upload android base code part6

android/system/core/libcutils/strdup16to8.c

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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;
+}