feat(config): add support for config store buffers longer than 8k

Author: zkat

runtime/fastly/host-api/fastly.h

@@ -47,8 +47,8 @@ typedef fastly_host_http_response fastly_world_tuple2_handle_handle;
 #define HEADER_MAX_LEN 69000
 #define METHOD_MAX_LEN 1024
 #define URI_MAX_LEN 8192
-#define CONFIG_STORE_ENTRY_MAX_LEN 8000
-#define DICTIONARY_ENTRY_MAX_LEN CONFIG_STORE_ENTRY_MAX_LEN
+#define CONFIG_STORE_INITIAL_BUF_LEN 256
+#define DICTIONARY_ENTRY_MAX_LEN 8000
 
 // Ensure that all the things we want to use the hostcall buffer for actually
 // fit into the buffer.

runtime/fastly/host-api/host_api.cpp

@@ -2647,6 +2647,7 @@ Result<std::optional<HostString>> Dict::get(std::string_view name) {
   auto name_str = string_view_to_world_string(name);
   fastly::fastly_world_string ret;
   fastly::fastly_host_error err;
+  uint32_t buf_len{initial_buf_len};
 
   ret.ptr = static_cast<uint8_t *>(cabi_malloc(DICTIONARY_ENTRY_MAX_LEN, 1));
   if (!convert_result(fastly::dictionary_get(this->handle, reinterpret_cast<char *>(name_str.ptr),
@@ -2686,25 +2687,46 @@ Result<ConfigStore> ConfigStore::open(std::string_view name) {
 }
 
 Result<std::optional<HostString>> ConfigStore::get(std::string_view name) {
+  return this->get(name, CONFIG_STORE_INITIAL_BUF_LEN);
+}
+
+Result<std::optional<HostString>> ConfigStore::get(std::string_view name, uint32_t initial_buf_len) {
   TRACE_CALL()
   Result<std::optional<HostString>> res;
 
   auto name_str = string_view_to_world_string(name);
   fastly::fastly_world_string ret;
   fastly::fastly_host_error err;
-  ret.ptr = static_cast<uint8_t *>(cabi_malloc(CONFIG_STORE_ENTRY_MAX_LEN, 1));
-  if (!convert_result(fastly::config_store_get(this->handle, reinterpret_cast<char *>(name_str.ptr),
+  uin32_t buf_len{initial_buf_len};
+
+  ret.ptr = static_cast<uint8_t *>(cabi_malloc(buf_len, 1));
+
+  bool succeeded{convert_result(fastly::config_store_get(this->handle, reinterpret_cast<char *>(name_str.ptr),
                                                name_str.len, reinterpret_cast<char *>(ret.ptr),
-                                               CONFIG_STORE_ENTRY_MAX_LEN, &ret.len),
-                      &err)) {
+                                               buf_len, &ret.len),
+                      &err)}
+
+  if (!succeeded && err == FASTLY_HOST_ERROR_BUFFER_LEN) {
+    buf_len = ret.len;
+    ret.len = 0;
+    ret.ptr = static_cast<uint8_t *>(cabi_realloc(ret.ptr, initial_buf_len, 1, new_len));
+    succeeded = convert_result(fastly::config_store_get(this->handle, reinterpret_cast<char *>(name_str.ptr),
+                                               name_str.len, reinterpret_cast<char *>(ret.ptr),
+                                               buf_len, &ret.len),
+                      &err)}
+  }
+
+  if (!succeeded) {
     cabi_free(ret.ptr);
     if (error_is_optional_none(err)) {
       res.emplace(std::nullopt);
+    } else if (err == FASTLY_HOST_ERROR_BUFFER_LEN) {
+
     } else {
       res.emplace_err(err);
     }
   } else {
-    ret.ptr = static_cast<uint8_t *>(cabi_realloc(ret.ptr, CONFIG_STORE_ENTRY_MAX_LEN, 1, ret.len));
+    ret.ptr = static_cast<uint8_t *>(cabi_realloc(ret.ptr, buf_len, 1, ret.len));
     res.emplace(make_host_string(ret));
   }
 

runtime/fastly/host-api/host_api_fastly.h

@@ -846,6 +846,7 @@ class ConfigStore final {
   static Result<ConfigStore> open(std::string_view name);
 
   Result<std::optional<HostString>> get(std::string_view name);
+  Result<std::optional<HostString>> get(std::string_view name, uint32_t initial_buf_len);
 };
 
 class ObjectStorePendingLookup final {