check adb runnable before starting scrcpy

There are many user who encounters missing adb.
To stop things happens again, we check it and show
sexy response to user.

Signed-off-by: yuchenlin <[email protected]>

app/src/main.c

@@ -5,6 +5,10 @@
 #include <libavformat/avformat.h>
 #include <SDL2/SDL.h>
 
+#ifdef __linux__
+#include <sys/stat.h>
+#endif
+
 #include "config.h"
 #include "log.h"
 
@@ -255,6 +259,53 @@ static SDL_bool parse_args(struct args *args, int argc, char *argv[]) {
     return SDL_TRUE;
 }
 
+static SDL_bool adb_runnable() {
+#ifdef __WINDOWS__
+    // Let windows ok now
+    return SDL_TRUE;
+#elif __linux__
+    const char *adb_command = getenv("ADB");
+    const char *path = getenv("PATH");
+    char *s = NULL;
+    char *s_head = NULL;
+    char *p = NULL;
+    char adb_path[PATH_MAX] = {0};
+    struct stat st;
+    SDL_bool runnable = SDL_FALSE;
+
+    if (adb_command) {
+        // if we have ADB env, we try it.
+        runnable = ((stat(adb_command, &st) == 0) && st.st_mode & S_IXUSR);
+    } else {
+        // otherwise, we parse PATH env, and try every possible.
+        s = SDL_malloc((strlen(path) + 1) * sizeof(char));
+        if (!s) {
+            LOGE("Insufficient memory.\n");
+            return SDL_FALSE;
+        }
+        s_head = strcpy(s, path);
+        do {
+            memset(adb_path, 0, sizeof(adb_path));
+            p = strchr(s, ':');
+            if (p != NULL) {
+                p[0] = 0;
+            }
+            snprintf(adb_path, sizeof(adb_path), "%s/adb", s);
+            runnable = ((stat(adb_path, &st) == 0) && st.st_mode & S_IXUSR);
+            s = p + 1;
+        } while (p != NULL && !runnable);
+    }
+
+    if (s_head) {
+        free(s_head);
+    }
+    return runnable;
+#else
+    // if we don't know what does scrcpy be compiled to, pass it.
+    return SDL_TRUE;
+#endif
+}
+
 int main(int argc, char *argv[]) {
 #ifdef __WINDOWS__
     // disable buffering, we want logs immediately
@@ -286,6 +337,11 @@ int main(int argc, char *argv[]) {
         return 0;
     }
 
+    if (!adb_runnable()) {
+        LOGE("Missing adb. You need adb, accessible from your PATH to execute %s.\n", argv[0]);
+        return 1;
+    }
+
 #if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(58, 9, 100)
     av_register_all();
 #endif