CODEWITHSUNDEEP
structzig
timbo
timbo

Reputation: 14354

Equivalent struct declaration in Zig

How would you declare the following struct equivalently in Zig?

static struct lws_protocols protocols[] = {
    { "http", lws_callback_http_dummy, 0, 0 },
    LWS_PLUGIN_PROTOCOL_MINIMAL,
    { NULL, NULL, 0, 0 } /* terminator */
};

Looking at the LWS_PLUGIN_PROTOCOL_MINIMAL, it's defined in a header as:

#define LWS_PLUGIN_PROTOCOL_MINIMAL \
    {  \
        "lws-minimal-proxy", \
        callback_minimal, \
        sizeof(struct per_session_data__minimal), \
        128, \
        0, NULL, 0 \
    }

and

struct lws_protocols {
    const char *name;
    lws_callback_function *callback;
    size_t per_session_data_size;
    size_t rx_buffer_size;
    unsigned int id;
    void *user;
    size_t tx_packet_size;
};

Upvotes: 0

Views: 844

Answers (1)

timbo
timbo

Reputation: 14354

I used zig translate-c -l libwebsockets minimal-ws-server.c > foo.zig to produce a zig source file from the original C source.

I then looked through the foo.zig file and extracted the following:

pub const struct_lws_protocols = extern struct {
    name: [*c]const u8,
    callback: ?lws.lws_callback_function,
    per_session_data_size: usize,
    rx_buffer_size: usize,
    id: c_uint,
    user: ?*c_void,
    tx_packet_size: usize,
};

pub var protocols: [0]struct_lws_protocols = [0]struct_lws_protocols{
    struct_lws_protocols{
        .name = "http",
        .callback = lws.lws_callback_http_dummy,
        .per_session_data_size = @bitCast(usize, @as(c_long, @as(c_int, 0))),
        .rx_buffer_size = @bitCast(usize, @as(c_long, @as(c_int, 0))),
        .id = 0,
        .user = null,
        .tx_packet_size = 0,
    },
};

I then discovered that using the zig C header import:

const lws = @cImport(@cInclude("libwebsockets.h"));

I could just reference the structs (or other definitions) provided by the header by prefixing the names with lws. e.g. lws.lws_callback_http_dummy (as used above) rather than duplicating those definitions in my zig source

Upvotes: 1

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