From ab6abea6a71f0a5be24d3fbfac123131047ae9c5 Mon Sep 17 00:00:00 2001
From: Eric House <xwords@eehouse.org>
Date: Tue, 23 Feb 2021 11:16:15 -0800
Subject: [PATCH] use a callback instead of malloc inside js

---
 xwords4/wasm/main.c    |  3 ---
 xwords4/wasm/wasmasm.c | 48 ++++++++++++++++++++++++------------------
 xwords4/wasm/wasmasm.h |  2 ++
 3 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/xwords4/wasm/main.c b/xwords4/wasm/main.c
index cc6c7f7de..631823cd2 100644
--- a/xwords4/wasm/main.c
+++ b/xwords4/wasm/main.c
@@ -99,9 +99,6 @@ static void ensureName( GameState* gs );
 static void loadName( GameState* gs );
 static void saveName( GameState* gs );
 
-
-typedef void (*StringProc)(void* closure, const char* str);
-
 EM_JS(void, show_name, (const char* name), {
         let jsname = UTF8ToString(name);
         document.getElementById('gamename').textContent = jsname;
diff --git a/xwords4/wasm/wasmasm.c b/xwords4/wasm/wasmasm.c
index 1a095a4f6..6a11b37bd 100644
--- a/xwords4/wasm/wasmasm.c
+++ b/xwords4/wasm/wasmasm.c
@@ -24,16 +24,12 @@
 #include "wasmasm.h"
 #include "comtypes.h"
 
-EM_JS(const char*, _get_stored_value, (const char* key), {
+EM_JS(void, _get_stored_value, (const char* key,
+                                StringProc proc, void* closure), {
         var result = null;
         var jsKey = UTF8ToString(key);
-        var jsString = localStorage.getItem(jsKey);
-        if ( jsString != null ) {
-            var lengthBytes = lengthBytesUTF8(jsString)+1;
-            result = _malloc(lengthBytes);
-            stringToUTF8(jsString, result, lengthBytes);
-        }
-        return result;
+        var val = localStorage.getItem(jsKey);
+        ccallString(proc, closure, val);
     });
 
 EM_JS(void, set_stored_value, (const char* key, const char* val), {
@@ -54,20 +50,30 @@ EM_JS(bool, have_stored_value, (const char* key), {
         return result;
     });
 
+typedef struct _ValState {
+    void* ptr;
+    size_t** len;
+    bool success;
+} ValState;
+
+static void
+onGotVal(void* closure, const char* val)
+{
+    if ( !!val ) {
+        ValState* vs = (ValState*)closure;
+        size_t slen = 1 + strlen(val);
+        if ( !!vs->ptr && slen <= **vs->len ) {
+            memcpy( vs->ptr, val, slen );
+            vs->success = true;
+        }
+        **vs->len = slen;
+    }
+}
+
 bool
 get_stored_value( const char* key, char out[], size_t* len )
 {
-    bool success = false;
-    const char* tmp = _get_stored_value( key );
-    if ( !!tmp ) {
-        size_t slen = 1 + strlen(tmp);
-        if ( !!out && slen <= *len ) {
-            memcpy( out, tmp, slen );
-            success = true;
-        }
-        *len = slen;
-        free( (void*)tmp );
-    }
-
-    return success;
+    ValState state = { .ptr = out, .len = &len, .success = false, };
+    _get_stored_value( key, onGotVal, &state );
+    return state.success;
 }
diff --git a/xwords4/wasm/wasmasm.h b/xwords4/wasm/wasmasm.h
index c6fd28327..a46a32865 100644
--- a/xwords4/wasm/wasmasm.h
+++ b/xwords4/wasm/wasmasm.h
@@ -23,6 +23,8 @@
 #include <stdbool.h>
 #include <unistd.h>
 
+typedef void (*StringProc)(void* closure, const char* str);
+
 void set_stored_value(const char* key, const char* val);
 bool get_stored_value(const char* key, char out[], size_t* len);
 void remove_stored_value(const char* key);