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Use iodata in the internal state of StringIO #14289

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Use iodata in the internal state of StringIO #14289

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7bcc4b2
Use iodata in the internal state of StringIO
sabiwara Feb 20, 2025
0658849
Use reverse string list instead
sabiwara Mar 1, 2025
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17 changes: 11 additions & 6 deletions lib/elixir/lib/string_io.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -183,7 +183,7 @@ defmodule StringIO do
_ = Process.monitor(pid)
capture_prompt = options[:capture_prompt] || false
encoding = options[:encoding] || :unicode
{:ok, %{encoding: encoding, input: string, output: "", capture_prompt: capture_prompt}}
{:ok, %{encoding: encoding, input: string, output: [], capture_prompt: capture_prompt}}
end

@impl true
Expand All @@ -208,15 +208,18 @@ defmodule StringIO do

@impl true
def handle_call(:contents, _from, %{input: input, output: output} = state) do
{:reply, {input, output}, state}
string_output = reverse_join(output)
# update the state too to avoid having to do the same joining in future calls
{:reply, {input, string_output}, %{state | output: [string_output]}}
end

def handle_call(:flush, _from, %{output: output} = state) do
{:reply, output, %{state | output: ""}}
{:reply, reverse_join(output), %{state | output: []}}
end

def handle_call(:close, _from, %{input: input, output: output} = state) do
{:stop, :normal, {:ok, {input, output}}, state}
string_output = reverse_join(output)
{:stop, :normal, {:ok, {input, string_output}}, %{state | output: [string_output]}}
end

defp io_request(from, reply_as, req, state) do
Expand Down Expand Up @@ -302,7 +305,7 @@ defmodule StringIO do
defp put_chars(encoding, chars, req, state) do
case :unicode.characters_to_binary(chars, encoding, state.encoding) do
string when is_binary(string) ->
{:ok, %{state | output: state.output <> string}}
{:ok, %{state | output: [string | state.output]}}

{_, _, _} ->
{{:error, {:no_translation, encoding, state.encoding}}, state}
Expand Down Expand Up @@ -450,12 +453,14 @@ defmodule StringIO do

## helpers

defp reverse_join(output), do: output |> :lists.reverse() |> IO.iodata_to_binary()

defp state_after_read(%{capture_prompt: false} = state, remainder, _prompt, _count) do
%{state | input: remainder}
end

defp state_after_read(%{capture_prompt: true, output: output} = state, remainder, prompt, count) do
output = <<output::binary, :binary.copy(IO.chardata_to_string(prompt), count)::binary>>
output = [:binary.copy(IO.chardata_to_string(prompt), count) | output]
%{state | input: remainder, output: output}
end

Expand Down
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