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This article covers features introduced in SpiderMonkey 31

Container class for passing in script source buffers to the JS engine.


enum Ownership {

JS::SourceBufferHolder(const char16_t *data, size_t dataLength,
                       Ownership ownership);
Name Type Description
data const char16_t * Source buffer containing the script to compile.
dataLength size_t The length of data, in characters.
ownership Ownership See description.


JS::SourceBufferHolder is the container class for passing in script source buffers to the JS engine. This not only groups the buffer and length values, it also provides a way to optionally pass ownership of the buffer to the JS engine without copying. Rules for use:

  1. The data array must be allocated with js_malloc or js_realloc if ownership is being granted to the SourceBufferHolder.
  2. If ownership is not given to the SourceBufferHolder, then the memory must be kept alive until the JS compilation is complete.
  3. Any code calling SourceBufferHolder::take() must guarantee to keep the memory alive until JS compilation completes. Normally only the JS engine should be calling take().


size_t length = 512;
char16_t* chars = static_cast<char16_t*>(js_malloc(sizeof(char16_t) * length));
JS::SourceBufferHolder srcBuf(chars, length, JS::SourceBufferHolder::GiveOwnership);
JS::Compile(cx, obj, options, srcBuf);

See Also