v/vlib/builtin/utf8.v

// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.

module builtin

pub fn utf8_char_len(b byte) int { 
	return (( 0xe5000000 >> (( b >> 3 ) & 0x1e )) & 3 ) + 1 
}

// Convert utf32 to utf8
// utf32 == Codepoint
pub fn utf32_to_str(code u32) string {
	icode := int(code) 	//Prevents doing casts everywhere
  mut buffer := malloc(5)
	if icode <= 127 /* 0x7F */ {
		buffer[0] = icode
		return tos(buffer, 1)
	}
	if (icode <= 2047 /* 0x7FF */) {
		buffer[0] = 192 /*0xC0*/ | (icode >> 6)                   /* 110xxxxx */
		buffer[1] = 128 /*0x80*/ | (icode & 63 /*0x3F*/)          /* 10xxxxxx */
		return tos(buffer, 2)
	}
	if (icode <= 65535 /* 0xFFFF */) {
		buffer[0] = 224 /*0xE0*/ | (icode >> 12)                  /* 1110xxxx */
		buffer[1] = 128 /*0x80*/ | ((icode >> 6) & 63 /*0x3F*/)   /* 10xxxxxx */
		buffer[2] = 128 /*0x80*/ | (icode & 63 /*0x3F*/)          /* 10xxxxxx */
		return tos(buffer, 3)
	}
	if (icode <= 1114111 /* 0x10FFFF */) {
		buffer[0] = 240 /*0xF0*/ | (icode >> 18)                  /* 11110xxx */
		buffer[1] = 128 /*0x80*/ | ((icode >> 12) & 63 /*0x3F*/)  /* 10xxxxxx */
		buffer[2] = 128 /*0x80*/ | ((icode >> 6) & 63 /*0x3F*/)   /* 10xxxxxx */
		buffer[3] = 128 /*0x80*/ | (icode & 63 /*0x3F*/)          /* 10xxxxxx */
		return tos(buffer, 4)
	}
	return ''
}

// TODO copypasta
pub fn utf32_to_str_no_malloc(code u32, buf voidptr) string {
	icode := int(code) 	//Prevents doing casts everywhere
  mut buffer := byteptr(buf)
	if icode <= 127 /* 0x7F */ {
		buffer[0] = icode
		return tos(buffer, 1)
	}
	if (icode <= 2047 /* 0x7FF */) {
		buffer[0] = 192 /*0xC0*/ | (icode >> 6)                   /* 110xxxxx */
		buffer[1] = 128 /*0x80*/ | (icode & 63 /*0x3F*/)          /* 10xxxxxx */
		return tos(buffer, 2)
	}
	if (icode <= 65535 /* 0xFFFF */) {
		buffer[0] = 224 /*0xE0*/ | (icode >> 12)                  /* 1110xxxx */
		buffer[1] = 128 /*0x80*/ | ((icode >> 6) & 63 /*0x3F*/)   /* 10xxxxxx */
		buffer[2] = 128 /*0x80*/ | (icode & 63 /*0x3F*/)          /* 10xxxxxx */
		return tos(buffer, 3)
	}
	if (icode <= 1114111 /* 0x10FFFF */) {
		buffer[0] = 240 /*0xF0*/ | (icode >> 18)                  /* 11110xxx */
		buffer[1] = 128 /*0x80*/ | ((icode >> 12) & 63 /*0x3F*/)  /* 10xxxxxx */
		buffer[2] = 128 /*0x80*/ | ((icode >> 6) & 63 /*0x3F*/)   /* 10xxxxxx */
		buffer[3] = 128 /*0x80*/ | (icode & 63 /*0x3F*/)          /* 10xxxxxx */
		return tos(buffer, 4)
	}
	return ''
}

// Convert utf8 to utf32
pub fn (_rune string) utf32_code() int {
	if _rune.len == 0 {
		return 0
	}
	// save ASC symbol as is
	if _rune.len == 1 {
		return int(_rune[0])
	}
	mut b := byte(int(_rune[0]))
	// TODO should be
	// res := int( rune[0] << rune.len)
	b = b << _rune.len
	mut res := int(b)
	mut shift := 6 - _rune.len
	for i := 1; i < _rune.len; i++ {
		c := int(_rune[i])
		res = res << shift
		res |= c & 63 /* 0x3f */
		shift = 6
	}
	return res
}

const (
		CP_UTF8 = 65001
	)

pub fn (_str string) to_wide() &u16 {
    $if windows {
   	    num_chars := int(C.MultiByteToWideChar(CP_UTF8, 0, _str.str, _str.len, 0, 0))
	    mut wstr := &u16(malloc((num_chars + 1) * 2)) // sizeof(wchar_t)
	    if wstr > 0 {
		    C.MultiByteToWideChar(CP_UTF8, 0, _str.str, _str.len, wstr, num_chars)
		    C.memset(&byte(wstr) + num_chars * 2, 0, 2)
	    }
	    return wstr
    } $else {
        return 0
    }
}

pub fn string_from_wide(_wstr &u16) string {
    $if windows {
	    wstr_len := int(C.wcslen(_wstr))
	    return string_from_wide2(_wstr, wstr_len)
    } $else {
        return ''
    }
}

pub fn string_from_wide2(_wstr &u16, len int) string {
    $if windows {
    	num_chars := int(C.WideCharToMultiByte(CP_UTF8, 0, _wstr, len, 0, 0, 0, 0))
    	mut str_to := &byte(malloc(num_chars + 1))
    	if str_to > 0 {
    		C.WideCharToMultiByte(CP_UTF8, 0, _wstr, len, str_to, num_chars, 0, 0)
		    C.memset(&byte(str_to) + num_chars, 0, 1)
	    }
	    return tos2(str_to)
    } $else {
        return ''
    }
}

// Calculate length to read from the first byte
fn utf8_len(c byte) int {
  mut b := 0
  mut x := c

  if ((x & 240) != 0) { //0xF0
    x >>= 4
  } else {
    b += 4
  }
  if ((x & 12) != 0) { //0x0C
    x >>= 2
  } else {
    b += 2
  }
  if ((x & 2) == 0) { //0x02
    b++
  }
  return b
}

// Reads an utf8 character from standard input
pub fn utf8_getchar() int {
  c := int(C.getchar())
  len := utf8_len(~c)

  if c < 0 {
    return 0
  } else if (len == 0) {
    return c
  } else if (len == 1) {
    return -1
  } else {
    mut uc := int(c & ((1 << (7 - len)) - 1))
    for i := 0; i + 1 < len; i++ {
      c2 := int(C.getchar())
      if c2 != -1 && (c2 >> 6) == 2 {
        uc <<= 6
        uc |= int((c2 & 63))
      }  else if (c2 == -1) {
        return 0
      } else {
        return -1
      }
    }
    return uc
  }
}