lib/json: Added ad-hoc string parser for JSON

[nit.git] / lib / core / text / native.nit

diff --git a/lib/core/text/native.nit b/lib/core/text/native.nit
index 170b196..9ea8382 100644 (file)
--- a/lib/core/text/native.nit
+++ b/lib/core/text/native.nit
@@ -16,7 +16,7 @@ import math
 
 redef class Byte
        # Gives the length of the UTF-8 char starting with `self`
-       private fun u8len: Int do
+       fun u8len: Int do
                if self & 0b1000_0000u8 == 0u8 then
                        return 1
                else if self & 0b1110_0000u8 == 0b1100_0000u8 then
@@ -31,6 +31,21 @@ redef class Byte
        end
 end
 
+redef class Int
+       # Returns the code_point from a utf16 surrogate pair
+       #
+       #     assert 0xD83DDE02.from_utf16_surr == 0x1F602
+       fun from_utf16_surr: Int do
+               var hi = (self & 0xFFFF0000) >> 16
+               var lo = self & 0xFFFF
+               var cp = 0
+               cp += (hi - 0xD800) << 10
+               cp += lo - 0xDC00
+               cp += 0x10000
+               return cp
+       end
+end
+
 # Native strings are simple C char *
 extern class NativeString `{ char* `}
        # Creates a new NativeString with a capacity of `length`
@@ -130,6 +145,29 @@ extern class NativeString `{ char* `}
                return ns_i
        end
 
+       # Gets the char index of byte at position `n` in a UTF-8 String
+       #
+       # `char_from` and `byte_from` are cached values to seek from.
+       #
+       # NOTE: char_from and byte_from are not guaranteed to be valid cache values
+       # It it up to the client to ensure the validity of the information
+       fun byte_to_char_index_cached(n, char_from, byte_from: Int): Int do
+               var ns_i = byte_from
+               var my_i = char_from
+
+               while ns_i < n do
+                       ns_i += length_of_char_at(ns_i)
+                       my_i += 1
+               end
+
+               while ns_i > n do
+                       ns_i = find_beginning_of_char_at(ns_i - 1)
+                       my_i -= 1
+               end
+
+               return my_i
+       end
+
        # Returns the beginning position of the char at position `pos`
        #
        # If the char is invalid UTF-8, `pos` is returned as-is
@@ -150,4 +188,16 @@ extern class NativeString `{ char* `}
                if length_of_char_at(stpos) >= (endpos - stpos + 1) then return pos
                return endpos
        end
+
+       # Number of UTF-8 characters in `self` between positions `from` and `to`
+       fun utf8_length(from, to: Int): Int do
+               var st = from
+               var lst = to
+               var ln = 0
+               while st <= lst do
+                       st += length_of_char_at(st)
+                       ln += 1
+               end
+               return ln
+       end
 end