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1083 | ------------------------------------------------------------------------------
-- G N A T C O L L --
-- --
-- Copyright (C) 2017-2018, AdaCore --
-- --
-- This library is free software; you can redistribute it and/or modify it --
-- under terms of the GNU General Public License as published by the Free --
-- Software Foundation; either version 3, or (at your option) any later --
-- version. This library is distributed in the hope that it will be useful, --
-- but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHAN- --
-- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
------------------------------------------------------------------------------
-- This package provides the implementation for XString.
-- Comparing with other string types
-- =================================
-- Ada provides several kinds of strings:
-- * A String
-- is a fixed-width string, but very fast in general. Functions returning
-- a String must do so on the secondary stack, which might be slow.
-- * A Bounded_String
-- has a known maximal size, but can represent any string smaller than this.
-- It also doesn't do any memory allocation, and therefore is fast. You
-- need one instance of the package for each size of bounded_string. This
-- is the type to use if your coding standard restricts memory allocations.
-- * An Unbounded_String
-- is a string of any size, which automatically allocates more memory when
-- needed. They are very flexible, but not very efficient.
-- This package provides a fourth type of string, which tries to combine the
-- advantages of all the above:
-- * Unlimited size of the string, which grows as necessary
-- More flexible than String and Bounded_String.
-- * No memory allocation for small strings (for a certain definition of
-- small, see the SSize parameter below). This means very fast handling of
-- those small strings.
-- Faster than Unbounded_String, both for small strings, as seen above,
-- but also for large strings since one can use the Reserve procedure to
-- preallocate enough space.
-- * More extensive interface.
-- For instance, you can use X(1) to get the first character of the string.
-- The index always starts at 1, just like unbounded strings.
-- * Supports various character types
-- See the encodings section below.
-- * Faster substrings
-- When using copy-on-write, returning a substring does not require any
-- copy of the data or memory allocation. This makes the operation much
-- faster, in particular for operations that return lots of substrings,
-- like Split.
-- * Easy iteration
-- It is possible to use a "for..of" loop to iterate on all valid indexes
-- or on all characters, with a speed similar to what is done for a String.
-- Task safety
-- ===========
-- Like Unbounded_String, a XString should not be accessed unprotected from
-- several different tasks. We do not use locks for maximum efficiency.
-- However, it is safe to pass a copy of a string to another thread, even when
-- they share some data internally. The sharing is an implementation detail,
-- and therefore properly encapsulated in this package. This package does not
-- use locks internally, but atomic operations.
-- So the following is invalid:
--
-- Thread 1 | Thread 2
-- S.Set ("..."); |
-- S.Append ("..."); | S.Append ("..."); -- invalid
-- S.Append ("..."); | S.To_String; -- also invalid
--
-- But the following is valid:
--
-- Thread 1 | Thread 2
-- S.Set ("..."); |
-- | lock; S2 := S; unlock;
-- |
-- S.Append ("..."); | S2.Append ("...");
-- at this point, they no longer share data, in fact
-- Memory management
-- =================
-- A major design decision for this package is that it does as little memory
-- allocations as possible. Therefore for small strings, it does none. When
-- the string grows, it ends up allocating a buffer, whose size will be
-- increased when the string keeps growing. The growth strategy attempts a
-- balance between speed and memory usage, so it will allocate more memory
-- than strictly needed for the string, in case it eventually grows. See the
-- Shrink subprogram if you need to restrict memory usage.
-- When this package needs to return a copy of a string, or a substring,
-- it has two possible strategies:
-- * Either it tries to share the already allocated memory. As explained
-- above, this is done in a thread-safe manner, and thus has a small
-- performance penalty. On the other hand, it doesn't need to copy
-- characters around, so it might be faster.
-- As soon as you modify a string, the buffer can no longer be shared,
-- and a copy is created (thus the term "copy on write").
-- * Or, if you disabled copy on write, it systematically allocates new
-- memory when you do a copy or take a substring. This removes the
-- need for atomic operations, and might be more efficient in heavily
-- multi-threaded applications.
-- We recommend doing actual performance measurement to decide which strategy
-- to use.
-- When you use this package, you could be seeing memory leaks when your
-- program exits. This is because, like unbounded_string, it uses the pragma
-- Finalize_Storage_Only which means that GNAT can skip the calls to free
-- memory on exit, for performance reasons. It should not have memory leaks
-- the rest of the time, though.
-- Indexing
-- =========
-- As opposed to what is done for standard Ada strings, all indexing always
-- start at index 1. Even if you take a substring from indices 5 to 6, for
-- instance, the resulting substring's first character is at index 1.
