measureJson()
Description
Computes the length of the minified JSON document that serializeJson() produces, excluding the null-terminator.
This function is handy to fill the Content-Length header in an HTTP message.
Signatures
size_t measureJson(const JsonDocument& doc);
Arguments
doc: the JsonDocument to serialize (in fact, you can also use a JsonArray, a JsonObject, or a JsonVariant).
Return value
The number of characters that serializeJson() produces, excluding the null-terminator.
Example
// Send headers
client.println("Content-Type: application/json");
client.print("Content-Length: ");
client.println(measureJson(doc));
// Terminate headers
client.println();
// Send body
serializeJson(doc, client);