js/xpconnect/loader/mozJSLoaderUtils.cpp
author Igor Bukanov <igor@mir2.org>
Mon, 20 Feb 2012 11:58:00 +0100
changeset 93571 30798fdc5bad0d4b899faf5f979e1caf5a901484
parent 93570 7a39ee24bd89ea0d9f3be6988b3642e64389af7a
child 93572 081b574dbad3ea95b40a458e036eabc7ed7ee7d3
permissions -rw-r--r--
bug 737624 - memory-only encoding/decoding of scripts and functions. r=:luke 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.

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#include "nsAutoPtr.h"
#include "nsScriptLoader.h"

#include "jsapi.h"
#include "jsdbgapi.h"

#include "nsJSPrincipals.h"

#include "mozilla/scache/StartupCache.h"
#include "mozilla/scache/StartupCacheUtils.h"

using namespace mozilla::scache;

// We only serialize scripts with system principals. So we don't serialize the
// principals when writing a script. Instead, when reading it back, we set the
// principals to the system principals.
nsresult
ReadCachedScript(StartupCache* cache, nsACString &uri, JSContext *cx,
                 nsIPrincipal *systemPrincipal, JSScript **scriptp)
{
    nsAutoArrayPtr<char> buf;
    PRUint32 len;
    nsresult rv = cache->GetBuffer(PromiseFlatCString(uri).get(),
                                   getter_Transfers(buf), &len);
    if (NS_FAILED(rv))
        return rv; // don't warn since NOT_AVAILABLE is an ok error

    JSScript *script = JS_DecodeScript(cx, buf, len, nsJSPrincipals::get(systemPrincipal), nsnull);
    if (!script)
        return NS_ERROR_OUT_OF_MEMORY;
    *scriptp = script;
    return NS_OK;
}

nsresult
WriteCachedScript(StartupCache* cache, nsACString &uri, JSContext *cx,
                  nsIPrincipal *systemPrincipal, JSScript *script)
{
    MOZ_ASSERT(JS_GetScriptPrincipals(script) == nsJSPrincipals::get(systemPrincipal));
    MOZ_ASSERT(JS_GetScriptOriginPrincipals(script) == nsJSPrincipals::get(systemPrincipal));

    uint32_t size;
    void *data = JS_EncodeScript(cx, script, &size);
    if (!data)
        return NS_ERROR_OUT_OF_MEMORY;

    MOZ_ASSERT(size);
    nsresult rv = cache->PutBuffer(PromiseFlatCString(uri).get(), static_cast<char *>(data), size);
    js_free(data);
    return rv;
}