我已从Github下载此程序：https://github.com/raph-amiard/ada-synth-lib
我已经提出了第一个示例，但我被发现例外。如果有人能够让我了解为什么会这样，将不胜感激。我已经为此困扰了很长时间，我真的很想让这个工作正常。
我收到的错误是：raised PROGRAM_ERROR : waves.adb:110 accessibility check failed
这里是主文件：
with Waves; use Waves;
with Write_To_Stdout;
procedure Main is
Sine_Gen : constant access Sine_Generator := Create_Sine (Fixed (440.0));
begin
Write_To_Stdout (Sine_Gen);
end Main;
这是waves.adb文件
with Effects; use Effects;
with Interfaces; use Interfaces;
package body Waves is
function Mod_To_Int (A : Unsigned_32) return Integer_32;
-------------------
-- Update_Period --
-------------------
procedure Update_Period
(Self : in out Wave_Generator'Class; Buffer : in out Period_Buffer)
is
begin
Self.Frequency_Provider.Next_Samples (Buffer);
for I in Buffer'Range loop
Buffer (I) :=
Utils.Period_In_Samples
(Frequency (Buffer (I)));
end loop;
end Update_Period;
------------
-- Create --
------------
function Create_Saw
(Freq_Provider : Generator_Access) return access Saw_Generator
is
begin
return new Saw_Generator'(Frequency_Provider => Freq_Provider,
Current => -1.0, others => <>);
end Create_Saw;
-----------------
-- Next_Sample --
-----------------
overriding procedure Next_Samples
(Self : in out Saw_Generator; Buffer : in out Generator_Buffer)
is
P_Buffer : Period_Buffer;
begin
Update_Period (Self, P_Buffer);
for I in Buffer'Range loop
Self.Step := 2.0 / Float (P_Buffer (I));
Self.Current := Self.Current + Sample (Self.Step);
if Self.Current > 1.0 then
Self.Current := Self.Current - 2.0;
end if;
Buffer (I) := Self.Current;
end loop;
end Next_Samples;
------------
-- Create --
------------
function Create_Square
(Freq_Provider : access Generator'Class) return access Square_Generator is
begin
return new Square_Generator'(Frequency_Provider =>
Generator_Access (Freq_Provider),
Is_High => True,
Current_Sample => 0,
others => <>);
end Create_Square;
-----------------
-- Next_Sample --
-----------------
overriding procedure Next_Samples
(Self : in out Square_Generator; Buffer : in out Generator_Buffer)
is
P_Buffer : Period_Buffer;
begin
Update_Period (Self, P_Buffer);
for I in Buffer'Range loop
Self.Current_Sample := Self.Current_Sample + 1;
declare
A : constant Period := Period (Self.Current_Sample)
/ P_Buffer (I);
begin
if A >= 1.0 then
Self.Current_Sample := 0;
Buffer (I) := 1.0;
end if;
Buffer (I) := (if A >= 0.5 then 1.0 else -1.0);
end;
end loop;
end Next_Samples;
------------
-- Create --
------------
function Create_Sine
(Freq_Provider : access Generator'Class) return access Sine_Generator
is
Ret : constant access Sine_Generator :=
new Sine_Generator'(Frequency_Provider =>
Generator_Access (Freq_Provider),
Current_Sample => 0,
Current_P => 0.0,
others => <>);
begin
Ret.Current_P := 0.0;
return Ret;
end Create_Sine;
-----------------
-- Next_Sample --
-----------------
overriding procedure Next_Samples
(Self : in out Sine_Generator; Buffer : in out Generator_Buffer)
is
P_Buffer : Period_Buffer;
begin
Update_Period (Self, P_Buffer);
for I in Buffer'Range loop
Self.Current_Sample := Self.Current_Sample + 1;
if Period (Self.Current_Sample) >= Self.Current_P then
Self.Current_P := P_Buffer (I) * 2.0;
Self.Current_Sample := 0;
end if;
Buffer (I) :=
Sample
(Sin
(Float (Self.Current_Sample)
/ Float (Self.Current_P) * Pi * 2.0));
end loop;
end Next_Samples;
------------
-- Create --
------------
function Create_Chain
(Gen : access Generator'Class;
Sig_Procs : Signal_Processors
:= No_Signal_Processors) return access Chain
is
Ret : constant access Chain :=
new Chain'(Gen => Generator_Access (Gen), others => <>);
begin
for P of Sig_Procs loop
Ret.Add_Processor (P);
end loop;
return Ret;
end Create_Chain;
-------------------
-- Add_Processor --
-------------------
procedure Add_Processor
(Self : in out Chain; P : Signal_Processor_Access) is
begin
Self.Processors (Self.Nb_Processors) := P;
Self.Nb_Processors := Self.Nb_Processors + 1;
end Add_Processor;
-----------------
-- Next_Sample --
-----------------
overriding procedure Next_Samples
