lfe_io.erl - I/O Interface

Purpose: Unified interface for reading and writing LFE S-expressions with delegation to specialized formatters.

Location: src/lfe_io.erl Size: 275 LOC, 9.6KB

Module Classification: I/O core, API facade

Public API

File Reading:

parse_file(FileName) -> {ok, [{Sexpr, Line}]} | {error, Error}
parse_file(FileName, StartLine) -> Result

Parse file returning sexprs with line numbers. Located at lfe_io.erl:72-77.

read_file(FileName) -> {ok, [Sexpr]} | {error, Error}
read_file(FileName, StartLine) -> Result

Read file returning sexprs only. Located at lfe_io.erl:98-103.

Interactive Reading:

read() -> {ok, Sexpr} | {error, Error} | eof
read(Prompt) -> Result
read(IoDevice, Prompt) -> Result

Read single sexpr with optional prompt. Located at lfe_io.erl:146-154.

read_line() -> {ok, Sexpr} | {error, Error} | eof
read_line(Prompt) -> Result
read_line(IoDevice, Prompt) -> Result

Line-oriented reading (for REPL). Located at lfe_io.erl:165-182.

String Reading:

read_string(String) -> {ok, [Sexpr]} | {error, Error}

Parse string into sexprs. Located at lfe_io.erl:221-226.

Writing:

print(Sexpr) -> ok
print(IoDevice, Sexpr) -> ok
print1(Sexpr) -> [char()]
print1(Sexpr, Depth) -> [char()]

Compact printing. Delegates to lfe_io_write. Lines 233-237.

prettyprint(Sexpr) -> ok
prettyprint(IoDevice, Sexpr) -> ok
prettyprint1(Sexpr) -> [char()]
prettyprint1(Sexpr, Depth, Indentation, LineLength) -> [char()]

Pretty printing. Delegates to lfe_io_pretty. Lines 244-253.

Formatted Output:

format(Format, Args) -> ok
format(IoDevice, Format, Args) -> ok
format1(Format, Args) -> [char()]

Formatted output (LFE's printf). Delegates to lfe_io_format. Lines 261-273.

Reading Architecture

Token-Based Reading (with_token_file/3 at lines 123-138):

with_token_file(File, DoFunc, Line) ->
    % 1. Open file
    {ok, Fd} = file:open(File, [read]),
    % 2. Scan tokens
    {ok, Tokens, LastLine} = io:request(Fd, {get_until, lfe_scan, tokens, [Line]}),
    % 3. Apply processing function
    Result = DoFunc(Tokens, LastLine),
    % 4. Close file
    file:close(Fd),
    Result.

Incremental Scanning (scan_sexpr/2 at lines 192-216):

Continuation-based scanning for interactive use:

scan_sexpr({ScanCont, ParseCont}, Chars, Line) ->
    case lfe_scan:token(ScanCont, Chars, Line) of
        {done, {ok, Token, Line1}, Rest} ->
            % Got token, try parsing
            case lfe_parse:sexpr(ParseCont, [Token]) of
                {ok, _, Sexpr, _} -> {done, {ok, Sexpr}, Rest};
                {more, ParseCont1} -> scan_sexpr_1([], ParseCont1, Rest, Line1)
            end;
        {more, ScanCont1} ->
            {more, {ScanCont1, ParseCont}}
    end.