support multiple deflate blocks. (76f36fc4) · Commits · derf / zlib-deflate-nostdlib

README.md

+14 −10

Original line number	Diff line number	Diff line
		@@ -87,16 +87,20 @@ checksum in `inflate_zlib`.

		## Compliance

		The code almost complies with RFC 1950 (decompression only), with the
		following exceptions.

		* Unless compiled with `-DDEFLATE_CHECKSUM`, zlib-deflate-nostdlib does not
		verify the ADLER32 checksum embedded into zlib-compressed data.

		The code almost complies with RFC 1951, with the following exceptions.

		* zlib-deflate-nostdlib does not yet support compressed items consisting of
		more than one deflate block. I intend to fix this.
		`inflate` is fully compliant with RFC 1951 for data with a decompressed size
		of up to 65 kB.

		When compiled with `-DDEFLATE_CHECKSUM`, `inflate_zlib` is fully compliant with
		RFC 1950 (decompression only) for data with a decompressed size of up to 65 kB.
		By default (without `-DDEFLATE_CHECKSUM`), it does not verify the ADLER32
		checksum embedded into zlib-compressed data and is therefore not compliant with
		RFC 1950.

		For files larger than 65 kB, you only need to change some size arguments to
		`uint32_t`. However, if you are decompressing files of that size, you probably
		have more RAM than this library is designed for. In that case, you may be
		better off with [udeflate](https://github.com/jlublin/udeflate),
		[uzlib](https://github.com/pfalcon/uzlib), or similar.

		## Requirements and Performance

src/inflate.c

+43 −24

Original line number	Diff line number	Diff line
		@@ -184,6 +184,12 @@ static void deflate_build_alphabet(uint8_t * lengths, uint16_t size,
		}
		}

		/*
		* This function trades speed for low memory requirements. Instead of building
		* an actual huffman tree (at a cost of about 650 Bytes of RAM), we iterate
		* through the code lengths whenever we have found a huffman code. This is
		* very slow, but memory-efficient.
		*/
		static uint16_t deflate_huff(uint8_t * lengths, uint16_t size,
		uint8_t * bl_count, uint16_t * next_code)
		{
		@@ -199,6 +205,7 @@ static uint16_t deflate_huff(uint8_t * lengths, uint16_t size,
		}
		uint8_t len_pos = next_bits;
		uint8_t cur_pos = next_code[num_bits];
		// This is slow, but memory-efficient
		for (uint16_t i = 0; i < size; i++) {
		if (lengths[i] == num_bits) {
		if (cur_pos == len_pos) {
		@@ -229,6 +236,8 @@ static int8_t deflate_huffman(uint8_t * ll_lengths, uint16_t ll_size,
		deflate_output_now++;
		} else if (code == 256) {
		return 0;
		} else if (code == 65535) {
		return DEFLATE_ERR_HUFFMAN;
		} else {
		uint16_t len_val = deflate_length_offsets[code - 257];
		uint8_t extra_bits = deflate_length_bits[code - 257];
		@@ -261,7 +270,10 @@ static int8_t deflate_huffman(uint8_t * ll_lengths, uint16_t ll_size,

		static int8_t deflate_uncompressed()
		{
		if (deflate_bit_offset) {
		deflate_input_now++;
		deflate_bit_offset = 0;
		}
		uint16_t len =
		((uint16_t) deflate_input_now[1] << 8) + deflate_input_now[0];
		uint16_t nlen =
		@@ -331,7 +343,8 @@ static int8_t deflate_dynamic_huffman()
		uint16_t items_processed = 0;
		while (items_processed < hlit + hdist) {
		uint8_t code =
		deflate_huff(deflate_hc_lengths, 19, deflate_bl_count_ll,
		deflate_huff(deflate_hc_lengths, sizeof(deflate_hc_lengths),
		deflate_bl_count_ll,
		deflate_next_code_ll);
		if (code == 16) {
		uint8_t copy_count = 3 + deflate_get_bits(2);
		@@ -370,17 +383,20 @@ static int8_t deflate_dynamic_huffman()
		int16_t inflate(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;
		int8_t ret;

		deflate_input_now = input_buf;
		deflate_input_end = input_buf + input_len;
		deflate_bit_offset = 3;
		deflate_bit_offset = 0;

		deflate_output_now = output_buf;
		deflate_output_end = output_buf + output_len;

		while (1) {
		uint8_t block_type = deflate_get_bits(3);
		uint8_t is_final = block_type & 0x01;
		int8_t ret;

		block_type >>= 1;

		switch (block_type) {
		case 0:
		ret = deflate_uncompressed();
		@@ -399,8 +415,11 @@ int16_t inflate(unsigned char *input_buf, uint16_t input_len,
		return ret;
		}

		if (is_final) {
		return deflate_output_now - output_buf;
		}
		}
		}

		int16_t inflate_zlib(unsigned char *input_buf, uint16_t input_len,
		unsigned char *output_buf, uint16_t output_len)

src/inflate.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -16,6 +16,7 @@
		#define DEFLATE_ERR_OUTPUT_LENGTH (-6)
		#define DEFLATE_ERR_FCHECK (-7)
		#define DEFLATE_ERR_NLEN (-8)
		#define DEFLATE_ERR_HUFFMAN (-9)

		int16_t inflate(unsigned char *input_buf, uint16_t input_len,
		unsigned char *output_buf, uint16_t output_len);

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