Re: Generators in PHP

From: Date: Fri, 08 Jun 2012 11:51:14 +0000
Subject: Re: Generators in PHP
References: 1 2 3 4 5  Groups: php.internals 
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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

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