Turn udeflate into a proper library

1 files changed, 454 insertions, 0 deletions

diff --git a/src/lib/udeflate.cc b/src/lib/udeflate.cc
new file mode 100644
index 0000000..31c0927
--- /dev/null
+++ b/src/lib/udeflate.cc
@@ -0,0 +1,454 @@
+/*
+ * Copyright 2021 Daniel Friesel
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "lib/udeflate.h"
+
+/*
+ * The compressed (inflated) input data.
+ */
+unsigned char *udeflate_input_now;
+unsigned char *udeflate_input_end;
+
+/*
+ * The decompressed (deflated) output stream.
+ */
+unsigned char *udeflate_output_now;
+unsigned char *udeflate_output_end;
+
+/*
+ * The current bit offset in the input stream, if any.
+ *
+ * Deflate streams are read from least to most significant bit.
+ * An offset of 1 indicates that the least significant bit is skipped
+ * (i.e., only bits 7, 6, 5, 4, 3, 2, and 1 are read).
+ */
+uint8_t udeflate_bit_offset = 0;
+
+/*
+ * Base lengths for length codes (code 257 to 285).
+ * Code 257 corresponds to a copy of 3 bytes, etc.
+ */
+uint16_t const udeflate_length_offsets[] = {
+	3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, 35, 43, 51, 59,
+	67, 83, 99, 115, 131, 163, 195, 227, 258
+};
+
+/*
+ * Extra bits for length codes (code 257 to 285).
+ * Code 257 has no extra bits, code 265 has 1 extra bit
+ * (and indicates a length of 11 or 12 depending on its value), etc.
+ */
+uint8_t const udeflate_length_bits[] = {
+	0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4,
+	5, 5, 5, 5, 0
+};
+
+// can also be expressed as (index < 4 || index == 28) ? 0 : (index-4) >> 2
+
+/*
+ * Base distances for distance codes (code 0 to 29).
+ * Code 0 indicates a distance of 1, etc.
+ */
+uint16_t const udeflate_distance_offsets[] = {
+	1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, 257, 385,
+	513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577
+};
+
+/*
+ * Extra bits for distance codes (code 0 to 29).
+ * Code 0 has no extra bits, code 4 has 1 bit, etc.
+ */
+uint8_t const udeflate_distance_bits[] = {
+	0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10,
+	10, 11, 11, 12, 12, 13, 13
+};
+
+// can also be expressed as index < 2 ? 0 : (index-2) >> 1
+
+/*
+ * In block type 2 (dynamic huffman codes), the code lengths of literal/length
+ * and distance alphabet are themselves stored as huffman codes. To save space
+ * in case only a few code lengths are used, the code length codes are stored
+ * in the following order. This allows a few bits to be saved if some code
+ * lengths are unused and the unused code lengths are at the end of the list.
+ */
+uint8_t const udeflate_hclen_index[] = {
+	16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
+};
+
+/*
+ * Code lengths of the "code length" code (see above).
+ */
+uint8_t udeflate_hc_lengths[19];
+
+/*
+ * Code lengths of the literal/length and distance alphabets.
+ */
+uint8_t udeflate_lld_lengths[318];
+
+/*
+ * Assumptions:
+ * * huffman code length is limited to 11 bits
+ * * there are no more than 255 huffman codes with the same length
+ *
+ * Rationale: longer huffman codes might appear when handling large data
+ * sets. We don't do that; instead, we expect the uncompressed source to
+ * be no more than a few kB of data.
+ */
+
+/*
+ * Bit length counts and next code entries for Literal/Length alphabet.
+ * Combined with the code lengths in udeflate_lld_lengths, these make up the
+ * Literal/Length alphabet. See the algorithm in RFC 1951 section 3.2.2 for
+ * details.
+ *
+ * In udeflate, these variables are also used for the huffman alphabet in
+ * dynamic huffman blocks.
+ */
+uint8_t udeflate_bl_count_ll[12];
+uint16_t udeflate_next_code_ll[12];
+
+/*
+ * Bit length counts and next code entries for Distance alphabet.
