pread/pwrite/ipf encoder/ipf decoder

assets/disk0/tvdos/bin/decodeipf.js

@@ -0,0 +1,47 @@
+if (exec_args[1] == undefined) {
+    println("decodeipf <input.ipf>")
+    return 1
+}
+
+let infile = files.open(_G.shell.resolvePathInput(exec_args[1]).full)
+
+// read input file
+let infilePtr = sys.malloc(infile.size)
+infile.pread(infilePtr, infile.size, 0)
+
+// check if magic number matches
+
+const MAGIC = [0x1F, 0x54, 0x53, 0x56, 0x4D, 0x69, 0x50, 0x46]
+let magicMatching = true
+
+MAGIC.forEach((b,i) => {
+    let testb = sys.peek(infilePtr + i) & 255 // for some reason this must be located here
+    if (testb != b) {
+        magicMatching = false
+    }
+})
+if (!magicMatching) {
+    println("Not an iPF file (MAGIC mismatch)")
+    return 1
+}
+
+// decode input image
+let width = sys.peek(infilePtr+8) | (sys.peek(infilePtr+9) << 8)
+let height = sys.peek(infilePtr+10) | (sys.peek(infilePtr+11) << 8)
+let hasAlpha = (sys.peek(infilePtr+12) != 0)
+let ipfType = sys.peek(infilePtr+13)
+let imgLen = sys.peek(infilePtr+24) | (sys.peek(infilePtr+25) << 8) | (sys.peek(infilePtr+26) << 16) | (sys.peek(infilePtr+27) << 24)
+let decodefun = undefined
+if (ipfType == 1) decodefun = graphics.decodeIpf1
+if (ipfType == 2) decodefun = graphics.decodeIpf2
+if (decodefun === undefined) throw Error(`Unknown IPF format: ${ipfType}`)
+
+let ipfbuf = sys.malloc(imgLen)
+gzip.decompFromTo(infilePtr + 28, infile.size - 28, ipfbuf) // should return FBUF_SIZE
+sys.free(infilePtr)
+
+graphics.setGraphicsMode(4)
+graphics.clearText(); graphics.clearPixels(0); graphics.clearPixels2(0)
+decodefun(ipfbuf, -1048577, -1310721, width, height, hasAlpha)
+
+sys.free(ipfbuf)