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pdp10_stdio:handle_fopen/2: handling writes after seeks may require reads, so try to get read access even if the user did not ask for it

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Mikael Pettersson
2023-09-06 20:28:31 +02:00
parent 61dcfccd0d
commit dc517a8710
1 changed files with 14 additions and 4 deletions
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18
erlang/apps/lib/src/pdp10_stdio.erl
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@@ -243,11 +243,21 @@ code_change(_OldVsn, State, _Extra) -> {ok, State}.
handle_fopen(Path, Modes) ->
case iodir(Modes) of
{ok, {Read, Write}} ->
case file_open(Path, fopen_modes(Modes)) of
{ok, IoDev} -> {ok, {IoDev, Read, Write}};
{error, _Reason} = Error -> Error
{ok, {Read = false, Write = true}} ->
%% A write after a seek to a non octet-aligned nonet needs to reload the
%% shiftreg, which requires a read. Therefore if the user did not request
%% read access try to get it anyway.
case file_open(Path, fopen_modes([read | Modes])) of
{ok, IoDev} -> {ok, {IoDev, _Read = true, Write}};
{error, _Reason} -> handle_fopen(Path, Modes, Read, Write)
end;
{ok, {Read, Write}} -> handle_fopen(Path, Modes, Read, Write);
{error, _Reason} = Error -> Error
end.
handle_fopen(Path, Modes, Read, Write) ->
case file_open(Path, fopen_modes(Modes)) of
{ok, IoDev} -> {ok, {IoDev, Read, Write}};
{error, _Reason} = Error -> Error
end.