From: Lucas Bajolet <r4pass@hotmail.com>
Date: Tue, 31 Mar 2015 20:31:07 +0000 (-0400)
Subject: lib/standard/string: Added faster cstring method on flatstring.
X-Git-Tag: v0.7.4~46^2
X-Git-Url: http://nitlanguage.org

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
--- 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
--- 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
--- 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])