Add util function to get the APK path

Use "pm list package -f" to find where the APK is actually installed on
the device.

app/src/adb/adb.c

@@ -713,3 +713,48 @@ sc_adb_get_device_ip(struct sc_intr *intr, const char *serial, unsigned flags) {
 
     return sc_adb_parse_device_ip(buf);
 }
+
+char *
+sc_adb_get_installed_apk_path(struct sc_intr *intr, const char *serial,
+                              unsigned flags) {
+    assert(serial);
+    const char *const argv[] =
+        SC_ADB_COMMAND("-s", serial, "shell", "pm", "list", "package", "-f",
+                       SC_ANDROID_PACKAGE);
+
+    sc_pipe pout;
+    sc_pid pid = sc_adb_execute_p(argv, flags, &pout);
+    if (pid == SC_PROCESS_NONE) {
+        LOGD("Could not execute \"pm list packages\"");
+        return NULL;
+    }
+
+    // "pm list packages -f <package>" output should contain only one line, so
+    // the output should be short
+    char buf[1024];
+    ssize_t r = sc_pipe_read_all_intr(intr, pid, pout, buf, sizeof(buf) - 1);
+    sc_pipe_close(pout);
+
+    bool ok = process_check_success_intr(intr, pid, "pm list packages", flags);
+    if (!ok) {
+        return NULL;
+    }
+
+    if (r == -1) {
+        return NULL;
+    }
+
+    assert((size_t) r < sizeof(buf));
+    if (r == sizeof(buf) - 1)  {
+        // The implementation assumes that the output of "pm list packages"
+        // fits in the buffer in a single pass
+        LOGW("Result of \"pm list package\" does not fit in 1Kb. "
+             "Please report an issue.");
+        return NULL;
+    }
+
+    // It is parsed as a NUL-terminated string
+    buf[r] = '\0';
+
+    return sc_adb_parse_installed_apk_path(buf);
+}

app/src/adb/adb.h

@@ -15,6 +15,8 @@
 
 #define SC_ADB_SILENT (SC_ADB_NO_STDOUT | SC_ADB_NO_STDERR | SC_ADB_NO_LOGERR)
 
+#define SC_ANDROID_PACKAGE "com.genymobile.scrcpy"
+
 const char *
 sc_adb_get_executable(void);
 
@@ -114,4 +116,11 @@ sc_adb_getprop(struct sc_intr *intr, const char *serial, const char *prop,
 char *
 sc_adb_get_device_ip(struct sc_intr *intr, const char *serial, unsigned flags);
 
+/**
+ * Return the path of the installed APK for com.genymobile.scrcpy (if any)
+ */
+char *
+sc_adb_get_installed_apk_path(struct sc_intr *intr, const char *serial,
+                              unsigned flags);
+
 #endif

app/src/adb/adb_parser.c

@@ -225,3 +225,31 @@ sc_adb_parse_device_ip(char *str) {
 
     return NULL;
 }
+
+char *
+sc_adb_parse_installed_apk_path(char *str) {
+    // str is expected to look like:
+    // "package:/data/app/.../base.apk=com.genymobile.scrcpy"
+    //          ^^^^^^^^^^^^^^^^^^^^^^
+    // We want to extract the path (which may contain '=', even in practice)
+
+    if (strncmp(str, "package:", 8)) {
+        // Does not start with "package:"
+        return NULL;
+    }
+
+    char *s = str + 8;
+    size_t len = strcspn(s, " \r\n");
+    s[len] = '\0';
+
+    char *p = strrchr(s, '=');
+    if (!p) {
+        // No '=' found
+        return NULL;
+    }
+
+    // Truncate at the last '='
+    *p = '\0';
+
+    return strdup(s);
+}

app/src/adb/adb_parser.h

@@ -27,4 +27,15 @@ sc_adb_parse_devices(char *str, struct sc_vec_adb_devices *out_vec);
 char *
 sc_adb_parse_device_ip(char *str);
 
+/**
+ * Parse the package path from the output of
+ * `adb shell pm list packages -f <package>`
+ *
+ * The parameter must be a NUL-terminated string.
+ *
+ * Warning: this function modifies the buffer for optimization purposes.
+ */
+char *
+sc_adb_parse_installed_apk_path(char *str);
+
 #endif

app/tests/test_adb_parser.c

@@ -241,6 +241,28 @@ static void test_get_ip_truncated(void) {
     assert(!ip);
 }
 
+static void test_apk_path(void) {
+    char str[] = "package:/data/app/~~71mguyc6p-kNjQdNaNkToA==/com.genymobile."
+                 "scrcpy-l6fiqqUSU7Ok7QLg-rIyJA==/base.apk=com.genymobile."
+                 "scrcpy\n";
+
+    const char *expected = "/data/app/~~71mguyc6p-kNjQdNaNkToA==/com.genymobile"
+                           ".scrcpy-l6fiqqUSU7Ok7QLg-rIyJA==/base.apk";
+    char *path = sc_adb_parse_installed_apk_path(str);
+    assert(!strcmp(path, expected));
+    free(path);
+}
+
+static void test_apk_path_invalid(void) {
+    // Does not start with "package:"
+    char str[] = "garbage:/data/app/~~71mguyc6p-kNjQdNaNkToA==/com.genymobile."
+                 "scrcpy-l6fiqqUSU7Ok7QLg-rIyJA==/base.apk=com.genymobile."
+                 "scrcpy\n";
+
+    char *path = sc_adb_parse_installed_apk_path(str);
+    assert(!path);
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -263,5 +285,8 @@ int main(int argc, char *argv[]) {
     test_get_ip_no_wlan_without_eol();
     test_get_ip_truncated();
 
+    test_apk_path();
+    test_apk_path_invalid();
+
     return 0;
 }