     determine_terminal_capabilities();
@@ -131,9 +144,6 @@ int main(int argc, char **argv) {
         color_format = terminal.optimum_format;
     }
 
-    /* TODO: multiple images OR stdin. */
-    image_name = argv[image_name_index];
-
     status = print_image(image_name, width, color_format);
 
     if (!status) {
@@ -191,6 +201,45 @@ static void determine_terminal_capabilities() {
     }
 }
 
+/**
+ * Removes the temporary file. Intended to be the atexit() callback.
+ */
+static void unlink_tempfile(void) {
+    remove(tempfile_name);
+}
+
+/**
+ * This is necessary because CImg likes to close and reopen the file it's
+ * reading, which discards header data when reading from /dev/stdin.
+ */
+static const char *dump_stdin_into_tempfile() {
+    int byte;
+    /* Set up the mutable buffer for mkstemp() to do its magic. */
+    strncpy(tempfile_name, "/tmp/image.XXXXXXXX", MAX_TEMPFILE_NAME);
+    int output_fd = mkstemp(tempfile_name);
+    if (output_fd == -1) {
+        fatal_error(EX_TEMPFAIL, "could not create temporary file: %s",
+                    strerror(errno));
+    }
+
+    FILE *output = fdopen(output_fd, "wb");
+    if (output == NULL) {
+        fatal_error(EX_IOERR, "could not open temporary file: %s",
+                    strerror(errno));
+    }
+
+    /* TODO: do something better than a byte-for-byte file transfer. */
+    while ((byte = getchar()) != EOF) {
+        fputc(byte, output);
+    }
+    fclose(output);
+
+    /* Remove the file at ordinary exit. */
+    atexit(unlink_tempfile);
+
+    return tempfile_name;
+}
+
 static void usage(FILE *dest) {
     const int field_width = strlen(program_name);
     fprintf(dest, "Usage:\n");
@@ -219,6 +268,18 @@ static void bad_usage(const char *msg, ...) {
     exit(EX_USAGE);
 }
 
+static void fatal_error(int code, const char *msg, ...) {
+    va_list args;
+
+    fprintf(stderr, "%s: ", program_name);
+
+    va_start(args, msg);
+    vfprintf(stderr, msg, args);
+    va_end(args);
+    fprintf(stderr, "\n");
+
+    exit(code);
+}
 
 static Format parse_format(const char *arg) {
 #   define argeq(b)     (strncmp(arg, (b), (sizeof(b))) == 0)
@@ -235,7 +296,7 @@ static Format parse_format(const char *arg) {
 #   undef argeq
 }
 
-static int parse_args(int argc, char **argv) {
+static const char* parse_args(int argc, char **argv) {
     int c;
     /* Disable getopt_long from printing to stderr. */
     extern int opterr;
@@ -287,5 +348,11 @@ static int parse_args(int argc, char **argv) {
         }
     }
 
-    return optind;
+    if (argc == optind) {
+        /* This means getopt() has exhausted all of argv and has not found a
+         * valid image name argument. */
+        return NULL;
+    } else {
+        return argv[optind];
+    }
 }

src/load_image.cc

@@ -38,7 +38,7 @@ bool load_image(const char *filename, Image *image, struct LoadOpts* options) {
     cimg_library::CImg<unsigned char> img;
     try {
         img.assign(filename);
-    } catch (cimg_library::CImgException& ex) {
+    } catch (cimg_library::CImgIOException& ex) {
         // Could not load the image for some reason.
         return false;
     }

tests/run

@@ -34,10 +34,14 @@ imgcat_tests() {
     assert_eq   1px_8_table.out     imgcat --8 1px_8_table.png
     assert_eq   1px_256_iterm2.out  imgcat --iterm2 1px_256_table.png
 
-    #           command that should fail
+    # Test invocations that should fail
+    assert_fail imgcat
     assert_fail imgcat --width=-3 "$ANY_IMAGE"
     assert_fail imgcat -w mank3y "$ANY_IMAGE"
     assert_fail imgcat --fake-option
+
+    # Test that we can pipe in images and have them render
+    assert_eq   1px_256_table.out   pipe 1px_256_table.png "$IMGCAT" --256
 }
 
 
@@ -111,6 +115,14 @@ _add_failure() {
     FAILURES+=("$((items - 1))")
 }
 
+# Can't specify command line redirection in assert commands,
+# so use this to do it for use.
+pipe() {
+    local filename="$1"; shift;
+    <"$filename" "$@"
+}
+
+
 print_success() {
     echo "${ANSI_GRN}$ncases tests passed${ANSI_RST}"
 }