+ */
+uint8_t udeflate_bl_count_d[12];
+uint16_t udeflate_next_code_d[12];
+
+static uint16_t udeflate_rev_word(uint16_t word, uint8_t bits)
+{
+	uint16_t ret = 0;
+	uint16_t mask = 1;
+	for (uint16_t rmask = 1 << (bits - 1); rmask > 0; rmask >>= 1) {
+		if (word & rmask) {
+			ret |= mask;
+		}
+		mask <<= 1;
+	}
+	return ret;
+}
+
+static uint8_t udeflate_bitmask(uint8_t bit_count)
+{
+	return (1 << bit_count) - 1;
+}
+
+static uint16_t udeflate_get_word()
+{
+	uint16_t ret = 0;
+	ret |= (udeflate_input_now[0] >> udeflate_bit_offset);
+	ret |= (uint16_t) udeflate_input_now[1] << (8 - udeflate_bit_offset);
+	if (udeflate_bit_offset) {
+		ret |=
+		    (uint16_t) (udeflate_input_now[2] &
+				udeflate_bitmask(udeflate_bit_offset)) << (16 -
+									   udeflate_bit_offset);
+	}
+#ifdef UDEFLATE_DEBUG
+	kout << "get_word = " << bin << ret << dec << endl;
+#endif
+	return ret;
+}
+
+static uint16_t udeflate_get_bits(uint8_t num_bits)
+{
+	uint16_t ret = udeflate_get_word();
+	udeflate_bit_offset += num_bits;
+	while (udeflate_bit_offset >= 8) {
+		udeflate_input_now++;
+		udeflate_bit_offset -= 8;
+	}
+	return ret & udeflate_bitmask(num_bits);
+}
+
+static void udeflate_build_alphabet(uint8_t * lengths, uint16_t size,
+				    uint8_t * bl_count, uint16_t * next_code)
+{
+	uint16_t i;
+	uint16_t code = 0;
+	uint16_t max_len = 0;
+	for (i = 0; i < 12; i++) {
+		bl_count[i] = 0;
+	}
+
+	for (i = 0; i < size; i++) {
+		if (lengths[i]) {
+			bl_count[lengths[i]]++;
+		}
+		if (lengths[i] > max_len) {
+			max_len = lengths[i];
+		}
+	}
+
+	for (i = 1; i < max_len + 1; i++) {
+		code = (code + bl_count[i - 1]) << 1;
+		next_code[i] = code;
+	}
+
+#ifdef UDEFLATE_DEBUG
+	for (i = 0; i < 12; i++) {
+		kout << "bl_count[" << i << "] = " << bl_count[i] << endl;
+	}
+	for (i = 0; i < 12; i++) {
+		kout << "next_code[" << i << "] = " << next_code[i] << endl;
+	}
+#endif
+}
+
+static uint16_t udeflate_huff(uint8_t * lengths, uint16_t size,
+			      uint8_t * bl_count, uint16_t * next_code)
+{
+	uint16_t next_word = udeflate_get_word();
+	for (uint8_t num_bits = 1; num_bits < 12; num_bits++) {
+		uint16_t next_bits = udeflate_rev_word(next_word, num_bits);
+		if (bl_count[num_bits] && next_bits >= next_code[num_bits]
+		    && next_bits < next_code[num_bits] + bl_count[num_bits]) {
+#ifdef UDEFLATE_DEBUG
+			kout << "found huffman code, length = " << num_bits <<
+			    endl;
+#endif
+			udeflate_bit_offset += num_bits;
+			while (udeflate_bit_offset >= 8) {
+				udeflate_input_now++;
+				udeflate_bit_offset -= 8;
+			}
+			uint8_t len_pos = next_bits;
+			uint8_t cur_pos = next_code[num_bits];
+			for (uint16_t i = 0; i < size; i++) {
+				if (lengths[i] == num_bits) {
+					if (cur_pos == len_pos) {
+						return i;
+					}
+					cur_pos++;
+				}
+			}
+		}
+	}
+	return 65535;
+}
+
+static int8_t udeflate_huffman(uint8_t * ll_lengths, uint16_t ll_size,
+			       uint8_t * d_lengths, uint8_t d_size)
+{
+	uint16_t code;
+	uint16_t dcode;
