note
	description: "Wrapper for the MPG123 internal library"
	author: "Louis Marchand"
	date: "Tue, 21 Feb 2017 01:08:21 +0000"
	revision: "0.2"

class 
	MPG_EXTERNAL

create 
	default_create

feature {NONE} -- Initialization

	default_create
			-- Process instances of classes with no creation clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end
	
feature -- Access

	generating_type: TYPE [detachable MPG_EXTERNAL]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generating_type_not_void: Result /= Void
		end

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty
		end
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_deep_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)
		end

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))
		end

	frozen is_deep_equal alias "≡≡≡" (other: MPG_EXTERNAL): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)
		end

	is_equal (other: MPG_EXTERNAL): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result
		end

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.standard_is_equal (b)
			end
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))
		end

	frozen standard_is_equal alias "≜" (other: MPG_EXTERNAL): BOOLEAN
			-- Is other attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
		end
	
feature -- Status report

	conforms_to (other: ANY): BOOLEAN
			-- Does type of current object conform to type
			-- of other (as per Eiffel: The Language, chapter 13)?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		end

	same_type (other: ANY): BOOLEAN
			-- Is type of current object identical to type of other?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
		end
	
feature -- Duplication

	frozen clone (other: detachable ANY): like other
		obsolete "Use `twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- equal to other
			--
			-- For non-void other, clone calls copy;
			-- to change copying/cloning semantics, redefine copy.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.twin
			end
		ensure -- from ANY
			instance_free: class
			equal: Result ~ other
		end

	copy (other: MPG_EXTERNAL)
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		external
			"built_in"
		ensure -- from ANY
			is_equal: Current ~ other
		end

	frozen deep_clone (other: detachable ANY): like other
		obsolete "Use `deep_twin' instead. [2017-05-31]"
			-- Void if other is void: otherwise, new object structure
			-- recursively duplicated from the one attached to other
			-- (from ANY)
		do
			if other /= Void then
				Result := other.deep_twin
			end
		ensure -- from ANY
			instance_free: class
			deep_equal: deep_equal (other, Result)
		end

	frozen deep_copy (other: MPG_EXTERNAL)
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		do
			copy (other.deep_twin)
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)
		end

	frozen deep_twin: MPG_EXTERNAL
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)
		end

	frozen standard_clone (other: detachable ANY): like other
		obsolete "Use `standard_twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.standard_twin
			end
		ensure -- from ANY
			instance_free: class
			equal: standard_equal (Result, other)
		end

	frozen standard_copy (other: MPG_EXTERNAL)
			-- Copy every field of other onto corresponding field
			-- of current object.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		external
			"built_in"
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)
		end

	frozen standard_twin: MPG_EXTERNAL
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)
		end

	frozen twin: MPG_EXTERNAL
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
		end
	
feature -- Basic operations

	frozen as_attached: attached MPG_EXTERNAL
		obsolete "Remove calls to this feature. [2017-05-31]"
			-- Attached version of Current.
			-- (Can be used during transitional period to convert
			-- non-void-safe classes to void-safe ones.)
			-- (from ANY)
		do
			Result := Current
		end

	frozen default: detachable MPG_EXTERNAL
			-- Default value of object's type
			-- (from ANY)
		do
		end

	frozen default_pointer: POINTER
			-- Default value of type POINTER
			-- (Avoid the need to write p.default for
			-- some p of type POINTER.)
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end

	default_rescue
			-- Process exception for routines with no Rescue clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end
	
feature -- Constants

	frozen mpg123_enc_signed_16: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"MPG123_ENC_SIGNED_16"
		end

	frozen mpg123_enc_ulaw_8: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"MPG123_ENC_ULAW_8"
		end

	frozen mpg123_err: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"MPG123_ERR"
		end

	frozen mpg123_id3_constant: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"MPG123_ID3"
		end

	frozen mpg123_ok: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"MPG123_OK"
		end

	frozen seek_set: INTEGER_32
		external
			"C inline use <stdio.h>"
		alias
			"SEEK_SET"
		end

	frozen sizeof_mpg123_id3v1_album: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"sizeof(((mpg123_id3v1*)0)->album)"
		end

	frozen sizeof_mpg123_id3v1_artist: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"sizeof(((mpg123_id3v1*)0)->artist)"
		end

	frozen sizeof_mpg123_id3v1_comment: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"sizeof(((mpg123_id3v1*)0)->comment)"
		end

	frozen sizeof_mpg123_id3v1_title: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"sizeof(((mpg123_id3v1*)0)->title)"
		end

	frozen sizeof_mpg123_id3v1_year: INTEGER_32
		external
			"C inline use <mpg123.h>"
		alias
			"sizeof(((mpg123_id3v1*)0)->year)"
		end
	
