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JSAutoByteString 编辑

This article covers features introduced in SpiderMonkey 17

Take ownership of a string and free it later.

Syntax

JSAutoByteString str;

JSAutoByteString(JSContext *cx, JSString *str);

Name	Type	Description
`cx`	`JSContext *`	The context in which to add the root. Requires request. In a `JS_THREADSAFE` build, the caller must be in a request on this `JSContext`.
`str`	`JSString *`	A pointer to `JSString` to get initial content by calling `JS_EncodeString(cx, str)`.

Methods

Method	Description
`void initBytes(char *bytes)`	Take ownership of the given byte array.
`char encodeLatin1(JSContext cx, JSString *str)`	Call `JS_EncodeString` and take ownership of the returned string, and return the string.
`char encodeLatin1(js::ExclusiveContext cx, JSString *str)`	Call `JS::LossyTwoByteCharsToNewLatin1CharsZ`, or allocate string and copy the content of `JSLinearString::latin1Chars`, and take the ownership of the string. This may fail if `str` is not linear.
`char encodeUtf8(JSContext cx, JS::HandleString str)`	Call `JS_EncodeStringToUTF8` and take ownership of the returned string, and return the string.
`void clear()`	Free the owned string. You should call this before calling `encode*` methods or `initBytes` method if a string is already owned, otherwise the string will never be freed.
`char *ptr() const`	Return a pointer to the owned string. This could be `NULL` if no string is owned.
`bool operator!() const`	Return `true` if no string is owned.
`size_t length() const`	Return the length of the owned string. Return `0` if no string is owned.

Description

JSAutoByteString takes the ownership of string and frees it in destructor.

If JSAutoByteString instance is initialized with JSAutoByteString bytes(cx, str); style, it calls JS_EncodeString(cx, str) to get the string to take ownership.

If JSAutoByteString instance is initialized with JSAutoByteString bytes; style, it does not own any string. You can call some methods to take ownership of other string.

Note that the JS_EncodeString call in constructor and some encode* methods may fail and get NULL. So ensure the string is returned by operator!() before using ptr() method.

Examples

Use constructor arguments

{
  JSString *str = JS::ToString(cx, strVal);
  if (!str)
    return false;

  JSAutoByteString bytes(cx, str); /* calls JS_EncodeString internally */
  if (!bytes)
    return false;

  /* ...do something with bytes... */

  /* when leaving this scope, the string returned by JS_EncodeString is freed. */
}

Use method to encode string

{
  JS::RootedString str(cx, JS::ToString(cx, strVal));
  if (!str)
    return false;

  JSAutoByteString bytes;
  if (!bytes.encodeUtf8(cx, str)) /* calls JS_EncodeStringToUTF8 internally */
    return false;

  /* ...do something with bytes... */

  /* when leaving this scope, the string returned by JS_EncodeStringToUTF8 is freed. */
}

Take ownership of other buffer

{
  char *buff = cx->pod_malloc<char>(length + 1);
  if (!buff)
    return false;
  memcpy(buff, other_buff, length + 1)

  JSAutoByteString bytes;
  bytes.initBytes(buff);

  /* ...do something with bytes... */

  /* when leaving this scope, buff is freed. */
}

JSAutoByteString 编辑

Syntax

Methods

Description

Examples

Use constructor arguments

Use method to encode string

Take ownership of other buffer

See Also

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友情链接

JSAutoByteString 编辑

如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

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友情链接

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。