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/* libs/cutils/strdup16to8.c
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
#include <limits.h> /* for SIZE_MAX */
#include <cutils/jstring.h>
#include <assert.h>
#include <stdlib.h>
/**
* Given a UTF-16 string, compute the length of the corresponding UTF-8
* string in bytes.
*/
extern size_t strnlen16to8(const char16_t* utf16Str, size_t len)
{
size_t utf8Len = 0;
/* A small note on integer overflow. The result can
* potentially be as big as 3*len, which will overflow
* for len > SIZE_MAX/3.
*
* Moreover, the result of a strnlen16to8 is typically used
* to allocate a destination buffer to strncpy16to8 which
* requires one more byte to terminate the UTF-8 copy, and
* this is generally done by careless users by incrementing
* the result without checking for integer overflows, e.g.:
*
* dst = malloc(strnlen16to8(utf16,len)+1)
*
* Due to this, the following code will try to detect
* overflows, and never return more than (SIZE_MAX-1)
* when it detects one. A careless user will try to malloc
* SIZE_MAX bytes, which will return NULL which can at least
* be detected appropriately.
*
* As far as I know, this function is only used by strndup16(),
* but better be safe than sorry.
*/
/* Fast path for the usual case where 3*len is < SIZE_MAX-1.
*/
if (len < (SIZE_MAX-1)/3) {
while (len != 0) {
len--;
unsigned int uic = *utf16Str++;
if (uic > 0x07ff)
utf8Len += 3;
else if (uic > 0x7f || uic == 0)
utf8Len += 2;
else
utf8Len++;
}
return utf8Len;
}
/* The slower but paranoid version */
while (len != 0) {
len--;
unsigned int uic = *utf16Str++;
size_t utf8Cur = utf8Len;
if (uic > 0x07ff)
utf8Len += 3;
else if (uic > 0x7f || uic == 0)
utf8Len += 2;
else
utf8Len++;
if (utf8Len < utf8Cur) /* overflow detected */
return SIZE_MAX-1;
}
/* don't return SIZE_MAX to avoid common user bug */
if (utf8Len == SIZE_MAX)
utf8Len = SIZE_MAX-1;
return utf8Len;
}
/**
* Convert a Java-Style UTF-16 string + length to a JNI-Style UTF-8 string.
*
* This basically means: embedded \0's in the UTF-16 string are encoded
* as "0xc0 0x80"
*
* Make sure you allocate "utf8Str" with the result of strlen16to8() + 1,
* not just "len".
*
* Please note, a terminated \0 is always added, so your result will always
* be "strlen16to8() + 1" bytes long.
*/
extern char* strncpy16to8(char* utf8Str, const char16_t* utf16Str, size_t len)
{
char* utf8cur = utf8Str;
/* Note on overflows: We assume the user did check the result of
* strnlen16to8() properly or at a minimum checked the result of
* its malloc(SIZE_MAX) in case of overflow.
*/
while (len != 0) {
len--;
unsigned int uic = *utf16Str++;
if (uic > 0x07ff) {
*utf8cur++ = (uic >> 12) | 0xe0;
*utf8cur++ = ((uic >> 6) & 0x3f) | 0x80;
*utf8cur++ = (uic & 0x3f) | 0x80;
} else if (uic > 0x7f || uic == 0) {
*utf8cur++ = (uic >> 6) | 0xc0;
*utf8cur++ = (uic & 0x3f) | 0x80;
} else {
*utf8cur++ = uic;
if (uic == 0) {
break;
}
}
}
*utf8cur = '\0';
return utf8Str;
}
/**
* Convert a UTF-16 string to UTF-8.
*
*/
char * strndup16to8 (const char16_t* s, size_t n)
{
char* ret;
size_t len;
if (s == NULL) {
return NULL;
}
len = strnlen16to8(s, n);
/* We are paranoid, and we check for SIZE_MAX-1
* too since it is an overflow value for our
* strnlen16to8 implementation.
*/
if (len >= SIZE_MAX-1)
return NULL;
ret = malloc(len + 1);
if (ret == NULL)
return NULL;
strncpy16to8 (ret, s, n);
return ret;
}
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