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add IO::-style user streams
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a thin layer over signal_connect, thanks @janko

see janko/image_processing#60 (comment)
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@jcupitt
jcupitt committed Dec 6, 2019
1 parent 0944c12 commit 6f55916
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Showing 4 changed files with 73 additions and 159 deletions.
94 changes: 12 additions & 82 deletions example/stream.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -2,85 +2,15 @@

require 'vips'

class Mystreami < Vips::Streamiu
def initialize(filename, pipe_mode=false)
@filename = filename
@contents = File.open(@filename, "rb").read
@length = @contents.length
@pipe_mode = pipe_mode
@read_point = 0

puts "Mystreami: loaded #{@length} bytes"

super()

signal_connect "read" do |buf, len|
puts "read: #{len} bytes from #{@read_point}"

bytes_available = @length - @read_point
bytes_to_copy = [bytes_available, len].min
buf.put_bytes(0, @contents, @read_point, bytes_to_copy)
@read_point += bytes_to_copy

puts " transferred #{bytes_to_copy} bytes"

bytes_to_copy
end

signal_connect "seek" do |offset, whence|
puts "seek: offset #{offset}, whence #{whence}"
if @pipe_mode
puts " new_position == -1 (pipe mode)"
return -1
end

case whence
when 0
# SEEK_SET
new_read_point = offset
when 1
# SEEK_CUR
new_read_point = self.read_point + offset
when 2
# SEEK_END
new_read_point = self.length + offset
else
raise "bad whence #{whence}"
end

@read_point = [0, [@length, new_read_point].min].max

puts " new_position = #{@read_point}"

@read_point
end
end
end

class Mystreamo < Vips::Streamou
def initialize(filename)
@filename = filename
@f = File.open(@filename, "wb")

super()

signal_connect "write" do |buf, len|
@f.write(buf.get_bytes(0, len))
len
end

signal_connect "finish" do
@f.close
@f = nil
end

end
end

streamiu = Mystreami.new ARGV[0]
image = Vips::Image.new_from_stream streamiu, "", access: "sequential"
#puts "avg = #{image.avg}"

streamio = Mystreamo.new ARGV[1]
image.write_to_stream streamio, ".png"

source = File.open ARGV[0], "rb"
input_stream = Vips::Streamiu.new
input_stream.on_read { |length| source.read length }
input_stream.on_seek { |offset, whence| source.seek(offset, whence) }

dest = File.open ARGV[1], "w"
output_stream = Vips::Streamou.new
output_stream.on_write { |chunk| dest.write(chunk) }
output_stream.on_finish { dest.close }

image = Vips::Image.new_from_stream input_stream, "", access: "sequential"
image.write_to_stream output_stream, ".png"
23 changes: 23 additions & 0 deletions lib/vips/streamiu.rb
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Expand Up @@ -46,5 +46,28 @@ def initialize
super pointer
end

# The block is executed to read data from the source. The interface is
# exactly as IO::seek, ie. it takes a maximum number of bytes to read and
# returns a string of bytes from the source, or nil if the source is already
# at eod of file.
def on_read &block
signal_connect "read" do |buf, len|
chunk = block.call len
return 0 if chunk == nil

buf.put_bytes(0, chunk, 0, chunk.bytesize)
chunk.bytesize
end
end

# The block is executed to seek the source. The interface is exactly as
# IO::seek, ie. it should take an offset and whence, and return the new read
# position.
def on_seek &block
signal_connect "seek" do |offset, whence|
block.call offset, whence
end
end

end
end
17 changes: 17 additions & 0 deletions lib/vips/streamou.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -46,5 +46,22 @@ def initialize
super pointer
end

# The block is executed to write data to the source. The interface is
# exactly as IO::write, ie. it should write the string and return the
# number of bytes written.
def on_write &block
signal_connect "write" do |p, len|
block.call(p.get_bytes(0, len))
end
end

# The block is executed at the end of write. It should do any necessary
# finishing action.
def on_finish &block
signal_connect "finish" do
block.call()
end
end

end
end
98 changes: 21 additions & 77 deletions spec/stream_spec.rb
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Expand Up @@ -107,82 +107,20 @@
end
end

if Vips::at_least_libvips?(8, 9)
class Mystreami < Vips::Streamiu
def initialize(filename, pipe_mode=false)
@filename = filename
@contents = File.open(@filename, "rb").read
@length = @contents.length
@pipe_mode = pipe_mode
@read_point = 0

super()

signal_connect "read" do |buf, len|
bytes_available = @length - @read_point
bytes_to_copy = [bytes_available, len].min
buf.put_bytes(0, @contents, @read_point, bytes_to_copy)
@read_point += bytes_to_copy

bytes_to_copy
end

signal_connect "seek" do |offset, whence|
if @pipe_mode
-1
else
case whence
when 0
# SEEK_SET
new_read_point = offset
when 1
# SEEK_CUR
new_read_point = self.read_point + offset
when 2
# SEEK_END
new_read_point = self.length + offset
else
raise "bad whence #{whence}"
end

@read_point = [0, [@length, new_read_point].min].max
end
end
end
end

class Mystreamo < Vips::Streamou
def initialize(filename)
@filename = filename
@f = File.open(@filename, "wb")

super()

signal_connect "write" do |buf, len|
@f.write(buf.get_bytes(0, len))
len
end

signal_connect "finish" do
@f.close
@f = nil
end

end
end
end

if Vips::at_least_libvips?(8, 9)
RSpec.describe Vips::Streamiu do
it 'can create a user input stream' do
streamiu = Mystreami.new simg('wagon.jpg')
input_stream = Vips::Streamiu.new

expect(streamiu)
expect(input_stream)
end

it 'can load a user stream' do
streamiu = Mystreami.new simg('wagon.jpg')
image = Vips::Image.new_from_stream streamiu, ''
source = File.open simg('wagon.jpg'), "rb"
input_stream = Vips::Streamiu.new
input_stream.on_read { |length| source.read length }
input_stream.on_seek { |offset, whence| source.seek(offset, whence) }
image = Vips::Image.new_from_stream input_stream, ""

expect(image)
expect(image.width).to eq(685)
Expand All @@ -191,9 +129,12 @@ def initialize(filename)
expect(image.avg).to be_within(0.001).of(109.789)
end

it 'can load a user stream in pipe mode' do
streamiu = Mystreami.new simg('wagon.jpg'), true
image = Vips::Image.new_from_stream streamiu, ''
it 'on_seek is optional' do
source = File.open simg('wagon.jpg'), "rb"
input_stream = Vips::Streamiu.new
input_stream.on_read { |length| source.read length }
input_stream.on_seek { |offset, whence| -1 }
image = Vips::Image.new_from_stream input_stream, ""

expect(image)
expect(image.width).to eq(685)
Expand All @@ -203,16 +144,19 @@ def initialize(filename)
end

it 'can create a user output stream' do
streamou = Mystreamo.new timg('x.jpg')
output_stream = Vips::Streamou.new

expect(streamou)
expect(output_stream)
end

it 'can write an image to a user output stream' do
image = Vips::Image.new_from_file simg('wagon.jpg')
filename = timg('x5.png')
streamou = Mystreamo.new filename
image.write_to_stream streamou, '.png'
dest = File.open filename, "wb"
output_stream = Vips::Streamou.new
output_stream.on_write { |chunk| dest.write(chunk) }
output_stream.on_finish { dest.close }
image = Vips::Image.new_from_file simg('wagon.jpg')
image.write_to_stream output_stream, ".png"

image = Vips::Image.new_from_file filename
expect(image)
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