-- This is both by design (for a lot of users, it is confusing to remember to
-- use the proper indexes 'First and 'Last with standard strings), but also is
-- needed because the internal buffer can be shared. For instance, when you
-- take a substring as above, the internal buffer is shared (so we are really
-- looking at characters 5 through 6 in this shared buffer). But as soon as
-- you modify the substring, for instance by appending some data, this package
-- needs to reallocate memory. In this case, it will move characters around,
-- and we will be looking at actual characters 1 through 2 in the internal
-- buffer.
-- Always using "1" as the user-visible index for the first character ensures
-- that any internal reallocation or move of data is transparent to the user.
-- Unicode, character encodings,...
-- ================================
-- When you need to manipulate characters outside of the ASCII character set
-- (for instance accented letters, or Chinese symbols), things get more
-- complicated.
-- The unicode body assigned unique code points to all possible characters
-- in use on Earth. These code points are 16 bits numbers. Ada provides
-- various types to deal with code points:
-- * A Character only represents code points 0 through 255.
-- It is typically used to represent the Latin1 subset of unicode,
-- i.e. western Europe characters.
--
-- * A Wide_Character can represent mode Unicode code points, but
-- requires twice as much memory to represent
--
-- * A Wide_Wide_Character can represent all characters, but is even
-- larger.
-- There exist other character sets than Unicode, which usually predate it.
-- They associate different character with codepoints. For instance, in the
-- Latin1 charset, the code point 192 is "a grave"). But in latin5, it is a
-- Russian letter. In Latin1, that Russian character cannot be represented.
-- So to represent a character on the screen, we have to know its code point,
-- but also its character set. The simplest, in terms of programming, it to
-- always convert the input string from a known charset (say latin5) to
-- unicode internally, so that we can always compare codepoints easily in the
-- code, without the need for conversions all over the place.
-- These code points (integers) need to be converted to strings so that we can
-- display them, store them in files, input them,... Here, there also exists
-- various ways to do that, called encodings:
--
-- * Historical charset always have codepoints between 0 and 255 (and
-- of course these are only a subset of all characters one might use
-- in the world). So we simply use a series of bytes to represent them.
-- In Ada, we would use a String for that purpose. But then, as stated
-- above, this means that to compare two strings we have to know that
-- they use the same charset.
--
-- * Unicode defines a UTF-8 encoding. It can represent any codepoint,
-- including greater than 255, but uses a variable number of bytes for
-- code points. This is efficient in terms of storage (most of the
-- time the characters only use a single byte), but costly in terms
-- of manipulation since we have to make sure not to cut the string
-- between two bytes of a multi-byte character.
--
-- * Unicode also defines UTF-16, which has two variants, depending on
-- whether the most significant byte goes first or not. Code points
-- are represented on two bytes, though sometimes they will need a
-- bit more for some rare codepoints.
--
-- * Unicode finally defined UTF-32 (also with two variants), where
-- codepoints are always represented as 4 bytes.
-- As seen above, this is a very complex topic, and manipulating strings with
-- different encodings, or comparing strings with different charsets becomes
-- complex and costly in terms of performance.
-- As a result, the choice taken in this package is to always store decoded
-- strings (i.e. we don't use utf-8, utf-16 or anything else, but just store
-- an array of code points). The Character_Type formal parameter can be used
-- to chose the range of code points you want to be able to represent.
-- Likewise, we always assume these are Unicode code points.
-- So the workflow is the following:
--
-- * Get an input string (from the user, a database,...), with a
-- known charset and encoding.
-- We call such a string a byte sequence since it cannot be
-- interpreted correctly without information on the charset and
-- encoding.
--
-- * Decode this byte sequence into an XString
--
-- * Manipulate the XString using any of the subprograms in this API.
--
-- * If you need to output the string (to the user, into a file,...)
-- encode it with an appropriate charset and encoding.
private with Ada.Finalization;
with Ada.Containers;
with Ada.Strings;
with GNATCOLL.Atomic;
with System;
package GNATCOLL.Strings_Impl is
type String_Size is mod 2 ** 32;
-- Internal size used for string sizes. This matches a Natural as used for
-- standard Ada strings.
