print.lua

---
-- Sink a signal to a file, formatted as a string. Samples are formatted
-- individually and newline delimited. This sink accepts any data type that
-- implements `__tostring()`.
--
-- @category Sinks
-- @block PrintSink
-- @tparam[opt=io.stdout] string|file|int file Filename, file object, or file descriptor
-- @tparam[opt={}] table options Additional options, specifying:
--                            * `title` (string, default nil)
--                            * `timestamp` (bool, default false)
--
-- @signature in:supported >
--
-- @usage
-- -- Sink string formatted samples to stdout
-- local snk = radio.PrintSink()
-- top:connect(src, snk)

local ffi = require('ffi')

local block = require('radio.core.block')

local PrintSink = block.factory("PrintSink")

function PrintSink:instantiate(file, options)
    if type(file) == "number" then
        self.fd = file
    elseif type(file) == "string" then
        self.filename = file
    elseif type(file) == "userdata" then
        self.file = file
    elseif file == nil then
        -- Default to io.stdout
        self.file = io.stdout
    end

    options = options or {}

    self.title = options.title
    self.timestamp = options.timestamp or false

    -- Accept all input types that implement __tostring()
    self:add_type_signature({block.Input("in", function (type) return type.__tostring ~= nil end)}, {})
end

function PrintSink:initialize()
    if self.filename then
        self.file = ffi.C.fopen(self.filename, "wb")
        if self.file == nil then
            error("fopen(): " .. ffi.string(ffi.C.strerror(ffi.errno())))
        end
    elseif self.fd then
        self.file = ffi.C.fdopen(self.fd, "wb")
        if self.file == nil then
            error("fdopen(): " .. ffi.string(ffi.C.strerror(ffi.errno())))
        end
    end

    -- Preformat title
    self.title = self.title and string.format("[%s] ", self.title) or ""

    -- Register open file
    self.files[self.file] = true
end

function PrintSink:process(x)
    for i = 0, x.length-1 do
        local timestamp = self.timestamp and os.date("![%Y-%m-%dT%TZ] ") or ""

        local s = timestamp .. self.title .. tostring(x.data[i]) .. "\n"

        -- Write to file
        if ffi.C.fwrite(s, 1, #s, self.file) ~= #s then
            error("fwrite(): " .. ffi.string(ffi.C.strerror(ffi.errno())))
        end
    end

    -- Flush file
    if ffi.C.fflush(self.file) ~= 0 then
        error("fflush(): " .. ffi.string(ffi.C.strerror(ffi.errno())))
    end
end

function PrintSink:cleanup()
    if self.filename then
        if ffi.C.fclose(self.file) ~= 0 then
            error("fclose(): " .. ffi.string(ffi.C.strerror(ffi.errno())))
        end
    elseif self.fd then
        if ffi.C.fflush(self.file) ~= 0 then
            error("fflush(): " .. ffi.string(ffi.C.strerror(ffi.errno())))
        end
    else
        self.file:flush()
    end
end

return PrintSink