libgo/runtime/go-int-to-string.c

   1 /* go-int-to-string.c -- convert an integer to a string in Go.
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include "runtime.h"
   8 #include "arch.h"
   9 #include "malloc.h"
  10
  11 String
  12 __go_int_to_string (intgo v)
  13 {
  14   char buf[4];
  15   int len;
  16   unsigned char *retdata;
  17   String ret;
  18
  19   /* A negative value is not valid UTF-8; turn it into the replacement
  20      character.  */
  21   if (v < 0)
  22     v = 0xfffd;
  23
  24   if (v <= 0x7f)
  25     {
  26       buf[0] = v;
  27       len = 1;
  28     }
  29   else if (v <= 0x7ff)
  30     {
  31       buf[0] = 0xc0 + (v >> 6);
  32       buf[1] = 0x80 + (v & 0x3f);
  33       len = 2;
  34     }
  35   else
  36     {
  37       /* If the value is out of range for UTF-8, turn it into the
  38          "replacement character".  */
  39       if (v > 0x10ffff)
  40         v = 0xfffd;
  41       /* If the value is a surrogate pair, which is invalid in UTF-8,
  42          turn it into the replacement character.  */
  43       if (v >= 0xd800 && v < 0xe000)
  44         v = 0xfffd;
  45
  46       if (v <= 0xffff)
  47         {
  48           buf[0] = 0xe0 + (v >> 12);
  49           buf[1] = 0x80 + ((v >> 6) & 0x3f);
  50           buf[2] = 0x80 + (v & 0x3f);
  51           len = 3;
  52         }
  53       else
  54         {
  55           buf[0] = 0xf0 + (v >> 18);
  56           buf[1] = 0x80 + ((v >> 12) & 0x3f);
  57           buf[2] = 0x80 + ((v >> 6) & 0x3f);
  58           buf[3] = 0x80 + (v & 0x3f);
  59           len = 4;
  60         }
  61     }
  62
  63   retdata = runtime_mallocgc (len, 0, FlagNoScan);
  64   __builtin_memcpy (retdata, buf, len);
  65   ret.str = retdata;
  66   ret.len = len;
  67
  68   return ret;
  69 }