feature -- Externals

	frozen mpg123_close (mh: POINTER): INTEGER_32
			-- Closes the source mh, if libmpg123 opened it.
		external
			"C (mpg123_handle *) : int | <mpg123.h>"
		alias
			"mpg123_close"
		end

	frozen mpg123_delete (mh: POINTER)
			-- Delete handle mh. mh is either a valid mpg123 handle or NULL.
		external
			"C (mpg123_handle *) | <mpg123.h>"
		alias
			"mpg123_delete"
		end

	frozen mpg123_exit
			-- Function to close down the mpg123 library.
			-- This function is not thread-safe. Call it exactly once per process.
		external
			"C | <mpg123.h>"
		alias
			"mpg123_exit"
		end

	frozen mpg123_format (mh: POINTER; rate, channels, encoding: INTEGER_32): INTEGER_32
			-- Set the audio format support (rate, channels and encoding) of a mpg123_handle mh
		external
			"C (mpg123_handle *, long, int, int) : int | <mpg123.h>"
		alias
			"mpg123_format"
		end

	frozen mpg123_format_none (mh: POINTER): INTEGER_32
			-- Configure a mpg123 handle mh to accept no output format at all.
			-- Use before specifying supported formats with mpg123_format
		external
			"C (mpg123_handle *) : int | <mpg123.h>"
		alias
			"mpg123_format_none"
		end

	frozen mpg123_getformat (mh, rate, channels, encoding: POINTER): INTEGER_32
			-- Get the current output format written to the addresses given.
		external
			"C (mpg123_handle *, long *, int *, int *) : int | <mpg123.h>"
		alias
			"mpg123_getformat"
		end

	frozen mpg123_id3 (mh, v1, v2: POINTER): INTEGER_32
			-- Point v1 and v2 to existing data structures wich may change
			-- on any next read/decode function call. v1 and/or v2 can be
			-- set to NULL when there is no corresponding data.
		external
			"C (mpg123_handle *, mpg123_id3v1 **, mpg123_id3v2 **) : int | <mpg123.h>"
		alias
			"mpg123_id3"
		end

	frozen mpg123_init: INTEGER_32
			-- Function to initialise the mpg123 library.
			-- This function is not thread-safe. Call it exactly once per process, before any other (possibly threaded) work with the library.
		external
			"C : int | <mpg123.h>"
		alias
			"mpg123_init"
		end

	frozen mpg123_length (mh: POINTER): INTEGER_32
			-- Return, if possible, the full (expected) length of current track in samples.
		external
			"C (mpg123_handle *) : int | <mpg123.h>"
		alias
			"mpg123_length"
		end

	frozen mpg123_meta_check (mh: POINTER): INTEGER_32
			-- Query if there is (new) meta info, be it ID3 or ICY (or something new in future).
		external
			"C (mpg123_handle *) : int | <mpg123.h>"
		alias
			"mpg123_meta_check"
		end

	frozen mpg123_new (decoder, error: POINTER): POINTER
			-- Create a handle with optional choice of decoder and optional retrieval of an error code.
			-- Any of or both the parameters may be NULL.
		external
			"C (const char *, int *) : mpg123_handle* | <mpg123.h>"
		alias
			"mpg123_new"
		end

	frozen mpg123_open (mh, path: POINTER): INTEGER_32
			-- Open in the handler mh and prepare to decode the specified file by filesystem path.
		external
			"C (mpg123_handle *, const char *) : int | <mpg123.h>"
		alias
			"mpg123_open"
		end

	frozen mpg123_plain_strerror (errcode: INTEGER_32): POINTER
			-- Look up error strings given errcode.
		external
			"C (int) : const char* | <mpg123.h>"
		alias
			"mpg123_plain_strerror"
		end

	frozen mpg123_read (mh, outmemory: POINTER; outmemsize: INTEGER_32; done: POINTER): INTEGER_32
			-- Read from stream and decode up to outmemsize bytes.
		external
			"C (mpg123_handle *, unsigned char *, size_t, size_t *) : int | <mpg123.h>"
		alias
			"mpg123_read"
		end

	frozen mpg123_scan (mh: POINTER): INTEGER_32
			-- Make a full parsing scan of each frame in the file.
		external
			"C (mpg123_handle *) : int | <mpg123.h>"
		alias
			"mpg123_scan"
		end

	frozen mpg123_seek (mh: POINTER; sampleoff, whence: INTEGER_32): INTEGER_32
			-- Seek to a desired sample offset. Usage is modelled afer the standard lseek().
		external
			"C (mpg123_handle *, off_t, int) : off_t | <mpg123.h>"
		alias
			"mpg123_seek"
		end

	frozen mpg123_tell (mh: POINTER): INTEGER_32
			-- Returns the current position in samples. On the next successful read, you'd get that sample.
		external
			"C (mpg123_handle *) : int | <mpg123.h>"
		alias
			"mpg123_tell"
		end
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		once
			create Result;
			Result.set_output_default
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void
		end