Big_String_Size : constant := 2 * System.Word_Size + 2 * String_Size'Size;
type Optimal_String_Size is mod (Big_String_Size / 8);
for Optimal_String_Size'Size use Character'Size;
-- Type used to instantiate GNATCOLL.Strings
-- Ideal size is 19 bytes on 32 bits system or 23 on 64 bits systems),
-- so that a small string (stored without memory allocation) takes the
-- same size as a big string (not counting the size of the allocated
-- memory).
function Default_Growth
(Current, Min_Size : String_Size) return String_Size;
-- The default growth strategy. This decides how much memory we should
-- allocate/reallocate for the internal buffer, based on the amount of
-- memory we already use (Current), and the minimal number characters
-- we need to store in the string.
-- Current and Min_Size are given in 'characters' not in 'bytes', since
-- a character could potentially take several bytes.
generic
type SSize is mod <>;
-- Number of characters that can be stored in the XString object itself,
-- without requiring memory allocations.
-- We pass a type as opposed to an actual number of character because we
-- need to apply representation clauses based on this type, which cannot
-- be done if we have the number of characters.
-- This type must be a range between 1 and 127.
type Character_Type is (<>);
-- The character type to use. You can use Character for compatibility
-- with an Ada string, or Wide_Character for better Unicode support,
-- or possibly other types.
type Character_String is array (Positive range <>) of Character_Type;
-- An array of Char_Type, i.e. a string as can be stored on the
-- stack.
Space : Character_Type := Character_Type'Val (Character'Pos (' '));
-- The space character
with function To_Lower
(Item : Character_Type) return Character_Type is <>;
with function To_Upper
(Item : Character_Type) return Character_Type is <>;
-- character-specific functions.
-- In general, you do not need to specify those if you have 'use'd
-- the package Ada.Characters.Handling or Ada.Wide_Characters.Handling.
Copy_On_Write : Boolean := GNATCOLL.Atomic.Is_Lock_Free;
-- Whether we only duplicate strings when they are actually modified.
-- The alternative is to duplicate them every time a xstring is copied
-- into another. The latter might be faster in some cases (less
-- contention in multithreading for instance).
with function Growth_Strategy
(Current, Min_Size : String_Size) return String_Size
is Default_Growth;
-- See the comment for Default_Growth
package Strings is
pragma Compile_Time_Error
(Natural (SSize'Last) > 2 ** 7, "SSize too large");
subtype Char_Type is Character_Type;
subtype Char_String is Character_String;
Null_Char_String : constant Char_String := (1 .. 0 => <>);
-- Local renamings, so that users of the package can use these types.
type XString is tagged private
with
Constant_Indexing => Get,
Variable_Indexing => Reference,
Iterable => (First => First,
Next => Next,
Has_Element => Has_Element,
Element => Get);
pragma Preelaborable_Initialization (XString);
Null_XString : constant XString;
-- This Null_XString is always equal to an empty string. So you
-- can use either
-- if Str = "" then
-- or if Str = Null_Xstring then
type Unconstrained_Char_Array is
array (1 .. Natural'Last) of aliased Char_Type;
type Char_Array is access all Unconstrained_Char_Array;
pragma Suppress_Initialization (Unconstrained_Char_Array);
pragma No_Strict_Aliasing (Char_Array);
for Char_Array'Storage_Size use 0;
-- Type used to obtain a string access to a given address.
-- Initialization is suppressed to handle pragma Normalize_Scalars.
-- No variable of this type can be declared. It is only used via an
-- access type (The storage size clause ensures we do not allocate
-- variables of this type).
-- It is the responsibility of the user to check the proper bounds.
type XString_Array is array (Positive range <>) of XString;
----------------
-- Properties --
----------------
function Length (Self : XString) return Natural;
-- The number of characters in the string
function Is_Empty (Self : XString) return Boolean
is (Self.Length = 0);
-- Whether the string is empty.
function Get (Self : XString; Index : Positive) return Char_Type
with Inline;
-- Return the Index-th character of the string.
-- The index always starts at 1.
--
-- raises Ada.Strings.Index_Error if this is not a valid index.
-- A simpler way to use this function is simply to use indexing:
-- Self (Index)
-- as done for a regular Ada string.
type Character_Reference (Char : not null access Char_Type)
is limited private
with Implicit_Dereference => Char;
-- A type through which we can modify a character of a string.
-- It is made limited to make it harder to keep such a reference and
-- pass it as parameter, for instance.
-- Such a reference becomes invalid as soon as the contents of the
-- string is modified, and could potentially reference freed memory.
function Reference
(Self : aliased in out XString;
Index : Positive) return Character_Reference
with Inline;
-- Returns a reference to a specific character in the string.
-- It is possible to change the contents of the string via this
-- function. It is meant to be used implicitly as in:
-- Self (Index) := 'A';
--
-- This makes Self unshareable, so that if you later do:
-- S2 := Self;
-- then S2 will have to make a copy of the string even when using
-- copy-on-write.
