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bug 737624 - memory-only encoding/decoding of scripts and functions. r=:luke

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The patch shrinks the API presented in jsxdrapi.h down to 4 functions to
encode/decode scripts and interpreted functions to/from the memory. The
newly introduced implementation header vm/Xdr.h replaces the former
JSXDRState with the template class XDRState parametrized by the enum
type with two constants, XDR_ENCODE and XDR_DECODE. This way a compiler
can fully eliminate the former runtime checks for the decoding/encoding
mode. As a drawback this required to explicitly instantiate the xdr
implementation as I do not want to put all the xdr code to header files.

The memory-only XDR allows to avoid coping filename and to-be-atomized
chars to a temporary buffer as the code can just access the buffer
directly. Another change is that new XDRScript takes as a parameter its
parent script. This allowed to avoid keeping filename in XDRState and
simplify the filename management.

Another change is the removal of JS_HAS_HDR. As CloneScript uses XDR to
copy a script, JS_HAS_XDR cannot be disabled.
This commit is contained in:
Igor Bukanov
2012-02-20 11:58:00 +01:00
parent 8f6cb2e834
commit fc5505b07d
37 changed files with 944 additions and 1192 deletions
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63
js/src/jsatom.cpp
View File

@@ -68,6 +68,7 @@
#include "jsobjinlines.h"
#include "vm/String-inl.h"
#include "vm/Xdr.h"
using namespace mozilla;
using namespace js;
@@ -657,3 +658,65 @@ js_InternNonIntElementIdSlow(JSContext *cx, JSObject *obj, const Value &idval,
return false;
}
#endif
template<XDRMode mode>
bool
js::XDRAtom(XDRState<mode> *xdr, JSAtom **atomp)
{
if (mode == XDR_ENCODE) {
JSString *str = *atomp;
return xdr->codeString(&str);
}
/*
* Inline XDRState::codeString when decoding to avoid JSString allocation
* for already existing atoms. See bug 321985.
*/
uint32_t nchars;
if (!xdr->codeUint32(&nchars))
return false;
JSContext *cx = xdr->cx();
JSAtom *atom;
#if IS_LITTLE_ENDIAN
/* Directly access the little endian chars in the XDR buffer. */
const jschar *chars = reinterpret_cast<const jschar *>(xdr->buf.read(nchars * sizeof(jschar)));
atom = js_AtomizeChars(cx, chars, nchars);
#else
/*
* We must copy chars to a temporary buffer to convert between little and
* big endian data.
*/
jschar *chars;
jschar stackChars[256];
if (nchars <= ArrayLength(stackChars)) {
chars = stackChars;
} else {
/*
* This is very uncommon. Don't use the tempLifoAlloc arena for this as
* most allocations here will be bigger than tempLifoAlloc's default
* chunk size.
*/
chars = static_cast<jschar *>(cx->runtime->malloc_(nchars * sizeof(jschar)));
if (!chars)
return false;
}
JS_ALWAYS_TRUE(xdr->codeChars(chars, nchars));
atom = js_AtomizeChars(cx, chars, nchars);
if (chars != stackChars)
Foreground::free_(chars);
#endif /* !IS_LITTLE_ENDIAN */
if (!atom)
return false;
*atomp = atom;
return true;
}
template bool
js::XDRAtom(XDRState<XDR_ENCODE> *xdr, JSAtom **atomp);
template bool
js::XDRAtom(XDRState<XDR_DECODE> *xdr, JSAtom **atomp);