Reading definition headers

src/bytes.jl

@@ -1,6 +1,6 @@
 module bytes
 
-export byte_vec_to_int, byte_vec_to_string, bit_at, bit_vector
+export byte_vec_to_int, byte_vec_to_string, bit_at, bit_vector, sum_bits
 
 """
     read_data_size(size::Vector{UInt8})::Real
@@ -53,5 +53,16 @@ function bit_vector(byte_vector::Vector{UInt8}; little_endian=false)::Vector{UIn
     reduce(vcat, vecs)
 end
 
+"""
+    sum_bits(bit_vector::Vector{UInt8})::Int64
+
+Sum the bits found in bit_vector, return a value in Int64, Calculate the value of
+each bit along the way.
+"""
+function sum_bits(bit_vector::Vector{UInt8})::Int64
+    rev = reverse(bit_vector)
+    sum([rev[i] * (2 ^ (i - 1)) for i ∈ eachindex(rev)])
+end
+
 end
 # byte_vec_to_string(UInt8.(collect("ABC")))

src/file.jl

@@ -1,8 +1,11 @@
 module file
 
-export FITFile, read_file
+import Base.show
+
+export FITFile, read_file, DataRecord
 
 include("bytes.jl"); using .bytes
+include("mesg_num.jl"); using .mesg_num
 
 
 HEADER_SZ = 14
@@ -16,9 +19,34 @@ struct FITHeader
     crc::AbstractVector{<:Real}
 end
 
-mutable struct DataRecord
+"""
+    RecordHeader
+
+Contains the header byte for a record row
+"""
+mutable struct RecordHeader
     definition::Bool
     data::Bool
+    local_mesg_type::Int64
+end
+
+mutable struct DefinitionBody
+    architecture::AbstractString
+    global_mesg_type::AbstractString # Read from mesg_num.jl using the bytes in this field.
+    num_fields::UInt8
+end
+
+mutable struct DataBody
+end
+
+"""
+    DataRecord
+
+Represents a DataRecord within the Garmin file.
+"""
+mutable struct DataRecord
+    hdr::Union{RecordHeader, Nothing}
+    body::Union{DefinitionBody, DataBody}
 end
 
 mutable struct FITFileReader
@@ -31,7 +59,8 @@ end
 
 
 blank_file(fp::AbstractString) = FITFileReader(fp, nothing, 0, nothing, nothing)
-blank_row() = DataRecord(false, false)
+blank_row() = DataRecord(nothing)
+blank_header_byte() = RecordHeader(false, false, 0)
 
 """
     open_fit_file!(f::FITFileReader)
@@ -81,15 +110,42 @@ function read_header!(f::FITFileReader)
 end
 
 """
-    decode_header(v::Vector{UInt8})
+    decode_header(v::Vector{UInt8})::RecordHeader
 
 Decode the header byte, determine if the record is a definition, data, or timestamp.
 """
-function decode_header(v::Vector{UInt8})::DataRecord
+function decode_header(v::Vector{UInt8})::RecordHeader
-    record = blank_row()
+    record = blank_header_byte()
-
     record.definition = v[7] === 0x01
     record.data = !record.definition
+    record.local_mesg_type = sum_bits(v[end-3:end])
+    record
+end
+
+"""
+    read_record_content!(f::FITFileReader, hdr::RecordHeader)::Union{DefinitionBody, DataBody}
+
+Using f, read the appropriate message body given the hdr (which tells us if this is def or data)
+"""
+function read_record_content!(f::FITFileReader, hdr::RecordHeader)::Union{DefinitionBody, DataBody}
+    # Read the definition record, return the body
+    if hdr.definition
+        # Read the fixed 5 bytes first.
+        def_header_bytes = read_bytes!(f, 5)
+        def_header_fields = read_bytes!(f, def_header_bytes[end] * 3)
+        
+        # See if there is developer data
+        def_header_developer_flag = read_bytes!(f, 1)
+        if def_header_developer_flag[1] > 0x00
+            def_header_developer_fields = read_bytes!(f, def_header_developer_flag * 3)
+        end
+
+        DefinitionBody(
+            def_header_bytes[2] == 0 ? "littleendian" : "bigendian",
+            get_mesg_num_string(byte_vec_to_int(def_header_bytes[3:4])),
+            def_header_bytes[end]
+        )
+    end
 end
 
 """
@@ -104,7 +160,11 @@ function read_records!(f::FITFileReader)
 
     # Read header byte - decode
     header_bits = bit_vector(read_bytes!(f, 1); little_endian=true)
-    record = decode_header(header_bits)
+    header = decode_header(header_bits)
+    
+    # Read the record content
+
+    record = DataRecord(header, read_record_content!(f, header))
 
     # Push record to the body.
     if isnothing(f.body)
@@ -132,4 +192,17 @@ function read_file(filepath::AbstractString)::FITFileReader
     f
 end
 
+function show(io::IO, hdr::RecordHeader)
+    type = hdr.definition ? "Definition" : "Data"
+    println(io, "Header($(type), local_message_type=$(hdr.local_mesg_type))")
+end
+
+function show(io::IO, ffr::FITFileReader)
+    println(io, "FITFileReader($(ffr.filepath), bytes_read=$(ffr.bytes_read), header=$(ffr.header), body=$(ffr.body))")
+end
+
+function show(io::IO, defbody::DefinitionBody)
+    println(io, "DefinitionBody(arch=$(defbody.architecture), global_type=$(defbody.global_mesg_type), num_fields=$(defbody.num_fields))")
+end
+
 end