--------------------------
-- Iteration on indexes --
--------------------------
type Index_Range is record
Low, High : Natural;
end record
with Iterable => (First => First,
Next => Next,
Has_Element => Has_Element,
Element => Element);
function First (Self : Index_Range) return Positive is (Self.Low);
function Next (Ignored_Self : Index_Range; Index : Positive)
return Positive is (Index + 1);
function Has_Element (Self : Index_Range; Index : Positive)
return Boolean is (Index <= Self.High);
function Element
(Ignored_Self : Index_Range; Index : Positive) return Positive
is (Index);
function Iterate (Self : XString) return Index_Range
is ((Low => 1, High => Self.Length));
-- Provide an iterator to get all indexes of the string.
-- This provides a convenient iterator:
-- for Index of Self.Iterate loop
-- C := Self (Index);
-- end loop;
-- This loop is about as fast as iterating directly on a
-- String via a 'Range attribute.
-----------------------------
-- Iteration on characters --
-----------------------------
function First (Self : XString) return Positive is (1);
function Next (Self : XString; Index : Positive) return Positive
is (Index + 1);
function Has_Element (Self : XString; Index : Positive) return Boolean
is (Index <= Self.Length);
-- Standard iteration functions.
-- Each iteration returns the next character in the string.
--
-- Although this is better used as
-- for C of Str loop
-- null;
-- end loop;
--
-- See the Iterate function if you need to get the indexes instead
----------------------
-- Building strings --
----------------------
-- No operator "&" is provided, for efficiency reasons. Such an
-- operator would need to create temporary strings which then
-- need to be freed almost immediately. Since this becomes a slow
-- operation, this API does not provide it by default.
procedure Set (Self : in out XString; Str : Char_String);
-- Store a string in Self
function To_XString (Str : Char_String) return XString;
-- Same as creating a temporary function and Set-ing its value.
-- This is less efficient that Set and results in more copies.
procedure Append (Self : in out XString; Str : Char_String);
procedure Append (Self : in out XString; Char : Char_Type);
procedure Append (Self : in out XString; Str : XString);
-- Append to the end of Self.
function "*" (Count : Natural; Right : Char_Type) return XString;
function "*" (Count : Natural; Right : Char_String) return XString;
function "*" (Count : Natural; Right : XString) return XString;
-- Build a new string that duplicates the Right parameter Count times
procedure Reserve (Self : in out XString; Capacity : String_Size);
-- Make sure Self has enough storage to contain a string of length
-- Size. This doesn't impact the current value of Self, so if the
-- current length is greater than Size, nothing is done.
-- More memory could be allocated, for performance reasons.
procedure Shrink (Self : in out XString);
-- Shrinks the memory used by Self to the minimum needed. This will
-- likely require some memory allocation and copying the characters.
procedure Swap (Self, Str : in out XString);
-- Swap the contents of the two strings.
-- This is more efficient than using an intermediate variable, and
-- is often useful in various algorithms.
------------------------
-- Justifying strings --
------------------------
procedure Center
(Self : in out XString;
Width : Positive;
Pad : Char_Type := Space);
function Center
(Self : XString;
Width : Positive;
Pad : Char_Type := Space) return XString;
-- Center Self, and surround it with Pad characters, such that the
-- total width is Width.
-- If Self is longer than Width, it is unmodified (so the result
-- could be longer than Width, use Head if you want to make sure
-- this isn't the case).
-- The function is not efficient since it needs to allocate memory
-- and copy the characters.
procedure Left_Justify
(Self : in out XString;
Width : Positive;
Pad : Char_Type := Space);
function Left_Justify
(Self : XString;
Width : Positive;
Pad : Char_Type := Space) return XString;
-- Add Pad characters at the end of Self, so that the resulting
-- string is of length Width.
-- If Self is longer than Width, it is returned as is.
-- The function is not efficient since it needs to allocate memory
-- and copy the characters.
procedure Right_Justify
(Self : in out XString;
Width : Positive;
Pad : Char_Type := Space);
function Right_Justify
(Self : XString;
Width : Positive;
Pad : Char_Type := Space) return XString;
-- Add Pad characters at the beginning of Self, so that the resulting
-- string is of length Width.
-- If Self is longer than Width, it is returned as is.
-- The function is not efficient since it needs to allocate memory
-- and copy the characters.
