lib/standard/string: Added faster cstring method on flatstring.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

diff --git a/lib/standard/string.nit b/lib/standard/string.nit
index e974d91..409b4ed 100644 (file)
--- a/lib/standard/string.nit
+++ b/lib/standard/string.nit
@@ -864,6 +864,23 @@ abstract class FlatText
        # Real items, used as cache for to_cstring is called
        private var real_items: nullable NativeString = null
 
+       # Returns a char* starting at position `index_from`
+       #
+       # WARNING: If you choose to use this service, be careful of the following.
+       #
+       # Strings and NativeString are *ideally* always allocated through a Garbage Collector.
+       # Since the GC tracks the use of the pointer for the beginning of the char*, it may be
+       # deallocated at any moment, rendering the pointer returned by this function invalid.
+       # Any access to freed memory may very likely cause undefined behaviour or a crash.
+       # (Failure to do so will most certainly result in long and painful debugging hours)
+       #
+       # The only safe use of this pointer is if it is ephemeral (e.g. read in a C function
+       # then immediately return).
+       #
+       # As always, do not modify the content of the String in C code, if this is what you want
+       # copy locally the char* as Nit Strings are immutable.
+       private fun fast_cstring: NativeString is abstract
+
        redef var length: Int = 0
 
        redef fun output
@@ -1119,6 +1136,8 @@ class FlatString
                return native.to_s_with_length(self.length)
        end
 
+       redef fun fast_cstring do return items.fast_cstring(index_from)
+
        redef fun substring(from, count)
        do
                assert count >= 0
@@ -1567,6 +1586,8 @@ class FlatBuffer
 
        private var capacity: Int = 0
 
+       redef fun fast_cstring do return items.fast_cstring(0)
+
        redef fun substrings do return new FlatSubstringsIter(self)
 
        # Re-copies the `NativeString` into a new one and sets it as the new `Buffer`
@@ -2289,6 +2310,12 @@ extern class NativeString `{ char* `}
        # Creates a new NativeString with a capacity of `length`
        new(length: Int) is intern
 
+       # Returns a char* starting at `index`.
+       #
+       # WARNING: Unsafe for extern code, use only for temporary
+       # pointer manipulation purposes (e.g. write to file or such)
+       fun fast_cstring(index: Int): NativeString is intern
+
        # Get char at `index`.
        fun [](index: Int): Char is intern
 

diff --git a/src/compiler/abstract_compiler.nit b/src/compiler/abstract_compiler.nit
index 43fd172..1a551d6 100644 (file)
--- a/src/compiler/abstract_compiler.nit
+++ b/src/compiler/abstract_compiler.nit
@@ -2204,6 +2204,9 @@ redef class AMethPropdef
                        else if pname == "atoi" then
                                v.ret(v.new_expr("atoi({arguments[0]});", ret.as(not null)))
                                return true
+                       else if pname == "fast_cstring" then
+                               v.ret(v.new_expr("{arguments[0]} + {arguments[1]}", ret.as(not null)))
+                               return true
                        else if pname == "new" then
                                v.ret(v.new_expr("(char*)nit_alloc({arguments[1]})", ret.as(not null)))
                                return true

diff --git a/src/interpreter/naive_interpreter.nit b/src/interpreter/naive_interpreter.nit
index aba779a..8818874 100644 (file)
--- a/src/interpreter/naive_interpreter.nit
+++ b/src/interpreter/naive_interpreter.nit
@@ -1016,6 +1016,9 @@ redef class AMethPropdef
                                return v.int_instance(res)
                        else if pname == "atof" then
                                return v.float_instance(recvval.to_f)
+                       else if pname == "fast_cstring" then
+                               var ns = recvval.to_cstring.to_s.substring_from(args[1].to_i)
+                               return v.native_string_instance(ns)
                        end
                else if cname == "String" then
                        var cs = v.send(v.force_get_primitive_method("to_cstring", args.first.mtype), [args.first])