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 "go-string.h"
   8 #include "runtime.h"
   9 #include "arch.h"
  10 #include "malloc.h"
  11
  12 struct __go_string
  13 __go_int_to_string (int v)
  14 {
  15   char buf[4];
  16   int len;
  17   unsigned char *retdata;
  18   struct __go_string ret;
  19
  20   /* A negative value is not valid UTF-8; turn it into the replacement
  21      character.  */
  22   if (v < 0)
  23     v = 0xfffd;
  24
  25   if (v <= 0x7f)
  26     {
  27       buf[0] = v;
  28       len = 1;
  29     }
  30   else if (v <= 0x7ff)
  31     {
  32       buf[0] = 0xc0 + (v >> 6);
  33       buf[1] = 0x80 + (v & 0x3f);
  34       len = 2;
  35     }
  36   else
  37     {
  38       /* If the value is out of range for UTF-8, turn it into the
  39          "replacement character".  */
  40       if (v > 0x10ffff)
  41         v = 0xfffd;
  42       /* If the value is a surrogate pair, which is invalid in UTF-8,
  43          turn it into the replacement character.  */
  44       if (v >= 0xd800 && v < 0xe000)
  45         v = 0xfffd;
  46
  47       if (v <= 0xffff)
  48         {
  49           buf[0] = 0xe0 + (v >> 12);
  50           buf[1] = 0x80 + ((v >> 6) & 0x3f);
  51           buf[2] = 0x80 + (v & 0x3f);
  52           len = 3;
  53         }
  54       else
  55         {
  56           buf[0] = 0xf0 + (v >> 18);
  57           buf[1] = 0x80 + ((v >> 12) & 0x3f);
  58           buf[2] = 0x80 + ((v >> 6) & 0x3f);
  59           buf[3] = 0x80 + (v & 0x3f);
  60           len = 4;
  61         }
  62     }
  63
  64   retdata = runtime_mallocgc (len, FlagNoPointers, 1, 0);
  65   __builtin_memcpy (retdata, buf, len);
  66   ret.__data = retdata;
  67   ret.__length = len;
  68
  69   return ret;
  70 }