---------------
-- Comparing --
---------------
function "=" (Left : XString; Right : Char_String) return Boolean;
function "=" (Left : XString; Right : XString) return Boolean;
function "=" (Left : Char_String; Right : XString) return Boolean
is (Right = Left);
function "<" (Left : XString; Right : Char_String) return Boolean;
function "<" (Left : Char_String; Right : XString) return Boolean;
function "<" (Left : XString; Right : XString) return Boolean;
function "<=" (Left : XString; Right : Char_String) return Boolean;
function "<=" (Left : Char_String; Right : XString) return Boolean;
function "<=" (Left : XString; Right : XString) return Boolean;
function ">" (Left : XString; Right : Char_String) return Boolean
is (not (Left <= Right));
function ">" (Left : Char_String; Right : XString) return Boolean
is (not (Left <= Right));
function ">" (Left : XString; Right : XString) return Boolean
is (not (Left <= Right));
function ">=" (Left : XString; Right : Char_String) return Boolean
is (not (Left < Right));
function ">=" (Left : Char_String; Right : XString) return Boolean
is (not (Left < Right));
function ">=" (Left : XString; Right : XString) return Boolean
is (not (Left < Right));
-- Compare strings
subtype Compare_Result is Integer range -1 .. 1;
function Compare
(Left : XString; Right : Char_String) return Compare_Result;
function Compare
(Left : XString; Right : XString) return Compare_Result
with Inline;
function Compare
(Left : Char_String; Right : XString) return Compare_Result
is (-Compare (Right, Left));
-- Compare two strings.
-- If they are equal, returns 0.
-- If Left is before Right in lexicographical order, return -1.
-- If Left is after Right in lexicographical order, return 1.
-- The standard operators above are not defined in terms of Compare
-- because the compiler is sometimes able to generate more efficient
-- code for them.
function Compare_Case_Insensitive
(Left : XString; Right : Char_String) return Compare_Result;
function Compare_Case_Insensitive
(Left : XString; Right : XString) return Compare_Result
with Inline;
function Compare_Case_Insensitive
(Left : Char_String; Right : XString) return Compare_Result
is (-Compare_Case_Insensitive (Right, Left));
-- Same as above, but ignore casing differences
function Equal_Case_Insensitive
(Left : XString; Right : Char_String) return Boolean
is (Compare_Case_Insensitive (Left, Right) = 0);
function Equal_Case_Insensitive
(Left : XString; Right : XString) return Boolean
is (Compare_Case_Insensitive (Left, Right) = 0);
function Equal_Case_Insensitive
(Left : Char_String; Right : XString) return Boolean
is (Compare_Case_Insensitive (Left, Right) = 0);
function Less_Case_Insensitive
(Left : XString; Right : Char_String) return Boolean
is (Compare_Case_Insensitive (Left, Right) = -1);
function Less_Case_Insensitive
(Left : XString; Right : XString) return Boolean
is (Compare_Case_Insensitive (Left, Right) = -1);
function Less_Case_Insensitive
(Left : Char_String; Right : XString) return Boolean
is (Compare_Case_Insensitive (Left, Right) = -1);
----------------
-- Converting --
----------------
procedure Get_String
(Self : XString;
S : out Char_Array;
L : out Natural)
with Inline;
-- Returns a pointer to the internal string data.
-- Do not modify the characters in this string, since it could be
-- shared among multiple strings.
-- S is only valid as long as Self is not accessed or modified.
procedure Access_String
(Self : XString;
Process : not null access procedure (S : Char_String));
-- Access the string contained in Self.
-- While Process is running, Self itself will not be destroyed, even
-- if Process should access Self and modify it.
--
-- This might easier to use than Get_String, and is more efficient
-- than To_String.
function To_String (Self : XString) return Char_String;
-- This functions returns the internal string.
-- As much as possible, you should use Get_String instead, which is
-- much more efficient. This function requires returning data whose
-- size is not known statically to the compiler, thus requires using
-- the secondary stack and copying the string. This can have significant
-- performance impact when the string is big.
-------------
-- Hashing --
-------------
function Hash (Self : XString) return Ada.Containers.Hash_Type;
-- Return a hash value suitable for the standard containers map.
-- This is not a cryptographic hash.
function Hash_Case_Insensitive
(Self : XString) return Ada.Containers.Hash_Type;
-- Same as above, but ignore casing
------------
-- Casing --
------------
procedure To_Upper (Self : in out XString);
function To_Upper (Self : XString) return XString;
-- Convert all characters of Self to upper case, using the formal
-- parameter To_Upper.
procedure To_Lower (Self : in out XString);
function To_Lower (Self : XString) return XString;
-- Convert all characters of Self to lower case, using the formal
-- parameter To_Lower.
procedure Capitalize (Self : in out XString);
-- Make sure the first letter of Self is upper cased.
