Add ability to quote responses as needed.

It's up to the protocol to know when quotes are required.  In the future
the response should probably all be binary blobs with lengths.

bug:6353048
Change-Id: I3f9b48ab0f4e6746d75cdc9c0c84d33f38f63661
diff --git a/include/sysutils/SocketClient.h b/include/sysutils/SocketClient.h
index 4d7c4fa..85b58ef 100644
--- a/include/sysutils/SocketClient.h
+++ b/include/sysutils/SocketClient.h
@@ -64,6 +64,9 @@
     void incRef();
     bool decRef(); // returns true at 0 (but note: SocketClient already deleted)
 
+    // return a new string in quotes with '\\' and '\"' escaped for "my arg" transmissions
+    static char *quoteArg(const char *arg);
+
 private:
     // Send null-terminated C strings
     int sendMsg(const char *msg);
diff --git a/libsysutils/src/SocketClient.cpp b/libsysutils/src/SocketClient.cpp
index 1533120..4a1227f 100644
--- a/libsysutils/src/SocketClient.cpp
+++ b/libsysutils/src/SocketClient.cpp
@@ -107,6 +107,29 @@
     return sendData(buf, sizeof(buf));
 }
 
+char *SocketClient::quoteArg(const char *arg) {
+    int len = strlen(arg);
+    char *result = (char *)malloc(len * 2 + 3);
+    char *current = result;
+    const char *end = arg + len;
+
+    *(current++) = '"';
+    while (arg < end) {
+        switch (*arg) {
+        case '\\':
+        case '"':
+            *(current++) = '\\'; // fallthrough
+        default:
+            *(current++) = *(arg++);
+        }
+    }
+    *(current++) = '"';
+    *(current++) = '\0';
+    result = (char *)realloc(result, current-result);
+    return result;
+}
+
+
 int SocketClient::sendMsg(const char *msg) {
     if (mSocket < 0) {
         errno = EHOSTUNREACH;