should also look into headers for input_size (JuliaLang#167)

If no content length is set while uploading some contents, Curl defaults to use
chunked transfer encoding. In some cases we want to prevent that because the
server may not support chunked transfers.

With this change, the request method will also look at the headers while
determining the input size and if found call `set_upload_size` as usual. So to
switch off chunked transfers, one must also know and set the content length
header while invoking `download` or `request` methods.

src/Downloads.jl

@@ -305,6 +305,10 @@ function request(
     input = something(input, devnull)
     output = something(output, devnull)
     input_size = arg_read_size(input)
+    if input_size === nothing
+        # take input_size from content-length header if one is supplied
+        input_size = content_length(headers)
+    end
     progress = p_func(progress, input, output)
     arg_read(input) do input
         arg_write(output) do output
@@ -395,4 +399,13 @@ arg_read_size(io::Base.GenericIOBuffer) = bytesavailable(io)
 arg_read_size(::Base.DevNull) = 0
 arg_read_size(::Any) = nothing
 
+function content_length(headers::Union{AbstractVector, AbstractDict})
+    for (key, value) in headers
+        if lowercase(key) == "content-length" && isa(value, AbstractString)
+            return tryparse(Int, value)
+        end
+    end
+    return nothing
+end
+
 end # module

test/runtests.jl

@@ -513,6 +513,8 @@ include("setup.jl")
         @test Downloads.arg_read_size(IOBuffer("αa")) == 3
         @test Downloads.arg_read_size(IOBuffer(codeunits("αa"))) == 3  # Issue #142
         @test Downloads.arg_read_size(devnull) == 0
+        @test Downloads.content_length(["Accept"=>"*/*",]) === nothing
+        @test Downloads.content_length(["Accept"=>"*/*", "Content-Length"=>"100"]) == 100
     end
 end