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NAME
epp - An Erlang code preprocessor.
DESCRIPTION
The Erlang code preprocessor includes functions that are used by the compile module to
preprocess macros and include files before the parsing takes place.
The Erlang source file encoding is selected by a comment in one of the first two lines of
the source file. The first string matching the regular expression coding\s*[:=]\s*([-a-zA-
Z0-9])+ selects the encoding. If the matching string is not a valid encoding, it is
ignored. The valid encodings are Latin-1 and UTF-8, where the case of the characters can
be chosen freely.
Examples:
%% coding: utf-8
%% For this file we have chosen encoding = Latin-1
%% -*- coding: latin-1 -*-
DATA TYPES
macros() =
[atom() | {atom(), term()} | {atom(), term(), redefine}]
epp_handle() = pid()
Handle to the epp server.
source_encoding() = latin1 | utf8
warning_info() = {erl_anno:location(), module(), term()}
EXPORTS
close(Epp) -> ok
Types:
Epp = epp_handle()
Closes the preprocessing of a file.
default_encoding() -> source_encoding()
Returns the default encoding of Erlang source files.
encoding_to_string(Encoding) -> string()
Types:
Encoding = source_encoding()
Returns a string representation of an encoding. The string is recognized by
read_encoding/1,2, read_encoding_from_binary/1,2, and set_encoding/1,2 as a valid
encoding.
format_error(ErrorDescriptor) -> io_lib:chars()
Types:
ErrorDescriptor = term()
Takes an ErrorDescriptor and returns a string that describes the error or warning.
This function is usually called implicitly when processing an ErrorInfo structure
(see section Error Information).
open(Options) ->
{ok, Epp} | {ok, Epp, Extra} | {error, ErrorDescriptor}
Types:
Options =
[{default_encoding, DefEncoding :: source_encoding()} |
{includes, IncludePath :: [DirectoryName :: file:name()]} |
{source_name, SourceName :: file:name()} |
{macros, PredefMacros :: macros()} |
{name, FileName :: file:name()} |
{location, StartLocation :: erl_anno:location()} |
{fd, FileDescriptor :: file:io_device()} |
extra]
Epp = epp_handle()
Extra = [{encoding, source_encoding() | none}]
ErrorDescriptor = term()
Opens a file for preprocessing.
If you want to change the file name of the implicit -file() attributes inserted
during preprocessing, you can do with {source_name, SourceName}. If unset it will
default to the name of the opened file.
If extra is specified in Options, the return value is {ok, Epp, Extra} instead of
{ok, Epp}.
The option location is forwarded to the Erlang token scanner, see
erl_scan:tokens/3,4.
open(FileName, IncludePath) ->
{ok, Epp} | {error, ErrorDescriptor}
Types:
FileName = file:name()
IncludePath = [DirectoryName :: file:name()]
Epp = epp_handle()
ErrorDescriptor = term()
Equivalent to epp:open([{name, FileName}, {includes, IncludePath}]).
open(FileName, IncludePath, PredefMacros) ->
{ok, Epp} | {error, ErrorDescriptor}
Types:
FileName = file:name()
IncludePath = [DirectoryName :: file:name()]
PredefMacros = macros()
Epp = epp_handle()
ErrorDescriptor = term()
Equivalent to epp:open([{name, FileName}, {includes, IncludePath}, {macros,
PredefMacros}]).
parse_erl_form(Epp) ->
{ok, AbsForm} |
{error, ErrorInfo} |
{warning, WarningInfo} |
{eof, Location}
Types:
Epp = epp_handle()
AbsForm = erl_parse:abstract_form()
Location = erl_anno:location()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
WarningInfo = warning_info()
Returns the next Erlang form from the opened Erlang source file. Tuple {eof,
Location} is returned at the end of the file. The first form corresponds to an
implicit attribute -file(File,1)., where File is the file name.
parse_file(FileName, Options) ->
{ok, [Form]} |
{ok, [Form], Extra} |
{error, OpenError}
Types:
FileName = file:name()
Options =
[{includes, IncludePath :: [DirectoryName :: file:name()]} |
{source_name, SourceName :: file:name()} |
{macros, PredefMacros :: macros()} |
{default_encoding, DefEncoding :: source_encoding()} |
{location, StartLocation :: erl_anno:location()} |
extra]
Form =
erl_parse:abstract_form() |
{error, ErrorInfo} |
{eof, Location}
Location = erl_anno:location()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
Extra = [{encoding, source_encoding() | none}]
OpenError = file:posix() | badarg | system_limit
Preprocesses and parses an Erlang source file. Notice that tuple {eof, Location}
returned at the end of the file is included as a "form".
