From 172ddd3e0fc0b2391e67604e78413d64d08ac6cb Mon Sep 17 00:00:00 2001
From: Rene Schallner <rene@renerocks.ai>
Date: Thu, 19 Jan 2023 21:24:22 +0100
Subject: [PATCH] Endpoint better json handling

---
 examples/endpoint/endpoint.zig | 27 ++++++++++++++++++++-------
 src/util.zig                   |  8 ++++----
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/examples/endpoint/endpoint.zig b/examples/endpoint/endpoint.zig
index a7523e5..77c771a 100644
--- a/examples/endpoint/endpoint.zig
+++ b/examples/endpoint/endpoint.zig
@@ -64,18 +64,31 @@ fn getUser(e: *zap.SimpleEndpoint, r: zap.SimpleRequest) void {
 
 fn listUsers(e: *zap.SimpleEndpoint, r: zap.SimpleRequest) void {
     _ = e;
+
+    // 1MB json buffer
+    var jsonbuf: [1024 * 1024]u8 = undefined;
+
     var l: std.ArrayList(User) = std.ArrayList(User).init(alloc);
     if (users.list(&l)) {} else |_| {
         return;
     }
-    // attention: if you add too many users, this will not be enough
-    var jsonbuf: [1024 * 1024]u8 = undefined;
-    if (zap.stringifyArrayListBuf(&jsonbuf, User, &l, .{})) |maybe_json| {
-        if (maybe_json) |json| {
-            _ = r.sendJson(json);
+    var maybe_json: ?[]const u8 = null;
+    var maybe_free: ?std.ArrayList(u8) = null;
+    // if (users.count > 0) {
+    if (users.count > 20000) {
+        // if > 20000 users, 1MB might not be enough for json
+        if (zap.stringifyArrayListAlloc(alloc, User, &l, .{}) catch null) |string| {
+            maybe_free = string;
+            maybe_json = string.items;
         }
-    } else |_| {
-        return;
+    } else {
+        maybe_json = zap.stringifyArrayListBuf(&jsonbuf, User, &l, .{}) catch null;
+    }
+    if (maybe_json) |json| {
+        _ = r.sendJson(json);
+    }
+    if (maybe_free) |free| {
+        free.deinit();
     }
 }
 
diff --git a/src/util.zig b/src/util.zig
index 237cf54..021524e 100644
--- a/src/util.zig
+++ b/src/util.zig
@@ -87,10 +87,10 @@ pub fn stringifyAlloc(
     a: std.mem.Allocator,
     value: anytype,
     options: std.json.StringifyOptions,
-) ?[]const u8 {
+) ?std.ArrayList(u8) {
     var string = std.ArrayList(u8).init(a);
     if (std.json.stringify(value, options, string.writer())) {
-        return string.items;
+        return string;
     } else |_| { // error
         return null;
     }
@@ -102,7 +102,7 @@ pub fn stringifyArrayListAlloc(
     comptime T: anytype,
     list: *std.ArrayList(T),
     options: std.json.StringifyOptions,
-) !?[]const u8 {
+) !?std.ArrayList(u8) {
     var string = std.ArrayList(u8).init(a);
     var writer = string.writer();
     try writer.writeByte('[');
@@ -113,5 +113,5 @@ pub fn stringifyArrayListAlloc(
         try std.json.stringify(user, options, string.writer());
     }
     try writer.writeByte(']');
-    return string.items;
+    return string;
 }