+	while (1) {
+		code =
+		    udeflate_huff(ll_lengths, ll_size, udeflate_bl_count_ll,
+				  udeflate_next_code_ll);
+#ifdef UDEFLATE_DEBUG
+		kout << "code " << code << endl;
+#endif
+		if (code < 256) {
+			*udeflate_output_now = code;
+			udeflate_output_now++;
+		} else if (code == 256) {
+			return 0;
+		} else {
+			uint16_t len_val = udeflate_length_offsets[code - 257];
+			uint8_t extra_bits = udeflate_length_bits[code - 257];
+			if (extra_bits) {
+				len_val += udeflate_get_bits(extra_bits);
+			}
+			dcode =
+			    udeflate_huff(d_lengths, d_size,
+					  udeflate_bl_count_d,
+					  udeflate_next_code_d);
+			uint16_t dist_val = udeflate_distance_offsets[dcode];
+			extra_bits = udeflate_distance_bits[dcode];
+			if (extra_bits) {
+				dist_val += udeflate_get_bits(extra_bits);
+			}
+			while (len_val--) {
+				udeflate_output_now[0] =
+				    udeflate_output_now[-dist_val];
+				udeflate_output_now++;
+			}
+		}
+	}
+}
+
+static int8_t udeflate_static_huffman()
+{
+	uint16_t i;
+	for (i = 0; i <= 143; i++) {
+		udeflate_lld_lengths[i] = 8;
+	}
+	for (i = 144; i <= 255; i++) {
+		udeflate_lld_lengths[i] = 9;
+	}
+	for (i = 256; i <= 279; i++) {
+		udeflate_lld_lengths[i] = 7;
+	}
+	for (i = 280; i <= 284; i++) {
+		udeflate_lld_lengths[i] = 8;
+	}
+	for (i = 285; i <= 285 + 29; i++) {
+		udeflate_lld_lengths[i] = 5;
+	}
+
+	udeflate_build_alphabet(udeflate_lld_lengths, 285, udeflate_bl_count_ll,
+				udeflate_next_code_ll);
+	udeflate_build_alphabet(udeflate_lld_lengths + 285, 29,
+				udeflate_bl_count_d, udeflate_next_code_d);
+	return udeflate_huffman(udeflate_lld_lengths, 285,
+				udeflate_lld_lengths + 285, 29);
+}
+
+static int8_t udeflate_dynamic_huffman()
+{
+	uint8_t i;
+	uint16_t hlit = 257 + udeflate_get_bits(5);
+	uint8_t hdist = 1 + udeflate_get_bits(5);
+	uint8_t hclen = 4 + udeflate_get_bits(4);
+
+#ifdef UDEFLATE_DEBUG
+	kout << "hlit=" << hlit << endl;
+	kout << "hdist=" << hdist << endl;
+	kout << "hclen=" << hclen << endl;
+#endif
+
+	for (i = 0; i < hclen; i++) {
+		udeflate_hc_lengths[udeflate_hclen_index[i]] =
+		    udeflate_get_bits(3);
+	}
+	for (i = hclen; i < sizeof(udeflate_hc_lengths); i++) {
+		udeflate_hc_lengths[udeflate_hclen_index[i]] = 0;
+	}
+
+	udeflate_build_alphabet(udeflate_hc_lengths,
+				sizeof(udeflate_hc_lengths),
+				udeflate_bl_count_ll, udeflate_next_code_ll);
+
+	uint16_t items_processed = 0;
+	while (items_processed < hlit + hdist) {
+		uint8_t code =
+		    udeflate_huff(udeflate_hc_lengths, 19, udeflate_bl_count_ll,
+				  udeflate_next_code_ll);
+#ifdef UDEFLATE_DEBUG
+		kout << "code = " << code << endl;
+#endif
+		if (code == 16) {
+			uint8_t copy_count = 3 + udeflate_get_bits(2);
+			for (uint8_t i = 0; i < copy_count; i++) {
+				udeflate_lld_lengths[items_processed] =
+				    udeflate_lld_lengths[items_processed - 1];
+				items_processed++;
+			}
+		} else if (code == 17) {
+			uint8_t null_count = 3 + udeflate_get_bits(3);
