Saxy v0.6.0 Saxy View Source

Saxy is a XML SAX parser which provides functions to parse XML file in both binary and streaming way. Comply with Extensible Markup Language (XML) 1.0 (Fifth Edition).

Parsing mode

Saxy can be used in two modes: SAX and simple form.

SAX (Simple API for XML)

SAX is an event driven algorithm for parsing XML documents. A SAX parser takes XML document as the input and emits events out to a pre-configured event handler during parsing.

There are 5 types of SAX events supported by Saxy:

  • :start_document - after prolog is parsed.
  • :start_element - when open tag is parsed.
  • :characters - when a chunk of CharData is parsed.
  • :end_element - when end tag is parsed.
  • :end_document - when the root element is closed.

See Saxy.Handler for more information.

Simple form

Saxy supports parsing XML documents into a simple format. See Saxy.SimpleForm for more details.

Encoding

Saxy only supports UTF-8 encoding. It also respects the encoding set in XML document prolog, which means that if the declared encoding is not UTF-8, the parser stops. Anyway, when there is no encoding declared, Saxy defaults the encoding to UTF-8.

Reference expansion

Saxy supports expanding character references and XML 1.0 predefined entity references, for example A is expanded to "A", & to "&", and & to "&".

Saxy does not expand external entity references, but provides an option to specify how they should be handled. See more in “Shared options” section.

Creation of atoms

Saxy does not create atoms during the parsing process.

DTD and XSD

Saxy does not support DTD (Doctype Definition) and XSD schemas.

Shared options

  • :expand_entity - specifies how external entity references should be handled. Three supported strategies respectively are:

    • :keep - keep the original binary, for example Orange ® will be expanded to "Orange ®", this is the default strategy.
    • :skip - skip the original binary, for example Orange ® will be expanded to "Orange ".
    • {mod, fun, args} - take the applied result of the specified MFA.

Link to this section Summary

Link to this section Functions

Link to this function parse_stream(stream, handler, initial_state, options \\ []) View Source
parse_stream(
  stream :: File.Stream.t() | Stream.t(),
  handler :: module() | function(),
  initial_state :: term(),
  options :: Keyword.t()
) :: {:ok, state :: term()} | {:error, exception :: Saxy.ParseError.t()}

Parses XML stream data.

This function takes a stream, SAX event handler (see more at Saxy.Handler) and an initial state as the input, it returns {:ok, state} if parsing is successful, otherwise {:error, exception}, where exception is a Saxy.ParseError struct which can be converted into readable message with Exception.message/1.

Examples

defmodule MyTestHandler do
  @behaviour Saxy.Handler

  def handle_event(:start_document, prolog, state) do
    {:ok, [{:start_document, prolog} | state]}
  end

  def handle_event(:end_document, _data, state) do
    {:ok, [{:end_document} | state]}
  end

  def handle_event(:start_element, {name, attributes}, state) do
    {:ok, [{:start_element, name, attributes} | state]}
  end

  def handle_event(:end_element, {name}, state) do
    {:ok, [{:end_element, name} | state]}
  end

  def handle_event(:characters, chars, state) do
    {:ok, [{:chacters, chars} | state]}
  end
end

iex> stream = File.stream!("/path/to/file.xml")
iex> Saxy.parse_stream(stream, MyEventHandler, [])
{:ok,
 [
   {:end_document},
   {:end_element, "foo"},
   {:start_element, "foo", [{"bar", "value"}]},
   {:start_document, [version: "1.0", encoding: "UTF-8", standalone: false]}
 ]}

Memory usage

Saxy.parse_stream/3 takes a File.Stream or Stream as the input, so the amount of bytes to buffer in each chunk can be controlled by File.stream!/3 API.

During parsing, the actual memory used by Saxy might be higher than the number configured for each chunk, since Saxy holds in memory some parsed parts of the original binary to leverage Erlang sub-binary extracting. Anyway, Saxy tries to free those up when it makes sense.

Options

See the “Shared options” section at the module documentation.

Link to this function parse_string(data, handler, initial_state, options \\ []) View Source
parse_string(
  data :: binary(),
  handler :: module() | function(),
  initial_state :: term(),
  options :: Keyword.t()
) :: {:ok, state :: term()} | {:error, exception :: Saxy.ParseError.t()}

Parses XML binary data.

This function takes XML binary, SAX event handler (see more at Saxy.Handler) and an initial state as the input, it returns {:ok, state} if parsing is successful, otherwise {:error, exception}, where exception is a Saxy.ParseError struct which can be converted into readable message with Exception.message/1.

The third argument state can be used to keep track of data and parsing progress when parsing is happening, which will be returned when parsing finishes.

Options

See the “Shared options” section at the module documentation.

Examples

defmodule MyTestHandler do
  @behaviour Saxy.Handler

  def handle_event(:start_document, prolog, state) do
    {:ok, [{:start_document, prolog} | state]}
  end

  def handle_event(:end_document, _data, state) do
    {:ok, [{:end_document} | state]}
  end

  def handle_event(:start_element, {name, attributes}, state) do
    {:ok, [{:start_element, name, attributes} | state]}
  end

  def handle_event(:end_element, {name}, state) do
    {:ok, [{:end_element, name} | state]}
  end

  def handle_event(:characters, chars, state) do
    {:ok, [{:chacters, chars} | state]}
  end
end

iex> xml = "<?xml version='1.0' ?><foo bar='value'></foo>"
iex> Saxy.parse_string(xml, MyEventHandler, [])
{:ok,
 [
   {:end_document},
   {:end_element, "foo"},
   {:start_element, "foo", [{"bar", "value"}]},
   {:start_document, [version: "1.0", encoding: "UTF-8", standalone: false]}
 ]}