with Ada.Streams; use Ada.Streams;
with Interfaces.C_Streams; use Interfaces.C_Streams;
-with System; use System;
-with System.Storage_Elements; use System.Storage_Elements;
with System.File_IO;
with System.CRTL;
with System.WCh_Cnv; use System.WCh_Cnv;
procedure Get_Line
(File : File_Type;
Item : out String;
- Last : out Natural)
- is
- Chunk_Size : constant := 80;
- -- We read into a fixed size auxiliary buffer. Because this buffer
- -- needs to be pre-initialized, there is a trade-off between size and
- -- speed. Experiments find returns are diminishing after 50 and this
- -- size allows most lines to be processed with a single read.
-
- ch : int;
- N : Natural;
-
- procedure memcpy (s1, s2 : chars; n : size_t);
- pragma Import (C, memcpy);
-
- function memchr (s : chars; ch : int; n : size_t) return chars;
- pragma Import (C, memchr);
-
- procedure memset (b : chars; ch : int; n : size_t);
- pragma Import (C, memset);
-
- function Get_Chunk (N : Positive) return Natural;
- -- Reads at most N - 1 characters into Item (Last + 1 .. Item'Last),
- -- updating Last. Raises End_Error if nothing was read (End_Of_File).
- -- Returns number of characters still to read (either 0 or 1) in
- -- case of success.
-
- ---------------
- -- Get_Chunk --
- ---------------
-
- function Get_Chunk (N : Positive) return Natural is
- Buf : String (1 .. Chunk_Size);
- S : constant chars := Buf (1)'Address;
- P : chars;
-
- begin
- if N = 1 then
- return N;
- end if;
-
- memset (S, 10, size_t (N));
-
- if fgets (S, N, File.Stream) = Null_Address then
- if ferror (File.Stream) /= 0 then
- raise Device_Error;
-
- -- If incomplete last line, pretend we found a LM
-
- elsif Last >= Item'First then
- return 0;
-
- else
- raise End_Error;
- end if;
- end if;
-
- P := memchr (S, LM, size_t (N));
-
- -- If no LM is found, the buffer got filled without reading a new
- -- line. Otherwise, the LM is either one from the input, or else one
- -- from the initialization, which means an incomplete end-of-line was
- -- encountered. Only in first case the LM will be followed by a 0.
-
- if P = Null_Address then
- pragma Assert (Buf (N) = ASCII.NUL);
- memcpy (Item (Last + 1)'Address,
- Buf (1)'Address, size_t (N - 1));
- Last := Last + N - 1;
-
- return 1;
-
- else
- -- P points to the LM character. Set K so Buf (K) is the character
- -- right before.
-
- declare
- K : Natural := Natural (P - S);
-
- begin
- -- Now Buf (K + 2) should be 0, or otherwise Buf (K) is the 0
- -- put in by fgets, so compensate.
-
- if K + 2 > Buf'Last or else Buf (K + 2) /= ASCII.NUL then
-
- -- Incomplete last line, so remove the extra 0
-
- pragma Assert (Buf (K) = ASCII.NUL);
- K := K - 1;
- end if;
-
- memcpy (Item (Last + 1)'Address,
- Buf (1)'Address, size_t (K));
- Last := Last + K;
- end;
-
- return 0;
- end if;
- end Get_Chunk;
-
- -- Start of processing for Get_Line
-
- begin
- FIO.Check_Read_Status (AP (File));
-
- -- Immediate exit for null string, this is a case in which we do not
- -- need to test for end of file and we do not skip a line mark under
- -- any circumstances.
-
- if Item'First > Item'Last then
- return;
- end if;
-
- N := Item'Last - Item'First + 1;
-
- Last := Item'First - 1;
-
- -- Here we have at least one character, if we are immediately before
- -- a line mark, then we will just skip past it storing no characters.
-
- if File.Before_LM then
- File.Before_LM := False;
- File.Before_LM_PM := False;
-
- -- Otherwise we need to read some characters
-
- else
- while N >= Chunk_Size loop
- if Get_Chunk (Chunk_Size) = 0 then
- N := 0;
- else
- N := N - Chunk_Size + 1;
- end if;
- end loop;
-
- if N > 1 then
- N := Get_Chunk (N);
- end if;
-
- -- Almost there, only a little bit more to read
-
- if N = 1 then
- ch := Getc (File);
-
- -- If we get EOF after already reading data, this is an incomplete
- -- last line, in which case no End_Error should be raised.
-
- if ch = EOF and then Last < Item'First then
- raise End_Error;
-
- elsif ch /= LM then
-
- -- Buffer really is full without having seen LM, update col
-
- Last := Last + 1;
- Item (Last) := Character'Val (ch);
- File.Col := File.Col + Count (Last - Item'First + 1);
- return;
- end if;
- end if;
- end if;
-
- -- We have skipped past, but not stored, a line mark. Skip following
- -- page mark if one follows, but do not do this for a non-regular file
- -- (since otherwise we get annoying wait for an extra character)
-
- File.Line := File.Line + 1;
- File.Col := 1;
-
- if File.Before_LM_PM then
- File.Line := 1;
- File.Before_LM_PM := False;
- File.Page := File.Page + 1;
-
- elsif File.Is_Regular_File then
- ch := Getc (File);
-
- if ch = PM and then File.Is_Regular_File then
- File.Line := 1;
- File.Page := File.Page + 1;
- else
- Ungetc (ch, File);
- end if;
- end if;
- end Get_Line;
+ Last : out Natural) is separate;
+ -- The implementation of Ada.Text_IO.Get_Line is split into a subunit so
+ -- that different implementations can be used on different systems. In
+ -- particular the standard implementation uses low level stuff that is
+ -- not appropriate for the JVM and .NET implementations.
procedure Get_Line
(Item : out String;
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