From 273dbef3da4a60a85db24bf7efd22ec411037dcf Mon Sep 17 00:00:00 2001
From: Soikk
Date: Wed, 22 Jun 2022 22:59:27 +0200
Subject: Initial commit

---
 decompress.c | 131 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 decompress.c

(limited to 'decompress.c')

diff --git a/decompress.c b/decompress.c
new file mode 100644
index 0000000..dae888d
--- /dev/null
+++ b/decompress.c
@@ -0,0 +1,131 @@
+/*
+
+Not implemented yet
+
+Currently using zlib's decompress (sane)
+
+
+
+
+
+uint8_t getCM(uint8_t b){
+	uint8_t r = b<<4;
+	return r>>4;
+}
+
+uint8_t getCINFO(uint8_t b){
+	return b>>4;
+}
+
+bool validateCMFFLG(uint8_t CMF, uint8_t FLG){
+	uint16_t CMFFLGcheck = (CMF<<8) + FLG;
+	return getCM(CMF) == 8 && CMFFLGcheck%31 == 0;
+}
+
+typedef bool bit;
+
+
+bool getBit(int n, int bit){
+	return n & (1 << bit);
+}
+
+void printBinary(uint8_t n){
+    for(int i = 7; i >= 0; --i)
+        printf("%d", getBit(n, i));
+}
+
+uint8_t reverseBits(uint8_t n){
+	uint8_t r = 0;
+	for(int i = 0; i < 8; ++i)
+		r |= ((bool)(n&(1<<(7-i))))<<i;
+	return r;
+}
+
+uint8_t read8(bit *data, uint32_t *i){
+	// This function is used for decompression
+	// The first bit is the LSB
+	uint8_t r = 0;
+	for(int j = 0; j < 8; ++j){
+		r += data[(*i)+j]<<j;
+	}
+	(*i) += 8;
+	return r;
+}
+
+uint16_t read16(bit *data, uint32_t *i){
+	// This function is used for decompression
+	// The first bit is the LSB
+	uint16_t r = 0;
+	for(int j = 0; j < 16; ++j){
+		r += data[(*i)+j]<<j;
+	}
+	(*i) += 16;
+	return r;
+}
+
+typedef enum compressionType{
+	NONE, FIXED, DYNAMIC, ERROR,
+} compressionType;
+
+bit *decompressData(bit *data, uint32_t len){
+	// we have to decompress with zlib
+				// in zlib the first bit is the least significant
+				// (b0 b1 b2 b3)
+				// ftp://ftp.isi.edu/in-notes/rfc1950.txt
+				// https://www.ietf.org/rfc/rfc1950.txt
+				// https://stackoverflow.com/questions/42934720/understanding-the-zlib-header-cmf-cm-cinfo-flg-fdict-dictid-flevel-rfc
+				
+				/*uint8_t CMF = data[0], FLG = data[1], FDICT, FLEVEL;
+				if(!validateCMFFLG(CMF, FLG)){
+					fprintf(stderr, "Invalid CMF+FLG check\n");
+					fclose(fp);
+					return 0;
+				}
+				uint32_t LZ77size = (1<<getCINFO(CMF))<<8;
+				FDICT = getBit(FLG, 5);
+				FLEVEL = getBit(FLG, 6) + (getBit(FLG, 7)<<1);
+				if(FDICT){
+					fprintf(stderr, "I dont know how to deal with DICT\n");
+					fclose(fp);
+					return 0;
+				}
+				
+				// Deflate data
+				// https://www.ietf.org/rfc/rfc1951.txt
+				/*
+				Data elements are packed into bytes in order of
+					increasing bit number within the byte, i.e., starting
+					with the least-significant bit of the byte.
+				Data elements other than Huffman codes are packed
+					starting with the least-significant bit of the data
+					element.
+				Huffman codes are packed starting with the most-
+					significant bit of the code.
+				*
+				/
+
+				// Adler32
+	bit *out = malloc(len);
+	bit BFINAL;
+	uint8_t BTYPE;
+	uint32_t ii = 0, oi = 0;
+	while(!BFINAL){
+		BFINAL = data[ii++];
+		if(BFINAL){
+			// TODO: exit
+		}
+		BTYPE = (data[ii]<<1) + data[ii+1];
+		ii += 2;
+		if(BTYPE == NONE){
+			ii += 8-(ii%8);
+		}
+		uint16_t LEN, NLEN;
+		LEN = read16(data, &ii);
+		NLEN = read16(data, &ii);
+
+		for(uint16_t j = 0; j < LEN; ++j){
+
+		}
+	}
+}
+*/
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