LFS upgrade

assets/disk0/tvdos/include/lfs.mjs

@@ -0,0 +1,171 @@
+/*
+ * lfs.mjs — programmatic extractor for TVDOS Linear File Strip archives.
+ *
+ *   let lfs = require("A:/tvdos/include/lfs.mjs")
+ *
+ *   // Pull one entry out:
+ *   let fd  = lfs.extractOne("A:/path/archive.lfs", "wanted.bin")
+ *   // → file descriptor for $:/TMP/<random>/wanted.bin
+ *
+ *   // Unpack the whole archive:
+ *   let dir = lfs.extractAll("A:/path/archive.lfs")
+ *   // → directory descriptor for $:/TMP/<random>/
+ *
+ * Both functions accept an `autoDecompress` boolean (default true). When
+ * a payload's first four bytes match the gzip (1F 8B 08 xx) or zstd
+ * (28 B5 2F FD) magic, the payload is inflated through gzip.decomp()
+ * before being written. The check is done on the payload bytes — the
+ * archived filename is irrelevant.
+ *
+ * Both functions require a relative-path archive (one produced by
+ * `lfs -c -r`); fully qualified archives carry drive letters that would
+ * not make sense rerooted under $:/TMP.
+ */
+
+const TMP_ROOT     = "$:/TMP"
+const HASH_ALPHABET = "YBNDRFG8EJKMCPQXOTLVWIS2A345H769"
+const HASH_LEN     = 32
+const LFS_HEADER   = "TVDOSLFS\x01"
+const LFS_HEADER_LEN = 16
+const LFS_FLAG_RELATIVE = 0x01
+
+
+function _makeHash(n) {
+    let s = ""
+    const m = HASH_ALPHABET.length
+    for (let i = 0; i < n; i++) s += HASH_ALPHABET[Math.floor(Math.random() * m)]
+    return s
+}
+
+function _isCompressed(s) {
+    if (s.length < 4) return false
+    const b0 = s.charCodeAt(0), b1 = s.charCodeAt(1)
+    const b2 = s.charCodeAt(2), b3 = s.charCodeAt(3)
+    if (b0 === 0x1f && b1 === 0x8b && b2 === 0x08) return true            // gzip
+    if (b0 === 0x28 && b1 === 0xb5 && b2 === 0x2f && b3 === 0xfd) return true  // zstd
+    return false
+}
+
+function _decompress(payload) {
+    // gzip.decomp transparently handles both gzip and zstd; returns Java byte[].
+    return btostr(gzip.decomp(payload))
+}
+
+function _readArchive(lfsPath) {
+    const fd = files.open(lfsPath)
+    if (!fd.exists)     throw new Error("LFS archive not found: " + lfsPath)
+    if (fd.isDirectory) throw new Error("LFS archive is a directory: " + lfsPath)
+
+    const bytes = fd.sread()
+    try { fd.close() } catch (_) {}
+
+    if (bytes.substring(0, LFS_HEADER.length) !== LFS_HEADER)
+        throw new Error("Not an LFS archive: " + lfsPath)
+
+    const flags = bytes.charCodeAt(11)
+    if ((flags & LFS_FLAG_RELATIVE) === 0)
+        throw new Error("LFS archive does not use relative paths: " + lfsPath)
+
+    return bytes
+}
+
+function _allocTmpDir() {
+    const path = TMP_ROOT + "/" + _makeHash(HASH_LEN)
+    const dir  = files.open(path)
+    dir.mkDir()
+    return { fd: dir, path: path }
+}
+
+function _normPath(p) {
+    return p.replace(/\//g, "\\")
+}
+
+function _writeFile(destDirPath, archivePath, payload) {
+    const parts = _normPath(archivePath).split("\\").filter(p => p.length > 0)
+    if (parts.length === 0) return null
+
+    const leaf = parts.pop()
+    let curPath = destDirPath
+    for (let i = 0; i < parts.length; i++) {
+        curPath = curPath + "/" + parts[i]
+        const cur = files.open(curPath)
+        if (!cur.exists) cur.mkDir()
+    }
+    const outfile = files.open(curPath + "/" + leaf)
+    if (!outfile.exists) outfile.mkFile()
+    outfile.swrite(payload)
+    return outfile
+}
+
+
+function extractOne(lfsPath, filename, autoDecompress) {
+    if (autoDecompress === undefined) autoDecompress = true
+    if (filename === undefined || filename === null || filename === "")
+        throw new Error("filename is required")
+
+    const bytes  = _readArchive(lfsPath)
+    const needle = _normPath(filename)
+
+    let curs = LFS_HEADER_LEN
+    while (curs < bytes.length) {
+        const fileType = bytes.charCodeAt(curs)
+        const pathlen  = (bytes.charCodeAt(curs+1) << 8) | bytes.charCodeAt(curs+2)
+        curs += 3
+        const path = bytes.substring(curs, curs + pathlen)
+        curs += pathlen
+        const filelen = (bytes.charCodeAt(curs) << 24)
+                      | (bytes.charCodeAt(curs+1) << 16)
+                      | (bytes.charCodeAt(curs+2) << 8)
+                      |  bytes.charCodeAt(curs+3)
+        curs += 4
+
+        if (_normPath(path) === needle) {
+            let payload = bytes.substring(curs, curs + filelen)
+            if (autoDecompress && _isCompressed(payload)) payload = _decompress(payload)
+
+            const dest  = _allocTmpDir()
+            const leaf  = needle.split("\\").pop()
+            const outfile = files.open(dest.path + "/" + leaf)
+            if (!outfile.exists) outfile.mkFile()
+            outfile.swrite(payload)
+            return outfile
+        }
+
+        curs += filelen
+    }
+
+    throw new Error("File not found in archive: " + filename)
+}
+
+
+function extractAll(lfsPath, autoDecompress) {
+    if (autoDecompress === undefined) autoDecompress = true
+
+    const bytes = _readArchive(lfsPath)
+    const dest  = _allocTmpDir()
+
+    let curs = LFS_HEADER_LEN
+    while (curs < bytes.length) {
+        const fileType = bytes.charCodeAt(curs)
+        const pathlen  = (bytes.charCodeAt(curs+1) << 8) | bytes.charCodeAt(curs+2)
+        curs += 3
+        const path = bytes.substring(curs, curs + pathlen)
+        curs += pathlen
+        const filelen = (bytes.charCodeAt(curs) << 24)
+                      | (bytes.charCodeAt(curs+1) << 16)
+                      | (bytes.charCodeAt(curs+2) << 8)
+                      |  bytes.charCodeAt(curs+3)
+        curs += 4
+
+        let payload = bytes.substring(curs, curs + filelen)
+        if (autoDecompress && _isCompressed(payload)) payload = _decompress(payload)
+        _writeFile(dest.path, path, payload)
+
+        curs += filelen
+    }
+
+    return dest.fd
+}
+
+
+exports = { extractOne, extractAll }