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		do
			Result := tagged_out
		ensure -- from ANY
			out_not_void: Result /= Void
		end

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		local
			s: READABLE_STRING_8
		do
			if attached o then
				s := o.out
				if attached {READABLE_STRING_32} s as s32 then
					Io.put_string_32 (s32)
				elseif attached {READABLE_STRING_8} s as s8 then
					Io.put_string (s8)
				else
					Io.put_string_32 (s.as_string_32)
				end
			end
		ensure -- from ANY
			instance_free: class
		end

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
		end
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		once
			create Result
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
		end
	
feature {NONE} -- Retrieval

	frozen internal_correct_mismatch
			-- Called from runtime to perform a proper dynamic dispatch on correct_mismatch
			-- from MISMATCH_CORRECTOR.
			-- (from ANY)
		local
			l_msg: STRING_32
			l_exc: EXCEPTIONS
		do
			if attached {MISMATCH_CORRECTOR} Current as l_corrector then
				l_corrector.correct_mismatch
			else
				create l_msg.make_from_string ("Mismatch: ".as_string_32)
				create l_exc;
				l_msg.append (generating_type.name_32);
				l_exc.raise_retrieval_exception (l_msg)
			end
		end
	
feature -- Structures

	frozen get_mpg123_id3v1_struct_album (a_mpg123_id3v1: POINTER): POINTER
			-- Album string of the ID3 V1 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"&(((mpg123_id3v1*)$a_mpg123_id3v1)->album[0])"
		end

	frozen get_mpg123_id3v1_struct_artist (a_mpg123_id3v1: POINTER): POINTER
			-- Artist string of the ID3 V1 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"&(((mpg123_id3v1*)$a_mpg123_id3v1)->artist[0])"
		end

	frozen get_mpg123_id3v1_struct_comment (a_mpg123_id3v1: POINTER): POINTER
			-- Comment string of the ID3 V1 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"&(((mpg123_id3v1*)$a_mpg123_id3v1)->comment[0])"
		end

	frozen get_mpg123_id3v1_struct_genre (a_mpg123_id3v1: POINTER): NATURAL_8
			-- Genre index of the ID3 V1 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v1*)$a_mpg123_id3v1)->genre"
		end

	frozen get_mpg123_id3v1_struct_title (a_mpg123_id3v1: POINTER): POINTER
			-- Title string of the ID3 V1 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"&(((mpg123_id3v1*)$a_mpg123_id3v1)->title[0])"
		end

	frozen get_mpg123_id3v1_struct_year (a_mpg123_id3v1: POINTER): POINTER
			-- Year string of the ID3 V1 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"&(((mpg123_id3v1*)$a_mpg123_id3v1)->year[0])"
		end

	frozen get_mpg123_id3v2_struct_album (a_mpg123_id3v1: POINTER): POINTER
			-- Album string of the ID3 V2 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v2*)$a_mpg123_id3v1)->album"
		end

	frozen get_mpg123_id3v2_struct_artist (a_mpg123_id3v1: POINTER): POINTER
			-- Artist string of the ID3 V2 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v2*)$a_mpg123_id3v1)->artist"
		end

	frozen get_mpg123_id3v2_struct_comment (a_mpg123_id3v1: POINTER): POINTER
			-- Comment string of the ID3 V2 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v2*)$a_mpg123_id3v1)->comment"
		end

	frozen get_mpg123_id3v2_struct_genre (a_mpg123_id3v1: POINTER): POINTER
			-- Genre string of the ID3 V2 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v2*)$a_mpg123_id3v1)->genre"
		end

	frozen get_mpg123_id3v2_struct_title (a_mpg123_id3v1: POINTER): POINTER
			-- Title string of the ID3 V2 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v2*)$a_mpg123_id3v1)->title"
		end

	frozen get_mpg123_id3v2_struct_year (a_mpg123_id3v1: POINTER): POINTER
			-- Year string of the ID3 V2 metadata
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_id3v2*)$a_mpg123_id3v1)->year"
		end

	frozen get_mpg123_string_struct_fill (a_mpg123_string: POINTER): INTEGER_32
			-- Get the data size from a mpg123_string
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_string*)$a_mpg123_string)->fill"
		end

	frozen get_mpg123_string_struct_p (a_mpg123_string: POINTER): POINTER
			-- Get the data pointer from a mpg123_string
		external
			"C inline use <mpg123.h>"
		alias
			"((mpg123_string*)$a_mpg123_string)->p"
		end
	
invariant
		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

end -- class MPG_EXTERNAL

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