If you want to change the file name of the implicit -file() attributes inserted
during preprocessing, you can do with {source_name, SourceName}. If unset it will
default to the name of the opened file.
If extra is specified in Options, the return value is {ok, [Form], Extra} instead
of {ok, [Form]}.
The option location is forwarded to the Erlang token scanner, see
erl_scan:tokens/3,4.
parse_file(FileName, IncludePath, PredefMacros) ->
{ok, [Form]} | {error, OpenError}
Types:
FileName = file:name()
IncludePath = [DirectoryName :: file:name()]
Form =
erl_parse:abstract_form() |
{error, ErrorInfo} |
{eof, Location}
PredefMacros = macros()
Location = erl_anno:location()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
OpenError = file:posix() | badarg | system_limit
Equivalent to epp:parse_file(FileName, [{includes, IncludePath}, {macros,
PredefMacros}]).
read_encoding(FileName) -> source_encoding() | none
read_encoding(FileName, Options) -> source_encoding() | none
Types:
FileName = file:name()
Options = [Option]
Option = {in_comment_only, boolean()}
Read the encoding from a file. Returns the read encoding, or none if no valid
encoding is found.
Option in_comment_only is true by default, which is correct for Erlang source
files. If set to false, the encoding string does not necessarily have to occur in a
comment.
read_encoding_from_binary(Binary) -> source_encoding() | none
read_encoding_from_binary(Binary, Options) ->
source_encoding() | none
Types:
Binary = binary()
Options = [Option]
Option = {in_comment_only, boolean()}
Read the encoding from a binary. Returns the read encoding, or none if no valid
encoding is found.
Option in_comment_only is true by default, which is correct for Erlang source
files. If set to false, the encoding string does not necessarily have to occur in a
comment.
scan_erl_form(Epp) ->
{ok, Tokens} |
{error, ErrorInfo} |
{warning, WarningInfo} |
{eof, Line}
Types:
Epp = epp_handle()
Tokens = erl_scan:tokens()
Line = erl_anno:line()
ErrorInfo = erl_scan:error_info() | erl_parse:error_info()
WarningInfo = warning_info()
Returns the raw tokens of the next Erlang form from the opened Erlang source file.
A tuple {eof, Line} is returned at the end of the file. The first form corresponds
to an implicit attribute -file(File,1)., where File is the file name.
scan_file(FileName, Options) ->
{ok, [Form], Extra} | {error, OpenError}
Types:
FileName = file:name()
Options =
[{includes, IncludePath :: [DirectoryName :: file:name()]} |
{source_name, SourceName :: file:name()} |
{macros, PredefMacros :: macros()} |
{default_encoding, DefEncoding :: source_encoding()}]
Form = erl_scan:tokens() | {error, ErrorInfo} | {eof, Loc}
Loc = erl_anno:location()
ErrorInfo = erl_scan:error_info()
Extra = [{encoding, source_encoding() | none}]
OpenError = file:posix() | badarg | system_limit
Preprocesses an Erlang source file returning a list of the lists of raw tokens of
each form. Notice that the tuple {eof, Line} returned at the end of the file is
included as a "form", and any failures to scan a form are included in the list as
tuples {error, ErrorInfo}.
set_encoding(File) -> source_encoding() | none
Types:
File = io:device()
Reads the encoding from an I/O device and sets the encoding of the device
accordingly. The position of the I/O device referenced by File is not affected. If
no valid encoding can be read from the I/O device, the encoding of the I/O device
is set to the default encoding.
Returns the read encoding, or none if no valid encoding is found.
set_encoding(File, Default) -> source_encoding() | none
Types:
Default = source_encoding()
File = io:device()
Reads the encoding from an I/O device and sets the encoding of the device
accordingly. The position of the I/O device referenced by File is not affected. If
no valid encoding can be read from the I/O device, the encoding of the I/O device
is set to the encoding specified by Default.
Returns the read encoding, or none if no valid encoding is found.
ERROR INFORMATION
ErrorInfo is the standard ErrorInfo structure that is returned from all I/O modules. The
format is as follows:
{ErrorLine, Module, ErrorDescriptor}
A string describing the error is obtained with the following call:
Module:format_error(ErrorDescriptor)
SEE ALSO
erl_parse(3erl)