Commit 9a609dc7 authored by Daniel Friesel's avatar Daniel Friesel
Browse files

this library implements inflate, not deflate

parent a288a4a4

README.md

+24 −19
Original line number Diff line number Diff line
@@ -11,12 +11,17 @@ for speed. Right now, the implementation is naive, but usable. See below for 
the current status and TODOs. Be aware that this library has not been

extensively tested yet.



Note: This library *inflates* (i.e., decompresses) data. The source files and

API are named as such, as is the corresponding function in the original zlib

implementation. However, as the algorithm is called *deflate*, the project is

named zlib-*deflate*-nostdlib even though it does not support compression.



## Usage



Embed `deflate.c` and `deflate.h` into your project. You can rename `deflate.c`

to `deflate.cc` and/or compile it with g++ instead of gcc, if you like. Use

`deflate_zlib(input, input_len, output, output_len)` to decompress zlib data,

and `deflate(input, input_len, output, output_len)` to decompress deflate data

Embed `inflate.c` and `inflate.h` into your project. You can rename `inflate.c`

to `inflate.cc` and/or compile it with g++ instead of gcc, if you like. Use

`inflate_zlib(input, input_len, output, output_len)` to decompress zlib data,

and `inflate(input, input_len, output, output_len)` to decompress deflate data

without zlib header.



input and output must be `unsigned char *`, input\_len and output\_len are
@@ -26,24 +31,24 @@ bytes written to `output`, or a negative value on error. 
Example for zlib decompression (RFC 1950):



```

#include "deflate.h"

#include "inflate.h"



unsigned char deflate_input[] = { /* some compressed data, e.g.: */

unsigned char inflate_input[] = { /* some compressed data, e.g.: */

    120, 156, 243, 72, 205, 201, 201, 215, 81, 8, 207, 47, 202, 73, 177, 87,

    240, 64, 226, 41, 2, 0, 128, 125, 9, 17

};



unsigned char deflate_output[128];

unsigned char inflate_output[128];



// within some function

{

    int16_t out_bytes = deflate_zlib(deflate_input, sizeof(deflate_input),

                                     deflate_output, sizeof(deflate_output));

    int16_t out_bytes = inflate_zlib(inflate_input, sizeof(inflate_input),

                                     inflate_output, sizeof(inflate_output));

    if (out_bytes < 0) {

        // error

    } else {

        // success. deflate_output contains "Hello, World? Hello, World!"

        // out_bytes contains the number of bytes written to deflate_output

        // success. inflate_output contains "Hello, World? Hello, World!"

        // out_bytes contains the number of bytes written to inflate_output

    }

}
@@ -52,24 +57,24 @@ unsigned char deflate_output[128]; 
Decompressing deflate (RFC 1951) data works as follows:



```

#include "deflate.h"

#include "inflate.h"



unsigned char deflate_input[] = { /* some compressed data, e.g.: */

unsigned char inflate_input[] = { /* some compressed data, e.g.: */

    243, 72, 205, 201, 201, 215, 81, 8, 207, 47, 202, 73, 177, 87,

    240, 64, 226, 41, 2, 0

};



unsigned char deflate_output[128];

unsigned char inflate_output[128];



// within some function

{

    int16_t out_bytes = deflate(deflate_input, sizeof(deflate_input),

                                deflate_output, sizeof(deflate_output));

    int16_t out_bytes = inflate(inflate_input, sizeof(inflate_input),

                                inflate_output, sizeof(inflate_output));

    if (out_bytes < 0) {

        // error

    } else {

        // success. deflate_output contains "Hello, World? Hello, World!"

        // out_bytes contains the number of bytes written to deflate_output

        // success. inflate_output contains "Hello, World? Hello, World!"

        // out_bytes contains the number of bytes written to inflate_output

    }

}
@@ -78,7 +83,7 @@ unsigned char deflate_output[128]; 
## Compilation flags



Compile with `-DDEFLATE_CHECKSUM` to enable verification of the zlib ADLER32

checksum in `deflate_zlib`.

checksum in `inflate_zlib`.



## Compliance

src/deflate.c→src/inflate.c

+4 −4
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ 
 * SPDX-License-Identifier: BSD-2-Clause

 */



#include "lib/deflate.h"

#include "lib/inflate.h"



/*

 * The compressed (inflated) input data.
@@ -370,7 +370,7 @@ static int8_t deflate_dynamic_huffman() 
			       deflate_lld_lengths + hlit, hdist);

}



int16_t deflate(unsigned char *input_buf, uint16_t input_len,

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;
@@ -405,7 +405,7 @@ int16_t deflate(unsigned char *input_buf, uint16_t input_len, 
	return deflate_output_now - output_buf;

}



int16_t deflate_zlib(unsigned char *input_buf, uint16_t input_len,

int16_t inflate_zlib(unsigned char *input_buf, uint16_t input_len,

		     unsigned char *output_buf, uint16_t output_len)

{

	if (input_len < 4) {
@@ -427,7 +427,7 @@ int16_t deflate_zlib(unsigned char *input_buf, uint16_t input_len, 
	}



	int16_t ret =

	    deflate(input_buf + 2, input_len - 2, output_buf, output_len);

	    inflate(input_buf + 2, input_len - 2, output_buf, output_len);



#ifdef DEFLATE_CHECKSUM

	if (ret >= 0) {

src/deflate.h→src/inflate.h

+2 −2
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ 
#define DEFLATE_ERR_FCHECK (-7)

#define DEFLATE_ERR_NLEN (-8)



int16_t deflate(unsigned char *input_buf, uint16_t input_len,

int16_t inflate(unsigned char *input_buf, uint16_t input_len,

		unsigned char *output_buf, uint16_t output_len);

int16_t deflate_zlib(unsigned char *input_buf, uint16_t input_len,

int16_t inflate_zlib(unsigned char *input_buf, uint16_t input_len,

		     unsigned char *output_buf, uint16_t output_len);