library enigmaxml extractor function working

src/library/enigmaxml.lua

@@ -0,0 +1,87 @@
+--[[
+$module Functions for accessing Enigma XML files.
+
+Enigma XML is the underlying file format of a Finale `.musx` file. It is undocumented
+by MakeMusic and must be extracted from the `.musx` file. There is an effort to document
+it underway at the [EnigmaXML Documentation](https://github.com/finale-lua/enigmaxml-documentation)
+repository.
+]] --
+local enigmaxml = {}
+
+local utils = require("library.utils")
+
+-- symmetrical encryption/decryption function
+local function crypt_enigmaxml_buffer(buffer)
+    local state = 0x28006D45 -- this value was determined empirically
+    local result = {}
+
+    for i = 1, #buffer do
+        -- BSD rand()
+        state = (state * 0x41c64e6d + 0x3039) & 0xFFFFFFFF  -- Simulate 32-bit overflow
+        local upper = state >> 16
+        local c = upper + math.floor(upper / 255)
+
+        local byte = string.byte(buffer, i)
+        byte = byte ~ (c & 0xFF)  -- XOR operation on the byte
+
+        table.insert(result, string.char(byte))
+    end
+
+    return table.concat(result)
+end
+
+--[[
+%extract_xml
+
+Extracts an enigmaxml buffer from a `.musx` file. Note that this function does not work with Finale's
+older `.mus` format.
+
+Windows users must have `7z` installed and macOS users must have `unzip`.
+
+@ filepath (string) a file path to a `.musx` file.
+: (string) buffer of xml data containing the EnigmaXml extracted from the `.musx`
+]]
+function enigmaxml.extract_xml(filepath)
+    if finenv.MajorVersion <= 0 and finenv.MinorVersion < 68 then
+        error("enigmaxml.extract_xml requires at least RGP Lua v0.68.", 2)
+    end
+    if finenv.TrustedMode == finenv.TrustedModeType.UNTRUSTED then
+        error("enigmaxml.extract_xml must run in Trusted mode.", 2)
+    end
+    local _, _, extension = utils.split_file_path(filepath)
+    if extension ~= ".musx" then
+        error(filepath .. " is not a .musx file.", 2)
+    end
+
+    local text = require("luaosutils").text
+    local process = require("luaosutils").process
+
+    local os_filepath = text.convert_encoding(filepath, text.get_utf8_codepage(), text.get_default_codepage())
+    local output_dir = os.tmpname()
+    local rmcommand = (finenv.UI():IsOnMac() and "rm " or "cmd /c del ") .. output_dir
+    process.execute(rmcommand)
+
+    local zipcommand
+    if finenv.UI():IsOnMac() then
+        zipcommand = "unzip \"" .. os_filepath .. "\" -d " .. output_dir
+    else
+        zipcommand = "cmd /c 7z x -o" .. output_dir .. " \"" .. os_filepath .. "\""
+    end
+    if not process.execute(zipcommand) then
+        error(zipcommand .. " failed")
+    end
+
+    local file <close> = io.open(output_dir .. "/score.dat", "rb")
+    if not file then
+        error("unable to read " .. output_dir .. "/score.dat")
+    end
+    local buffer = file:read("*all")
+    file:close()
+
+    local delcommand = (finenv.UI():IsOnMac() and "rm -r " or "cmd /c rmdir /s /q ") .. output_dir
+    process.execute(delcommand)
+
+    return crypt_enigmaxml_buffer(buffer)
+end
+
+return enigmaxml

src/library/general_library.lua

@@ -632,41 +632,4 @@ function library.get_default_music_font_name()
     end
 end
 
---[[
-%crypt_musx_file_buffer
-
-Symmetrical encryption/decryption for `.musx` files. Finale `.musx` files are byte-for-byte encrypted
-gzip archives. The archives contain xml and other data for the Finale document. This function accepts
-either a buffer of encrypted text and returns plaintext or accepts plaintext and returns encrypted text.
-
-To decrypt a `.musx`,
-
-- read the `.musx` file into a buffer using binary read mode
-- pass it to this function
-- save the return buffer as `.gz` using binary write mode
-
-Reverse the process to create a `.musx` from a `.gz` file.
-
-@ buffer (string) buffer of binary data containing plaintext or encrypted text of a `.musx` file.
-: (string) buffer of binary data containing encrypted text or plaintext corresponding to the input buffer.
-]]
-function library.crypt_musx_file_buffer(buffer)
-    local state = 0x28006D45 -- this value was determined empirically
-    local result = {}
-
-    for i = 1, #buffer do
-        -- BSD rand()
-        state = (state * 0x41c64e6d + 0x3039) & 0xFFFFFFFF  -- Simulate 32-bit overflow
-        local upper = state >> 16
-        local c = upper + math.floor(upper / 255)
-
-        local byte = string.byte(buffer, i)
-        byte = byte ~ (c & 0xFF)  -- XOR operation on the byte
-
-        table.insert(result, string.char(byte))
-    end
-
-    return table.concat(result)
-end
-
 return library