-- All other characters are lower cased.
procedure Title (Self : in out XString);
-- The first letter and all letters after a space are upper cased,
-- and all other characters are lower cased.
function Is_Upper (Self : XString) return Boolean;
function Is_Lower (Self : XString) return Boolean;
-- True if all characters in Self are upper or lower cased
-------------
-- Testing --
-------------
function Starts_With
(Self : XString; Prefix : Char_String) return Boolean;
function Starts_With (Self : XString; Prefix : XString) return Boolean;
-- Whether Self starts with the specific prefix.
function Ends_With
(Self : XString; Suffix : Char_String) return Boolean;
function Ends_With (Self : XString; Suffix : XString) return Boolean;
-- Whether Self ends with the specific suffix.
---------------
-- Searching --
---------------
-- These functions do not use advanced algorithms like Boyer-Moore,
-- so do not take take advantage of the pattern to optimize the
-- search.
-- See also GNATCOLL.Boyer_Moore for more advanced algorithms
function Count
(Self : XString;
Char : Char_Type;
Low : Positive := 1;
High : Natural := Natural'Last) return Natural;
function Count
(Self : XString;
Str : Char_String;
Low : Positive := 1;
High : Natural := Natural'Last) return Natural;
-- Return the number of non-overlapping occurrences of Char or Str.
-- If Str is the empty string, returns Natural'Last (infinite).
-- The search is done in the substring Low..High (by default the
-- whole string).
-- Index_Error is raised if Low is not a valid index (unless Self
-- is the empty string).
function Find
(Self : XString;
Char : Char_Type;
Low : Positive := 1;
High : Natural := Natural'Last) return Natural;
function Find
(Self : XString;
Str : Char_String;
Low : Positive := 1;
High : Natural := Natural'Last) return Natural;
function Right_Find
(Self : XString;
Char : Char_Type;
Low : Positive := 1;
High : Natural := Natural'Last) return Natural;
function Right_Find
(Self : XString;
Str : Char_String;
Low : Positive := 1;
High : Natural := Natural'Last) return Natural;
-- Return the index of the first occurrence of Char or Str,
-- in the substring Self(Low..High).
-- Index_Error is raised if Low is not a valid index (unless Self
-- is the empty string).
--
-- The Right_Find functions start searching from the right of
-- Self.
--
-- 0 is returned when no match was found or Str is the empty string.
----------------
-- Substrings --
----------------
-- The following subprograms return a substring of Self, based on
-- various criteria.
--
-- When using copy-on-write, these subprograms will share the storage
-- of Self, and thus will not require new memory allocation. This
-- makes them fast.
-- When not using copy-on-write, however, they require copy of the
-- characters and memory allocations. The functions are even more
-- expensive, since they require additional copies, so we recommend
-- using the procedures instead.
--
-- All returned substrings always start at index 1, even if you took
-- a slice from another index on.
procedure Slice
(Self : in out XString; Low : Positive; High : Natural);
function Slice
(Self : XString; Low : Positive; High : Natural) return XString;
procedure Slice
(Self : XString;
Low : Positive;
High : Natural;
Into : in out XString);
-- Return a substring of Self.
-- The first character of Self is always at index 1, so this function
-- returns a slice from the Low-th character of Self to the High-th
-- character of Self.
--
-- raises Ada.Strings.Index_Error if any of the indexes is invalid.
procedure Trim
(Self : in out XString;
Side : Ada.Strings.Trim_End := Ada.Strings.Both;
Chars : Char_Type := Space);
function Trim
(Self : XString;
Side : Ada.Strings.Trim_End := Ada.Strings.Both;
Chars : Char_Type := Space) return XString;
-- Remove characters on either end of the string.
-- All characters equal to Chars are removed from either ends.
function Head (Self : XString; Count : Natural) return XString;
-- Return the first Count characters of Self.
-- If Self is smaller, it is returned as is.
function Tail (Self : XString; Count : Natural) return XString;
-- Return the last Count characters of Self.
-- If Self is smaller, it is returned as is.
function Split
(Self : XString;
Sep : Char_Type;
Max_Split : Positive := Positive'Last;
Omit_Empty : Boolean := False) return XString_Array;
procedure Split
(Self : XString;
Sep : Char_Type;
Omit_Empty : Boolean := False;
Into : out XString_Array;
Last : out Natural);
function Split
(Self : XString;
Sep : Char_String;
Max_Split : Positive := Positive'Last;
Omit_Empty : Boolean := False) return XString_Array;
procedure Split
(Self : XString;
Sep : Char_String;
Omit_Empty : Boolean := False;
Into : out XString_Array;
Last : out Natural);
-- Split self into chunks, on every occurrence of Sep.
