http/stream_common: Add .count option to write_body_from_file

doc/interfaces/stream.md

@@ -93,6 +93,8 @@ Writes the string `str` to the stream and ends the stream. On error, returns `ni
 
   - `options` is a table containing:
 	- `.file` (file)
+	- `.count` (positive integer): number of bytes of `file` to write  
+	  defaults to infinity (the whole file will be written)
 
 Writes the contents of file `file` to the stream and ends the stream. `file` will not be automatically seeked, so ensure it is at the correct offset before calling. On error, returns `nil`, an error message and an error number.
 

http/stream_common.lua

@@ -154,25 +154,33 @@ end
 
 function stream_methods:write_body_from_file(options, timeout)
 	local deadline = timeout and (monotime()+timeout)
-	local file
+	local file, count
 	if io.type(options) then -- lua-http <= 0.2 took a file handle
 		file = options
 	else
 		file = options.file
+		count = options.count
 	end
-	-- Can't use :lines here as in Lua 5.1 it doesn't take a parameter
-	while true do
-		local chunk, err = file:read(CHUNK_SIZE)
+	if count == nil then
+		count = math.huge
+	elseif type(count) ~= "number" or count < 0 or count % 1 ~= 0 then
+		error("invalid .count parameter (expected positive integer)")
+	end
+	while count > 0 do
+		local chunk, err = file:read(math.min(CHUNK_SIZE, count))
 		if chunk == nil then
 			if err then
 				error(err)
+			elseif count ~= math.huge and count > 0 then
+				error("unexpected EOF")
 			end
 			break
 		end
 		local ok, err2, errno2 = self:write_chunk(chunk, false, deadline and (deadline-monotime()))
 		if not ok then
 			return nil, err2, errno2
 		end
+		count = count - #chunk
 	end
 	return self:write_chunk("", true, deadline and (deadline-monotime()))
 end

spec/stream_common_spec.lua

@@ -127,5 +127,73 @@ describe("http.stream_common", function()
 			client:close()
 			server:close()
 		end)
+		it("validates .count option", function()
+			local server, client = new_pair(1.1)
+			local cq = cqueues.new()
+			cq:wrap(function()
+				local stream = client:new_stream()
+				assert(stream:write_headers(new_request_headers(), false))
+				assert.has_error(function()
+					stream:write_body_from_file({
+						file = io.tmpfile();
+						count = "invalid count field";
+					})
+				end)
+			end)
+			cq:wrap(function()
+				assert(server:get_next_incoming_stream())
+			end)
+			assert_loop(cq, TEST_TIMEOUT)
+			assert.truthy(cq:empty())
+			client:close()
+			server:close()
+		end)
+		it("limits number of bytes when using .count option", function()
+			local server, client = new_pair(1.1)
+			local cq = cqueues.new()
+			cq:wrap(function()
+				local file = io.tmpfile()
+				assert(file:write("hello world!"))
+				assert(file:seek("set"))
+				local stream = client:new_stream()
+				assert(stream:write_headers(new_request_headers(), false))
+				assert(stream:write_body_from_file({
+					file = file;
+					count = 5;
+				}))
+			end)
+			cq:wrap(function()
+				local stream = assert(server:get_next_incoming_stream())
+				assert.same("hello", assert(stream:get_body_as_string()))
+			end)
+			assert_loop(cq, TEST_TIMEOUT)
+			assert.truthy(cq:empty())
+			client:close()
+			server:close()
+		end)
+		it("reports an error on early EOF", function()
+			local server, client = new_pair(1.1)
+			local cq = cqueues.new()
+			cq:wrap(function()
+				local file = io.tmpfile()
+				assert(file:write("hello world!"))
+				assert(file:seek("set"))
+				local stream = client:new_stream()
+				assert(stream:write_headers(new_request_headers(), false))
+				assert.has_error(function()
+					assert(stream:write_body_from_file({
+						file = file;
+						count = 50; -- longer than the file
+					}))
+				end)
+			end)
+			cq:wrap(function()
+				assert(server:get_next_incoming_stream())
+			end)
+			assert_loop(cq, TEST_TIMEOUT)
+			assert.truthy(cq:empty())
+			client:close()
+			server:close()
+		end)
 	end)
 end)