(Self : in out Chain; Buffer : in out Generator_Buffer)
is
S : Sample;
begin
Self.Gen.Next_Samples (Buffer);
for J in Buffer'Range loop
S := Buffer (J);
for I in 0 .. Self.Nb_Processors - 1 loop
S := Self.Processors (I).Process (S);
end loop;
Buffer (J) := S;
end loop;
end Next_Samples;
---------
-- LFO --
---------
function LFO (Freq : Frequency; Amplitude : Float) return Generator_Access
is
Sin : constant Generator_Access := Create_Sine (Fixed (Freq));
begin
return new Attenuator'
(Level => Amplitude,
Source => new Transposer'(Source => Sin, others => <>), others => <>);
end LFO;
------------
-- Create --
------------
function Create_ADSR
(Attack, Decay, Release : Millisecond; Sustain : Scale;
Source : access Note_Generator'Class := null) return access ADSR
is
begin
return new ADSR'
(State => Off,
Source => Source,
Attack => Msec_To_Period (Attack),
Decay => Msec_To_Period (Decay),
Release => Msec_To_Period (Release),
Sustain => Sustain,
Current_P => 0, others => <>);
end Create_ADSR;
-----------------
-- Next_Sample --
-----------------
overriding procedure Next_Samples
(Self : in out ADSR; Buffer : in out Generator_Buffer)
is
Ret : Sample;
begin
for I in Buffer'Range loop
case Self.Source.Buffer (I).Kind is
when On =>
Self.Current_P := 0;
Self.State := Running;
when Off =>
Self.State := Release;
Self.Cur_Sustain := Scale (Self.Memo_Sample);
Self.Current_P := 0;
when No_Signal => null;
end case;
Self.Current_P := Self.Current_P + 1;
case Self.State is
when Running =>
if Self.Current_P in 0 .. Self.Attack then
Ret := Exp8_Transfer
(Sample (Self.Current_P) / Sample (Self.Attack));
elsif
Self.Current_P in Self.Attack + 1 .. Self.Attack + Self.Decay
then
Ret :=
Exp8_Transfer
(Float (Self.Decay + Self.Attack - Self.Current_P)
/ Float (Self.Decay));
Ret := Ret
* Sample (1.0 - Self.Sustain)
+ Sample (Self.Sustain);
else
Ret := Sample (Self.Sustain);
end if;
Self.Memo_Sample := Ret;
when Release =>
if Self.Current_P in 0 .. Self.Release then
Ret :=
Exp8_Transfer
(Sample (Self.Release - Self.Current_P)
/ Sample (Self.Release))
* Sample (Self.Cur_Sustain);
else
Self.State := Off;
Ret := 0.0;
end if;
when Off => Ret := 0.0;
end case;
Buffer (I) := Ret;
end loop;
end Next_Samples;
----------------------
-- Next_Sample --
----------------------
overriding procedure Next_Samples
(Self : in out Pitch_Gen; Buffer : in out Generator_Buffer)
is
Ret : Sample;
begin
if Self.Proc /= null then
Self.Proc.Next_Samples (Buffer);
end if;
for I in Buffer'Range loop
case Self.Source.Buffer (I).Kind is
when On =>
Self.Current_Note := Self.Source.Buffer (I).Note;
Self.Current_Freq :=
Note_To_Freq (Self.Current_Note, Self.Relative_Pitch);
when others => null;
end case;
Ret := Sample (Self.Current_Freq);
if Self.Proc /= null then
Ret := Ret + Buffer (I);
end if;
Buffer (I) := Ret;
end loop;
end Next_Samples;
------------------
-- Create_Noise --
------------------
function Create_Noise return access Noise_Generator
is
N : constant access Noise_Generator := new Noise_Generator;
begin
return N;
end Create_Noise;
F_Level : constant Sample := 2.0 / Sample (16#FFFFFFFF#);
G_X1 : Unsigned_32 := 16#67452301#;
G_X2 : Unsigned_32 := 16#EFCDAB89#;
Z : constant := 2 ** 31;
----------------
-- Mod_To_Int --
----------------
function Mod_To_Int (A : Unsigned_32) return Integer_32 is
Res : Integer_32;
begin
if A < Z then
return Integer_32 (A);
else
Res := Integer_32 (A - Z);
Res := Res - (Z - 1) - 1;
return Res;
end if;
end Mod_To_Int;
------------------
-- Next_Samples --
------------------
overriding procedure Next_Samples
(Self : in out Noise_Generator; Buffer : in out Generator_Buffer)
is
pragma Unreferenced (Self);
begin
for I in Buffer'Range loop
G_X1 := G_X1 xor G_X2;
Buffer (I) := Sample (Mod_To_Int (G_X2)) * F_Level;
G_X2 := G_X2 + G_X1;
end loop;
end Next_Samples;
------------------
-- Next_Samples --
------------------
overriding procedure Next_Samples
(Self : in out Fixed_Gen; Buffer : in out Generator_Buffer) is
begin
if Self.Proc /= null then
Self.Proc.Next_Samples (Buffer);
