Responses

Status and headers

on_response runs once the final response head has been parsed. From then until the next request, these accessors describe it:

static bool on_response(lwhttp_client_t *client, void *arg)
{
  uint16_t status = lwhttp_client_status(client);
  const char *type = lwhttp_client_header(client, "content-type");
  return status == 200;
}

Header names are matched case-insensitively. When a field appears more than once, lwhttp_client_header() returns the first; walk all of them with lwhttp_client_headers() and lwhttp_headers_at().

Returning false from on_response aborts the request with LWHTTP_ERR_ABORTED before any body arrives.

Bodies

on_body receives the body in pieces as it arrives. Chunked bodies are already decoded. The pointer refers to the client’s receive buffer, so copy what you need before returning.

static bool on_body(lwhttp_client_t *client, const uint8_t *data, size_t len, void *arg)
{
  return ti_Write(data, 1, len, *(uint8_t *)arg) == len;
}

Responses to HEAD, 204 No Content and 304 Not Modified never have a body, whatever their headers say.

Trailers

Fields sent after a chunked body are appended to the same header store as the response head. They are visible through lwhttp_client_header() once on_complete runs.

Interim responses

100 Continue, 103 Early Hints and other 1xx responses are consumed silently; on_response only ever sees the final response. 101 Switching Protocols is final, see upgrades.

Content codings

LWHTTP does not decompress bodies. To make that safe it asks for uncompressed responses with Accept-Encoding: identity, and rejects any response whose body is encoded anyway:

• a Content-Encoding other than identity (gzip, deflate, br, …)

• a Transfer-Encoding other than chunked

Both end the request with LWHTTP_ERR_UNSUPPORTED before on_response or on_body run.

Tip

To receive compressed bytes on purpose, send your own Accept-Encoding header. LWHTTP then leaves the Content-Encoding check to you and passes the body through untouched.

Limits

The whole response head and any trailers must fit in lwhttp_client_config_t.header_size bytes (4096 by default). Exceeding it ends the request with LWHTTP_ERR_HEADERS_TOO_LARGE. See memory.