Class: Streamdal::HostFunc

Inherits:
Object
  • Object
show all
Defined in:
lib/hostfunc.rb

Instance Method Summary collapse

Constructor Details

#initialize(kv) ⇒ HostFunc

This class holds methods that are called by wasm modules



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# File 'lib/hostfunc.rb', line 11

def initialize(kv)
  @kv = kv
end

Instance Method Details

#encode(str) ⇒ Object 



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# File 'lib/hostfunc.rb', line 65

def encode(str)
  str.force_encoding('ascii-8bit').encode('utf-8', invalid: :replace, undef: :replace, replace: '?')
end

#http_request(caller, ptr, len) ⇒ Object

http_request performs a http request on behalf of a wasm module since WASI cannot talk sockets



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# File 'lib/hostfunc.rb', line 39

def http_request(caller, ptr, len)
  data = caller.export('memory').to_memory.read(ptr, len)

  # Read request from memory and decode into HttpRequest
  req = Streamdal::Protos::WASMRequest.decode(data)

  begin
    req_body = _get_request_body_for_mode(req)
  rescue => e
    return _http_request_response(caller, 400, e.to_s, {})
  end

  # Attempt to make HTTP request
  # On error, return a mock 400 response with the error as the body
  begin
    response = _make_http_request(req.step.http_request.request, req_body)
  rescue => e
    return _http_request_response(caller, 400, "Unable to execute HTTP request: #{e}", {})
  end

  # Convert body to utf8
  out = encode(response.body)

  _http_request_response(caller, response.code, out, response.headers)
end

#kv_exists(caller, ptr, len) ⇒ Object

kv_exists is a host function that is used to check if a key exists in the KV store



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# File 'lib/hostfunc.rb', line 17

def kv_exists(caller, ptr, len)

  data = caller.export('memory').to_memory.read(ptr, len)

  # Read request from memory and decode into HttpRequest
  req = Streamdal::Protos::KVStep.decode(data)

  exists = @kv.exists(req.key)

  msg = exists ? "Key '#{req.key}' exists" : "Key #{req.key} does not exist"

  status = exists ? :KV_STATUS_SUCCESS : :KV_STATUS_FAILURE

  wasm_resp = Streamdal::Protos::KVStepResponse.new
  wasm_resp.status = status
  wasm_resp.message = msg

  write_to_memory(caller, wasm_resp)
end