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adding yaml streaming api

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1 parent aa5e67a commit 01b3d734cd685516ae4cba5bd4dbb7daab4931ee @tenderlove tenderlove committed May 20, 2010
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@@ -97,6 +97,8 @@ module Psych
class Exception < RuntimeError
end
+ autoload :Stream, 'psych/stream'
+
###
# Load +yaml+ in to a Ruby data structure. If multiple documents are
# provided, the object contained in the first document will be returned.
View
@@ -211,5 +211,11 @@ def empty
# Called when the YAML stream ends
def end_stream
end
+
+ ###
+ # Is this handler a streaming handler?
+ def streaming?
+ false
+ end
end
end
@@ -8,7 +8,7 @@ def start_document version, tag_directives, implicit
super(version, tag_directives, true)
end
- def end_document implicit_end
+ def end_document implicit_end = !streaming?
super(true)
end
View
@@ -0,0 +1,53 @@
+module Psych
+ ###
+ # Psych::Stream is a streaming YAML emitter. It will not buffer your YAML,
+ # but send it straight to an IO.
+ #
+ # Here is an example use:
+ #
+ # stream = Psych::Stream.new($stdout)
+ # stream.start
+ # stream.push({:foo => 'bar'})
+ # stream.finish
+ #
+ # YAML will be immediately emitted to $stdout with no buffering.
+ #
+ # Psych::Stream#start will take a block and ensure that Psych::Stream#finish
+ # is called, so you can do this form:
+ #
+ # stream = Psych::Stream.new($stdout)
+ # stream.start do |em|
+ # em.push(:foo => 'bar')
+ # end
+ #
+ class Stream < Psych::Visitors::YAMLTree
+ class Emitter < Psych::Emitter # :nodoc:
+ def end_document implicit_end = !streaming?
+ super
+ end
+
+ def streaming?
+ true
+ end
+ end
+
+ ###
+ # Create a new streaming emitter. Emitter will print to +io+. See
+ # Psych::Stream for an example.
+ def initialize io
+ super({}, Emitter.new(io))
+ end
+
+ ###
+ # Start streaming using +encoding+
+ def start encoding = Nodes::Stream::UTF8
+ super.tap { yield self if block_given? }
+ ensure
+ finish if block_given?
+ end
+
+ private
+ def register target, obj
+ end
+ end
+end
@@ -57,7 +57,7 @@ def start_document version, tag_directives, implicit
# and +implicit+ styling.
#
# See Psych::Handler#start_document
- def end_document implicit_end
+ def end_document implicit_end = !streaming?
@last.implicit_end = implicit_end
pop
end
@@ -1,6 +1,15 @@
module Psych
module Visitors
class Visitor
+ attr_reader :started, :finished
+ alias :finished? :finished
+ alias :started? :started
+
+ def initialize
+ @started = false
+ @finished = false
+ end
+
def accept target
case target
when Psych::Nodes::Scalar then visit_Psych_Nodes_Scalar target
@@ -10,11 +10,9 @@ module Visitors
class YAMLTree < Psych::Visitors::Visitor
def initialize options = {}, emitter = Psych::TreeBuilder.new
super()
- @emitter = emitter
- @st = {}
- @ss = ScalarScanner.new
-
- @emitter.start_stream Psych::Nodes::Stream::UTF8
+ @emitter = emitter
+ @st = {}
+ @ss = ScalarScanner.new
@dispatch_cache = Hash.new do |h,klass|
method = "visit_#{(klass.name || '').split('::').join('_')}"
@@ -27,15 +25,29 @@ def initialize options = {}, emitter = Psych::TreeBuilder.new
end
end
+ def start encoding = Nodes::Stream::UTF8
+ @emitter.start_stream(encoding).tap do
+ @started = true
+ end
+ end
+
+ def finish
+ @emitter.end_stream.tap do
+ @finished = true
+ end
+ end
+
def tree
- @emitter.end_stream
+ finish unless finished?
end
- def << object
+ def push object
+ start unless started?
@emitter.start_document [], [], false
accept object
- @emitter.end_document true
+ @emitter.end_document
end
+ alias :<< :push
def accept target
# return any aliases we find
View
@@ -0,0 +1,49 @@
+require_relative 'helper'
+
+module Psych
+ class TestStream < TestCase
+ def test_explicit_documents
+ io = StringIO.new
+ stream = Psych::Stream.new(io)
+ stream.start
+ stream.push({ 'foo' => 'bar' })
+
+ assert !stream.finished?, 'stream not finished'
+ stream.finish
+ assert stream.finished?, 'stream finished'
+
+ assert_match(/^---/, io.string)
+ assert_match(/\.\.\.$/, io.string)
+ end
+
+ def test_start_takes_block
+ io = StringIO.new
+ stream = Psych::Stream.new(io)
+ stream.start do |emitter|
+ emitter.push({ 'foo' => 'bar' })
+ end
+
+ assert stream.finished?, 'stream finished'
+ assert_match(/^---/, io.string)
+ assert_match(/\.\.\.$/, io.string)
+ end
+
+ def test_no_backreferences
+ io = StringIO.new
+ stream = Psych::Stream.new(io)
+ stream.start do |emitter|
+ x = { 'foo' => 'bar' }
+ emitter.push x
+ emitter.push x
+ end
+
+ assert stream.finished?, 'stream finished'
+ assert_match(/^---/, io.string)
+ assert_match(/\.\.\.$/, io.string)
+ assert_equal 2, io.string.scan('---').length
+ assert_equal 2, io.string.scan('...').length
+ assert_equal 2, io.string.scan('foo').length
+ assert_equal 2, io.string.scan('bar').length
+ end
+ end
+end

2 comments on commit 01b3d73

Owner

tenderlove replied May 20, 2010

Hahaha! Thanks! Now I just need to finish the streaming JSON bit, and we'll really be cooking.

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