Be more mindful of output file name lengths

This makes the following two changes:

 - open files for writing by their relative path, which will often be
   shorter than the absolute path (and in any case the user has more
   control over any path length issues if they have the option to either
   expand it or not _before_ calling `statprofhtml()`)

 - Put a cap on the output file name lengths by using a hash instead
   of an encoding. This means we have to use bytes2hex rather than
   base64 because `/` is a valid base64 character. (This was already
   a bug before, but I probably never ran into it because encoding
   only paths never results in a `/`.)

Author: tkluck

Project.toml

@@ -4,16 +4,16 @@ author = ["Timo Kluck <tkluck@infty.nl>"]
 version = "1.3.0"
 
 [deps]
-Base64 = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
 DataStructures = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 FlameGraphs = "08572546-2f56-4bcf-ba4e-bab62c3a3f89"
 HAML = "0bc81568-2411-4001-9bf1-c899fa54f385"
 Profile = "9abbd945-dff8-562f-b5e8-e1ebf5ef1b79"
+SHA = "ea8e919c-243c-51af-8825-aaa63cd721ce"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [compat]
-julia = "1.3"
 DataStructures = "0.17, 0.18"
 FlameGraphs = "0.1, 0.2"
 HAML = "0.3.1"
+julia = "1.3"

src/HTML.jl

@@ -1,12 +1,17 @@
 module HTML
 
-import Base64: base64encode
+import SHA: sha1
 
 import Dates: format, RFC1123Format
 import HAML: includehaml, @include, @surround, @cdatafile, @output
 
 import ..Reports: Report, FunctionPoint, TracePoint
 
+# needs to be smaller than 250 on MacOS, and anecdotally, the length of a full
+# path needs to be at most 260 on Windows. This should give some spare room
+# in either case.
+const MAX_OUTPUT_FILE_NAME_LENGTH = 150
+
 templatefile(name...) = joinpath(@__DIR__, "..", "haml", name...)
 
 includehaml(@__MODULE__,
@@ -21,7 +26,8 @@ includehaml(@__MODULE__,
 outputfilename(::Nothing) = ""
 outputfilename(sourcefile::Symbol) = begin
     b = basename(string(sourcefile))
-    x = base64encode(string(sourcefile))
+    x = bytes2hex(sha1(String(sourcefile)))
+    b = first(b, MAX_OUTPUT_FILE_NAME_LENGTH - length(x) - length("-.html"))
     return "$b-$x.html"
 end
 

src/StatProfilerHTML.jl

@@ -22,7 +22,7 @@ function statprofilehtml(data::Vector{<:Unsigned} = UInt[], litrace::LineInfoDic
 
     report = Report(data, litrace, from_c)
     sort!(report)
-    HTML.output(report, fullpath)
+    HTML.output(report, path)
 
     @info "Wrote profiling output to file://$fullpath/index.html ."
 end