C++ io_chain_t::push_back方法代码示例

/// Execute a block node or function "process".
/// \p user_ios contains the list of user-specified ios, used so we can avoid stomping on them with
/// our pipes. \return true on success, false on error.
static bool exec_block_or_func_process(parser_t &parser, job_t *j, process_t *p,
                                       const io_chain_t &user_ios, io_chain_t io_chain) {
    assert((p->type == INTERNAL_FUNCTION || p->type == INTERNAL_BLOCK_NODE) &&
           "Unexpected process type");

    // Create an output buffer if we're piping to another process.
    shared_ptr<io_buffer_t> block_output_io_buffer{};
    if (!p->is_last_in_job) {
        // Be careful to handle failure, e.g. too many open fds.
        block_output_io_buffer = io_buffer_t::create(STDOUT_FILENO, user_ios);
        if (!block_output_io_buffer) {
            job_mark_process_as_failed(j, p);
            return false;
        } else {
            // This looks sketchy, because we're adding this io buffer locally - they
            // aren't in the process or job redirection list. Therefore select_try won't
            // be able to read them. However we call block_output_io_buffer->read()
            // below, which reads until EOF. So there's no need to select on this.
            io_chain.push_back(block_output_io_buffer);
        }
    }

    if (p->type == INTERNAL_FUNCTION) {
        const wcstring func_name = p->argv0();
        auto props = function_get_properties(func_name);
        if (!props) {
            debug(0, _(L"Unknown function '%ls'"), p->argv0());
            return false;
        }

        const std::map<wcstring, env_var_t> inherit_vars = function_get_inherit_vars(func_name);

        function_block_t *fb =
            parser.push_block<function_block_t>(p, func_name, props->shadow_scope);
        function_prepare_environment(func_name, p->get_argv() + 1, inherit_vars);
        parser.forbid_function(func_name);

        internal_exec_helper(parser, props->parsed_source, props->body_node, io_chain);

        parser.allow_function();
        parser.pop_block(fb);
    } else {
        assert(p->type == INTERNAL_BLOCK_NODE);
        assert(p->block_node_source && p->internal_block_node && "Process is missing node info");
        internal_exec_helper(parser, p->block_node_source, p->internal_block_node, io_chain);
    }

    int status = proc_get_last_status();

    // Handle output from a block or function. This usually means do nothing, but in the
    // case of pipes, we have to buffer such io, since otherwise the internal pipe
    // buffer might overflow.
    if (!block_output_io_buffer.get()) {
        // No buffer, so we exit directly. This means we have to manually set the exit
        // status.
        if (p->is_last_in_job) {
            proc_set_last_status(j->get_flag(job_flag_t::NEGATE) ? (!status) : status);
        }
        p->completed = 1;
        return true;
    }

    // Here we must have a non-NULL block_output_io_buffer.
    assert(block_output_io_buffer.get() != NULL);
    io_chain.remove(block_output_io_buffer);
    block_output_io_buffer->read();

    const std::string buffer_contents = block_output_io_buffer->buffer().newline_serialized();
    const char *buffer = buffer_contents.data();
    size_t count = buffer_contents.size();
    if (count > 0) {
        // We don't have to drain threads here because our child process is simple.
        const char *fork_reason =
            p->type == INTERNAL_BLOCK_NODE ? "internal block io" : "internal function io";
        if (!fork_child_for_process(j, p, io_chain, false, fork_reason, [&] {
                exec_write_and_exit(block_output_io_buffer->fd, buffer, count, status);
            })) {
            return false;
        }
    } else {
        if (p->is_last_in_job) {
            proc_set_last_status(j->get_flag(job_flag_t::NEGATE) ? (!status) : status);
        }
        p->completed = 1;
    }
    return true;
}