for I in Buffer'Range loop
Buffer (I) := Self.Val + Buffer (I);
end loop;
else
for I in Buffer'Range loop
Buffer (I) := Self.Val;
end loop;
end if;
end Next_Samples;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out ADSR) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Source);
Self.Memo_Sample := 0.0;
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Saw_Generator) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Frequency_Provider);
Self.Current := -1.0;
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Square_Generator) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Frequency_Provider);
Self.Current_Sample := 0;
Self.Is_High := True;
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Sine_Generator) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Frequency_Provider);
Self.Current_Sample := 0;
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Noise_Generator) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Frequency_Provider);
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Pitch_Gen) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Source);
Reset_Not_Null (Self.Proc);
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Fixed_Gen) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Proc);
end Reset;
-----------
-- Reset --
-----------
overriding procedure Reset (Self : in out Chain) is
begin
Base_Reset (Self);
Reset_Not_Null (Self.Gen);
end Reset;
-----------
-- Fixed --
-----------
function Fixed
(Freq : Frequency;
Modulator : Generator_Access := null;
Name : String := "";
Min : Float := 0.0;
Max : Float := 5_000.0;
Param_Scale : Param_Scale_T := Linear)
return access Fixed_Gen
is
begin
return new
Fixed_Gen'
(Val => Sample (Freq),
Proc => Modulator,
Name => To_Unbounded_String (Name),
Min => Min,
Max => Max,
Param_Scale => Param_Scale,
others => <>);
end Fixed;
---------------
-- Set_Value --
---------------
overriding procedure Set_Value
(Self : in out Fixed_Gen; I : Natural; Val : Float)
is
pragma Unreferenced (I);
begin
Self.Val := Sample (Val);
end Set_Value;
---------------
-- Set_Value --
---------------
overriding procedure Set_Value
(Self : in out ADSR; I : Natural; Val : Float)
is
begin
case I is
when 0 => Self.Attack := Sec_To_Period (Val);
when 1 => Self.Decay := Sec_To_Period (Val);
when 2 => Self.Sustain := Scale (Val);
when 3 => Self.Release := Sec_To_Period (Val);
when others => raise Constraint_Error;
end case;
end Set_Value;
end Waves;
最后是write_to_stdout.adb文件
with Utils; use Utils;
with GNAT.OS_Lib;
procedure Write_To_Stdout (G : access Generator'Class)
is
function Sample_To_Int16 is new Sample_To_Int (Short_Integer);
Int_Smp : Short_Integer := 0;
Ignore : Integer;
Buffer : Generator_Buffer;
begin
loop
Next_Steps;
G.Next_Samples (Buffer);
for I in Buffer'Range loop
Int_Smp := Sample_To_Int16 (Buffer (I));
Ignore := GNAT.OS_Lib.Write
(GNAT.OS_Lib.Standout, Int_Smp'Address, Int_Smp'Size / 8);
end loop;
exit when Sample_Nb > 10_000_000;
Sample_Nb := Sample_Nb + Generator_Buffer_Length;
end loop;
end Write_To_Stdout;
非常感谢您的阅读，对于解决此问题的任何指导将是不胜感激的。
干杯，
劳埃德
有关功能：
function Create_Sine
(Freq_Provider : access Generator'Class) return access Sine_Generator
is
Ret : constant access Sine_Generator :=
new Sine_Generator'(Frequency_Provider =>
Generator_Access (Freq_Provider),
Current_Sample => 0,
Current_P => 0.0,
others => <>);
begin
Ret.Current_P := 0.0;
return Ret;
end Create_Sine;
创建一个新对象，该对象可以在其本地作用域中由访问类型访问，并返回该访问的副本。在这种情况下，可能还可以，但是在类似的情况下，当函数返回时，对象本身超出范围，并留下了悬而未决的访问的可能性。
在这种情况下，这可能是谨慎的，因为对对象的唯一引用是返回的，但是可访问性检查禁止整个类别的潜在bug缠身构造。
有一个解决方案：在返回的对象中而不是在立即丢弃的本地对象中创建访问。 Ada-2005及更高版本提供了“扩展的回报”构造来允许这种情况。看起来像：
function Create_Sine
(Freq_Provider : access Generator'Class) return access Sine_Generator
is
begin
return Ret : constant access Sine_Generator :=
new Sine_Generator'( Frequency_Provider =>
Generator_Access (Freq_Provider),
Current_Sample => 0,
Current_P => 0.0,
others => <>)
do
-- initialisation actions here
Ret.Current_P := 0.0;
end return;
end Create_Sine;
未经测试！但是，一旦您知道它的名字，任何通常的消息来源都应该使您保持直觉。