restrict numeric values to fit in 8 ASCII characters per EDF spec (#30)

Project.toml

@@ -1,10 +1,11 @@
 name = "EDF"
 uuid = "ccffbfc1-f56e-50fb-a33b-53d1781b2825"
 authors = ["Beacon Biosignals, Inc."]
-version = "0.4.0"
+version = "0.4.1"
 
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
+Printf = "de0858da-6303-5e67-8744-51eddeeeb8d7"
 
 [compat]
 julia = "1.4"

src/EDF.jl

@@ -1,6 +1,6 @@
 module EDF
 
-using Dates
+using Dates, Printf
 
 include("types.jl")
 include("read.jl")

src/write.jl

@@ -2,28 +2,54 @@
 ##### utilities
 #####
 
-_edf_write(io::IO, value::Union{String,Char}) = Base.write(io, value)
-_edf_write(io::IO, date::Date) = Base.write(io, uppercase(Dates.format(date, dateformat"dd-u-yyyy")))
-_edf_write(io::IO, date::DateTime) = Base.write(io, Dates.format(date, dateformat"dd\.mm\.yyHH\.MM\.SS"))
-_edf_write(io::IO, x::Integer) = Base.write(io, string(x))
-_edf_write(io::IO, x::AbstractFloat) = Base.write(io, string(isinteger(x) ? trunc(Int, x) : x))
+_edf_repr(value::Union{String,Char}) = value
+_edf_repr(date::Date) = uppercase(Dates.format(date, dateformat"dd-u-yyyy"))
+_edf_repr(date::DateTime) = Dates.format(date, dateformat"dd\.mm\.yyHH\.MM\.SS")
 
-function _edf_write(io::IO, metadata::T) where T<:Union{PatientID,RecordingID}
-    bytes_written = 0
-    for name in fieldnames(T)
-        field = getfield(metadata, name)
-        if T <: RecordingID && name === :startdate
-            bytes_written += _edf_write(io, "Startdate ")
+# XXX this is really really hacky and doesn't support use of scientific notation
+# where appropriate; keep in mind if you do improve this to support scientific
+# notation, that scientific is NOT allowed in EDF annotation onset/duration fields
+function _edf_repr(x::Real)
+    result = missing
+    if isinteger(x)
+        str = string(trunc(Int, x))
+        if length(str) <= 8
+            result = str
+        end
+    else
+        fpart, ipart = modf(x)
+        ipart_str = string('-'^signbit(x), Int(abs(ipart))) # handles `-0.0` case
+        fpart_str = @sprintf "%.7f" abs(fpart)
+        fpart_str = fpart_str[3:end] # remove leading `0.`
+        if length(ipart_str) < 7
+            result = ipart_str * '.' * fpart_str[1:(7 - length(ipart_str))]
+        elseif length(ipart_str) <= 8
+            result = ipart_str
         end
-        bytes_written += field isa Missing ? Base.write(io, 'X') : _edf_write(io, field)
-        bytes_written += Base.write(io, ' ')
     end
-    return bytes_written
+    if !ismissing(result)
+        if all(c -> c in ('0', '.', '-'), result)
+            x == 0 && return result
+        else
+            return result
+        end
+    end
+    error("failed to fit number into EDF's 8 ASCII character limit: $x")
+end
+
+_edf_metadata_repr(::Missing) = 'X'
+_edf_metadata_repr(x) = _edf_repr(x)
+
+function _edf_repr(metadata::T) where T<:Union{PatientID,RecordingID}
+    header = T <: RecordingID ? String["Startdate"] : String[]
+    return join([header; [_edf_metadata_repr(getfield(metadata, name)) for name in fieldnames(T)]], ' ')
 end
 
 function edf_write(io::IO, value, byte_limit::Integer)
-    bytes_written = _edf_write(io, value)
-    bytes_written <= byte_limit || error("Written value $value contains more bytes than limit $byte_limit")
+    edf_value = _edf_repr(value)
+    @assert isascii(edf_value)
+    size = length(edf_value)
+    bytes_written = Base.write(io, edf_value)
     while bytes_written < byte_limit
         bytes_written += Base.write(io, UInt8(' '))
     end
@@ -35,6 +61,7 @@ end
 #####
 
 function write_header(io::IO, file::File)
+    length(file.signals) <= 9999 || error("EDF does not allow files with more than 9999 signals")
     bytes_written = 0
     bytes_written += edf_write(io, file.header.version, 8)
     bytes_written += edf_write(io, file.header.patient, 80)
@@ -81,11 +108,13 @@ end
 function write_signal_record(io::IO, signal::AnnotationsSignal, record_index::Int)
     bytes_written = 0
     for tal in signal.records[record_index]
-        bytes_written += Base.write(io, signbit(tal.onset_in_seconds) ? '-' : '+')
-        bytes_written += _edf_write(io, tal.onset_in_seconds)
+        if !signbit(tal.onset_in_seconds) # otherwise, the `-` will already be in number string
+            bytes_written += Base.write(io, '+')
+        end
+        bytes_written += Base.write(io, _edf_repr(tal.onset_in_seconds))
         if tal.duration_in_seconds !== nothing
             bytes_written += Base.write(io, 0x15)
-            bytes_written += _edf_write(io, tal.duration_in_seconds)
+            bytes_written += Base.write(io, _edf_repr(tal.duration_in_seconds))
         end
         bytes_written += Base.write(io, 0x14)
         for annotation in tal.annotations

test/runtests.jl

@@ -93,6 +93,14 @@ const DATADIR = joinpath(@__DIR__, "data")
         @test eof(io)
     end
 
+    @test EDF._edf_repr(34577777) == "34577777"
+    @test EDF._edf_repr(0.0345) == "0.034500"
+    @test EDF._edf_repr(-0.02) == "-0.02000"
+    @test EDF._edf_repr(-187.74445) == "-187.744"
+    @test_throws ErrorException EDF._edf_repr(123456789)
+    @test_throws ErrorException EDF._edf_repr(-12345678)
+    @test_throws ErrorException EDF._edf_repr(0.00000000024)
+
     uneven = EDF.read(joinpath(DATADIR, "test_uneven_samp.edf"))
     @test sprint(show, uneven) == "EDF.File with 2 signals"
     @test uneven.header.version == "0"