+			for (uint8_t i = 0; i < null_count; i++) {
+				udeflate_lld_lengths[items_processed] = 0;
+				items_processed++;
+			}
+		} else if (code == 18) {
+			uint8_t null_count = 11 + udeflate_get_bits(7);
+			for (uint8_t i = 0; i < null_count; i++) {
+				udeflate_lld_lengths[items_processed] = 0;
+				items_processed++;
+			}
+		} else {
+			udeflate_lld_lengths[items_processed] = code;
+			items_processed++;
+		}
+	}
+
+	udeflate_build_alphabet(udeflate_lld_lengths, hlit,
+				udeflate_bl_count_ll, udeflate_next_code_ll);
+	udeflate_build_alphabet(udeflate_lld_lengths + hlit, hdist,
+				udeflate_bl_count_d, udeflate_next_code_d);
+
+	return udeflate_huffman(udeflate_lld_lengths, hlit,
+				udeflate_lld_lengths + hlit, hdist);
+
+	return 0;
+}
+
+int8_t udeflate(unsigned char *input_buf, uint16_t input_len,
+		unsigned char *output_buf, uint16_t output_len)
+{
+	uint8_t is_final = input_buf[0] & 0x01;
+	uint8_t block_type = (input_buf[0] & 0x06) >> 1;
+#ifdef UDEFLATE_DEBUG
+	kout << "is_final=" << is_final << " block_type=" << block_type << endl;
+#endif
+
+	udeflate_input_now = input_buf;
+	udeflate_input_end = input_buf + input_len;
+	udeflate_bit_offset = 3;
+
+	udeflate_output_now = output_buf;
+	udeflate_output_end = output_buf + output_len;
+
+	if (block_type == 1) {
+		return udeflate_static_huffman();
+	}
+	if (block_type == 2) {
+		return udeflate_dynamic_huffman();
+	}
+
+	return UDEFLATE_ERR_BLOCK;
+}
+
+int8_t udeflate_zlib(unsigned char *input_buf, uint16_t input_len,
+		     unsigned char *output_buf, uint16_t output_len)
+{
+	if (input_len < 4) {
+		return UDEFLATE_ERR_LENGTH;
+	}
+	uint8_t zlib_method = input_buf[0] & 0x0f;
+	uint16_t zlib_window_size = 1 << (8 + ((input_buf[0] & 0xf0) >> 4));
+	uint8_t zlib_flags = input_buf[1];
+
+#ifdef UDEFLATE_DEBUG
+	kout << "zlib_method=" << zlib_method << endl;
+	kout << "zlib_window_size=" << zlib_window_size << endl;
+#endif
+
+	if (zlib_method != 8) {
+		return UDEFLATE_ERR_METHOD;
+	}
+
+	if (zlib_flags & 0x10) {
+		return UDEFLATE_ERR_FDICT;
+	}
+
+	uint8_t ret =
+	    udeflate(input_buf + 2, input_len - 2, output_buf, output_len);
+
+#ifdef UDEFLATE_CHECKSUM
+	if (ret == 0) {
+		uint16_t udeflate_s1 = 1;
+		uint16_t udeflate_s2 = 0;
+
+		udeflate_output_end = udeflate_output_now;
+		for (udeflate_output_now = output_buf;
+		     udeflate_output_now < udeflate_output_end;
+		     udeflate_output_now++) {
+			udeflate_s1 =
+			    ((uint32_t) udeflate_s1 +
+			     (uint32_t) (*udeflate_output_now)) % 65521;
+			udeflate_s2 =
+			    ((uint32_t) udeflate_s2 +
+			     (uint32_t) udeflate_s1) % 65521;
+		}
+
+		if (udeflate_bit_offset) {
+			udeflate_input_now++;
+		}
+
+		if ((udeflate_s2 !=
+		     (((uint16_t) udeflate_input_now[0] << 8) | (uint16_t)
+		      udeflate_input_now[1]))
+		    || (udeflate_s1 !=
+			(((uint16_t) udeflate_input_now[2] << 8) | (uint16_t)
+			 udeflate_input_now[3]))) {
+			return UDEFLATE_ERR_CHECKSUM;
+		}
+	}
+#endif
+
+	return ret;
+}