Add support for external image data source

Allows to load image by reading stdout from external command.

Relates to #145, #146.

Signed-off-by: Artem Senichev <[email protected]>

extra/swayimg.1

@@ -17,6 +17,9 @@ same directory as the image being loaded. This behavior can be changed with
 the \fBlist.all\fR parameter in the config file.
 .PP
 Use '-' as \fIFILE\fR to read image data from stdin.
+.PP
+Use prefix 'exec://' to get image data from stdout printed by external command,
+e.g. `swayimg "exec://wget -qO- https://www.kernel.org/theme/images/logos/tux.png"`.
 .\" ****************************************************************************
 .\" Options
 .\" ****************************************************************************

src/imagelist.c

@@ -303,11 +303,13 @@ size_t image_list_init(const char** sources, size_t num)
         add_dir(".", ctx.recursive);
     } else if (num == 1 && strcmp(sources[0], ALT_STDIN_FILE_NAME) == 0) {
         // pipe mode
-        add_file(STDIN_FILE_NAME);
+        add_file(LDRSRC_STDIN);
     } else {
         for (size_t i = 0; i < num; ++i) {
             struct stat file_stat;
-            if (stat(sources[i], &file_stat) == 0) {
+            if (strncmp(sources[i], LDRSRC_EXEC, LDRSRC_EXEC_LEN) == 0) {
+                add_entry(sources[i]);
+            } else if (stat(sources[i], &file_stat) == 0) {
                 if (S_ISDIR(file_stat.st_mode)) {
                     add_dir(sources[i], ctx.recursive);
                 } else {
@@ -362,7 +364,7 @@ size_t image_list_find(const char* source)
     }
     // handle alternate name for stdio
     if (strcmp(source, ALT_STDIN_FILE_NAME) == 0) {
-        source = STDIN_FILE_NAME;
+        source = LDRSRC_STDIN;
     }
 
     for (size_t i = 0; i < ctx.size; ++i) {

src/loader.c

@@ -20,6 +20,7 @@
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <unistd.h>
 
 #ifdef HAVE_INOTIFY
@@ -401,11 +402,12 @@ static enum loader_status image_from_file(struct image* img, const char* file)
 }
 
 /**
- * Load image from stdin.
+ * Load image from stream file (stdin).
  * @param img destination image
+ * @param fd file descriptor for read
  * @return loader status
  */
-static enum loader_status image_from_stdin(struct image* img)
+static enum loader_status image_from_stream(struct image* img, int fd)
 {
     enum loader_status status = ldr_ioerror;
     uint8_t* data = NULL;
@@ -425,7 +427,7 @@ static enum loader_status image_from_stdin(struct image* img)
             capacity = new_capacity;
         }
 
-        rc = read(STDIN_FILENO, data + size, capacity - size);
+        rc = read(fd, data + size, capacity - size);
         if (rc == 0) {
             status = image_from_memory(img, data, size);
             break;
@@ -440,6 +442,44 @@ static enum loader_status image_from_stdin(struct image* img)
     return status;
 }
 
+/**
+ * Load image from stdout printed by external command.
+ * @param img destination image
+ * @param cmd execution command to get stdout data
+ * @return loader status
+ */
+static enum loader_status image_from_exec(struct image* img, const char* cmd)
+{
+    enum loader_status status = ldr_ioerror;
+    int pfd[2];
+    pid_t pid;
+
+    if (pipe(pfd) == -1) {
+        abort();
+        return ldr_ioerror;
+    }
+
+    pid = fork();
+    if (pid == -1) {
+        abort();
+        return ldr_ioerror;
+    }
+
+    if (pid == 0) { // child
+        dup2(pfd[1], STDOUT_FILENO);
+        close(pfd[1]);
+        execlp("sh", "/bin/sh", "-c", cmd, NULL);
+        exit(1);
+    } else { // parent
+        close(pfd[1]);
+        status = image_from_stream(img, pfd[0]);
+        close(pfd[0]);
+        waitpid(pid, NULL, 0);
+    }
+
+    return status;
+}
+
 struct image* loader_load_image(const char* source, enum loader_status* status)
 {
     struct image* img = NULL;
@@ -453,15 +493,17 @@ struct image* loader_load_image(const char* source, enum loader_status* status)
     // save image source info
     img->source = str_dup(source, NULL);
     img->name = strrchr(img->source, '/');
-    if (!img->name) {
+    if (!img->name || strcmp(img->name, "/") == 0) {
         img->name = img->source;
     } else {
         ++img->name; // skip slash
     }
 
     // decode image
-    if (strcmp(source, STDIN_FILE_NAME) == 0) {
-        rc = image_from_stdin(img);
+    if (strcmp(source, LDRSRC_STDIN) == 0) {
+        rc = image_from_stream(img, STDIN_FILENO);
+    } else if (strncmp(source, LDRSRC_EXEC, LDRSRC_EXEC_LEN) == 0) {
+        rc = image_from_exec(img, source + LDRSRC_EXEC_LEN);
     } else {
         rc = image_from_file(img, source);
     }

src/loader.h

@@ -7,7 +7,11 @@
 #include "image.h"
 
 // File name used for image, that is read from stdin through pipe
-#define STDIN_FILE_NAME "{STDIN}"
+#define LDRSRC_STDIN "stdin://"
+
+// Special prefix used to load images from external command output
+#define LDRSRC_EXEC     "exec://"
+#define LDRSRC_EXEC_LEN (sizeof(LDRSRC_EXEC) - 1)
 
 /** Loader status. */
 enum loader_status {