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Date: Fri, 08 Jun 2012 13:51:14 +0200
To: Nikita Popov <nikita.ppv@googlemail.com>
Cc: internals PHP <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Generators in PHP
From: glopes@nebm.ist.utl.pt (Gustavo Lopes)

On Fri, 8 Jun 2012 13:24:49 +0200, Nikita Popov wrote:
>> Are you planning on any internal API for functions to implement 
>> generators
>> (though I really haven't thought how that would work)?
> I don't think that this is possible. Generators require that the
> execution context is suspended in some way and we have to that 
> control
> only over userland code, not internal C code.
>

Couldn't we simulate this by saving the state in a heap allocated 
structure (whose exact form would depend on the generator 
implementation). Something like:

struct generator_context {
     zval *(*yield_next)(struct generator_context*);
}

struct spec_generator_context {
     struct generator_context parent;
     int foo;
}

PHP_FUNCTION(get_generator)
{
     struct spec_generator_context *ctx = emalloc(*ctx);
     ctx->parent.yield_next = foo_bar();
     return_value = make_internal_generator(ctx);
}

And you could also change the yield_next pointer in foo_bar() to avoid 
going through goto's or switch statements. Possibly yield_next could be 
take the arg with double indirection and you could also completely 
replace the context.

I understand this has the problem that the internal and userspace 
implementations would be markedly different.

-- 
Gustavo Lopes