--
-- The procedure is faster since it does fewer copies of the strings,
-- in particular when not using Copy-On-Write. Only elements from
-- Into'First .. Last have been set or modified. Others are left
-- untouched.
--
-- If Max_Split is specified, at most that many substrings are
-- returned, and the last one extends till the end of Self.
-- The procedure uses the size of Into has the maximum number of
-- splits that are allowed.
-- Specifying a Max_Split is more efficient, since otherwise these
-- subprograms need to count the number of times splitting is
-- necessary.
--
-- If Omit_Empty is true, then none of the returned substring will
-- be the empty string.
--
-- For instance, if Self = "1,,2,3,,4", then:
-- * Sep=',' => ["1", "2", "", "3", "", "4"]
-- * Sep=',' and Omit_Empty=True => ["1", "2", "3", "4"]
-- * Sep=',' and Max_Split=3 => ["1", "2", "3,,4"]
-- As another example, if you need to split on consecutive whitespaces
-- you can use Omit_Empty=True and Sep=' ', for instance:
-- " 2 3 4" => ["2", "3", "4"]
--
-- Splitting an empty string will return an empty array.
-- Splitting on an empty Sep has the same effect.
function Right_Split
(Self : XString;
Sep : Char_Type;
Max_Split : Positive := Positive'Last;
Omit_Empty : Boolean := False) return XString_Array;
procedure Right_Split
(Self : XString;
Sep : Char_Type;
Omit_Empty : Boolean := False;
Into : out XString_Array;
Last : out Natural);
function Right_Split
(Self : XString;
Sep : Char_String;
Max_Split : Positive := Positive'Last;
Omit_Empty : Boolean := False) return XString_Array;
procedure Right_Split
(Self : XString;
Sep : Char_String;
Omit_Empty : Boolean := False;
Into : out XString_Array;
Last : out Natural);
-- Same as Split, but starting from the right.
-- The substrings are returned in the reverse order, from right to
-- left in Self.
procedure Set_As_Join
(Self : out XString;
Sep : Char_String;
Items : XString_Array;
Prefix : Char_String := Null_Char_String;
Suffix : Char_String := Null_Char_String);
function Join
(Sep : Char_String;
Items : XString_Array;
Prefix : Char_String := Null_Char_String;
Suffix : Char_String := Null_Char_String)
return XString;
function Join
(Sep : XString;
Items : XString_Array;
Prefix : Char_String := Null_Char_String;
Suffix : Char_String := Null_Char_String) return XString;
procedure Set_As_Join
(Self : out XString;
Sep : Char_Type;
Items : XString_Array;
Prefix : Char_String := Null_Char_String;
Suffix : Char_String := Null_Char_String);
function Join
(Sep : Char_Type;
Items : XString_Array;
Prefix : Char_String := Null_Char_String;
Suffix : Char_String := Null_Char_String) return XString;
-- Return a string that contains all elements from Items, separated
-- by Self.
-- Prefix is automatically added before the string,
-- while Suffix is added after the string. Using them might save some
-- extra memory allocation or copying.
-- The function versions are less efficient (more so when not using
-- copy-on-write).
---------------
-- Modifying --
---------------
procedure Replace
(Self : in out XString; Index : Positive; Char : Char_Type);
-- Replace a specific character in the string.
-- Index_Error is raised if the index is invalid.
procedure Replace
(Self : in out XString;
Low : Positive;
High : Natural;
By : Char_String);
procedure Replace_Slice
(Self : in out XString;
Low : Positive;
High : Natural;
By : XString) with Inline;
-- Replace the substring Low..High with By.
-- Low must be a valid index (but High might be larger than the
-- string's length).
-- If High < Low, this is the equivalent of inserting the new
-- string at position Low.
procedure Insert
(Self : in out XString;
Before : Positive;
New_Item : Char_String) with Inline;
procedure Insert
(Self : in out XString;
Before : Positive;
New_Item : XString) with Inline;
-- Insert the new item at the given position in Self.
procedure Overwrite
(Self : in out XString;
Position : Positive;
New_Item : Char_String) with Inline;
procedure Overwrite
(Self : in out XString;
Position : Positive;
New_Item : XString) with Inline;
-- Replace the substring at the given Position with the new
-- item. If Self is longer, characters after are preserved.
procedure Delete
(Self : in out XString;
Low : Positive;
High : Natural)
with Inline;
-- Delete the substring Low..High.
