Merge branch 'release/0.18'

crystal-lang · Jun 23, 2016 · 6dced6c · 6dced6c
2 parents ca6154d + 5fa22e6
commit 6dced6c
Showing 2 changed files with 39 additions and 0 deletions.
diff --git a/spec/std/io/io_spec.cr b/spec/std/io/io_spec.cr
@@ -155,6 +155,23 @@ describe IO do
     dst.to_s.should eq(string)
   end
 
+  it "copies with limit" do
+    string = "abcあぼ"
+    src = MemoryIO.new(string)
+    dst = MemoryIO.new
+    IO.copy(src, dst, 3).should eq(3)
+    dst.to_s.should eq("abc")
+  end
+
+  it "raises on copy with negative limit" do
+    string = "abcあぼ"
+    src = MemoryIO.new(string)
+    dst = MemoryIO.new
+    expect_raises(ArgumentError, "negative limit") do
+      IO.copy(src, dst, -10)
+    end
+  end
+
   it "reopens" do
     File.open("#{__DIR__}/../data/test_file.txt") do |file1|
       File.open("#{__DIR__}/../data/test_file.ini") do |file2|

diff --git a/src/io.cr b/src/io.cr
@@ -896,6 +896,28 @@ module IO
     len < 0 ? len : count
   end
 
+  # Copy at most *limit* bytes from *src* to *dst*.
+  #
+  # ```
+  # io = MemoryIO.new "hello"
+  # io2 = MemoryIO.new
+  #
+  # IO.copy io, io2, 3
+  #
+  # io2.to_s # => "hel"
+  # ```
+  def self.copy(src, dst, limit : Int)
+    raise ArgumentError.new("negative limit") if limit < 0
+
+    buffer = uninitialized UInt8[1024]
+    remaining = limit
+    while (len = src.read(buffer.to_slice[0, Math.min(buffer.size, Math.max(remaining, 0))])) > 0
+      dst.write buffer.to_slice[0, len]
+      remaining -= len
+    end
+    limit - remaining
+  end
+
   # :nodoc:
   struct LineIterator(I, A)
     include Iterator(String)