There are dozens of places in Gfx where the following pattern is used (some are hidden under the hood of macros): PRUnichar gBuffer[BUFFER_SIZE]; ....... In some function, PRUnichar *buffer= gBuffer; if ( len > BUFFER_SIZE) { buffer = new PRUnichar[len]; if (!buffer) return NS_ERROR_OUT_OF_MEMORY; } use buffer ..... if (buffer != gBuffer) delete [] buffer; It's not PRUnichar but other types(PRUint8, PRUint32) are used in this pattern as well. It'd be nice if we could write a portable AutoBuffer with two template parameters (class T, PRInt32 static_buffer_size). I used a simple implementation at http://lxr.mozilla.org/seamonkey/source/gfx/src/windows/nsFontMetricsWin.cpp#551 In nsFontMetricsXft.cpp, I just used a non-template version lest I'd introduce a portability problem with some picky Unix compilers. http://lxr.mozilla.org/seamonkey/source/gfx/src/gtk/nsFontMetricsXft.cpp#327 I'm filing this under gfx not because it's the best but because I'm not sure where to file this bug under. Please, feel free to change the component as you see fit. I think it needs to go somewhere under xpcom/ds because I also found that this may be useful in intl/ctl as well (bug 215219)

Looks like a dup of bug 70870.

Thanks for the info. on bug 70870. This is a subset of bug 70870 in a sense. If bug 70870 is not gonna be fixed soon, would it be a good idea to implement this one first (with narrower scope than bug 70870) and later to recast it in terms of nsBuffer?

Since you are aiming at xpcom/ds, you might as well go for bug 70870 since scc said that the underlying infrastructure is there, meaning that the thorny portability issues have been worked out. However, extras (such as those Append/Insert/etc) can't be left out. Seems it is the desire to have those extras that has caused that there is nothing at all. It is not necessary to achieve "completeness" at the first shot.

> extras (such as those Append/Insert/etc) can't be left out. You meant 'can be left out', didn't you? I don't know when I'll be able to give it a shot. Anyway, I'll take a look at nsBuffer.

Yeah, that was a typo... I hadn't look at the foundational files that scc mentioned, but a quick look now seems to suggest those unadvertised (under-utilized) nsBufferHandle<PRUnichar>, nsAutoBufferHandle<PRUnichar> might do the job and be of help in your bug 215219.

Just a note to myself: nsTextFrame.cpp has nsAutoIndexBuffer http://lxr.mozilla.org/mozilla/source/layout/html/base/src/nsTextFrame.cpp#161 nsAutoTextBuffer is defined with several useful methods: http://lxr.mozilla.org/mozilla/source/layout/html/base/src/nsTextTransformer.h#100

resolving as dupe of bug 233485 which was fixed a while ago. *** This bug has been marked as a duplicate of 233485 ***