-- Both indexes must be valid.
procedure Clear (Self : in out XString);
-- Reset the contents of Self, and frees all allocated memory.
-- You do not need to call this procedure in general, since memory
-- is handled automatically. For instance, when Self goes out of
-- scope, memory is freed.
-- In general, it is more efficient to call Set on the string without
-- calling Clear first, since GNATCOLL will be able to reuse already
-- allocated memory in such a case.
private
Max_Small_Length : constant String_Size := String_Size (SSize'Last);
-- Number of bytes in the small_string buffer, as decided by the user.
type Character_Reference (Char : not null access Char_Type)
is null record;
type Big_String_Data (Copy_On_Write : Boolean) is limited record
case Copy_On_Write is
when False =>
Bytes1 : Unconstrained_Char_Array;
when True =>
Refcount : aliased GNATCOLL.Atomic.Atomic_Counter;
Bytes2 : Unconstrained_Char_Array;
end case;
end record with Unchecked_Union;
type Big_String_Data_Access is access all Big_String_Data;
pragma Suppress_Initialization (Big_String_Data);
pragma No_Strict_Aliasing (Big_String_Data_Access);
-- Unsafe: this is the data used by big strings to store the actual
-- byte sequence. When we use refcounting, we need to have an explicit
-- refcount, which is not needed otherwise.
type Small_String is record
Is_Big : Boolean;
Size : SSize;
Data : Char_String (1 .. Natural (Max_Small_Length));
end record;
for Small_String use record
Is_Big at 0 range 0 .. 0;
Size at 0 range 1 .. 7;
end record;
pragma Suppress_Initialization (Small_String);
-- Hard-code the fact that we can represent the small size on 7 bits
-- (the pragma Compile_Time_Error ensures this is the case). Would be
-- nice if we could use "15" of "7" for larger small string, but we
-- would need static constants for this, and generic formal are not
-- (so that compilers can implement shared generics).
subtype Half_Capacity_Size is String_Size range 0 .. 2 ** 31 - 1;
type Big_String is record
Is_Big : Boolean;
Half_Capacity : Half_Capacity_Size;
Size : String_Size;
Data : aliased Big_String_Data_Access;
-- This field must be aligned on multiple of word_size, so can't
-- be last.
First : Positive;
-- Index of the first character in data.
-- This is used to share the data between substrings. When we
-- do not use copy-on-write, part of the buffer might becomes
-- useless but this is faster than reallocating and copying.
-- On 64-bits platforms, we have 32 bits unused here.
end record;
for Big_String use record
Is_Big at 0 range 0 .. 0;
Half_Capacity at 0 range 1 .. 31;
Size at 4 range 0 .. 31;
Data at 8 range 0 .. System.Word_Size - 1;
First at 8 + System.Word_Size / 8 range 0 .. 31;
end record;
for Big_String'Size use Big_String_Size;
pragma Suppress_Initialization (Big_String);
-- Capacity is always an even number, and we store half of it, so that
-- it leaves one bit for the flag.
type String_Data (Is_Big : Boolean := False) is record
case Is_Big is
when False => Small : Small_String;
when True => Big : Big_String;
end case;
end record
with Unchecked_Union;
type XString is new Ada.Finalization.Controlled with record
Data : String_Data := (Is_Big => False, Small => <>);
end record;
overriding procedure Adjust (Self : in out XString);
overriding procedure Finalize (Self : in out XString);
pragma Finalize_Storage_Only (XString);
-- Finalization is only required for freeing storage
pragma Stream_Convert (XString, To_XString, To_String);
-- provide stream routines without dragging in Ada.Streams
Null_XString : constant XString :=
(Ada.Finalization.Controlled with
Data => (Is_Big => False, Small => <>));
end Strings;
-- Unbounded strings have:
-- Index_Non_Blank Find_Token Translate
-- Ada.Strings.UTF_Encoding
-- Can we reorganize to share code between various instances that
-- use the same Char_Type and Char_String ?
-- C++ has:
-- rfind find_first_of find_last_of
-- find_first_not_of find_last_not_of
-- Python adds:
-- "in" isalpha isprintable
-- format isdecimal isspace partition
-- splitlines expandtabs isdigit istitle
-- zfill isidentifier isalnum swapcase
-- casefold isnumeric
end GNATCOLL.Strings_Impl;
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