LXR qemu/util/unicode.c

   1/*
   2 * Dealing with Unicode
   3 *
   4 * Copyright (C) 2013 Red Hat, Inc.
   5 *
   6 * Authors:
   7 *  Markus Armbruster <armbru@redhat.com>
   8 *
   9 * This work is licensed under the terms of the GNU GPL, version 2 or
  10 * later.  See the COPYING file in the top-level directory.
  11 */
  12
  13#include "qemu/osdep.h"
  14#include "qemu/unicode.h"
  15
  16static bool is_valid_codepoint(int codepoint)
  17{
  18    if (codepoint > 0x10FFFFu) {
  19        return false;            /* beyond Unicode range */
  20    }
  21    if ((codepoint >= 0xFDD0 && codepoint <= 0xFDEF)
  22        || (codepoint & 0xFFFE) == 0xFFFE) {
  23        return false;            /* noncharacter */
  24    }
  25    if (codepoint >= 0xD800 && codepoint <= 0xDFFF) {
  26        return false;            /* surrogate code point */
  27    }
  28    return true;
  29}
  30
  31/**
  32 * mod_utf8_codepoint:
  33 * @s: string encoded in modified UTF-8
  34 * @n: maximum number of bytes to read from @s, if less than 6
  35 * @end: set to end of sequence on return
  36 *
  37 * Convert the modified UTF-8 sequence at the start of @s.  Modified
  38 * UTF-8 is exactly like UTF-8, except U+0000 is encoded as
  39 * "\xC0\x80".
  40 *
  41 * If @n is zero or @s points to a zero byte, the sequence is invalid,
  42 * and @end is set to @s.
  43 *
  44 * If @s points to an impossible byte (0xFE or 0xFF) or a continuation
  45 * byte, the sequence is invalid, and @end is set to @s + 1
  46 *
  47 * Else, the first byte determines how many continuation bytes are
  48 * expected.  If there are fewer, the sequence is invalid, and @end is
  49 * set to @s + 1 + actual number of continuation bytes.  Else, the
  50 * sequence is well-formed, and @end is set to @s + 1 + expected
  51 * number of continuation bytes.
  52 *
  53 * A well-formed sequence is valid unless it encodes a codepoint
  54 * outside the Unicode range U+0000..U+10FFFF, one of Unicode's 66
  55 * noncharacters, a surrogate codepoint, or is overlong.  Except the
  56 * overlong sequence "\xC0\x80" is valid.
  57 *
  58 * Conversion succeeds if and only if the sequence is valid.
  59 *
  60 * Returns: the Unicode codepoint on success, -1 on failure.
  61 */
  62int mod_utf8_codepoint(const char *s, size_t n, char **end)
  63{
  64    static int min_cp[5] = { 0x80, 0x800, 0x10000, 0x200000, 0x4000000 };
  65    const unsigned char *p;
  66    unsigned byte, mask, len, i;
  67    int cp;
  68
  69    if (n == 0 || *s == 0) {
  70        /* empty sequence */
  71        *end = (char *)s;
  72        return -1;
  73    }
  74
  75    p = (const unsigned char *)s;
  76    byte = *p++;
  77    if (byte < 0x80) {
  78        cp = byte;              /* one byte sequence */
  79    } else if (byte >= 0xFE) {
  80        cp = -1;                /* impossible bytes 0xFE, 0xFF */
  81    } else if ((byte & 0x40) == 0) {
  82        cp = -1;                /* unexpected continuation byte */
  83    } else {
  84        /* multi-byte sequence */
  85        len = 0;
  86        for (mask = 0x80; byte & mask; mask >>= 1) {
  87            len++;
  88        }
  89        assert(len > 1 && len < 7);
  90        cp = byte & (mask - 1);
  91        for (i = 1; i < len; i++) {
  92            byte = i < n ? *p : 0;
  93            if ((byte & 0xC0) != 0x80) {
  94                cp = -1;        /* continuation byte missing */
  95                goto out;
  96            }
  97            p++;
  98            cp <<= 6;
  99            cp |= byte & 0x3F;
 100        }
 101        if (!is_valid_codepoint(cp)) {
 102            cp = -1;
 103        } else if (cp < min_cp[len - 2] && !(cp == 0 && len == 2)) {
 104            cp = -1;            /* overlong, not \xC0\x80 */
 105        }
 106    }
 107
 108out:
 109    *end = (char *)p;
 110    return cp;
 111}
 112
 113/**
 114 * mod_utf8_encode:
 115 * @buf: Destination buffer
 116 * @bufsz: size of @buf, at least 5.
 117 * @codepoint: Unicode codepoint to encode
 118 *
 119 * Convert Unicode codepoint @codepoint to modified UTF-8.
 120 *
 121 * Returns: the length of the UTF-8 sequence on success, -1 when
 122 * @codepoint is invalid.
 123 */
 124ssize_t mod_utf8_encode(char buf[], size_t bufsz, int codepoint)
 125{
 126    assert(bufsz >= 5);
 127
 128    if (!is_valid_codepoint(codepoint)) {
 129        return -1;
 130    }
 131
 132    if (codepoint > 0 && codepoint <= 0x7F) {
 133        buf[0] = codepoint & 0x7F;
 134        buf[1] = 0;
 135        return 1;
 136    }
 137    if (codepoint <= 0x7FF) {
 138        buf[0] = 0xC0 | ((codepoint >> 6) & 0x1F);
 139        buf[1] = 0x80 | (codepoint & 0x3F);
 140        buf[2] = 0;
 141        return 2;
 142    }
 143    if (codepoint <= 0xFFFF) {
 144        buf[0] = 0xE0 | ((codepoint >> 12) & 0x0F);
 145        buf[1] = 0x80 | ((codepoint >> 6) & 0x3F);
 146        buf[2] = 0x80 | (codepoint & 0x3F);
 147        buf[3] = 0;
 148        return 3;
 149    }
 150    buf[0] = 0xF0 | ((codepoint >> 18) & 0x07);
 151    buf[1] = 0x80 | ((codepoint >> 12) & 0x3F);
 152    buf[2] = 0x80 | ((codepoint >> 6) & 0x3F);
 153    buf[3] = 0x80 | (codepoint & 0x3F);
 154    buf[4] = 0;
 155    return 4;
 156}
 157