Added read and write support for v4 mat files (#186)

* initial read support * v4 write support * add tests for v4 * move check routine * edit docs * added functionality to write into v4 mat files using keyword argument * Reset version number * Updated readme * Updated readme --------- Co-authored-by: vsaase <[email protected]> Co-authored-by: Quadras <[email protected]>
JuliaIO · Jun 7, 2023 · 095d2a6 · 095d2a6
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diff --git a/README.md b/README.md
@@ -3,7 +3,7 @@
 
 ### Read and write MATLAB files in Julia
 
-This library can read MATLAB `.mat` files, both in the older v5/v6/v7 format, as well as the newer v7.3 format.
+This library can read MATLAB `.mat` files, both in the older v4/v5/v6/v7 format, as well as the newer v7.3 format.
 
 ## Installation
 
@@ -56,6 +56,15 @@ matwrite("matfile.mat", Dict(
 ); compress = true)
 ```
 
+To write in MATLAB v4 format:
+
+```julia
+matwrite("matfile.mat", Dict(
+	"myvar1" => 0,
+	"myvar2" => 1
+);version="v4")
+```
+
 To get a list of variable names in a MAT file:
 
 ```julia
@@ -76,9 +85,9 @@ close(file)
 
 ## Caveats
 
-* All files are written in MATLAB v7.3 format.
-* MATLAB v4 files are not currently supported.
+* All files are written in MATLAB v7.3 format by default.
+* Writing in MATLAB v4 format is provided by the matwrite function with keyword argument.
 
 ## Credits
 
-The MAT_HDF5 module, which provides read/write support for MATLAB v7.3 files, was written primarily by [Tim Holy](https://github.com/timholy/). The MAT_v5 module, which provides read support for MATLAB v5/v6/v7 files, was written primarily by [Simon Kornblith](https://github.com/simonster/).
+The MAT_HDF5 module, which provides read/write support for MATLAB v7.3 files, was written primarily by [Tim Holy](https://github.com/timholy/). The MAT_v5 module, which provides read support for MATLAB v5/v6/v7 files, was written primarily by [Simon Kornblith](https://github.com/simonster/). The MAT_v4 module, which provides read and write support for MATLAB v4 files, was written primarily by [Victor Saase](https://github.com/vsaase/).
diff --git a/src/MAT.jl b/src/MAT.jl
@@ -28,8 +28,9 @@ using HDF5, SparseArrays
 
 include("MAT_HDF5.jl")
 include("MAT_v5.jl")
+include("MAT_v4.jl")
 
-using .MAT_HDF5, .MAT_v5
+using .MAT_HDF5, .MAT_v5, .MAT_v4
 
 export matopen, matread, matwrite, @read, @write
 
@@ -44,19 +45,18 @@ function matopen(filename::AbstractString, rd::Bool, wr::Bool, cr::Bool, tr::Boo
         error("File \"$filename\" does not exist and create was not specified")
     end
 
-    # Test whether this is a MAT file
-    if fs < 128
-        error("File \"$filename\" is too small to be a supported MAT file")
-    end
     rawfid = open(filename, "r")
 
     # Check for MAT v4 file
-    magic = read!(rawfid, Vector{UInt8}(undef, 4))
-    for i = 1:length(magic)
-        if magic[i] == 0
-            close(rawfid)
-            error("\"$filename\" is not a MAT file, or is an unsupported (v4) MAT file")
-        end
+    (isv4, swap_bytes) = MAT_v4.checkv4(rawfid)
+    if isv4
+        return MAT_v4.matopen(rawfid, swap_bytes)
+    end
+
+    # Test whether this is a MAT file
+    if fs < 128
+        close(rawfid)
+        error("File \"$filename\" is too small to be a supported MAT file")
     end
 
     # Check for MAT v5 file
@@ -139,25 +139,47 @@ end
 
 # Write a dict to a MATLAB file
 """
-    matwrite(filename, d::Dict; compress::Bool = false)
+    matwrite(filename, d::Dict; compress::Bool = false, version::String)
 
 Write a dictionary containing variable names as keys and values as values
 to a Matlab file, opening and closing it automatically.
 """
-function matwrite(filename::AbstractString, dict::AbstractDict{S, T}; compress::Bool = false) where {S, T}
-    file = matopen(filename, "w"; compress = compress)
-    try
-        for (k, v) in dict
-            local kstring
-            try
-                kstring = ascii(convert(String, k))
-            catch x
-                error("matwrite requires a Dict with ASCII keys")
+function matwrite(filename::AbstractString, dict::AbstractDict{S, T}; compress::Bool = false, version::String ="") where {S, T}
+
+    if version == "v4"
+        file = open(filename, "w")
+        m = MAT_v4.Matlabv4File(file, false)
+        try
+            for (k, v) in dict
+                local kstring
+                try
+                    kstring = ascii(convert(String, k))
+                catch x
+                    error("matwrite requires a Dict with ASCII keys")
+                end
+                write(m, kstring, v)
             end
-            write(file, kstring, v)
+        finally
+            close(file)
         end
-    finally
-        close(file)
+
+    else
+
+        file = matopen(filename, "w"; compress = compress)
+        try
+            for (k, v) in dict
+                local kstring
+                try
+                    kstring = ascii(convert(String, k))
+                catch x
+                    error("matwrite requires a Dict with ASCII keys")
+                end
+                write(file, kstring, v)
+            end
+        finally
+            close(file)
+        end
+
     end
 end
 
@@ -166,11 +188,11 @@ end
 ###
 
 export exists
-@noinline function exists(matfile::Union{MAT_v5.Matlabv5File,MAT_HDF5.MatlabHDF5File}, varname::String)
+@noinline function exists(matfile::Union{MAT_v4.Matlabv4File,MAT_v5.Matlabv5File,MAT_HDF5.MatlabHDF5File}, varname::String)
     Base.depwarn("`exists(matfile, varname)` is deprecated, use `haskey(matfile, varname)` instead.", :exists)
     return haskey(matfile, varname)
 end
-@noinline function Base.names(matfile::Union{MAT_v5.Matlabv5File,MAT_HDF5.MatlabHDF5File})
+@noinline function Base.names(matfile::Union{MAT_v4.Matlabv4File,MAT_v5.Matlabv5File,MAT_HDF5.MatlabHDF5File})
     Base.depwarn("`names(matfile)` is deprecated, use `keys(matfile)` instead.", :names)
     return keys(matfile)
 end